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The sulfur content in dense molecular regions of the interstellar medium is highly depleted in comparison to diffuse clouds. The reason of this phenomenon is unclear, thus it is necessary to carry out observational studies of sulfur-bearing species towards dense regions, mainly at early evolutive stages to uncover the early sulfur chemistry. Using data from the Atacama Large Millimeter Array (ALMA) data archive, we investigated a sample of 37 dense cores embedded in the most massive infrared-quiet molecular clumps from the ATLASGAL survey. Lines of 34SO, SO2, NS, SO, SO+, and H2CS were analyzed and column densities of each molecular species were obtained. From the continuum emission, and two CH3OH lines, the 37 cores were characterized in density and temperature, and the corresponding H2 column densities were derived. The abundances of such sulfur-bearing species were derived and studied. We find that the abundances of the analyzed species increase with the growth of the gas temperature, suggesting that the chemistry involved in the formation of each of the analyzed molecule may have a similar dependence with Tk in the range 20 to 100 K. We find that the comparisons among abundances are, in general, highly correlated. Given that such correlation decreases in more evolved sources, we suggest that the sulfur-bearing species here analyzed should have a similar chemical origin. From the measured line widths we point out that molecules with oxygen content (34SO, SO2, SO, and SO+) may be associated with warmer and more turbulent gas than the other ones. H2CS and NS are associated with more quiescent gas, probably in the external envelopes of the cores. This work gives quantitative information about abundances that could be useful in chemical models pointing to explain the sulfur chemistry in the interstellar medium., Comment: Accepted for publication in A&A (October 31, 2024)

Most of the $\gamma$-ray sources in the Fermi-LAT 14-year Source Catalogue are associated with pulsars and blazars. However, unveiling the nature of the still unassociated $\gamma$-ray sources is important for the understanding of high energy emission mechanisms in astrophysical objects. This work presents a comprehensive study towards the region covered by the Fermi source 4FGL J1846.9$-$0227, previously suggested to be a blazar and a massive protostar. Using multiwavelength observations, we analysed several astrophysical objects in the region as possible counterparts of the Fermi-LAT source. Having discarded most of them after a detailed and comprehensive analysis, we suggest that the most likely candidate to be such a counterpart is IRAS 18443$-$0231, a likely proto-planetary nebula. We found that the radio continuum emission at 3 GHz of IRAS 18443$-$0231 shows a compact source related to faint emission with jet-like morphology. Additionally, we identified an associated red-shifted CO molecular outflow. Using data from several catalogues, we obtained radio spectral index values ranging from $-$0.57 to $-$0.39 for IRAS 18443$-$0231, indicating syncrothron emission due to particles accelerated by the jets. We point out that these jets could explain the $\gamma$-ray emission through mechanisms such as proton-proton collisions and relativistic Bremsstrahlung. IRAS 18443$-$0231, lying almost at the centre of the Fermi confidence ellipse and related to the hard X-ray source 4XMM J184700.4$-$022752, would be the first association between a proto-planetary nebula and $\gamma$-ray emission., Comment: Accepted to be published in MNRAS (July 8, 2024)

In previous works, we have investigated the star-forming region G29.96$-$0.02 where the massive young stellar object (MYSO) G29.862$-$0.0044 (hereafter G29) is embedded in a hot molecular core. In one of them, of multiwavelength nature, using data from the Atacama Submillimeter Telescope Experiment (ASTE), data from the Atacama Large Millimeter Array (ALMA), and photometric data from NIRI-Gemini, G29 was investigated at different spatial scales. However, the intriguing morphology of G29 in the near-infrared, together with the distribution of the associated molecular gas, reveals that the star-formation scenario is far from being understood. This work incorporates the analysis of the emission of several molecular lines acquired with ALMA that were not previously examined (eg.,~CH$_{3}$OH, HC$_{3}$N, H$_{ 2}$CO, C$^{34}$S, H$_{2}$CS) as well as a new determination of the temperature of the region. Additionally, we present the progress of results obtained through new observations in the near-infrared, in this case spectroscopic, using NIFS-Gemini, and in radio continnum obtained with the Karl G. Jansky Very Large Array (JVLA). This research allows us to carry out a detailed chemical study of the region, which will contribute to the understanding of the physical processes involved in the high-mass star formation., Comment: accepted to be published in Bolet\'in de la Asociaci\'on Argentina de Astronom\'ia

The formation of stars, particularly the high-mass star formation, poses several still open questions. Nowadays, thanks to the most modern telescopes and instruments, we are able to observe and analyse many physical and chemical processes involved in the birth of massive stars. This work introduces to the interstellar medium, cradle of the stars, and makes focus on the interstellar structures distributed in the different spatial scales related to the collapse of the gas that gives rise to the star formation processes. Through some current works done by the investigation group of Interstellar Medium, Star Formation and Astrochemistry belonging to Instituto de Astronom\'ia y F\'isica del Espacio (https://interestelariafe.wixsite.com/mediointerestelar), it is shown that the observational study of the star formation is a research that must be carried out in a multispectral way, pointing to the spatial multiscale., Comment: To appear in Bolet\'in de la Asociaci\'on Argentina de Astronom\'ia (BAAA). Invited contribution

The star forming processes strongly influence the ISM chemistry. Nowadays, there are available many high-quality databases at millimeter wavelengths. Using them, it is possible to carry out studies that review and deepen previous results. If these studies involve large samples of sources, it is preferred to use direct tools to study the molecular gas. With the aim of testing these tools such as the use of the HCN/HNC ratio as a thermometer, and the use of H$^{13}$CO$^{+}$, HC$_{3}$N, N$_{2}$H$^{+}$, and C$_{2}$H as "chemical clocks", we present a molecular line study towards 55 sources representing massive young stellar objects (MYSOs) at different evolutive stages: infrared dark clouds (IRDCs), high-mass protostellar objects (HMPOs), hot molecular cores (HMCs) and ultracompact HII regions (UCHII). We found that the use of HCN/HNC ratio as an universal thermometer in the ISM should be taken with care because the HCN optical depth is a big issue that can affect the method. Hence, this tool should be used only after a careful analysis of the HCN spectrum, checking that no line, neither the main nor the hyperfine ones, present absorption features. We point out that the analysis of the emission of H$^{13}$CO$^{+}$, HC$_{3}$N, N$_{2}$H$^{+}$, and C$_{2}$H could be useful to trace and distinguish regions among IRDCs, HMPOs and HMCs. The molecular line widths of these four species increase from the IRDC to the HMC stage, which can be a consequence of the gas dynamics related to the star-forming processes taking place in the molecular clumps. Our results do not only contribute with more statistics regarding to probe such chemical tools, useful to obtain information in large samples of sources, but also complement previous works through the analysis on other types of sources., Comment: accepted to be published in Research in Astronomy & Astrophysics, October 13, 2023

We present a comprehensive physical and chemical study of the fragmentation and star formation activity towards the massive clump AGAL G338.9188+0.5494 harbouring the extended green object EGO 338.92+0.55(b). The presence of an EGO embedded in a massive clump, suggests, at clump scale, that high-mass star formation is occurring. The main goal of this work is to find evidence of such high-mass star formation, but at core scale. Using mm observations of continuum and lines obtained from the ALMA database at Bands 6 and 7, we study the substructure of the massive clump. The angular resolution of the data is about 0.5'', which allow us to resolve structures of about 0.01pc ($\sim$ 2000 au) at the distance of 4.4 kpc. The continuum emission at 340 GHz reveals that the molecular clump is fragmented in five cores, labeled from C1 to C5. The $^{12}$CO J=3--2 emission shows the presence of molecular outflows related to three of them. The analysis of the CH$_3$CN and CH$_3$CCH emissions suggests temperatures of about 340 and 72~K, respectively, for C1, showing that the methyl cyanide would trace a gas layer closer to the protostar than the methyl acetylene. The obtained mass of core C1 ranges from 3 to 10 M$_{\odot}$. We found that the discovered molecular outflow arising from core C1 should be the main responsible for the 4.5 $\mu$m extended emission. The average mass and energy of such a molecular outflow is about 0.5 M$_{\odot}$~and $10^{46}$~erg, respectively, which suggest that 10 M$_{\odot}$ is the most likely mass value for core C1. Additionally we found that the region is chemically very rich with several complex molecular species. Particularly, from the analysis of the CN emission we found strong evidence that such a radical is indirectly tracing the molecular outflows, more precisely the border of the cavity walls carved out by such outflows., Comment: Accepted for publication in A&A (July 5, 2023)

The study of molecules and their chemistry in star-forming regions is fundamental to understand the physical process occurring in such regions. The HCN and HNC J=1-0 emissions were used to derive their integrated line intensities (I), to probe a relation recently appeared in the literature between the kinetic temperatures (T$_{K}$) and the isomeric (I) ratio, and to obtain the isomers abundances (X) in 55 high-mass star-forming regions. These last ones are classified, according to the evolutive stage, as infrared dark clouds, high-mass protostellar objects, hot molecular cores, and ultracompact HII regions. It is inferred that the T$_{K}$ obtained from the isomeric integrated intensity ratio (I$^{HCN/HNC}$) are underestimated, and hence we suggest that this relation cannot be employed as an universal thermometer in the interstellar medium. The isomers abundances show a behavior that can be explained from the chemistry occurring as the temperature and the UV radiation increase according to the evolutive stage. We found that the abundance ratio (X$^{HCN/HNC}$) hardly could be used as a chemical clock, and we suggest that it can be approximated by I$^{HCN/HNC}$. This work is part of an on-going study of multiple molecules that stand in the sample of analyzed regions which intends to contribute in the chemical knowledge of high-mass star formation., Comment: to appear in Bolet\'in de la Asociaci\'on Argentina de Astronom\'ia

In addition to the large surveys and catalogs of massive young stellar objects and outflows, dedicated studies of particular sources, in which high-angular observations (mainly at near-IR and mm) are analyzed in depth, are needed to shed light on the processes involved in the formation of massive stars. The galactic source G079.1272+02.2782 (G79), a MYSO at about 1.4 kpc, is an ideal source to carry out this kind of studies. Near-IR integral field spectroscopic observations were carried out using NIFS at Gemini-North. The spectral and angular resolutions, allow us to perform a detailed study of the source and its southern jet, resolving structures with sizes between 200 and 300 au. As a complement, millimeter data retrieved from the JCMT and the IRAM 30m telescope databases were analyzed to study the molecular gas at a larger spatial scale. The analysis of a jet extending southwards shows cork-screw like structures at 2.2 um continuum, strongly suggesting that the jet is precessing. The jet velocity is estimated in 30-43 km/s and it is coming to us along the line of sight. We suggest that the precession may be produced by the gravitational tidal effects generated in a probable binary system, and we estimate a jet precession period of about 10^3 yr, indicating a slow-precessing jet, which is in agreement with the observed helical features. An analysis of H2 lines along the jet allows us to investigate in detail a bow-shock produced by this jet. We find that this bow-shock is indeed generated by a C-type shock and it is observed coming to us, with some inclination angle, along the line of sight. This is confirmed by the analysis of molecular outflows at a larger spatial scale. A brief analysis of several molecular species at millimeter wavelengths indicates a complex chemistry developing at the external layers of the molecular clump in which MYSO G79 is embedded., Comment: Accepted to be published in A&A (August 4, 2022)

At the first Galactic quadrant, at l=33.134, b=-0.091, an extended photodissociation region generated by an HII region complex lies. This region is related to abundant molecular gas, and particularly, a hot molecular core, known as G33.133-mm3, appears embedded in a molecular clump. Using data from the James Clerk Maxwell Telescope with an angular resolution of about 15", we studied the 13CO/C18O abundance ratio towards the mentioned molecular clump and its relation with the ultraviolet radiation. At smaller spatial scales, using data from the Atacama Large Millimeter Array (angular resolution about 0.7\arcsec), the hot molecular core G33.133-mm3, that has a size of about 2600 au, and is an appropriate site to form stars, was characterized. In particular, some points about its chemistry are mentioned based on the emission of the cyanide or nitrile radical (CN) and others more complex molecules, such as CH3OH, CH3CN, CH3OCHO, and CH3CCH., Comment: accepted to be published in Bolet\'in de la Asociaci\'on Argentina de Astronom\'ia (BAAA)

It is known that massive stars form as result of the fragmentation of molecular clumps. However, what is not clear is whether this fragmentation gives rise to cores massive enough to form directly high-mass stars, or leads to cores of low and intermediate mass that generate massive stars acquiring material from their environment. Detailed studies towards clumps at early stages of star formation are needed to collect observational evidence that shed light on this issue. The infrared-quiet massive clump AGAL G035.1330-00.7450, located at a distance of 2.1 kpc, is a promising object to study both the fragmentation and the star formation activity at early stages. Using millimeter observations of continuum and molecular lines obtained from the Atacama Large Millimeter Array database at Bands 6 and 7, we study the substructure of this source. The angular resolution of the data at Band 7 is about 0\farcs7, which allow us to resolve structures of about 0.007 pc ($\sim$1500 au). We found that the clump harbours four dust cores (C1-C4) with masses below 3 M$_{\odot}$. Cores C3 and C4 exhibit well collimated, young, and low-mass molecular outflows. C1 and C2 present CH$_3$CN J=13--12 emission, from which we derive rotational temperatures of about 180 and 100 K, and masses of about 1.4 and 0.9 M$_{\odot}$, respectively. The moment 1 map of the CH$_3$CN emission suggests the presence of a rotating disk towards C1, which is confirmed by the CH$_3$OH and CH$_3$OCHO (20-19) emissions. On the other hand, CN N=2-1 emission shows a clumpy and filamentary structure that seems to connect all the cores. These filaments might be tracing the remnant gas of the fragmentation processes taking place within the clump, or gas that is being transported towards the cores, which would imply a competitive accretion scenario., Comment: Accepted for publication in A&A (December 26, 2021)

The cyano radical (CN), one of the first detected interstellar molecular species, is a key molecule in many astrochemical chains. Particularly, it is detected towards molecular cores, the birth places of the stars, and it is known that it is involved in the rich chemistry that takes place in these sites. At present there are not so many studies about the emission of this molecular species at small spatial scales towards massive young stellar objects. Thus, we present a high-angular resolution CN study towards a sample of massive protostars, with the aim of unveiling the spatial distribution at the small scale of the emission of this radical in relation to the star-forming processes. The interstellar CN has a strong emission line at the rest frequency 226874.764 MHz, thus, we search for observing projects in the ALMA database regarding high-mass star-forming regions observed at Band 6. A sample of ten high-mass star-forming regions were selected in base on that they present a clear emission of CN at the mentioned frequency. We found that the CN traces both molecular condensations and diffuse and extended gas surrounding them. In general, the molecular condensations traced by the maximums of the CN emission do not spatially coincide with the peaks of the continuum emission at 1.3 mm, which trace the molecular cores where the massive stars born. Based on the presence or lack of near-IR emission associated with such cores, we suggest that our sample is composed by sources at different stages of evolution. The CN is present at both, suggesting that this radical may be ubiquitous along the different star formation stages, and hence it may be involved in different chemical reactions occurring along the time in the formation of the stars. Additionally, other complex molecules were detected towards the continuum peaks of some of the analyzed cores., Comment: Accepted for publication in A&A. July 23, 2021

Evidence of triggered star formation at large spatial scales involving stellar clusters is scarce. We investigate a Galactic region (l=130.0, b=0.35) populated by several open stellar clusters that according to the last GAIA data release, are located at a distance of about 2.9 kpc. By analyzing the interstellar medium (ISM) at infrared, centimeter, and millimeter wavelengths towards this group of clusters we discovered a shell of material of about 2 degree in size at the same distance. We suggest that the shell, mainly observed at 12 um and in the Hi emission at 21 cm, was generated by the action of massive stars belonging to clusters Berkeley 7 and UBC 414, that lie at its center. Five clusters (MWSC0152, Czernik 6, Czernik 7, Berkeley 6, NGC 663, and NGC 654) lie at the border of this shell. From the comparison between the dynamical time of the discovered Hi shell and the analysis of the ages of stellar populations in these clusters, we conclude that the expansion of the shell could have triggered in the past the formation of stars in some of them. We point out that in order to find physical evidence supporting a genetic connection between stellar clusters, it is necessary not only to study the individual clusters and their stellar populations, but also to investigate their surrounding ISM at a large spatial scale., Comment: Accepted in MNRAS (June 3, 2021)

This paper presents a review of ideas that interconnect Astrochemistry and Galactic Dynamics. Since these two areas are vast and not recent, each one has already been covered separately by several reviews. After a general historical introduction, and a needed quick review of processes like the stellar nucleosynthesis which gives the base to understand the interstellar formation of simple chemical compounds (H2, CO, NH3 and H2O), we focus on a number of topics which are at the crossing of the two areas, Dynamics and Astrochemistry. Astrochemistry is a flourishing field which intends to study the presence and formation of molecules as well as the influence of them into the structure, evolution and dynamics of astronomical objects. The progress in the knowledge on the existence of new complex molecules and of their process of formation originates from the observational, experimental and theoretical areas which compose the field. The interfacing areas include star formation, protoplanetary disks, the role of the spiral arms and the chemical abundance gradients in the galactic disk. It often happens that the physical conditions in some regions of the ISM are only revealed by means of molecular observations. To organise a classification of chemical evolution processes, we discuss about how astrochemistry can act in three different contexts: i. the chemistry of the early universe, including external galaxies, ii. star forming regions, and iii. AGB stars and circumstellar envelopes. We mention that our research is stimulated by plans for instruments and projects, such as the on-going LLAMA, which consists in the construction of a 12m sub-mm radio telescope in the Andes. Thus, modern and new facilities can play a key role in new discoveries not only in astrochemistry but also in radio astronomy and related areas. Furthermore, the research of the origin of life is also a stimulating perspective., Comment: 29 pages, 10 figures. Article type: Review. Manuscript accepted for publication in Frontiers in Astronomy and Space Sciences, section Fundamental Astronomy

The fragmentation of a molecular cloud that leads to the formation of high-mass stars occurs on a hierarchy of different spatial scales. The large molecular clouds harbour massive molecular clumps with massive cores embedded in them. The fragmentation of these cores may determine the initial mass function and the masses of the final stars. Therefore, studying the fragmentation processes in the cores is crucial to understand how massive stars form. The hot molecular core G34-MM1, embedded in IRDC G34.34+00.24 located at a distance of 3.6 kpc, is a promising object to study both the fragmentation and outflow processes. Using data at 93 and 334 GHz obtained from the Atacama Large Millimeter Array (ALMA) database we studied G34-MM1 with great detail. The angular resolution of the data at 334 GHz allowed us to resolve structures of about 0.014 pc ($\sim$2900 au). We found evidence of fragmentation towards the molecular hot core G34-MM1 at two different spatial scales. The dust condensation MM1-A (about 0.06 pc in size) harbours three molecular subcores candidates (SC1 through SC3) detected in $^{12}$CO J=3-2 emission, with typical sizes of about 0.02 pc. From the HCO$^+$ J=1-0 emission, we identify, with better angular resolution than previous observations, two perpendicular molecular outflows arising from MM1-A. We suggest that subcores SC1 and SC2, embedded in MM1-A, harbour the sources responsible of the main and the secondary molecular outflow, respectively. Finally, from the radio continuum emission at 334 GHz, we marginally detected another dust condensation, named MM1-E, from which a young, massive, and energetic molecular outflow arises. The fragmentation of the hot molecular core G34-MM1 at two different spatial scales, together with the presence of multiple molecular outflows associated with it, would support a competitive accretion scenario., Comment: Accepted in A&A. March 8, 2021

Massive molecular clumps fragment into cores where star formation takes place, hence star-forming studies should be done at different spatial scales. Using near-IR data obtained with Gemini, data of CH3OCHO and CH3CN from the ALMA database, observations of HCN, HNC, HCO+, and C2H carried out with ASTE, and CO data from public surveys, we perform a deep study of the YSO G29.86-0.004 at core and clump spatial scales. The near-IR emission shows two nebulosities separated by a dark lane, suggesting a typical disk-jets system, but highly asymmetric. They are likely produced by scattered light in cavities carved out by jets on an infalling envelope of material, which also present line emission of H2 and [FeII]. The presence of the complex molecular species observed with ALMA confirms that we are mapping a hot molecular core. The CH3CN emission concentrates at the position of the dark lane and it appears slightly elongated from southwest to northeast in agreement with the inclination of the system as observed at near-IR. The morphology of the CH3OCHO emission is more complex and extends along some filaments and concentrates in knots and clumps, mainly southwards the dark-lane, suggesting that the southern jet is encountering a dense region. The northern jet flows more freely, generating more extended features. This is in agreement with the red-shifted molecular outflow traced by the 12CO J=3-2 line extending towards the northwest and the lack of a blue-shifted outflow. This configuration can be explained by considering that the YSO is located at the furthest edge of the molecular clump along the line of sight, which is consistent with the position of the source in the cloud mapped in the C18O J=3-2 line. The detection of HCN, HNC, HCO+, and C2H allowed us to characterize the dense gas at clump scales, yielding results that are in agreement with the presence of a high-mass protostellar object., Comment: Accepted to be published in A&A (July 13, 2020)

Evidence for triggered star formation linking three generations of stars is difficult to assemble, as it requires convincingly associating evolved massive stars with Hii regions that, in turn, would need to present signs of active star formation. We present observational evidence for triggered star formation relating three generations of stars in the neighbourhood of the star LS II +26 8. We carried out new spectroscopic observations of LS II +26 8, revealing that it is a B0 III-type star. We note that LS II +26 8 is located exactly at the geometric centre of a semi-shell-like Hii region complex. The most conspicuous component of this complex is the Hii region Sh2-90, which is probably triggering a new generation of stars. The distances to LS II +26 8 and to Sh2-90 are in agreement (between 2.6 and 3 kpc). Analysis of the interstellar medium on a larger spatial scale shows that Hii region complex lies on the northwestern border of an extended H2 shell. The radius of this molecular shell is about 13 pc, which is in agreement with what an O9V star (the probable initial spectral type of LS II +26 8 as inferred from evolutive tracks) can generate through its winds in the molecular environment. In conclusion, the spatial and temporal correspondences derived in our analysis enable us to propose a probable triggered star formation scenario initiated by the evolved massive star LS II +26 8 during its main sequence stage, followed by stars exciting the Hii region complex formed in the molecular shell, and culminating in the birth of YSOs around Sh2-90., Comment: Accepted in MNRAS (2020, May 28)

We present a study on the molecular gas towards a bright-rimmed cloud located to the north of the infrared dust bubble N30. Using the emission from the 12CO, 13CO, and C18O J=3-2 line, together with infrared and radio continuum data, we characterized the bubble and the related molecular cloud. In addition, we show an analysis of the behaviour of the abundance ratio 13CO/C18O towards the bright-rimmed cloud, and we search for clues on recent star-formation., Comment: Accepted to be published in BAAA

Cometary globules, dense molecular gas structures exposed to the UV radiation, are found inside HII regions. Understanding the nature and origin of these structures through a kinematic study of the molecular gas is useful to advance in our knowledge of the interplay between radiation and molecular gas. Using ASTE we carried out molecular observations towards two cometary globules (Sim129 and Sim130) in the HII region Sh2-236. We mapped two regions with the 12CO J=3-2 and HCO+ J=4-3 lines. Additionally, two single pointings of C2H (N=4-3), HNC and HCN J=4-3 were observed. We combined our observations with public infrared and optical data to analyse the distribution and kinematics of the gas. We found kinematic signatures of infalling gas in the 12CO J=3-2 and C2H J=4-3 spectra towards Sim129 . We detected HCO+, HCN, and HNC J=4-3 only towards Sim130. The HCN/HNC integrated ratio of about 3 found in Sim130 suggests that the possible star formation activity within the globule has not yet ionized the gas. The location of NVSS 052255+33315, which peaks towards the brightest border of the globule, supports this scenario. The non-detection of these molecules towards Sim129 could be due to the radiation arising from the star formation activity inside this globule. The ubiquitous presence of the C2H molecule towards both globules shows the action of nearby O-B stars irradiating their external layers. Based on mid-infrared emission, we identified two new structures: a region of diffuse emission (R1) located, in projection, in front of the head of Sim129, and a pillar-like feature (P1) placed besides Sim130. Based on 12CO J=3-2, we found molecular gas associated with Sim129, Sim130, R1 and P1 at radial velocities of -1.5, -11, +10, and +4 km/s, respectively. Therefore, while Sim129 and P1 are located at the far side of the shell, Sim130 is placed at the near side, consistent with earlier results., Comment: Accepted for publication in A&A

Nowadays there are several observational studies about the 13CO/C18O abundance ratio (X) towards nearby molecular clouds. These works give observational support to the C18O selective photodissociation due to the interaction between the FUV radiation and the molecular gas. It is necessary to increase the sample of molecular clouds located at different distances and affected in different ways by nearby or embedded HII regions and OB associations to study the selective photodissociation. Using 12CO, 13CO, and C18O J=1-0 data obtained from the FOREST Survey, we analyze the filamentary infrared dark cloud IRDC34.43+0.24 located at the distance of about 3.9 kpc. This IRDC is related to several HII regions and YSOs. Assuming LTE we obtain: 0.8x10^16

After 30 Doradus, N11 is the second largest and brightest nebula in the LMC. This large nebula has several OB associations with bright nebulae at its surroundings. N11 was previously mapped at the lowest rotational transitions of $^{12}$CO (J=1--0 and 2--1), and in some particular regions pointings of the $^{13}$CO J=1--0 and 2--1 lines were also performed. Using ASTE we mapped the whole extension of the N11 nebula in the $^{12}$CO J=3--2 line, and three sub-regions in the $^{13}$CO J=3--2 line. The regions mapped in the $^{13}$CO J=3--2 were selected based on that they may be exposed to the radiation at different ways: a region lying over the nebula related to the OB association LH10 (N11B), another one that it is associated with the southern part of the nebula related to the OB association LH13 (N11D), and finally a farther area at the southwest without any embedded OB association (N11I). We found that the morphology of the molecular clouds lying in each region shows some signatures that could be explained by the expansion of the nebulae and the action of the radiation. Fragmentation generated in a molecular shell due to the expansion of the N11 nebula is suggested. The integrated line ratios $^{12}$CO/$^{13}$CO show evidences of selective photodissociation of the $^{13}$CO, and probably other mechanisms such as chemical fractionation. The CO contribution to the continuum at 870 $\mu$m was directly derived. The distribution of the integrated line ratios $^{12}$CO J=3--2/2--1 show hints of stellar feedback in N11B and N11D. The ratio between the virial and LTE mass (M$_{\rm vir}$/M$_{\rm LTE}$) is higher than unity in all analyzed molecular clumps, which suggests that the clumps are not gravitationally bounded and may be supported by external pressure. A non-LTE analysis suggests that we are mapping gas with densities about a few 10$^{3}$ cm$^{-3}$., Comment: Accepted to be published in A&A. Figures were degraded

We present a multiwavelength study towards the young stellar object (YSO) G29.862-0.044 (hereafter G29), which is embedded in the massive star-forming region G29.96-0.02, located at a distance of about 6.5 kpc. The surrounding interstellar medium of G29 is studied using molecular lines data (angular resolution about 15'') obtained from the databases of the James Clerk Maxwell Telescope. The physical conditions of G29 molecular outflows and the clump where the YSO is embedded are characterized. Near-IR data is also analyzed (spatial resolution of about 0.5'') obtained with NIRI at Gemini North to have a detailed view of the circumstellar ambient of G29. The Ks emission towards G29 exhibits a cone-like feature pointing to the red molecular outflow. The aim of this work is to obtain a complete picture of this YSO, the related star-forming processes, and the interstellar medium around it. Studies like this are important because they contribute to a comprehensive understanding of star formation., Comment: to be published in BAAA

We study three subregions in the HII region N11 which is located at the northeast side of the Large Magellanic Cloud (LMC). We used $^{12}$CO and $^{13}$CO J=3--2 data observed with the Atacama Submillimeter Telescope Experiment (ASTE) with an angular and spectral resolution of 22$^{\prime\prime}$ and 0.11 km s$^{-1}$ respectively. From the $^{12}$CO J=3--2 and $^{13}$CO J=3--2 integrated maps we estimated, assuming local thermodynamic equilibrium (LTE), masses in about $10^4$ M$_\odot$ for the molecular clouds associated with each subregion. Additionally, from the mentioned maps we study the $^{12}$CO /$^{13}$CO integrated ratios for each subregion, obtaining values between 8 and 10.

Estimating molecular abundances ratios from the direct measurement of the emission of the molecules towards a variety of interstellar environments is indeed very useful to advance in our understanding of the chemical evolution of the Galaxy, and hence of the physical processes related to the chemistry. It is necessary to increase the sample of molecular clouds, located at different distances, in which the behavior of molecular abundance ratios, such as the 13CO/C18O ratio (X), is studied in detail. We selected the well-studied high-mass star-forming region G29.96-0.02, located at a distance of about 6.2 kpc, which is an ideal laboratory to perform this kind of studies. To study the X towards this region it was used 12CO J=3-2 data obtained from COHRS, 13CO and C18O J=3-2 data from CHIMPS, and 13CO and C18O J=2-1 data retrieved from the CDS database (observed with the IRAM 30m telescope). The distribution of column densities and X throughout the molecular cloud was studied based on LTE and non-LTE methods. Values of X between 1.5 to 10.5, with an average of 5, were found, showing that, besides the dependency between X and the galactocentric distance, the local physical conditions may strongly affect this abundance ratio. We found that correlating the X map with the location of the ionized gas and dark clouds allows us to suggest in which regions the far-UV radiation stalls in dense gaseous components, and in which ones it escapes and selectively photodissociates the C18O isotope. The non-LTE analysis shows that the molecular gas has very different physical conditions, not only spatially across the cloud, but also along the line of sight. This kind of studies may represent a tool to indirectly estimate (from molecular lines observations) the degree of photodissociation in molecular clouds, which is indeed useful to study the chemistry in the interstellar medium., Comment: Accepted in A&A (July 10, 2018)

The interstellar medium (ISM) is a very complex medium which contains the matter needed to form stars and planets. The ISM is in permanent interaction with radiation, turbulence, magnetic and gravitational fields, and accelerated particles. Everything that happens in this medium has consequences on the dynamics and evolution of the Galaxy, resulting the link that relates the stellar scale with the galactic one. Thus, the study of the ISM is crucial to advance in the knowledge of stellar and galactic astrophysics. In this article I present a summary of what we know about the physics and chemistry of this medium, giving an special emphasis on star formation, and how the processes related to the stars birth and evolution interrelate with the environment that surrounds them., Comment: Invited contribution. To appear in the Boletin de la Asociacion Argentina de Astronomia (BAAA)

Determining molecular abundance ratios is important not only for the study of the Galactic chemistry but also because they are useful to estimate physical parameters in a large variety of interstellar medium environments. The CO is one of the most important molecules to trace the molecular gas in the interstellar medium, and the 13CO/C18O abundance ratio is usually used to estimate molecular masses and densities of regions with moderate to high densities. Nowadays this kind of isotopes ratios are in general indirectly derived from elemental abundances ratios. We present the first 13CO/C18O abundance ratio study performed from CO isotopes observations towards a large sample of Galactic sources of different nature at different locations. To study the 13CO/C18O abundance ratio it was used 12CO J=3-2 data obtained form the CO High-Resolution Survey, 13CO and C18O J=3-2 data from the 13CO/C18O (J=3-2) Heterodyne Inner Milky Way Plane Survey, and some complementary data extracted from the James Clerk Maxwell Telescope database. It was analyzed a sample of 198 sources composed by young stellar objects (YSOs), HII and diffuse HII regions as catalogued in the Red MSX Source Survey in 27.5 < l < 46.5 and |b| < 0.5. Most of the analyzed sources are located in the galactocentric distance range 4.0-6.5 kpc. We found that YSOs have, in average, smaller 13CO/C18O abundance ratios than HII and diffuse HII regions. Taking into account that the gas associated with YSOs should be less affected by the radiation than in the case of the others sources, selective far-UV photodissociation of C18O is confirmed. The 13CO/C18O abundance ratios obtained in this work are systematically lower than the predicted from the known elemental abundance relations. These results would be useful in future studies of molecular gas related to YSOs and HII regions based on the observation of these isotopes., Comment: Accepted in A&A. (2017, December 22). Large Tables were converted to figures and included at the end of the manuscript

We study the molecular and the ionized gas in a possible precursor of an UC HII region to contribute to the understanding of how high-mass stars build-up their masses once they have reached the zero-age main secuence. We carried out molecular observations toward the position of the Red MSX source G052.9221-00.4892, using ASTE in the 12CO, 13CO, and C18O J=3-2, and HCO+ J=4-3 lines. We also present radio continuum observations at 6 GHz carried out with the JVLA interferometer. Combining these observations with public infrared data allowed us to inquire about the nature of the source. The analysis of the molecular observations reveals the presence of a kinetic temperature and H2 column density gradients across the molecular clump in which the source is embedded, with the hotter and less dense gas in the inner region. The 12CO J=3-2 emission shows evidence of misaligned massive molecular outflows, with the blue lobe in positional coincidence with a jet-like feature seen at 8 um. The radio continuum emission shows a slightly elongated compact radio source in positional coincidence with the Red MSX source. The polar-like morphology of this compact radio source perfectly matches the hourglass-like morphology exhibited by the source in the Ks-band. The axes of symmetry of the radio source and the near-IR nebula are perfectly aligned. Based on the multiwavelength analysis, we suggest that the analyzed source could be transiting a HC HII region phase, in which the young central star emits winds and ionizing radiation through the poles. By the other hand, according to a comparison between the Br-gamma and the radio flux density, the source would be in a more evolved evolutionary stage of an optically thin UC HII region in photoionization equilibrium. If this is the case, from the radio continuum emission, we can conjecture upon the spectral type of its exciting star which would be a B0.5V., Comment: Accepted in A&A. August 22, 2017

At the interface of HII regions and molecular gas peculiar structures appear, some of them with pillar-like shapes. Understanding their origin is important for characterizing triggered star formation and the impact of massive stars on the interstellar medium. In order to study the molecular environment and the influence of the radiation on two pillar-like features related to the HII region G46.5-0.2, we performed molecular line observations with the Atacama Submillimeter Telescope Experiment, and spectroscopic optical observations with the Isaac Newton Telescope. From the optical observations we identified the star that is exciting the HII region as a spectral type O4-6. The molecular data allowed us to study the structure of the pillars and a HCO+ cloud lying between them. In this HCO+ cloud, which have not any well defined 12CO counterpart, we found direct evidence of star formation: two molecular outflows and two associated near-IR nebulosities. The outflows axis orientation is perpendicular to the direction of the radiation flow from the HII region. Several Class I sources are also embedded in this HCO+ cloud, showing that it is usual that the YSOs form large associations occupying a cavity bounded by pillars. On the other hand, it was confirmed that the RDI process is not occurring in one of the pillar tips., Comment: Accepted in MNRAS (2017 June 13)

At present there are many studies concerning jets towards low-mass young stellar objects, while equivalent studies towards massive or intermediate-mass young stellar objects are scarce. In a previous study, we found highly misaligned molecular outflows towards the infrared point source IRS. Using near-IR data acquired with Gemini-NIRI at the JHKs-broad-bands and narrow-bands centered at the emission lines of [FeII], H2 1-0 S(1), H2 2-1 S(1), Br-gamma, and CO 2-0 (bh), we studied the circumstellar environment of IRS with an angular resolution between 0.35" and 0.45". The emission in the JHKs-broad-bands shows, with great detail, the presence of a cone-like shape nebula extending to the north/northeast of the point source, which appears to be attached to it by a jet-like structure. In the three bands the nebula is resolved in a twisted-shaped feature composed by two arc-like features and a bow shock-like structure seen mainly in the Ks-band, which strongly suggests the presence of a precessing jet. An analysis of proper motions based on our Gemini observations and UKIDSS data gives additional support to the precession scenario. We are presenting one of the best resolved cone-like nebula likely related to a precessing jet up to date. The analysis of the observed near-infrared lines shows that the H2 is collisionally excited, and the spatially coincidence of the [FeII] and H2 emissions in the closer arc-like feature suggests that this region is affected by a J-shock. The second arc-like feature presents H2 emission without [FeII] which suggests the presence of a nondisociative C-shock or a less energetic J-shock. The H2 1-0 S(1) continuum subtracted image, reveals several knots and filaments at a larger spatial scale around IRS, in perfect matching with the distribution of the red and blueshifted molecular outflows discovered in our previous work., Comment: Accepted to be published in A&A (August 3, 2016)

We used combined data from XMM-Newton and Chandra observatories to study the X-ray morphology of SNR G306.3-0.9. A spatially-resolved spectral analysis was used to obtain physical and geometrical parameters of different regions of the remnant. Spitzer infrared observations were also used to constrain the progenitor supernova and study the environment in which the SNR evolved. The X-ray morphology of the remnant displays a non-uniform structure of semi-circular appearance, with a bright southwest region and very weak or almost negligible X-ray emission in its northern part. These results indicate that the remnant is propagating in a non-uniform environment as the shock fronts are encountering a high-density medium, where enhanced infrared emission is detected. The X-ray spectral analysis of the selected regions shows distinct emission-line features of several metal elements, confirming the thermal origin of the emission. The X-ray spectra are well represented by a combination of two absorbed thermal plasma models: one in equilibrium ionization with a mean temperature of ~0.19 keV, and another out of equilibrium ionization at a higher temperature of ~1.1 or 1.6-1.9 keV. For regions located in the northeast, central, and southwest part of the SNR, we found elevated abundances of Si, S, Ar, Ca, and Fe, typical of ejecta material. The outer regions located northwest and south show values of the abundances above solar but lower than to those found in the central regions. This suggests that the composition of the emitting outer parts of the SNR is a combination of ejecta and shocked material of the interstellar medium. The comparison between the S/Si, Ar/Si, and Ca/Si abundances ratios (1.75, 1.27, and 2.72 in the central region, respectively), favor a Type Ia progenitor for this SNR, a result that is also supported by an independent morphological analysis using X-ray and IR data., Comment: 8 pages, 7 figures. Accepted by Astronomy and Astrophysics

The R Coronae Australis dark cloud is one of the closest star-forming regions to the Sun. The cloud is known to be very active in star formation, harboring many Herbig-Haro objects (HHs) and Molecular Hydrogen emission-line Objects (MHOs). In this work we present results from molecular observations (a $5.5^{'}\times5.5^{'}$ map of $^{12}$CO J$=3-2$ and HCO$^{+}$ J$=4-3$, and a single spectrum of N$_{2}$H$^{+}$ J$=4-3$) obtained with the Atacama Submillimeter Telescope Experiment (ASTE) towards the R CrA dark cloud with an angular and spectral resolution of 22$^{"}$ and 0.11 km s$^{-1}$, respectively. From the $^{12}$CO J$=3-2$ line we found kinematical spectral features strongly suggesting the presence of outflows towards a region populated by several HHs and MHOs. Moreover, most of these objects lie within an HCO$^{+}$ maximum, suggesting that its emission arises from an increasement of its abundance due to the chemistry triggered by the outflow activity. Additionally, we are presenting the first reported detection of N$_{2}$H$^{+}$ in the J$=4-3$ line towards the R CrA dark cloud., Comment: accepted for publication in Bolet\'in de la Asociaci\'on Argentina de Astronom\'ia (BAAA)

The physical mechanisms that induce the transformation of a certain mass of gas in new stars are far from being well understood. Infrared bubbles associated with HII regions have been considered to be good samples of investigating triggered star formation. In this paper we report on the investigation of the dust properties of the infrared bubble N4 around the HII region G11.898+0.747, analyzing its interaction with its surroundings and star formation histories therein, with the aim of determining the possibility of star formation triggered by the expansion of the bubble. Using Herschel PACS and SPIRE images with a wide wavelength coverage, we reveal the dust properties over the entire bubble. Meanwhile, we are able to identify six dust clumps surrounding the bubble, with a mean size of 0.50 pc, temperature of about 22 K, mean column density of 1.7 $\times10^{22}$ cm$^{-2}$, mean volume density of about 4.4 $\times10^{4}$ cm$^{-3}$, and a mean mass of 320 $M_{\odot}$. In addition, from PAH emission seen at 8 $\mu$m, free-free emission detected at 20 cm and a probability density function in special regions, we could identify clear signatures of the influence of the HII region on the surroundings. There are hints of star formation, though further investigation is required to demonstrate that N4 is the triggering source., Comment: Accepted by ApJ (16 pages, 11 figures, 9 tables)

We present results obtained towards the HII regions N159, N166, and N132 from the emission of several molecular lines in the 345 GHz window. Using ASTE we mapped a 2.4' $\times$ 2.4' region towards the molecular cloud N159-W in the $^{13}$CO J=3-2 line and observed several molecular lines at an IR peak very close to a massive young stellar object. $^{12}$CO and $^{13}$CO J=3-2 were observed towards two positions in N166 and one position in N132. The $^{13}$CO J=3-2 map of the N159-W cloud shows that the molecular peak is shifted southwest compared to the peak of the IR emission. Towards the IR peak we detected emission from HCN, HNC, HCO$^{+}$, C$_{2}$H J=4-3, CS J=7-6, and tentatively C$^{18}$O J=3-2. This is the first reported detection of these molecular lines in N159-W. The analysis of the C$_{2}$H line yields more evidence supporting that the chemistry involving this molecular species in compact and/or UCHII regions in the LMC should be similar to that in Galactic ones. A non-LTE study of the CO emission suggests the presence of both cool and warm gas in the analysed region. The same analysis for the CS, HCO$^{+}$, HCN, and HNC shows that it is very likely that their emissions arise mainly from warm gas with a density between $5 \times 10^5$ to some $10^6$ cm$^{-3}$. The obtained HCN/HNC abundance ratio greater than 1 is compatible with warm gas and with an star-forming scenario. From the analysis of the molecular lines observed towards N132 and N166 we propose that both regions should have similar physical conditions, with densities of about 10$^3$ cm$^{-3}$., Comment: accepted in MNRAS (October 5, 2015)

In a previous paper we have investigated the molecular environment towards the eastern border of the SNR G18.8+0.3. Continuing with the study of the surroundings of this SNR, in this work we focus on its southern border, which in the radio continuum emission shows a very peculiar morphology with a corrugated corner and a very flattened southern flank. We observed two regions towards the south of SNR G18.8+0.3 using the Atacama Submillimeter Telescope Experiment (ASTE) in the 12CO J=3-2. One of these regions was also surveyed in 13CO and C18O J=3-2. The angular and spectral resolution of these observations were 22", and 0.11 km/s. We compared the CO emission to 20 cm radio continuum maps obtain as part of the Multi-Array Galactic Plane Imaging Survey (MAGPIS) and 870 um dust emission extracted from the APEX Telescope Large Area Survey of the Galaxy. We discovered a molecular feature with a good morphological correspondence with the SNR's southernmost corner. In particular, there are indentations in the radio continuum map that are complemented by protrusions in the molecular CO image, strongly suggesting that the SNR shock is interacting with a molecular cloud. Towards this region we found that the 12CO peak is not correlated with the observed 13CO peaks, which are likely related to a nearby \hii~region. Regarding the most flattened border of SNR G18.8+0.3, where an interaction of the SNR with dense material was previously suggested, our 12CO J=3-2 map show no obvious indication that this is occurring., Comment: accepted for publication in A&A, July 2015

HII regions are particularly interesting because they can generate dense layers of gas and dust, elongated columns or pillars of gas pointing towards the ionizing sources, and cometary globules of dense gas, where triggered star formation can occur. Understanding the interplay between the ionizing radiation and the dense surrounding gas is very important to explain the origin of these peculiar structures, and hence to characterize triggered star formation. G46.5-0.2 (G46), a poorly studied galactic HII region located at about 4 kpc, is an excellent target to perform this kind of studies. Using public molecular data extracted from the Galactic Ring Survey (13CO J=1-0) and from the James Clerk Maxwell Telescope data archive (12CO, 13CO, C18O J=3-2, HCO+ and HCN J=4-3), and infrared data from the GLIMPSE and MIPSGAL surveys, we perform a complete study of G46, its molecular environment and the young stellar objects placed around it. We found that G46, probably excited by an O7V star, is located close to the edge of the GRSMC G046.34-00.21 molecular cloud. It presents a horse-shoe morphology opening in direction of the cloud. We observed a filamentary structure in the molecular gas likely related to G46 and not considerable molecular emission towards its open border. We found that about 10' towards the southwest of G46 there are some pillar-like features, shining at 8 um and pointing towards the HII region open border. We propose that the pillar-like features were carved and sculpted by the ionizing flux from G46. We found several young stellar objects likely embedded in the molecular cloud grouped in two main concentrations: one, closer to the G46 open border consisting of Class II type sources, and other one mostly composed by Class I type YSOs located just ahead the pillars-like features, strongly suggesting an age gradient in the YSOs distribution., Comment: Accepted for publication in The Astronomical Journal (April 14, 2015). Some figures were degraded to reduce file size

N113 is an HII region located in the central part of the Large Magellanic Cloud (LMC) with an associated molecular cloud very rich in molecular species. Most of the previously observed molecular lines cover the frequency range 85-270 GHz. Thus, a survey and study of lines at the 345 GHz window is required in order to have a more complete understanding of the chemistry and excitation conditions of the region. We mapped a region of 2.5' x 2.5' centered at N113 using the Atacama Submillimeter Telescope Experiment in the 13CO J=3-2 line with an angular and spectral resolution of 22" and 0.11 km/s, respectively. In addition, we observed 16 molecular lines as single pointings towards its center. For the molecular cloud associated with N113, from the 13CO J=3-2 map we estimate LTE and virial masses of about 1x10^4 and 4.5x10^4 M_sun, respectively. Additionally, from the dust continuum emission at 500 micron we obtain a mass of gas of 7x10^3 M_sun. Towards the cloud center we detected emission from: 12CO, 13CO, C18O (3-2), HCN, HNC, HCO+, C2H (4-3), and CS (7-6); being the first reported detection of HCN, HNC, and C2H (4-3) lines from this region. The CS (7-6) which was previously tentatively detected is confirmed in this study. By analyzing the HCN, HNC, and C2H, we suggest that their emission may arise from a photodissociation region (PDR). Moreover, we suggest that the chemistry involving the C2H in N113 can be similar to that in Galactic PDRs. Using the HCN J=4-3, J=3-2, and J=1-0 lines in a RADEX analysis we conclude that we are observing very high density gas, between some 10^5 and 10^7 cm-3., Comment: accepted for publication in A&A, September 9, 2014

The red MSX source G034.5964-01.0292 (MSXG34), catalogued as a massive YSO, was observed in molecular lines with the aim of discover and study molecular outflows. We mapped a region of 3'x3' centered at MSXG34 using the Atacama Submillimeter Telescope Experiment in the 12CO J=3-2 and HCO+ J=4-3 lines with an angular and spectral resolution of 22" and 0.11 km/s, respectively. Additionally, public 13CO J=1-0 and near-IR UKIDSS data obtained from the Galactic Ring Survey and the WFCAM Sciencie Archive, respectively, were analyzed. We found that the 12CO spectra towards the YSO present a self-absorption dip, as it is usual in star forming regions, and spectral wings evidencing outflow activity. The HCO+ was detected only towards the MSXG34 position at v_LSR ~ 14.2 km/s, in coincidence with the 12CO absorption dip and approximately with the velocity of previous ammonia observations. HCO+ and NH3 are known to be enhanced in molecular outflows. Analyzing the spectral wings of the 12CO line, we discovered misaligned red- and blue-shifted molecular outflows associated with MSXG34. The near-IR emission shows a cone-like shape nebulosity composed by two arc-like features related to the YSO, which can be due to a cavity cleared in the circumstellar material by a precessing jet. This can explain the misalignment in the molecular outflows. From the analysis of the 13CO J=1--0 data we suggest that the YSO is very likely related to a molecular clump ranging between 10 and 14 km/s. This suggests that MSXG34, with an associated central velocity of about 14 km/s, may be located in the background of this clump. Thus, the blue-shifted outflow is probably deflected by the interaction with dense gas along the line of sight., Comment: Accepted in A&A June 10, 2014

As a continuation of a previous work, in which we found strong evidence of massive molecular outflows towards a massive star forming site, we present a new study of this region based on very high angular resolution observations with the aim of discovering the outflow driven mechanism. Using near-IR data acquired with Gemini-NIRI at the broad H- and Ks-bands, we study a region of 22" x 22" around the UCHII region G045.47+0.05, a massive star forming site at the distance of about 8 kpc. To image the source with the highest spatial resolution possible we employed the adaptative optic system ALTAIR, achieving an angular resolution of about 0.15". We discovered a cone-like shape nebula with an opening angle of about 90 degree extending eastwards the IR source 2MASS J19142564+1109283, a very likely MYSO. This morphology suggests a cavity that was cleared in the circumstellar material and its emission may arise from scattered continuum light, warm dust, and likely emission lines from shock-excited gas. The nebula, presenting arc-like features, is connected with the IR source through a jet-like structure, which is aligned with the blue shifted CO outflow found in a previous study. The near-IR structure lies ~3" north of the radio continuum emission, revealing that it is not spatially coincident with the UCHII region. The observed morphology and structure of the near-IR nebula strongly suggest the presence of a precessing jet. In this study we have resolved the circumstellar ambient (in scale of a thousand A.U.) of a distant MYSO, indeed one of the farthest cases., Comment: Accepted in A&A Letters (October 2013)

We are performing a systematic study of the interstellar medium around extended green objects (EGOs), likely massive young stellar objects driving outflows. EGO G35.04-0.47 is located towards a dark cloud at the northern-west edge of an HII region. Recently, H2 jets were discovered towards this source, mainly towards its southwest, where the H2 1-0 S(1) emission peaks. Therefore, the source was catalogued as the Molecular Hydrogen emission-line object MHO 2429. In order to study the molecular ambient towards this star-forming site, we observed a region around the aforementioned EGO using the Atacama Submillimeter Telescope Experiment in the 12CO J=3--2, 13CO J=3--2, HCO+ J=4--3, and CS J=7--6 lines with an angular and spectral resolution of 22" and 0.11 km s-1, respectively. The observations revealed a molecular clump where the EGO is embedded at v_LSR ~ 51 km s-1, in coincidence with the velocity of a Class I 95 GHz methanol maser previously detected. Analyzing the 12CO line we discovered high velocity molecular gas in the range from 34 to 47 km s-1, most likely a blueshifted outflow driven by the EGO. The alignment and shape of this molecular structure coincide with those of the southwest lobe of MHO 2429 mainly between 46 and 47 km s-1, confirming that we are mapping its CO counterpart. Performing a SED analysis of EGO G35.04-0.47 we found that its central object should be an intermediate-mass young stellar object accreting mass at a rate similar to those found in some massive YSOs. We suggest that this source can become a massive YSO., Comment: accepted to be published in PASJ - 24 September 2013

To characterize a bright-rimmed cloud embedded in the HII region Sh2-48 searching for evidence of triggered star formation. We carried out observations towards a region of 2'x2' centered at RA=18h 22m 11.39s, dec.=-14deg 35m 24.81s (J2000) using the Atacama Submillimeter Telescope Experiment (ASTE; Chile) in the 12CO J=3-2,13CO J=3-2, HCO+ J=4-3, and CS J=7-6 lines with an angular resolution of about 22". We also present radio continuum observations at 5 GHz carried out with the Jansky Very Large Array (JVLA; EEUU) interferometer with a synthetized beam of 7"x5". The analysis of our molecular observations reveals the presence of a relatively dense clump with n(H_2)~3x10^3 cm^-3, located in projection onto the interior of the HII region Sh2-48. The emission distribution of the four observed molecular transitions has, at VLSR~38 kms^-1, morphological anti-correlation with the bright-rimmed cloud as seen in the optical emission. From the new radio continuum observations we identify a thin layer of ionized gas located at the border of the clump which is facing to the ionizing star. The ionized gas has an electron density of about 73 cm^-3 which supports the hypothesis that the clump is being photoionized by the nearby star, BD-14 5014. From the evaluation of the pressure balance between the ionized and molecular gas, we conclude that the clump would be in a pre-pressure balance state with the shocks being driven into the surface layer. Two YSO candidates (class I), are placed slightly beyond the bright rim suggesting that their formation could have been triggered via the radiation-driven implosion process., Comment: Accepted for publication in Astronomy and Astrophysics

We perform a multiwavelength study toward the SNR G18.1-0.1 and nearby several HII regions (infrared dust bubbles N21 and N22, and the HII regions G018.149-00.283 and G18.197-00.181). Our goal is to provide observational evidence supporting that massive stars usually born in clusters from the same molecular cloud, which then produce, along their evolution, different neighboring objects such as HII regions, interstellar bubbles and supernova remnants. We suggest that the objects analysed in this work belong to a same complex located at the distance of about 4 kpc. Using molecular data we inspected the interstellar medium toward this complex and from optical and X-ray observations we looked for OB-type stars in the region. Analysing public 13CO J=1--0 data we found several molecular structures very likely related to the HII region/SNR complex. We suggest that the molecular gas is very likely being swept and shaped by the expansion of the HII regions. From spectroscopic optical observations obtained with the 2.15 m telescope at CASLEO, Argentina, we discovered three O-type stars very likely exciting the bubbles N21 and N22, and an uncatalogued HII region northward bubble N22, respectively. Also we found four B0-5 stars, one toward the bubble N22 and the others within the HII region G18.149-0.283. By inspecting the Chandra Source Catalog we found two point X-ray sources and we suggest that one of them is an early O-type star. Finally we inspected the large scale interstellar medium around this region. We discovered a big molecular shell of about 70 pc x 28 pc in which the analysed complex appears to be located in its southern border., Comment: To be published in MNRAS: Accepted 2013 May 9. Received 2013 May 9; in original form 2012 December 27

The eastern border of the SNR G18.8+0.3, close to an HII regions complex, is a very interesting region to study the molecular gas that it is probably in contact with the SNR shock front. We observed the aforementioned region using the Atacama Submillimeter Telescope Experiment (ASTE) in the 12CO J=3-2, 13CO J=3-2, HCO+ J=4-3, and CS J=7-6 lines with an angular resolution of 22". To complement these observations, we analyzed IR, submillimeter and radio continuum archival data. In this work, we clearly show that the radio continuum "protrusion" that was early thought to belong to the SNR is an HII regions complex deeply embedded in a molecular clump. The new molecular observations reveal that this dense clump, belonging to an extended molecular cloud that surrounds the SNR southeast border, is not physically in contact with SNR G18.8+0.3, suggesting that the SNR shock front have not yet reached it or maybe they are located at different distances. We found some young stellar objects embedded in the molecular clump, suggesting that their formation should be approximately coeval with the SN explosion., Comment: Accepted for publication in A&A (Sept. 7, 2012)

Aims. This work aims at investigating the molecular gas in the surroundings of the ultra-compact HII region G045.47+0.05 looking for evidence of molecular outflows. Methods. We carried out observations towards a region of 2 arcmin x 2 arcmin centered at RA=19h 14m 25.6s, dec.= 11deg 09m 27.6s (J2000) using the Atacama Submillimeter Telescope Experiment (ASTE; Chile) in the 12CO J=3-2, 13CO J=3-2, HCO+ J=4-3 and CS J=7-6 lines with an angular resolution of 22 arcsec. We complement these observations with public infrared data. Results. We characterize the physical parameters of the molecular clump where G045.47+0.0 is embedded. The detection of the CS J=7-6 line emission in the region reveals that the ultra-compact HII region G045.47+0.0 has not completely disrupted the dense gas where it was born. The HCO+ abundance observed towards G045.47+0.0 suggests the presence of molecular outflow activity in the region. From the analysis of the 12CO J=3-2 transition we report the presence of bipolar molecular outflows with a total mass of about 300 solar masses . We derive a dynamical time (flow's age) of about 10^5 yr for the outflow gas, in agreement with the presence of an ultra-compact HII region. We identify the source 2MASS 19142564+1109283 as the massive protostar candidate to drive the molecular outflows. Based on the analysis of its spectral energy distribution we infer that it is an early B-type star of about 15 solar masses. The results of this work support the scenario where the formation of massive stars, at least up to early B-type stars, is similar to that of low mass stars., Comment: Recently accepted for publication in A&A

The luminous blue variable (LBV) stars are peculiar very massive stars. The study of these stellar objects and their surroundings is important for understanding the evolution of massive stars and its effects on the interstellar medium. We study the LBV star candidate G26.47+0.02. Using several large-scale surveys in different frequencies we performed a multiwavelength study of G26.47+0.02 and its surroundings. We found a molecular shell (seen in the 13CO J=1-0 line) that partially surrounds the mid-infrared nebula of G26.47+0.02, which suggests an interaction between the strong stellar winds and the molecular gas. From the HI absorption and the molecular gas study we conclude that G26.47+0.02 is located at a distance of ~4.8 kpc. The radio continuum analysis shows a both thermal and non-thermal emission toward this LBV candidate, pointing to wind-wind collision shocks from a binary system. This hypothesis is supported by a search of near-IR sources and the Chandra X-ray analysis. Additional multiwavelength and long-term observations are needed to detect some possible variable behavior, and if that is found, to confirm the binary nature of the system., Comment: accepted in A&A 01/05/2012

Aims: We study the molecular environment of the luminous blue variable star G24.73+0.69 to investigate the origin of the two infrared shells around this massive star and to determine its effects on the surrounding interstellar medium. Methods: We analyze the distribution of the molecular gas using the 13CO J=1-0 emission extracted from the Galactic Ring Survey. We use near- and mid-infrared data from 2MASS and GLIMPSE to identify the young stellar objects in the field. Results: We discover the molecular counterpart of the outer infrared shell around G24.73+0.69. The CO shell was probably blown by the stellar wind of the star mainly during its main sequence phase. We also find molecular gas that corresponds to the inner infrared shell, although its origin remains uncertain. We find seven young stellar objects upon the molecular material, whose birth might have been triggered by the stellar wind of the luminous blue variable star. We suggest that both G24.73+0.69 and the progenitor of the nearby supernova remnant G24.7+0.6 were formed from the same natal cloud and represent the most evolved members of a so far undetected cluster of other massive stars., Comment: 11 pages, 4 figures degraded to reduce file size. Accepted for publication in A&A

We present the results of a new study of the molecular gas associated with the "extended green object" (EGO) G35.03+0.35. This object, very likely a massive young stellar object, is embedded in a molecular cloud at the border of an HII region. The observations were performed with the Atacama Submillimeter Telescope Experiment (ASTE) in the 12CO and 13CO J=3-2, HCO+ J=4-3, and CS J=7-6 lines with an angular resolution about 22". From the 12CO J=3-2 line we discovered outflowing activity of the massive young stellar object. We obtained a total mass and kinetic energy for the outflows of 30 M_sun and 3000 M_sun (km/s)^2 (6 x 10^{46} ergs), respectively. We discovered a HCO+ and CS clump towards the EGO G35.03+0.35. The detection of these molecular species supports the presence of molecular outflows and a dense molecular envelope with temperatures and densities above 40 K and 6 x 10^{6} cm^{-3}, respectively. Using public near- and mid-IR, and sub-mm data we investigated the spectral energy distribution confirming that EGO G35.03+0.35 is a massive young stellar object at the earliest evolutionary stage (i.e. a class I young stellar object). By anlysing radio continuum archival data we found three radio sources towards the object, suggesting the presence of several young stellar objects in the region. Our radio continuum analysis is consistent with the presence of at least one ultracompact HII region and an hypercompact HII region or a constant-velocity ionized wind source., Comment: Accepted (September 21, 2011) to be published in MNRAS

HESS J1858+020 is a weak gamma-ray source lying near the southern border of the SNR G35.6-0.4. A molecular cloud, composed by two clumps, shows signs of interaction with the SNR and with a nearby extended HII region. In particular, the southernmost clump coincides with the center of the HESS source. In this work we study this clump in detail with the aim of adding information that helps in the identification of the nature of the very-high energy emission. We observed the mentioned molecular clump using the Atacama Submillimeter Telescope Experiment (ASTE) in the 12CO J=3-2, 13CO J=3-2, HCO+ J=4-3 and CS J=7-6 lines with an angular resolution of 22". To complement this observations we analyzed IR and submillimeter continuum archival data. From the 12CO and 13CO J=3-2 lines and the 1.1 mm continuum emission we derived a density of between 10^{3} and 10^{4} cm^-3 for the clump. We discovered a young stellar object (YSO), probably a high mass protostar, embedded in the molecular clump. However, we did not observe any evidence of molecular outflows from this YSO which would reveal the presence of a thermal jet capable of generating the observed gamma-rays. We conclude that the most probable origin for the TeV gamma-ray emission are the hadronic interactions between the molecular gas and the cosmic rays accelerated by the shock front of the SNR G35.6-0.4., Comment: 11 pages, 5 figures. Accepted for publication in A&A (March 25, 2011)

As part of a systematic study that we are performing with the aim to increase the observational evidence of triggered star formation in the surroundings of HII regions, we analyze the ISM around the HII region G35.673-00.847, a poorly studied source. Using data from large-scale surveys: Two Micron All Sky Survey, Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE), MIPSGAL, Galactic Ring Survey (GRS), VLA Galactic Plane Survey (VGPS), and NRAO VLA Sky Survey (NVSS) we performed a multiwavelength study of G35.673-00.847 and its surroundings. The mid IR emission, shows that G35.673-00.847 has an almost semi-ring like shape with a cut towards the galactic west. The radius of this semi-ring is about 1.5' (~1.6 pc, at the distance of ~3.7 kpc). The distance was estimated from an HI absorption study and from the analysis of the molecular gas. Indeed, we find a molecular shell composed by several clumps distributed around the HII region, suggesting that its expansion is collecting the surrounding material. We find several YSO candidates over the molecular shell. Finally, comparing the HII region dynamical age and the fragmentation time of the molecular shell, we discard the collect and collapse as the mechanism responsible for the YSOs formation, suggesting other processes such as radiative driven implosion and/or small-scale Jeans gravitational instabilities., Comment: Accepted for publication in A&A, 18 October 2010. Some figures were degraded to reduce file size

AIMS: We investigate the environment of the infrared dust bubble N65 and search for evidence of triggered star formation in its surroundings. METHODS: We performed a multiwavelength study of the region around N65 with data taken from large-scale surveys: Two Micron All Sky Survey, GLIMPSE, MIPSGAL, SCUBA, and GRS. We analyzed the distribution of the molecular gas and dust in the environment of N65 and performed infrared photometry and spectral analysis of point sources to search for young stellar objects and identify the ionizing star candidates. RESULTS: We found a molecular cloud that appears to be fragmented into smaller clumps along the N65 PDR. This indicates that the so-called collect and collapse process may be occurring. Several young stellar objects are distributed among the molecular clumps. They may represent a second generation of stars whose formation was triggered by the bubble expanding into the molecular gas. We dentified O-type stars inside N65, which are the most reliable ionizing star candidates., Comment: 15 pages, 10 figures, accepted for publication in A&A. Figures degraded to reduce file size