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This paper reconsiders the use Byzantine domes as components of the urban skyline, through a detailed study of the transformations of Justinian’s church of Sts. Sergius and Baccus. This domed church has long been considered as one of the earliest additions of the period of Justinian to the cityscape of Constantinople. Recent scholarship, however, has questioned the attribution of its dome to the sixth century, inviting us to view this building as a palimpsest of different historic layers rather than as landmark of a single era. The church of Sts. Sergius and Bacchus lends itself ideally to such an approach. The Ottoman reuse of the church as a mosque is just one of several fascinating transformations of the church in the last fifteen hundred years. Despite the existence of several architectural surveys of the building, our understanding of the form of the original building and its later transformation is limited. This paper tries to fill this lacuna through a re-examination of the church’s fabric, with an emphasis on its dome. This is largely based on the reinterpretation of evidence provided in previous studies, especially those of Jonathan Bardill, as well as on the author’s observation of the building in 2006. Providing a new model for visualizing Justinian’s church and analyzing its transformations through time, this paper redefines the form of this church and its role alongside other Justinianic monuments in transforming the urban skyline of Constantinople.

This paper reconsiders the use Byzantine domes as components of the urban skyline, through a detailed study of the transformations of Justinian’s church of Sts. Sergius and Baccus. This domed church has long been considered as one of the earliest additions of the period of Justinian to the cityscape of Constantinople. Recent scholarship, however, has questioned the attribution of its dome to the sixth century, inviting us to view this building as a palimpsest of different historic layers rather than as landmark of a single era. The church of Sts. Sergius and Bacchus lends itself ideally to such an approach. The Ottoman reuse of the church as a mosque is just one of several fascinating transformations of the church in the last fifteen hundred years. Despite the existence of several architectural surveys of the building, our understanding of the form of the original building and its later transformation is limited. This paper tries to fill this lacuna through a re-examination of the church’s fabric, with an emphasis on its dome. This is largely based on the reinterpretation of evidence provided in previous studies, especially those of Jonathan Bardill, as well as on the author’s observation of the building in 2006. Providing a new model for visualizing Justinian’s church and analyzing its transformations through time, this paper redefines the form of this church and its role alongside other Justinianic monuments in transforming the urban skyline of Constantinople.

The relative importance of magnetic fields, turbulence, and gravity in the early phases of star formation is still not well understood. We report the first high-resolution dust polarization observations at 850 $\mu$m around the most massive clump, located at the hub of the Giant Molecular Cloud G148.24+00.41, using SCUBA-2/POL-2 at the James Clerk Maxwell Telescope. We find that the degree of polarization decreases steadily towards the denser portion of the cloud. Comparing the intensity gradients and local gravity with the magnetic field orientations, we find that local gravity plays a dominant role in driving the gas collapse as the magnetic field orientations and gravity vectors seem to point towards the dense clumps. We also find evidence of U-shaped magnetic field morphology towards a small-scale elongated structure associated with the central clump, hinting at converging accretion flows towards the clump. Our observation has resolved the massive clump into multiple substructures. We study the magnetic field properties of two regions, central clump (CC) and northeastern elongated structure (NES). Using the modified Davis-Chandrasekhar Fermi method, we determine that the magnetic field strengths of CC and NES are $\sim$24.0 $\pm$ 6.0 $\mu$G and 20.0 $\pm$ 5.0 $\mu$G, respectively. The mass-to-flux ratios are found to be magnetically transcritical/supercritical, while the Alfv$\acute{\text{e}}$n Mach number indicates a trans-Alfv$\acute{\text{e}}$nic state in both regions. These results, along with Virial analysis, suggest that at the hub of G148.24+00.41, gravitational energy has an edge over magnetic and kinetic energies., Comment: 17 pages, 23 figures

Filamentary flows toward the centre of molecular clouds have been recognized as a crucial process in the formation and evolution of stellar clusters. In this paper, we present a comprehensive observational study that investigates the gas properties and kinematics of the Giant Molecular Cloud G148.24+00.41 using the observations of CO (1-0) isotopologues. We find that the cloud is massive (10$^5$ M$_\odot$) and is one of the most massive clouds of the outer Galaxy. We identified six likely velocity coherent filaments in the cloud having length, width, and mass in the range of 14$-$38 pc, 2.5$-$4.2 pc, and (1.3$-$6.9) $\times$ 10$^3$ M$_\odot$, respectively. We find that the filaments are converging towards the central area of the cloud, and the longitudinal accretion flows along the filaments are in the range of $\sim$ 26$-$264 M$_\odot$ Myr$^{-1}$. The cloud has fragmented into 7 clumps having mass in the range of $\sim$ 260$-$2100 M$_\odot$ and average size around $\sim$ 1.4 pc, out of which the most massive clump is located at the hub of the filamentary structures, near the geometric centre of the cloud. Three filaments are found to be directly connected to the massive clump and transferring matter at a rate of $\sim$ 675 M$_\odot$ Myr$^{-1}$. The clump hosts a near-infrared cluster. Our results show that large-scale filamentary accretion flows towards the central region of the collapsing cloud is an important mechanism for supplying the matter necessary to form the central high-mass clump and subsequent stellar cluster., Comment: 21 pages, 20 figures

We present results from two experiments aimed at studying the direction of Mona Lisa’s gaze and its affective expression. In experiment 1 we studied the effect of retinal image size on the perception of her gaze by manipulating observation distances of a high-quality print of the painting. Participants (N = 30) were asked to answer a simple question (is the person portrayed looking at you?) from six different distances ranging from 55 to 755 cm. One group of participants started evaluations from 55 cm; the other group did the opposite. Results show an effect of distance on the perception of Mona Lisa’s gaze as staring at the observer: from the furthest distances, the impression of a staring Mona Lisa is robust; from the nearest distances, such impression becomes ambiguous. Experiment 2 presents data concerning the direction of Mona Lisa’s gaze and whether this appears to be smiling, derived from an experiment aimed at studying the impression of gaze (direction and emotional content) in portraits (paintings and photographs). Only data concerning Mona Lisa are reported. Participants (N = 41) were randomly assigned to one of two groups: on a LCD screen, one group saw the entire head, and the other group saw only a section reproducing Mona Lisa’s eyes. Experimental sessions were two: in session 1 participants had to decide whether the image (whole-head or eyes only) was looking at them; in session 2 participants had to decide whether the head (or the eyes) was smiling. RTs from the two groups of participants were not statistically significant. Results for session 1 confirm experiment 1’s general findings. Results for session 2 clearly show that Mona Lisa is not only smiling with her face, but also with her eyes. Results are discussed in relation to the literature on Mona Lisa’s gaze and smile.

We report an effect of anomalous transparency that is similar to other phantom effects. In an experiment aimed at testing the combined role of (i) motion of the occluding surface and (ii) lightness contrast and polarity on the perception of anomalous transparency, we found that transparency is perceived only with low contrast, and enhanced when the occluding surface is moving. A tentative explanation is suggested, based on simultaneous lightness contrast as a segregation factor and on motion as an integration factor, and discussed in light of previous studies conducted in the theoretical framework of Gestalt theories in perception.

We present results from two experiments aimed at studying the direction of Mona Lisa’s gaze and its affective expression. In experiment 1 we studied the effect of retinal image size on the perception of her gaze by manipulating observation distances of a high-quality print of the painting. Participants (N = 30) were asked to answer a simple question (is the person portrayed looking at you?) from six different distances ranging from 55 to 755 cm. One group of participants started evaluations from 55 cm; the other group did the opposite. Results show an effect of distance on the perception of Mona Lisa’s gaze as staring at the observer: from the furthest distances, the impression of a staring Mona Lisa is robust; from the nearest distances, such impression becomes ambiguous. Experiment 2 presents data concerning the direction of Mona Lisa’s gaze and whether this appears to be smiling, derived from an experiment aimed at studying the impression of gaze (direction and emotional content) in portraits (paintings and photographs). Only data concerning Mona Lisa are reported. Participants (N = 41) were randomly assigned to one of two groups: on a LCD screen, one group saw the entire head, and the other group saw only a section reproducing Mona Lisa’s eyes. Experimental sessions were two: in session 1 participants had to decide whether the image (whole-head or eyes only) was looking at them; in session 2 participants had to decide whether the head (or the eyes) was smiling. RTs from the two groups of participants were not statistically significant. Results for session 1 confirm experiment 1’s general findings. Results for session 2 clearly show that Mona Lisa is not only smiling with her face, but also with her eyes. Results are discussed in relation to the literature on Mona Lisa’s gaze and smile.

Illusions are important ‘tools’ in the study of perceptual processes. Their conception is typically linked to the notion of veridicality in a dual-world framework, in which we either see the macro physical world as it is (ecological approaches) or we derive a faithful representation (cognitive approaches) of it. Within such theoretical views, illusions are errors caused by inadequate sensory information (because of poor quality, insufficient quantity, contradictory, etc.). From a phenomenological stance, however, experiencing an illusion does not relate to the physical quality of the distal or proximal stimulus; rather, it depends on a comparison between the actual perception and what one believes should be perceived given the knowledge s/he has gained about the physical stimulus. Within such a framework, illusions are still considered of extreme importance in the study of the processes underpinning perception, but they are not conceived as errors. They represent instead a cognitive clash between actual perception and hypothesized perception based on some sort of comparison, thus also showing their potential as a tool for studying the underpinnings of cognitive processes.

This work explores the Takete/Maluma and Bouba/Kiki crossmodal correspondence. The phenomenon involves presenting participants with two abstract shapes – one characterised as curvy/roundish, and the other as angular/pointy – and two sets of meaningless words/sounds, one characterised by rounded vowels or a ‘smooth’ sound, the other by unrounded vowels or a ‘sharp’ sound. Participants tend to associate the curvy shape with the rounded vowel/smooth sounding non-word, while linking the angular shape to the unrounded vowel/sharp sounding non-word. The phenomenon is quite intriguing as it is a showcase for structural commonalities among perceptions deriving from different sensory channels. Nevertheless, there are concerns regarding the methodology used to define it. Specifically, what happens if people are given more choices in terms of shapes and non-words, will the reported correspondences hold under these expanded conditions? Additionally, the study seeks to verify whether abstract shapes possess other tertiary qualities, such as an ‘affective personality’. The study was conducted by means of an online experiment involving 122 native Italian speakers. Participants were presented with 9 abstract shapes and 10 non-words: three characterised as sharp sounding (takete, kiki, and tidi), three as soft sounding (maluma, bouba, and puloma), two as mixed sounding (kalute and bouki), and two which sounds may remotely recall the name of the shapes (tigano for triangolo-triangle and kiquoda for quadrato-square). Each shape was presented singularly, and participants were asked first to choose a name for the shape among the non-words and then to select an affective characteristic that best described each shape from the following list of options: good, bad, angry, sad, scared, joyful, calm, pleasant, bored, and melancholic. Results show strong convergences among participants in assigning affective characteristics to the abstract shapes. However, it should be noticed that only certai

The role of arm posture in the Uznadze haptic aftereffect is investigated: two identical test stimuli (i.e., spheres, TS) clenched simultaneously appear haptically different in size after hands have been adapted to two spheres (adapting stimuli, AS) differing in size: the hand adapted to a small AS feels TS bigger than the hand adapted to a big AS. In two experiments, participants evaluated the haptic impressions of two TS after adaptation by finding their match on a visual scale. In Experiment 1, all tasks were carried out with arms either uncrossed or crossed. In Experiment 2, only the matching task was performed with arms either uncrossed or crossed while adaptation was conducted by continuously changing arm posture from uncrossed to crossed and vice versa. The illusion occurred irrespectively of arm posture; however, its magnitude was smaller when adaptation was carried out in the classical condition of uncrossed arms. Results are discussed in light of two functional mechanisms: low-level somatotopic mapping (i.e., stimuli conformation) and high-level level factors (i.e., arm posture) that could modulate the haptic perception.

It has long been discussed whether stellar feedback in the form of winds and/or radiation can shred the nascent molecular cloud, thereby controlling the star formation rate. However, directly probing and quantifying the impact of stellar feedback on the neutral gas of the nascent clouds is challenging. We present an investigation doing exactly that toward the RCW 79 HII region using the ionized carbon line at 158 $\mu$m ([CII]) from the FEEDBACK Legacy Survey. We combine this data with information on the dozen ionizing O stars responsible for the evolution of the region, and observe in [CII] for the first time both blue- and red-shifted mostly neutral high-velocity gas which reaches velocities up to 25 km s$^{-1}$ relative to the bulk emission of the molecular cloud. This high-velocity gas mostly contains neutral gas and partly forms a fragmented shell, similar to recently found shells in a few Galactic HII regions. However, this shell does not account for all of the observed neutral high-velocity gas. We also find high-velocity gas streaming out of the nascent cloud through holes and obtain a range of dynamical timescales below 1.0 Myr for the high-velocity gas which is well below the 2.3$\pm$0.5 Myr age of the OB cluster. This suggests a different scenario for the evolution of RCW 79, where the high-velocity gas is not solely stemming from a spherical expanding bubble, but also from gas recently ablated at the edge of the turbulent molecular cloud into the surrounding interstellar medium through low-pressure holes or chimneys. The resulting mass ejection rate estimate for the cloud is 0.9-3.5$\times$10$^{-2}$ M$_{\odot}$~yr$^{-1}$, which leads to short erosion timescales, i.e. $<$5 Myr, for the nascent molecular cloud. This finding provides direct observational evidence of rapid molecular cloud dispersal., Comment: 9 pages, 7 figures, accepted in A&A Letters

Clouds more massive than about $10^5$ M$_\odot$ are potential sites of massive cluster formation. Studying the properties of such clouds in the early stages of their evolution offers an opportunity to test various cluster formation processes. We make use of CO, Herschel, and UKIDSS observations to study one such cloud, G148.24+00.41. Our results show the cloud to be of high mass ($\sim$ $1.1\times10^5$ M$_\odot$), low dust temperature ($\sim$ 14.5 K), nearly circular (projected radius $\sim$ 26 pc), and gravitationally bound with a dense gas fraction of $\sim 18$% and a density profile with a power-law index of $\sim -1.5$. Comparing its properties with those of nearby molecular clouds, we find that G148.24+00.41 is comparable to the Orion-A molecular cloud in terms of mass, size, and dense gas fraction. From our analyses, we find that the central area of the cloud is actively forming protostars and is moderately fractal with a Q-value of $\sim$ 0.66. We also find evidence of global mass-segregation in the cloud, with a degree of mass-segregation ($\Lambda_{MSR}) \approx3.2$. We discuss these results along with the structure and compactness of the cloud, the spatial and temporal distribution of embedded stellar population, and their correlation with the cold dust distribution, in the context of high-mass cluster formation. Comparing our results with models of star cluster formation, we conclude that the cloud has the potential to form a cluster in the mass range $\sim$ 2000--3000 M$_\odot$ through dynamical hierarchical collapse and assembly of both gas and stars., Comment: It is accepted for publication in Monthly Notices of the Royal Astronomical Society (MNRAS). The unedited version of the manuscript has been published

Whether ionization feedback triggers the formation of massive stars is highly debated. Using ALMA 3 mm observations with a spatial resolution of $\sim 0.05$ pc and a mass sensitivity of 1.1 $\rm M_\odot$ beam$^{-1}$ at 20 K, we investigate the star formation and gas flow structures within the ionizing feedback-driven structure, a clump-scale massive ($\gtrsim 1500$ $\rm M_\odot$) bright-rimmed cloud (BRC) associated with IRAS 18290-0924. This BRC is bound only if external compression from ionized gas is considered. A small-scale ($\lesssim1$ pc) age sequence along the direction of ionizing radiation is revealed for the embedded cores and protostars, which suggests triggered star formation via radiation-driven implosion (RDI). Furthermore, filamentary gas structures converge towards the cores located in the BRC's center, indicating that these filaments are fueling mass towards cores. The local core-scale mass infall rate derived from H$^{13}$CO$^+$ $J=1-0$ blue profile is of the same order of magnitude as the filamentary mass inflow rate, approximately 1 $\rm M_\odot$ kyr$^{-1}$. A photodissociation region (PDR) covering the irradiated clump surface is detected in several molecules, such as CCH, HCO$^+$, and CS whereas the spatial distribution stratification of these molecules is indistinct. CCH spectra of the PDR possibly indicate a photoevaporation flow leaving the clump surface with a projected velocity of $\sim2$ km s$^{-1}$. Our new observations show that RDI accompanied by a clump-fed process is operating in this massive BRC. Whether this combined process works in other massive BRCs is worth exploring with dedicated surveys., Comment: 34 pages with 20 figures, Accepted by MNRAS on 2022 December 28

Context. The impact of stellar feedback on the Kennicutt-Schmidt law (KS law), which relates star formation rate (SFR) to surface gas density, is a topic of ongoing debate. The interpretation of individual cloud observations is challenging due to the various processes at play simultaneously and inherent biases. Therefore, a numerical investigation is necessary to understand the role of stellar feedback and identify observable signatures. Aims. We investigate the role of stellar feedback on the KS law, aiming to identify distinct signatures that can be observed and analysed. Methods. We analyse MHD numerical simulations of a $10^4\,M_{\odot}$ cloud evolving under different feedback prescriptions. The set of simulations contains four types of feedback: with only protostellar jets, with ionising radiation from massive stars $(>8\,M_{\odot})$, with both of them and without any stellar feedback. To compare these simulations with the existing observational results, we analyse their evolution by adopting the same techniques applied in observational studies. Then, we simulate how the same analyses would change if the data were affected by typical observational biases. Conclusions. The presence of stellar feedback strongly influences the KS relation and the star formation efficiency per free-fall time ($\epsilon_\mathrm{ff}$). Its impact is primarily governed by its influence on the cloud's structure. Although the $\epsilon_\mathrm{ff}$ measured in our clouds results to be higher than what is usually observed in real clouds, upon applying prescriptions to mimic observational biases we recover good agreement with the expected values. Therefore, we can infer that observations tend to underestimate the total SFR. Moreover, this likely indicates that the physics included in our simulations is sufficient to reproduce the basic mechanisms contributing to set $\epsilon_\mathrm{ff}$., Comment: 16 pages, 13 figures, accepted for publication to A&A

The visual system often relies on prior assumptions when interpreting ambiguous visual inputs. A well-known example is the light-from-above prior, which aids the judgment of an object's three-dimensional (3-D) shape (i.e., convex or concave). Recent studies have revealed that the light-from-above prior also helps solve lightness ambiguity. This study aimed to examine whether 3-D shape perception and lightness perception share the same lighting prior. The study participants performed two tasks: one focusing on lightness perception and another focusing on 3-D shape perception. The dominant directions of the assumed lighting were calculated from participants' performance in the two tasks. The results showed that the assumed lighting direction for 3-D shape perception were considerably biased toward the left, whereas the one for lightness perception was almost from directly above. The clear difference between these two directions supports the hypothesis that the visual system uses distinct lighting priors for 3-D shape perception and lightness perception. Experiments 1 and 2 involved Japanese speaking participants and European participants, respectively. The Japanese language can be read and written both horizontally (i.e., left to right) and vertically (i.e., up to down) with lines progressing from right to left. Nevertheless, the two experiments still produced the same result, which suggests that the present finding is universal regardless of reading/writing direction.

The visual system often relies on prior assumptions when interpreting ambiguous visual inputs. A well-known example is the light-from-above prior, which aids the judgment of an object's three-dimensional (3-D) shape (i.e., convex or concave). Recent studies have revealed that the light-from-above prior also helps solve lightness ambiguity. This study aimed to examine whether 3-D shape perception and lightness perception share the same lighting prior. The study participants performed two tasks: one focusing on lightness perception and another focusing on 3-D shape perception. The dominant directions of the assumed lighting were calculated from participants' performance in the two tasks. The results showed that the assumed lighting direction for 3-D shape perception were considerably biased toward the left, whereas the one for lightness perception was almost from directly above. The clear difference between these two directions supports the hypothesis that the visual system uses distinct lighting priors for 3-D shape perception and lightness perception. Experiments 1 and 2 involved Japanese speaking participants and European participants, respectively. The Japanese language can be read and written both horizontally (i.e., left to right) and vertically (i.e., up to down) with lines progressing from right to left. Nevertheless, the two experiments still produced the same result, which suggests that the present finding is universal regardless of reading/writing direction.

E-motions are defined as those affective states the expressions of which-conveyed either by static faces or body posture-embody a dynamic component and, consequently, convey a higher sense of dynamicity than other emotional expressions. An experiment is presented, aimed at testing whether e-motions are perceived as such also by individuals with autism spectrum disorders (ASDs), which have been associated with impairments in emotion recognition and in motion perception. To this aim we replicate with ASD individuals a study, originally conducted with typically developed individuals (TDs), in which we showed to both ASD and TD participants 14 bodiless heads and 14 headless bodies taken from eleven static artworks and four drawings. The Experiment was divided into two sessions. In Session 1 participants were asked to freely associate each stimulus to an emotion or an affective state (Task 1, option A); if they were unable to find a specific emotion, the experimenter showed them a list of eight possible emotions (words) and asked them to choose one from such list, that best described the affective state portrayed in the image (Task 1, option B). After their choice, they were asked to rate the intensity of the perceived emotion on a seven point Likert scale (Task 2). In Session 2 participants were requested to evaluate the degree of dynamicity conveyed by each stimulus on a 7 point Likert scale. Results showed that ASDs and TDs shared a similar range of verbal expressions defining emotions; however, ASDs (i) showed an impairment in the ability to spontaneously assign an emotion to a headless body, and (ii) they more frequently used terms denoting negative emotions (for both faces and bodies) as compared to neutral emotions, which in turn were more frequently used by TDs. No difference emerged between the two groups for positive emotions, with happiness being the emotion better recognized in both faces and in bodies. Although overall there are no significant differences be

The purpose of this research is to present the employment of a simple-to-use crossmodal method for measuring haptic size illusions. The method, that we call See what you feel, was tested by employing Uznadze’s classic haptic aftereffect in which two spheres physically identical (test spheres) appear different in size after that the hands holding them underwent an adaptation session with other two spheres (adapting spheres), one bigger and the other smaller than the two test spheres. To measure the entity of the illusion, a three-dimensional visual scale was created and participants were asked to find on it the spheres that corresponded in size to the spheres they were holding in their hands out of sight. The method, tested on 160 right-handed participants, is robust and easily understood by participants.

The purpose of this research is to present the employment of a simple-to-use crossmodal method for measuring haptic size illusions. The method, that we call See what you feel, was tested by employing Uznadze’s classic haptic aftereffect in which two spheres physically identical (test spheres) appear different in size after that the hands holding them underwent an adaptation session with other two spheres (adapting spheres), one bigger and the other smaller than the two test spheres. To measure the entity of the illusion, a three-dimensional visual scale was created and participants were asked to find on it the spheres that corresponded in size to the spheres they were holding in their hands out of sight. The method, tested on 160 right-handed participants, is robust and easily understood by participants.

Perceptual grouping is, along with figure-ground segmentation, a core topic in the studies of perceptual organization, i.e., of those processes that structure the sensory input into coherent units (visual objects, entities, and events), thus contributing significantly to the layout of the visual scene. From such a definition, it is clear that grouping and segmentation are two faces of the same coin, as originally postulated by the fathers of Gestalt psychology Max Wertheimer, Wolfgang Köhler [3], and Kurt Koffka [4]

L’articolo bersaglio di Mastandrea (2020) è un’ardita ed encomiabile sintesi di una miriade di riflessioni e di lavori sperimentali sulla natura e sulla fruizione di opere d’arte, realizzati all’interno di discipline piuttosto eterogenee tra loro, quali la psicologia, le neuroscienze, la filosofia. Mastandrea però, partendo dalla «triade estetica » postulata da Chatterjee e Vartanian (2016) e guidato dal modello multi-componenziale di Leder e Nadal (2014), va ben oltre la sintesi e traccia un possibile percorso che si snoda tra quelle ricerche, mostrando i vantaggi portati da un approccio multidisciplinare al fenomeno artistico. Il suo discorso è infatti funzionale al superamento di una certa Psicologia dell’arte a favore di una disciplina in cui gli apporti delle diverse scienze possono integrarsi. Tale disciplina, ormai una realtà, è l’Estetica empirica.

[Abridged] The interstellar medium is observed to be organised in filamentary structures, as well as neutral (HI) and ionized (HII) bubbles. The expanding nature of these bubbles makes them shape their surroundings and possibly play a role in the formation and evolution of interstellar filaments. We present APEX $^{13}$CO and C$^{18}$O(2-1) observations of the NGC 6334 molecular cloud. We investigate the gas velocity structure along and across the 50 pc-long cloud and towards 75 identified velocity-coherent-filaments (VCFs). We measure a wealth of velocity gradients along the VCFs. We derive the column density and velocity power spectra of the VCFs. These power spectra are well represented with power laws showing similar slopes for both quantities (with a mean of about -2), albeit some differ by up to a factor of two. The position velocity diagrams perpendicular to three VCFs show the V-shaped velocity pattern, corresponding to a bent structure in velocity space with the filament at the tip of the V surrounded by an extended structure connected to it with a velocity gradient. This velocity structure is qualitatively similar to that resulting from numerical simulations of filament formation from large-scale compression from propagating shock fronts. In addition, the radial profiles perpendicular to these VCFs hint to small-scale internal impacts from neighbouring HII bubbles. The observed opposite curvature in velocity space towards the VCFs points to various origins of large-scale external compressions from propagating HI bubbles. This suggests the plausible importance of multiple HI compressions, separated in space and time, in the formation and evolution of molecular clouds and their star formation history. These latter atomic compressions due to past and distant star formation events are complemented by the impact of HII bubbles from present time and local star formation activity., Comment: Accepted for publication in Astronomy & Astrophysics

We present [C ii] 158 mu m and [O i] 63 mu m observations of the bipolar H ii region RCW 36 in the Vela C molecular cloud, obtained within the SOFIA legacy project FEEDBACK, which is complemented with APEX (CO)-C-12/13 (3-2) and Chandra X-ray (0.5-7 keV) data. This shows that the molecular ring, forming the waist of the bipolar nebula, expands with a velocity of 1-1.9 km s(-1). We also observe an increased line width in the ring, indicating that turbulence is driven by energy injection from the stellar feedback. The bipolar cavity hosts blueshifted expanding [C ii] shells at 5.2 +/- 0.5 +/- 0.5 km s(-1) (statistical and systematic uncertainty), which indicates that expansion out of the dense gas happens nonuniformly and that the observed bipolar phase might be relatively short (similar to 0.2 Myr). The X-ray observations show diffuse emission that traces a hot plasma, created by stellar winds, in and around RCW 36. At least 50% of the stellar wind energy is missing in RCW 36. This is likely due to leakage that is clearing even larger cavities around the bipolar RCW 36 region. Lastly, the cavities host high-velocity wings in [C ii], which indicates relatively high mass ejection rates (similar to 5 x 10(-4) M (circle dot) yr(-1)). This could be driven by stellar winds and/or radiation but remains difficult to constrain. This local mass ejection, which can remove all mass within 1 pc of RCW 36 in 1-2 Myr, and the large-scale clearing of ambient gas in the Vela C cloud indicate that stellar feedback plays a significant role in suppressing the star formation efficiency.

Aims. Revealing the 3D dynamics of H-II region bubbles and their associated molecular clouds and H-I envelopes is important for developing an understanding of the longstanding problem as to how stellar feedback affects the density structure and kinematics of the different phases of the interstellar medium. Methods. We employed observations of the H-II region RCW 120 in the [C-II] 158 mu m line, observed within the Stratospheric Observatory for Infrared Astronomy (SOFIA) legacy program FEEDBACK, and in the (CO)-C-12 and (CO)-C-13 (3 -> 2) lines, obtained with the Atacama Pathfinder Experiment (APEX) to derive the physical properties of the gas in the photodissociation region (PDR) and in the molecular cloud. We used high angular resolution H-I data from the Southern Galactic Plane Survey to quantify the physical properties of the cold atomic gas through H-I self-absorption. The high spectral resolution of the heterodyne observations turns out to be essential in order to analyze the physical conditions, geometry, and overall structure of the sources. Two types of radiative transfer models were used to fit the observed [C-II] and CO spectra. A line profile analysis with the 1D non-LTE radiative transfer code SimLine proves that the CO emission cannot stem from a spherically symmetric molecular cloud configuration. With a two-layer multicomponent model, we then quantified the amount of warm background and cold foreground gas. To fully exploit the spectral-spatial information in the CO spectra, a Gaussian mixture model was introduced that allows for grouping spectra into clusters with similar properties. Results. The CO emission arises mostly from a limb-brightened, warm molecular ring, or more specifically a torus when extrapolated in 3D. There is a deficit of CO emission along the line-of-sight toward the center of the H-II region which indicates that the H-II region is associated with a flattened molecular cloud. Self-absorption in the CO line may hide signatures of i

Context. The interstellar medium is observed to be organized in filamentary structures, and in neutral (H I) and ionized (H II) bubbles. The expanding nature of these bubbles shapes the surrounding medium and possibly plays a role in the formation and evolution of the interstellar filaments. The impact of the expansion of these bubbles on the interstellar medium is not well understood. Aims. Our aim is to describe the kinematics of a filamentary molecular cloud forming high-mass stars and hosting multiple H II regions in order to study the possible environmental impact on the properties of molecular filaments. Methods. We present APEX (CO)-C-13 and (CO)-O-18(2-1) mapping observations of the 10 x 50 pc NGC 6334 molecular cloud complex. We investigated the gas velocity structure along and across the 50 pc long cloud and toward velocity-coherent filaments (VCFs). Results. The NGC 6334 complex is observed to have a coherent velocity structure smoothly varying by similar to 5 km s(-1) over its 50 pc elongation parallel to the Galactic plane. We identify a sample of 75 VCFs in the (CO)-O-18(2-1) position-position-velocity cube and present the properties of 47 VCFs with a length greater than or similar to 1 pc (five beams). We measure a large number of velocity gradients along the VCFs. The amplitudes of these velocity gradients and the velocity dispersion measured along the crests increase with the column density of the VCFs. We derive the column density and velocity power spectra of the VCFs. These power spectra are well represented with power laws showing similar slopes for the two quantities (with a mean of about -2), although some differ by up to a factor of 2. The position velocity diagrams perpendicular to three VCFs (selected from different physical environments) show the V-shaped velocity pattern corresponding to a bent structure in velocity space with the filament at the tip of the V surrounded by an extended structure connected to it with a velocity gradient. Th

Context. Filaments are ubiquitous in the Galaxy, and they host star formation. Detecting them in a reliable way is therefore key towards our understanding of the star formation process. Aims. We explore whether supervised machine learning can identify filamentary structures on the whole Galactic plane. Methods. We used two versions of UNet-based networks for image segmentation.We used H2 column density images of the Galactic plane obtained with Herschel Hi-GAL data as input data. We trained the UNet-based networks with skeletons (spine plus branches) of filaments that were extracted from these images, together with background and missing data masks that we produced. We tested eight training scenarios to determine the best scenario for our astrophysical purpose of classifying pixels as filaments. Results. The training of the UNets allows us to create a new image of the Galactic plane by segmentation in which pixels belonging to filamentary structures are identified. With this new method, we classify more pixels (more by a factor of 2 to 7, depending on the classification threshold used) as belonging to filaments than the spine plus branches structures we used as input. New structures are revealed, which are mainly low-contrast filaments that were not detected before.We use standard metrics to evaluate the performances of the different training scenarios. This allows us to demonstrate the robustness of the method and to determine an optimal threshold value that maximizes the recovery of the input labelled pixel classification. Conclusions. This proof-of-concept study shows that supervised machine learning can reveal filamentary structures that are present throughout the Galactic plane. The detection of these structures, including low-density and low-contrast structures that have never been seen before, offers important perspectives for the study of these filaments., Comment: 27 pages, 22 figures, accepted by Astronomy & Astrophysics

We present a new derivation of the Milky Way's current star formation rate (SFR) based on the data of the Hi-GAL Galactic plane survey. We estimate the distribution of the SFR across the Galactic plane from the star-forming clumps identified in the Hi-GAL survey and calculate the total SFR from the sum of their contributions. The estimate of the global SFR amounts to $2.0 \pm 0.7$~M$_{\odot}$~yr$^{-1}$, of which $1.7 \pm 0.6$~M$_{\odot}$~yr$^{-1}$ coming from clumps with reliable heliocentric distance assignment. This value is in general agreement with estimates found in the literature of last decades. The profile of SFR density averaged in Galactocentric rings is found to be qualitatively similar to others previously computed, with a peak corresponding to the Central Molecular Zone and another one around Galactocentric radius $R_\mathrm{gal} \sim 5$~kpc, followed by an exponential decrease as $\log(\Sigma_\mathrm{SFR}/[\mathrm{M}_\odot~\mathrm{yr}^{-1}~\mathrm{kpc}^{-2}])=a\,R_\mathrm{gal}/[\mathrm{kpc}]+b $, with $a=-0.28 \pm 0.01$. In this regard, the fraction of SFR produced within and outside the Solar circle is 84\% and 16\%, respectively; the fraction corresponding to the far outer Galaxy ($R_\mathrm{gal} > 13.5$~kpc) is only 1\%. We also find that, for $R_\mathrm{gal}>3$~kpc, our data follow a power law as a function of density, similarly to the Kennicutt-Schmidt relation. Finally, we compare the distribution of the SFR density across the face-on Galactic plane and those of median parameters, such as temperature, luminosity/mass ratio and bolometric temperature, describing the evolutionary stage of Hi-GAL clumps. We found no clear correlation between the SFR and the clump evolutionary stage., Comment: To be published in ApJ

We present [CII] 158 $\mu$m and [OI] 63 $\mu$m observations of the bipolar HII region RCW 36 in the Vela C molecular cloud, obtained within the SOFIA legacy project FEEDBACK, which is complemented with APEX $^{12/13}$CO(3-2) and Chandra X-ray (0.5-7 keV) data. This shows that the molecular ring, forming the waist of the bipolar nebula, expands with a velocity of 1 - 1.9 km s$^{-1}$. We also observe an increased linewidth in the ring indicating that turbulence is driven by energy injection from the stellar feedback. The bipolar cavity hosts blue-shifted expanding [CII] shells at 5.2$\pm$0.5$\pm$0.5 km s$^{-1}$ (statistical and systematic uncertainty) which indicates that expansion out of the dense gas happens non-uniformly and that the observed bipolar phase might be relatively short ($\sim$0.2 Myr). The X-ray observations show diffuse emission that traces a hot plasma, created by stellar winds, in and around RCW 36. At least 50 \% of the stellar wind energy is missing in RCW 36. This is likely due to leakage which is clearing even larger cavities around the bipolar RCW 36 region. Lastly, the cavities host high-velocity wings in [CII] which indicates relatively high mass ejection rates ($\sim$5$\times$10$^{-4}$ M$_{\odot}$ yr$^{-1}$). This could be driven by stellar winds and/or radiation pressure, but remains difficult to constrain. This local mass ejection, which can remove all mass within 1 pc of RCW 36 in 1-2 Myr, and the large-scale clearing of ambient gas in the Vela C cloud indicates that stellar feedback plays a significant role in suppressing the star formation efficiency (SFE)., Comment: 38 pages, 27 figures, 8 tables, accepted in ApJ

Ionized gas probes the influence of massive stars on their environment. The Cygnus X region (d~1.5 kpc) is one of the most massive star forming complexes in our Galaxy, in which the Cyg OB2 association (age of 3-5 Myr and stellar mass $2 \times 10^{4}$ M$_{\odot}$) has a dominant influence. We observe the Cygnus X region at 148 MHz using the Low Frequency Array (LOFAR) and take into account short-spacing information during image deconvolution. Together with data from the Canadian Galactic Plane Survey, we investigate the morphology, distribution, and physical conditions of low-density ionized gas in a $4^{\circ} \times 4^{\circ}$ (100 pc $\times$ 100 pc) region at a resolution of 2' (0.9 pc). The Galactic radio emission in the region analyzed is almost entirely thermal (free-free) at 148 MHz, with emission measures of $10^3 < EM~{\rm[pc~cm^{-6}]} < 10^6$. As filamentary structure is a prominent feature of the emission, we use DisPerSE and FilChap to identify filamentary ridges and characterize their radial ($EM$) profiles. The distribution of radial profiles has a characteristic width of 4.3 pc and a power-law distribution ($\beta = -1.8 \pm 0.1$) in peak $EM$ down to our completeness limit of 4200 pc cm$^{-6}$. The electron densities of the filamentary structure range from $10 < n_e~{\rm[cm^{-3}]} < 400$ with a median value of 35 cm$^{-3}$, remarkably similar to [N II] surveys of ionized gas. Cyg OB2 may ionize at most two-thirds of the total ionized gas and the ionized gas in filaments. More than half of the filamentary structures are likely photoevaporating surfaces flowing into a surrounding diffuse (~5 cm$^{-3}$) medium. However, this is likely not the case for all ionized gas ridges. A characteristic width in the distribution of ionized gas points to the stellar winds of Cyg OB2 creating a fraction of the ionized filaments through swept-up ionized gas or dissipated turbulence., Comment: 19 pages, 14 figures, 1 table; accepted for publication in A&A

The study of the development of structures on multiple scales in the cold interstellar medium has experienced rapid expansion in the past decade, on both the observational and the theoretical front. Spectral line studies at (sub-)millimeter wavelengths over a wide range of physical scales have provided unique probes of the kinematics of dense gas in star-forming regions, and have been complemented by extensive, high dynamic range dust continuum surveys of the column density structure of molecular cloud complexes, while dust polarization maps have highlighted the role of magnetic fields. This has been accompanied by increasingly sophisticated numerical simulations including new physics (e.g., supernova driving, cosmic rays, non-ideal magneto-hydrodynamics, radiation pressure) and new techniques such as zoom-in simulations allowing multi-scale studies. Taken together, these new data have emphasized the anisotropic growth of dense structures on all scales, from giant ISM bubbles driven by stellar feedback on $\sim$50-100 pc scales through parsec-scale molecular filaments down to $<$0.1 pc dense cores and $<$1000 au protostellar disks. Combining observations and theory, we present a coherent picture for the formation and evolution of these structures and synthesize a comprehensive physical scenario for the initial conditions and early stages of star and disk formation., Comment: 42 pages, 20 figures. To appear in Protostars and Planets VII, Editors: Shu-ichiro Inutsuka, Yuri Aikawa, Takayuki Muto, Kengo Tomida, and Motohide Tamura. Small changes to match proofs and the updated format

[Abridged] The interstellar medium is observed to be organised in filamentary structures, as well as neutral (HI) and ionized (HII) bubbles. The expanding nature of these bubbles makes them shape their surroundings and possibly play a role in the formation and evolution of interstellar filaments. We present APEX $^{13}$CO and C$^{18}$O(2-1) observations of the NGC 6334 molecular cloud. We investigate the gas velocity structure along and across the 50 pc-long cloud and towards 75 identified velocity-coherent-filaments (VCFs). We measure a wealth of velocity gradients along the VCFs. We derive the column density and velocity power spectra of the VCFs. These power spectra are well represented with power laws showing similar slopes for both quantities (with a mean of about -2), albeit some differ by up to a factor of two. The position velocity diagrams perpendicular to three VCFs show the V-shaped velocity pattern, corresponding to a bent structure in velocity space with the filament at the tip of the V surrounded by an extended structure connected to it with a velocity gradient. This velocity structure is qualitatively similar to that resulting from numerical simulations of filament formation from large-scale compression from propagating shock fronts. In addition, the radial profiles perpendicular to these VCFs hint to small-scale internal impacts from neighbouring HII bubbles. The observed opposite curvature in velocity space towards the VCFs points to various origins of large-scale external compressions from propagating HI bubbles. This suggests the plausible importance of multiple HI compressions, separated in space and time, in the formation and evolution of molecular clouds and their star formation history. These latter atomic compressions due to past and distant star formation events are complemented by the impact of HII bubbles from present time and local star formation activity., Comment: Accepted for publication in Astronomy & Astrophysics

Two experiments are described, the purpose of which was to investigate the presence of a misalignment illusion caused by Poggendorff-like conditions in two paintings by Peter Paul Rubens, both depicting the Descent from the Cross, one located in Antwerp (Belgium), the other in Lille (France). The first shows a geometrical misalignment made by Rubens in a minor detail, which is considered proof that the artist observed the Poggendorff illusion. The second painting, instead, shows a perfect geometrical alignment in a similar detail. In experiment 1, participants were asked to align a top segment to a lower one in two types of stimuli: a full-size digitally manipulated reproduction of the painting and a Poggendorff-like configuration that recalled the painting's lines displacement and tilt. Adjustments were performed from two distances, one up close (painting distance) and one from below and far (observation distance). Results confirmed the presence of the Poggendorff illusion, but mean adjustments significantly differed from the misalignment perpetrated by Rubens. Experiment 2 was set up in a similar fashion with the Lille painting. Results confirmed the presence of the Poggendorff illusion also in this painting; however, the alignment by Rubens coincides with the geometrical one. Results from both experiments do not support the claim that Rubens observed the Poggendorff illusion and therefore corrected for it in the Antwerp painting. An alternative account is discussed, which relates to the structural layout of the painting.

Transcranial direct current stimulation (tDCS) has been widely used for modulating sensory, motor and cognitive functions, but there are only few attempts to induce and change illusory perception. Visual illusions have been the most traditional and effective way to investigate visual processing through the comparison between physical reality and subjective reports. Here we used tDCS to modulate two different visual illusions, namely the Brentano illusion and the glare effect, with the aim of uncovering the influence of top-down mechanisms on bottom-up visual perception in two experiments. In Experiment 1, to a first group of subjects, real and sham cathodal tDCS (2 mA, 10 min) were applied over the left and right posterior parietal cortices (PPC). In Experiment 2, real and sham cathodal tDCS were applied to the left and right occipital cortices (OC) to a second group of participants. Results showed that tDCS was effective in modulating only the Brentano illusion, but not the glare effect. tDCS increased the Brentano illusion but specifically for the stimulated cortical area (right PPC), illusion direction (leftward), visual hemispace (left), and illusion length (160 mm). These findings suggest the existence of an inhibitory modulation of top-down mechanisms on bottom-up visual processing specifically for the Brentano illusion, but not for the glare effect. The lack of effect of occipital tDCS should consider the possible role of ocular compensation or of the unstimulated hemisphere, which deserves further investigations.

Context. The Orion molecular cloud is the closest region of high-mass star formation. It is an ideal target for investigating the detailed structure of massive star-forming filaments at high resolution and the relevance of the filament paradigm for the earliest stages of intermediate- to high-mass star formation. Aims. Within the Orion A molecular cloud, the integral-shaped filament (ISF) is a prominent, degree-long structure of dense gas and dust with clear signs of recent and ongoing high-mass star formation. Our aim is to characterise the structure of this massive filament at moderately high angular resolution (800 or ∼ 0.016 pc) in order to measure the intrinsic width of the main filament, down to scales well below 0.1 pc, which has been identified as the characteristic width of filaments. Methods. We used the ArTéMiS bolometer camera at APEX to map a ∼0.6×0.2 deg2 region covering OMC-1, OMC-2, and OMC-3 at 350 and 450 µm. We combined these data with Herschel-SPIRE maps to recover extended emission. The combined Herschel�ArTéMiS maps provide details on the distribution of dense cold material, with a high spatial dynamic range, from our 800 resolution up to the transverse angular size of the map, ∼ 10–150. By combining Herschel and ArTéMiS data at 160, 250, 350, and 450 µm, we constructed high-resolution temperature and H2 column density maps. We extracted radial intensity profiles from the column density map in several representative portions of the ISF, which we fitted with Gaussian and Plummer models to derive their intrinsic widths. We also compared the distribution of material traced by ArTéMiS with that seen in the higher-density tracer N2H+(1–0) that was recently observed with the ALMA interferometer. Results. All the radial profiles that we extracted show a clear deviation from a Gaussian, with evidence for an inner plateau that had not previously been seen clearly using Herschel-only data. We measure intrinsic half-power widths in the range 0.06 to 0.11

Context. The Orion molecular cloud is the closest region of high-mass star formation. It is an ideal target for investigating the detailed structure of massive star-forming filaments at high resolution and the relevance of the filament paradigm for the earliest stages of intermediate- to high-mass star formation. Aims. Within the Orion A molecular cloud, the integral-shaped filament (ISF) is a prominent, degree-long structure of dense gas and dust with clear signs of recent and ongoing high-mass star formation. Our aim is to characterise the structure of this massive filament at moderately high angular resolution (800 or ∼ 0.016 pc) in order to measure the intrinsic width of the main filament, down to scales well below 0.1 pc, which has been identified as the characteristic width of filaments. Methods. We used the ArTéMiS bolometer camera at APEX to map a ∼0.6×0.2 deg2 region covering OMC-1, OMC-2, and OMC-3 at 350 and 450 µm. We combined these data with Herschel-SPIRE maps to recover extended emission. The combined Herschel�ArTéMiS maps provide details on the distribution of dense cold material, with a high spatial dynamic range, from our 800 resolution up to the transverse angular size of the map, ∼ 10–150. By combining Herschel and ArTéMiS data at 160, 250, 350, and 450 µm, we constructed high-resolution temperature and H2 column density maps. We extracted radial intensity profiles from the column density map in several representative portions of the ISF, which we fitted with Gaussian and Plummer models to derive their intrinsic widths. We also compared the distribution of material traced by ArTéMiS with that seen in the higher-density tracer N2H+(1–0) that was recently observed with the ALMA interferometer. Results. All the radial profiles that we extracted show a clear deviation from a Gaussian, with evidence for an inner plateau that had not previously been seen clearly using Herschel-only data. We measure intrinsic half-power widths in the range 0.06 to 0.11

Revealing the 3D dynamics of HII regions and their associated molecular clouds is important for understanding the longstanding problem as to how stellar feedback affects the density structure and kinematics of the interstellar medium. We employed observations of the HII region RCW 120 in [CII], observed within the SOFIA legacy program FEEDBACK, and the $^{12}$CO and $^{13}$CO (3$\to$2) lines, obtained with APEX. In addition we used HI data from the Southern Galactic Plane Survey. Two radiative transfer models were used to fit the observed data. A line profile analysis with the 1D non-LTE radiative transfer code SimLine proves that the CO emission cannot stem from a spherically symmetric molecular cloud configuration. With a two-layer multicomponent model, we then quantified the amount of warm background and cold foreground gas. There is a deficit of CO emission along the line-of-sight toward the center of the HII region which indicates that the HII region is associated with a flattened molecular cloud. Self-absorption in the CO line may hide signatures of infalling and expanding molecular gas. The [CII] emission arises from an expanding [CII] bubble and from the PDRs. A significant part of [CII] emission is absorbed in a cool (~60-100 K), low-density (<500 cm$^{-3}$) atomic foreground layer with a thickness of a few parsec. We propose that the RCW 120 HII region formed in a flattened molecular cloud and is now bursting out of its parental cloud. The compressed surrounding molecular layer formed a torus around the spherically expanding HII bubble. This scenario can possibly be generalized for other HII bubbles and would explain the observed "flat" structure of molecular clouds associated with HII bubbles. We suggest that the [CII] absorption observed in many star-forming regions is at least partly caused by low-density, cool, HI-envelopes surrounding the molecular clouds.

We present a comprehensive multiwavelength investigation of a likely massive young cluster `IRAS 05100+3723' and its environment with the aim to understand its formation history and feedback effects. We find that IRAS 05100+3723 is a distant ($\sim$3.2 kpc), moderate mass ($\sim$500 \msun), young ($\sim$3 Myr) cluster with its most massive star being an O8.5V-type. From spectral modeling, we estimate the effective temperature and log $g$ of the star as $\sim$33,000 K and $\sim$3.8, respectively. Our radio continuum observations reveal that the star has ionized its environment forming an HII region of size $\sim$2.7 pc, temperature $\sim$5,700 K, and electron density $\sim$165 cm$^{-3}$. However, our large-scale dust maps reveal that it has heated the dust up to several parsecs ($\sim$10 pc) in the range 17$-$28 K and the morphology of warm dust emission resembles a bipolar HII region. From dust and $^{13}$CO gas analyses, we find evidences that the formation of the HII region has occurred at the very end of a long filamentary cloud around 3 Myr ago, likely due to edge collapse of the filament. We show that the HII region is currently compressing a clump of mass $\sim$2700 \msun at its western outskirts, at the junction of the HII region and filament. We observe several 70 $\mu$m point sources of intermediate-mass and class 0 nature within the clump. We attribute these sources as the second generation stars of the complex. We propose that the star formation in the clump is either induced or being facilitated by the compression of the expanding HII region onto the inflowing filamentary material., Comment: ApJ, accepted

We present the 360 degrees catalogue of physical properties of Hi-GAL compact sources, detected between 70 and 500 mu m. This release not only completes the analogous catalogue previously produced by the Hi-GAL collaboration for -71 degrees less than or similar to l less than or similar to 67 degrees, but also meaningfully improves it because of a new set of heliocentric distances, 120 808 in total. About a third of the 150 223 entries are located in the newly added portion of the Galactic plane. A first classification based on detection at 70 mu m as a signature of ongoing star-forming activity distinguishes between protostellar sources (23 per cent of the total) and starless sources, with the latter further classified as gravitationally bound (pre-stellar) or unbound. The integral of the spectral energy distribution, including ancillary photometry from lambda = 21 to 1100 mu m, gives the source luminosity and other bolometric quantities, while a modified blackbody fitted to data for lambda >= 160 mu m yields mass and temperature. All tabulated clump properties are then derived using photometry and heliocentric distance, where possible. Statistics of these quantities are discussed with respect to both source Galactic location and evolutionary stage. No strong differences in the distributions of evolutionary indicators are found between the inner and outer Galaxy. However, masses and densities in the inner Galaxy are on average significantly larger, resulting in a higher number of clumps that are candidates to host massive star formation. Median behaviour of distance-independent parameters tracing source evolutionary status is examined as a function of the Galactocentric radius, showing no clear evidence of correlation with spiral arm positions.

We present the 360 degrees catalogue of physical properties of Hi-GAL compact sources, detected between 70 and 500m. This release not only completes the analogous catalogue previously produced by the Hi-GAL collaboration for -71 degrees less than or similar to l less than or similar to 67 degrees, but also meaningfully improves it because of a new set of heliocentric distances, 120808 in total. About a third of the 150223 entries are located in the newly added portion of the Galactic plane. A first classification based on detection at 70 mu m as a signature of ongoing star-forming activity distinguishes between protostellar sources (23percent of the total) and starless sources, with the latter further classified as gravitationally bound (pre-stellar) or unbound. The integral of the spectral energy distribution, including ancillary photometry from lambda = 21 to 1100m, gives the source luminosity and other bolometric quantities, while a modified blackbody fitted to data for lambda >= 160 mu m yields mass and temperature. All tabulated clump properties are then derived using photometry and heliocentric distance, where possible. Statistics of these quantities are discussed with respect to both source Galactic location and evolutionary stage. No strong differences in the distributions of evolutionary indicators are found between the inner and outer Galaxy. However, masses and densities in the inner Galaxy are on average significantly larger, resulting in a higher number of clumps that are candidates to host massive star formation. Median behaviour of distance-independent parameters tracing source evolutionary status is examined as a function of the Galactocentric radius, showing no clear evidence of correlation with spiral arm positions.

We use the (CO)-C-13(2-1) emission from the SEDIGISM (Structure, Excitation, and Dynamics of the Inner Galactic InterStellar Medium) high-resolution spectral-line survey of the inner Galaxy, to extract the molecular cloud population with a large dynamic range in spatial scales, using the Spectral Clustering for Interstellar Molecular Emission Segmentation (SCIMES) algorithm. This work compiles a cloud catalogue with a total of 10 663 molecular clouds, 10 300 of which we were able to assign distances and compute physical properties. We study some of the global properties of clouds using a science sample, consisting of 6664 well-resolved sources and for which the distance estimates are reliable. In particular, we compare the scaling relations retrieved from SEDIGISM to those of other surveys, and we explore the properties of clouds with and without high-mass star formation. Our results suggest that there is no single global property of a cloud that determines its ability to form massive stars, although we find combined trends of increasing mass, size, surface density, and velocity dispersion for the sub-sample of clouds with ongoing high-mass star formation. We then isolate the most extreme clouds in the SEDIGISM sample (i.e. clouds in the tails of the distributions) to look at their overall Galactic distribution, in search for hints of environmental effects. We find that, for most properties, the Galactic distribution of the most extreme clouds is only marginally different to that of the global cloud population. The Galactic distribution of the largest clouds, the turbulent clouds and the high-mass star-forming clouds are those that deviate most significantly from the global cloud population. We also find that the least dynamically active clouds (with low velocity dispersion or low virial parameter) are situated further afield, mostly in the least populated areas. However, we suspect that part of these trends may be affected by some observational biases (such as comp

The SEDIGISM (Structure, Excitation and Dynamics of the Inner Galactic InterstellarMedium) survey used the APEX telescope to map 84 deg(2) of the Galactic plane between l = -60 degrees and +31 degrees in several molecular transitions, including (CO)-C-13(2 - 1) and (CO)-O-18(2 - 1), thus probing the moderately dense (similar to 10(3) cm(-3)) component of the interstellar medium. With an angular resolution of 30 arcsec and a typical 1 sigma sensitivity of 0.8-1.0K at 0.25 km s(-1) velocity resolution, it gives access to a wide range of structures, from individual star-forming clumps to giant molecular clouds and complexes. The coverage includes a good fraction of the first and fourth Galactic quadrants, allowing us to constrain the large-scale distribution of cold molecular gas in the inner Galaxy. In this paper, we provide an updated overview of the full survey and the data reduction procedures used. We also assess the quality of these data and describe the data products that are being made publicly available as part of this First Data Release (DR1). We present integrated maps and position-velocity maps of the molecular gas and use these to investigate the correlation between the molecular gas and the large-scale structural features of the Milky Way such as the spiral arms, Galactic bar and Galactic Centre. We find that approximately 60 per cent of the molecular gas is associated with the spiral arms and these appear as strong intensity peaks in the derived Galactocentric distribution. We also find strong peaks in intensity at specific longitudes that correspond to the Galactic Centre and well-known star-forming complexes, revealing that the 13CO emission is concentrated in a small number of complexes rather than evenly distributed along spiral arms.

Radiative and mechanical feedback of massive stars regulates star formation and galaxy evolution. Positive feedback triggers the creation of new stars by collecting dense shells of gas, while negative feedback disrupts star formation by shredding molecular clouds. Although key to understanding star formation, their relative importance is unknown. Here, we report velocity-resolved observations from the SOFIA (Stratospheric Observatory for Infrared Astronomy) legacy program FEEDBACK of the massive star-forming region RCW 120 in the [CII] 1.9-THz fine-structure line, revealing a gas shell expanding at 15 km/s. Complementary APEX (Atacama Pathfinder Experiment) CO J = 3-2 345-GHz observations exhibit a ring structure of molecular gas, fragmented into clumps that are actively forming stars. Our observations demonstrate that triggered star formation can occur on much shorter time scales than hitherto thought (< 0.15 million years), suggesting that positive feedback operates on short time periods.

We use the (CO)-C-13(2-1) emission from the SEDIGISM (Structure, Excitation, and Dynamics of the Inner Galactic InterStellar Medium) high-resolution spectral-line survey of the inner Galaxy, to extract the molecular cloud population with a large dynamic range in spatial scales, using the Spectral Clustering for Interstellar Molecular Emission Segmentation (SCIMES) algorithm. This work compiles a cloud catalogue with a total of 10 663 molecular clouds, 10 300 of which we were able to assign distances and compute physical properties. We study some of the global properties of clouds using a science sample, consisting of 6664 well-resolved sources and for which the distance estimates are reliable. In particular, we compare the scaling relations retrieved from SEDIGISM to those of other surveys, and we explore the properties of clouds with and without high-mass star formation. Our results suggest that there is no single global property of a cloud that determines its ability to form massive stars, although we find combined trends of increasing mass, size, surface density, and velocity dispersion for the sub-sample of clouds with ongoing high-mass star formation. We then isolate the most extreme clouds in the SEDIGISM sample (i.e. clouds in the tails of the distributions) to look at their overall Galactic distribution, in search for hints of environmental effects. We find that, for most properties, the Galactic distribution of the most extreme clouds is only marginally different to that of the global cloud population. The Galactic distribution of the largest clouds, the turbulent clouds and the high-mass star-forming clouds are those that deviate most significantly from the global cloud population. We also find that the least dynamically active clouds (with low velocity dispersion or low virial parameter) are situated further afield, mostly in the least populated areas. However, we suspect that part of these trends may be affected by some observational biases (such as comp

The SEDIGISM (Structure, Excitation and Dynamics of the Inner Galactic InterstellarMedium) survey used the APEX telescope to map 84 deg(2) of the Galactic plane between l = -60 degrees and +31 degrees in several molecular transitions, including (CO)-C-13(2 - 1) and (CO)-O-18(2 - 1), thus probing the moderately dense (similar to 10(3) cm(-3)) component of the interstellar medium. With an angular resolution of 30 arcsec and a typical 1 sigma sensitivity of 0.8-1.0K at 0.25 km s(-1) velocity resolution, it gives access to a wide range of structures, from individual star-forming clumps to giant molecular clouds and complexes. The coverage includes a good fraction of the first and fourth Galactic quadrants, allowing us to constrain the large-scale distribution of cold molecular gas in the inner Galaxy. In this paper, we provide an updated overview of the full survey and the data reduction procedures used. We also assess the quality of these data and describe the data products that are being made publicly available as part of this First Data Release (DR1). We present integrated maps and position-velocity maps of the molecular gas and use these to investigate the correlation between the molecular gas and the large-scale structural features of the Milky Way such as the spiral arms, Galactic bar and Galactic Centre. We find that approximately 60 per cent of the molecular gas is associated with the spiral arms and these appear as strong intensity peaks in the derived Galactocentric distribution. We also find strong peaks in intensity at specific longitudes that correspond to the Galactic Centre and well-known star-forming complexes, revealing that the 13CO emission is concentrated in a small number of complexes rather than evenly distributed along spiral arms.

We present the 360 degrees catalogue of physical properties of Hi-GAL compact sources, detected between 70 and 500 mu m. This release not only completes the analogous catalogue previously produced by the Hi-GAL collaboration for -71 degrees less than or similar to l less than or similar to 67 degrees, but also meaningfully improves it because of a new set of heliocentric distances, 120 808 in total. About a third of the 150 223 entries are located in the newly added portion of the Galactic plane. A first classification based on detection at 70 mu m as a signature of ongoing star-forming activity distinguishes between protostellar sources (23 per cent of the total) and starless sources, with the latter further classified as gravitationally bound (pre-stellar) or unbound. The integral of the spectral energy distribution, including ancillary photometry from lambda = 21 to 1100 mu m, gives the source luminosity and other bolometric quantities, while a modified blackbody fitted to data for lambda >= 160 mu m yields mass and temperature. All tabulated clump properties are then derived using photometry and heliocentric distance, where possible. Statistics of these quantities are discussed with respect to both source Galactic location and evolutionary stage. No strong differences in the distributions of evolutionary indicators are found between the inner and outer Galaxy. However, masses and densities in the inner Galaxy are on average significantly larger, resulting in a higher number of clumps that are candidates to host massive star formation. Median behaviour of distance-independent parameters tracing source evolutionary status is examined as a function of the Galactocentric radius, showing no clear evidence of correlation with spiral arm positions.

We present the 360 degrees catalogue of physical properties of Hi-GAL compact sources, detected between 70 and 500m. This release not only completes the analogous catalogue previously produced by the Hi-GAL collaboration for -71 degrees less than or similar to l less than or similar to 67 degrees, but also meaningfully improves it because of a new set of heliocentric distances, 120808 in total. About a third of the 150223 entries are located in the newly added portion of the Galactic plane. A first classification based on detection at 70 mu m as a signature of ongoing star-forming activity distinguishes between protostellar sources (23percent of the total) and starless sources, with the latter further classified as gravitationally bound (pre-stellar) or unbound. The integral of the spectral energy distribution, including ancillary photometry from lambda = 21 to 1100m, gives the source luminosity and other bolometric quantities, while a modified blackbody fitted to data for lambda >= 160 mu m yields mass and temperature. All tabulated clump properties are then derived using photometry and heliocentric distance, where possible. Statistics of these quantities are discussed with respect to both source Galactic location and evolutionary stage. No strong differences in the distributions of evolutionary indicators are found between the inner and outer Galaxy. However, masses and densities in the inner Galaxy are on average significantly larger, resulting in a higher number of clumps that are candidates to host massive star formation. Median behaviour of distance-independent parameters tracing source evolutionary status is examined as a function of the Galactocentric radius, showing no clear evidence of correlation with spiral arm positions.

Radiative and mechanical feedback of massive stars regulates star formation and galaxy evolution. Positive feedback triggers the creation of new stars by collecting dense shells of gas, while negative feedback disrupts star formation by shredding molecular clouds. Although key to understanding star formation, their relative importance is unknown. Here, we report velocity-resolved observations from the SOFIA (Stratospheric Observatory for Infrared Astronomy) legacy program FEEDBACK of the massive star-forming region RCW 120 in the [CII] 1.9-THz fine-structure line, revealing a gas shell expanding at 15 km/s. Complementary APEX (Atacama Pathfinder Experiment) CO J = 3-2 345-GHz observations exhibit a ring structure of molecular gas, fragmented into clumps that are actively forming stars. Our observations demonstrate that triggered star formation can occur on much shorter time scales than hitherto thought (< 0.15 million years), suggesting that positive feedback operates on short time periods.

This work summarizes research conducted by the author over the years aimed at studying the perception of light in achromatic settings carried out by combining an experimental phenomenological approach with psychophysical methods. Concepts such as “reality” and “illusion” and basic lightness/brightness terminology are briefly analyzed. The perception of light is then treated in three paragraphs, each dedicated to a specific aspect: Luminosity, environmental illumination, and surface illumination (the last largely in relation to lightness perception). For each type of light perception, demos are presented along with a brief discussion of experimental studies conducted by the author and collaborators.

Revealing the 3D dynamics of HII regions and their associated molecular clouds is important for understanding the longstanding problem as to how stellar feedback affects the density structure and kinematics of the interstellar medium. We employed observations of the HII region RCW 120 in [CII], observed within the SOFIA legacy program FEEDBACK, and the $^{12}$CO and $^{13}$CO (3$\to$2) lines, obtained with APEX. In addition we used HI data from the Southern Galactic Plane Survey. Two radiative transfer models were used to fit the observed data. A line profile analysis with the 1D non-LTE radiative transfer code SimLine proves that the CO emission cannot stem from a spherically symmetric molecular cloud configuration. With a two-layer multicomponent model, we then quantified the amount of warm background and cold foreground gas. There is a deficit of CO emission along the line-of-sight toward the center of the HII region which indicates that the HII region is associated with a flattened molecular cloud. Self-absorption in the CO line may hide signatures of infalling and expanding molecular gas. The [CII] emission arises from an expanding [CII] bubble and from the PDRs. A significant part of [CII] emission is absorbed in a cool (~60-100 K), low-density (<500 cm$^{-3}$) atomic foreground layer with a thickness of a few parsec. We propose that the RCW 120 HII region formed in a flattened molecular cloud and is now bursting out of its parental cloud. The compressed surrounding molecular layer formed a torus around the spherically expanding HII bubble. This scenario can possibly be generalized for other HII bubbles and would explain the observed "flat" structure of molecular clouds associated with HII bubbles. We suggest that the [CII] absorption observed in many star-forming regions is at least partly caused by low-density, cool, HI-envelopes surrounding the molecular clouds.