Search

Several powerful outbursts have been observed during many years of observations of the symbiotic object MWC 560. The last active stage began in the autumn of 2018 and continues to the present. Observations of this event began at the Fesenkov Astrophysical Institute at the beginning of 2019. In our previous article we published the results obtained in early 2019. A light curve of the object and emission line profiles are presented; it is noted that a broad absorption band formed in a high velocity collimated jet vanishes. In this article we present the results of further spectral and photometric observations of MWC 560. It is to be noted that in 2021 the brightness of this object is sustained at a high level exceeding that obtained during the previous outbursts. In addition, at the end of 2020 a tendency toward a gradual weakening of the radiative fluxes in the emission lines was remarked. The profiles of all the lines have absorption components shifted to the "blue" by 52±5 km/s. It may be assumed that during this outburst there was partial (or complete) destruction of the accretion disk, so that the source of the high velocity collimated jet vanished. The gradual reduction in the radiative fluxes in the emission lines may be caused by a drop in the power of ionizing radiation. [ABSTRACT FROM AUTHOR]

We present the first three-dimensional (3D) morpho-kinematic (MK) model of a supernova remnant (SNR), using as a case study the Galactic SNR VRO 42.05.01. We employed the astrophysical code SHAPE in which wide field imaging and high-resolution spectroscopic data were utilized, to reconstruct its 3D morphology and kinematics. We found that the remnant consists of three basic distinctive components that we call: a 'shell', a 'wing', and a 'hat'. With respect to their kinematical behaviour, we found that the 'wing'  and the 'shell'  have similar expansion velocities (V exp = 115 ± 5 km s−1). The 'hat'  presents the lowest expansion velocity of the remnant (V exp = 90 ± 20 km s−1), while the upper part of the 'shell'  presents the highest velocity with respect to the rest of the remnant (V exp = 155 ± 15 km s−1). Furthermore, the whole nebula has an inclination of ∼3°–5° with respect to the plane of the sky and a systemic velocity of V sys = −17 ± 3 km s−1. We discuss the interpretation of our model results regarding the origin and evolution of the SNR and we suggest that VRO 42.05.01 had an interaction history with an inhomogeneous ambient medium most likely shaped by the mass outflows of its progenitor star. [ABSTRACT FROM AUTHOR]

This is a study of spectral and photometric observations of the binary system with an X-ray component V725 Tauri=A0535+262. It consists of a giant star HDE 245770 of spectral class O9.7 and the pulsar A0535+26 with a pulsation period of ~103 s. Active stages of this object, accompanied by "giant" X-ray outbursts, have been observed repeatedly. The last events occurred during 2009-2011. Our studies in 2017-2020 yielded the following data: over the last three years the B and V band brightness of the object has remained at a high level and began to decrease at the end of 2019. Here, beginning in 2016 a gradual increase in the radiative fluxes in the Hβ and Hα emission lines has been observed. At present the equivalent widths of these lines exceed the values recorded during the time of the gigan X-ray outburst of 2011. Previous studies have shown that a similar combination of the characteristics of this object, specifically an increase in emission line fluxes as the brightness decreases. is detected just before the onset of an active stage. [ABSTRACT FROM AUTHOR]

We present Low-Frequency Array (LOFAR) high-band data over the frequency range 115-189 MHz for the X-ray binary SS433, obtained in an observing campaign from 2013 February to 2014 May. Our results include a deep, wide-field map, allowing a detailed view of the surrounding supernova remnant W 50 at low radio frequencies, as well as a light curve for SS433 determined from shorter monitoring runs. The complex morphology of W50 is in excellent agreement with previously published higher frequency maps; we find additional evidence for a spectral turnover in the eastern wing, potentially due to foreground free-free absorption. Furthermore, SS433 is tentatively variable at 150 MHz, with both a debiased modulation index of 11 per cent and a x² probability of a flat light curve of 8.2 x 10-3. By comparing the LOFAR flux densities with contemporaneous observations carried out at 4800 MHz with the RATAN-600 telescope, we suggest that an observed ~0.5-1 Jy rise in the 150-MHz flux density may correspond to sustained flaring activity over a period of approximately 6 months at 4800 MHz. However, the increase is too large to be explained with a standard synchrotron bubble model. We also detect a wealth of structure along the nearby Galactic plane, including the most complete detection to date of the radio shell of the candidate supernova remnant G 38.7-1.4. This further demonstrates the potential of supernova remnant studies with the current generation of low-frequency radio telescopes. [ABSTRACT FROM AUTHOR]

Infrared dark clouds (IRDCs) are cold, dense regions of high (optical and infrared) extinction, believed to be the birthplace of high-mass stars and stellar clusters. The physical mechanisms leading to the formation of these IRDCs are not completely understood and it is thus important to study their molecular gas kinematics and chemical content to search for any signature of the IRDCs formation process. Using the 30-m-diameter antenna at the Instituto de Radioastronomía Milimétrica (IRAM), we have obtained emission maps of dense gas tracers (H13CO+ and HN13C) and typical shock tracers (SiO and CH3OH) towards three IRDCs, G028.37+00.07, G034.43+00.24, and G034.77-00.55 (clouds C, F, and G, respectively).We have studied the molecular gas kinematics in these clouds and, consistent with previous works towards other IRDCs, the clouds show complex gas kinematics with several velocity-coherent substructures separated in velocity space by a few km s-1. Correlated with these complex kinematic structures, widespread (parsec-scale) emission of SiO and CH3OH is present in all the three clouds. For clouds C and F, known to be actively forming stars, widespread SiO and CH3OH is likely associated with on-going star formation activity. However, for cloud G, which lacks either 8 or 24 μm sources and 4.5 μm H2 shock-excited emission, the detected widespread SiO and CH3OH emission may have originated in a large-scale shock interaction, although a scenario involving a population of low-mass stars driving molecular outflows cannot be fully ruled out. [ABSTRACT FROM AUTHOR]

In this paper, we present a multiwavelength investigation of the star-forming complex IRAS 20286+4105, located in the Cygnus X region. Near-infrared K-band data are used to revisit the cluster/stellar group identified in previous studies. Radio continuum observations at 610 and 1280 MHz show the presence of a H II region possibly powered by a star of spectral type B0-B0.5. The cometary morphology of the ionized region is explained by invoking the bow-shock model, where the likely association with a nearby supernova remnant is also explored. A compact radio knot with a non-thermal spectral index is detected towards the centre of the cloud. Mid-infrared data from the Spitzer Legacy Survey of the Cygnus X region show the presence of six Class I young stellar objects inside the cloud. Thermal dust emission in this complex is modelled using Herschel far-infrared data to generate dust temperature and column density maps. Herschel images also show the presence of two clumps in this region, the masses of which are estimated to be ~175 and 30 Mʘ. The mass-radius relation and the surface density of the clumps mean that they do not qualify as massive star-forming sites. An overall picture of a runaway star ionizing the cloud and a triggered population of intermediate-mass, Class I sources located towards the cloud centre emerges from this multiwavelength study. Variation in the dust emissivity spectral index is shown to exist in this region and is seen to have an inverse relation with the dust temperature. [ABSTRACT FROM AUTHOR]

Observations of Comet C/2010 X1 (Elenin) in August 2011 showed a pattern of evolution of coma morphology into an expanding, amorphous cloud of rapidly decreasing surface brightness shortly before perihelion passage, similar to C/1999 S4 (LINEAR) in 2000. However, the comet's difficult viewing geometry at the time of disruption made it impossible to study the event using high-resolution imaging techniques and, in particular, to measure the ratio of dust to cometessimals which gives information on the internal structure of the nucleus before disruption. We report Herschel/PACS observations of the defunct Comet C/2010 X1 (Elenin), aimed at detecting its infrared ghost: the debris cloud and any remaining inert, or low-activity cometessimals that may have been released in the break-up of the nucleus, taking advantage of the comet's close pass to Earth in mid-October 2011. These observations would have allowed us to detect, potentially, both individual surviving inert fragments of the nucleus of ≈260 m diameter (and significantly smaller, active cometessimals) and the expanding dust cloud, being particularly sensitive to coarse dust and boulders in the millimetre to metre size range. No discrete bodies were detected by Herschel to this limiting size. [ABSTRACT FROM AUTHOR]

Context. We analyse 134 ks Chandra ACIS-I observations of the Galactic Centre (GC) performed in July 2011. The X-ray image with the field of view 17' x 17' contains the hot plasma surrounding the Sgr A*. The obtained surface brightness map allows us to fit the Bondi hot accretion flow to the innermost hot plasma around the GC. Aims. Contrary to the XMM-Newton data where a strong 6.4 keV iron line was observed andinterpreted as a reflection from molecular clouds, we search here for the diffuse X-ray emission with prominent 6.69 keV iron line. We found a surface brightness profile that allowed us to determine the stagnation radius of the flow around Sgr A*. Methods. We fitted spectra from the region up to 5'' from Sgr A* using a thermal bremsstrahlung model and four Gaussian profiles responsible for Kα emission lines of Fe, S, Ar, and Ca. The X-ray surface brightness profile up to 3'' from Sgr A* found in our data image was successfully fitted with the dynamical model of Bondi spherical accretion. Results. We show that the temperature of the hot plasma derived from our spectral fitting is of the order of 2.2-2.7 keV depending on the choice of background. By modelling the surface brightness profile, we derived the temperature and number density profiles in the vicinity of the black hole. The best fitted model of spherical Bondi accretion shows that this type of flow works only up to 3'' and implies that the outer plasma density and temperature are n™1 = 18.3 ± 0.1 cm-3 and re™1 = 3.5 ± 0.3 keV, respectively. Conclusions. We show that the Bondi flow can reproduce observed surface brightness profiles up to 3'' from Sgr A* in the Galactic centre. This result strongly suggests the position of stagnation radius in the complicated dynamics around GC. The temperature at the outer radius of the flow is higher by 1 keV than the value found by our spectral fitting of thermal plasma within the circle of 5''. The Faraday rotation computed from our model towards the pulsar PSR J1745-2900 near the GC agrees with the observed one, recently reported. We speculate here that the emission lines observed in spectra up to 5'' can be interpreted as the reflection of the radiation from two-phase regions occurring at distances between 3-5'' of the flow. The hot plasma in Sgr A* illuminated in the past by a strong radiation field may be a seed for thermal instabilities and eventual strong clumpiness. [ABSTRACT FROM AUTHOR]

Aims. Our goal is to identify bipolar HII regions and to understand their morphology, their evolution, and the role they play in the formation of new generations of stars. Methods. We use the Spitzer-GLIMPSE, -MIPSGAL, and Herschel-Hi-GAL surveys to identify bipolar HII regions, looking for (ionized) lobes extending perpendicular to dense filamentary structures. We search for their exciting star(s) and estimate their distances using near-IR data from the 2MASS or UKIDSS surveys. Dense molecular clumps are detected using Herschel-SPIRE data, and we estimate their temperature, column density, mass, and density. MALT90 observations allow us to ascertain their association with the central HII region (association based on similar velocities). We identify Class 0/I young stellar objects (YSOs) using their Spitzer and Herschel-PACS emissions. These methods will be applied to the entire sample of candidate bipolar H II regions to be presented in a forthcoming paper. Results. This paper focuses on two bipolar HII regions, one that is especially interesting in terms of its morphology, G319.88+00.79, and one in terms of its star formation, G010.32-00.15. Their exciting clusters are identified and their photometric distances estimated to be 2.6 kpc and 1.75 kpc, respectively; thus G010.32-00.15 (known as W31 north) lies much closer than previously assumed. We suggest that these regions formed in dense and flat structures that contain filaments. They have a central ionized region and ionized lobes extending perpendicular to the parental cloud. The remains of the parental cloud appear as dense (more than 104 cm-3) and cold (14-17 K) condensations. The dust in the photodissociation regions (in regions adjacent to the ionized gas) is warm (19-25 K). Dense massive clumps are present around the central ionized region. G010.32-00.14 is especially remarkable because five clumps of several hundred solar masses surround the central H II region; their peak column density is a few 1023 cm-2, and the mean density in their central regions reaches several 105 cm-3. Four of them contain at least one massive YSO (including an ultracompact HII region and a high-luminosity Class I YSO); these clumps also contain extended green objects (EGOs) and Class II methanol masers. This morphology suggests that the formation of a second generation of massive stars has been triggered by the central bipolar H II region. It occurs in the compressed material of the parental cloud. [ABSTRACT FROM AUTHOR]

The rate at which interstellar gas is converted into stars, and its dependence on environment, is one of the pillars on which our understanding of the visible Universe is build. We present a comparison of the surface density of young stars (Σ*) and dust surface density (Σdust) across NGC 346 (N66) in 115 independent pixels of 6 x 6 pc². We find a correlation between Σ* and Σdust with a considerable scatter. A power-law fit to the data yields a steep relation with an exponent of 2.6 ± 0.2. We convert Σdust to gas surface density (Σgas) and Σ* to star formation rate (SFR) surface densities (ΣSFR), using simple assumptions for the gas-to-dust mass ratio and the duration of star formation. The derived total SFR (4 ± 1 x 10-3 M⊙ yr-1) is consistent with SFR estimated from the Ha emission integrated over the Ha nebula. On small scales the ΣSFR derived using Hα systematically underestimates the count-based ΣSFR, by up to a factor of 10. This is due to ionizing photons escaping the area, where the stars are counted. We find that individual 36 pc² pixels fall systematically above integrated disc galaxies in the Schmidt-Kennicutt diagram by on average a factor of ~7. The NGC 346 average SFR over a larger area (90 pc radius) lies closer to the relation but remains high by a factor of ~3. The fraction of the total mass (gas plus young stars) locked in young stars is systematically high (~ 10 per cent) within the central 15 pc and systematically lower outside (2 per cent), which we interpret as variations in star formation efficiency. The inner 15 pc is dominated by young stars belonging to a centrally condensed cluster, while the outer parts are dominated by a dispersed population. Therefore, the observed trend could reflect a change of star formation efficiency between clustered and non-clustered star formation. [ABSTRACT FROM AUTHOR]

Hydrides represent the first steps of interstellar chemistry. Sulfanylium (SH+), in particular, is a key tracer of energetic processes. We used ALMA and the IRAM 30m telescope to search for the lowest frequency rotational lines of SH+ toward the Orion Bar, the prototypical photo-dissociation region illuminated by a strong UV radiation field. On the basis of previous Herschel/HIFI observations of SH+, we expected to detect emission of the two SH+ hyperfine structure (HFS) components of the NJ = 10-01 fine structure (FS) component near 346 GHz. While we did not observe any lines at the frequencies predicted from laboratory data, we detected two emission lines, each ∼15MHz above the SH+ predictions and with relative intensities and HFS splitting expected for SH+. The rest frequencies of the two newly detected lines are more compatible with the remainder of the SH+ laboratory data than the single line measured in the laboratory near 346 GHz and previously attributed to SH+. Therefore, we assign these new features to the two SH+ HFS components of the NJ = 10-01 FS component and re-determine its spectroscopic parameters, which will be useful for future observations of SH+, in particular if its lowest frequency FS components are studied. Our observations demonstrate the suitability of these lines for SH+ searches at frequencies easily accessible from the ground. [ABSTRACT FROM AUTHOR]

Aims. We aim to investigate the polarization properties of a starless core in an early evolutionary stage. Linear polarization data reveal the properties of the dust grains in the distinct phases of the interstellar medium. Our goal is to investigate how the polarization degree and angle correlate with the cloud and core gas. Methods. We use optical, near infrared, and submillimeter polarization observations on the starless object Pipe-109 in the Pipe nebula. Our data cover a physical scale range of 0.08 to 0.4 pc, comprising the dense gas, envelope, and the surrounding cloud. Results. The cloud polarization is well traced by the optical data. The near infrared polarization is produced by a mixed population of grains from the core border and the cloud gas. The optical and near infrared polarization toward the cloud reaches the maximum possible value and saturates with respect to the visual extinction. The core polarization is predominantly traced by the submillimeter data and has a steep decrease with respect to the visual extinction. Modeling of the submillimeter polarization indicates a magnetic field main direction projected onto the plane-of-sky and loss of grain alignment for densities higher than 6 × 104 cm-3 (or AV > 30 mag). Conclusions. The object is immersed in a magnetized medium with a very ordered magnetic field. The absence of internal source of radiation significantly affects the polarization efficiencies in the core, creating a polarization hole at the center of the starless core. This result supports the theory of dust grain alignment via radiative torques. [ABSTRACT FROM AUTHOR]

Context. Herschel observations suggest that the H2O distribution in outflows from low-mass stars resembles the H2 emission. It is still unclear which of the different excitation components that characterise the mid- and near-IR H2 distribution is associated with H2O. Aims. The aim is to spectrally resolve the different excitation components observed in the H2 emission. This will allow us to identify the H2 counterpart associated with H2O and finally derive directly an H2O abundance estimate with respect to H2. Methods. We present new high spectral resolution observations of H2 0-0 S(4), 0-0 S(9), and 1-0 S(1) towards HH 54, a bright nearby shock region in the southern sky. In addition, new Herschel/HIFI H2O (212-101) observations at 1670 GHz are presented. Results. Our observations show for the first time a clear separation in velocity of the different H2 lines: the 0-0 S(4) line at the lowest excitation peaks at -7 kms-1, while the more excited 0-0 S(9) and 1-0 S(1) lines peak at -15 km s-1. H2O and high-J CO appear to be associated with the H2 0-0 S(4) emission, which traces a gas component with a temperature of 700-1000 K. The H2O abundance with respect to H2 0-0 S(4) is estimated to be X(H2O) < 1.4 × 10-5 in the shocked gas over an area of 13" . Conclusions. We resolve two distinct gas components associated with the HH 54 shock region at different velocities and excitations. This allows us to constrain the temperature of the H2O emitting gas (≤1000 K) and to derive correct estimates of H2O abundance in the shocked gas, which is lower than what is expected from shock model predictions. [ABSTRACT FROM AUTHOR]

Context. High methanol (CH3OH) deuteration has been revealed in Class 0 protostars with the detection of singly, doubly, and even triply D-substituted forms. Methanol is believed to form during the pre-collapse phase via gas-grain chemistry and then eventually injected into the gas when the heating produced by the newly formed protostar sublimates the grain mantles. The molecular deuterium fraction of the warm gas is thus a relic of the cold pre-stellar era and provides hints of the past history of the protostars. Aims. Pre-stellar cores represent the preceding stages in the process of star formation. We aim at measuring methanol deuteration in L1544, a prototypical dense and cold core on the verge of gravitational collapse. The aim is to probe the deuterium fractionation process while the "frozen" molecular reservoir is accumulated onto dust grains. Methods. Using the IRAM 30m telescope, we mapped the methanol emission in the pre-stellar core L1544 and observed singly deuterated methanol (CH2DOH and CH3OD) towards the dust peak of L1544. Non-LTE radiative transfer modelling was performed on three CH3OH emissions lines at 96.7 GHz, using a Bonnor-Ebert sphere as a model for the source. We have also assumed a centrally decreasing abundance profile to take the molecule freeze-out in the inner core into account. The column density of CH2DOH was derived assuming LTE excitation and optically thin emission. Results. The CH3OH emission has a highly asymmetric morphology, resembling a non-uniform ring surrounding the dust peak, where CO is mainly frozen onto dust grains. The observations provide an accurate measure of methanol deuteration in the cold pre-stellar gas. The derived abundance ratio is [CH2DOH]/[CH3OH] = 0.10 ± 0.03, which is significantly smaller than the ones found in lowmass Class 0 protostars and smaller than the deuterium fraction measured in other molecules towards L1544. The singly-deuterated form CH3OD was not detected at 3σ sensitivity of 7 mKkms-1, yielding a lower limit of [CH2DOH]/[CH3OD] ≥ 10, consistent with previous measurements towards Class 0 protostars. Conclusions. The low deuterium fractionation observed in L1544 and the morphology of the CH3OH emission suggest that we are mainly tracing the outer parts of the core, where CO just started to freeze-out onto dust grains. [ABSTRACT FROM AUTHOR]

Many supernova remnants (SNRs) are characterized by a knotty ejecta structure. The Vela SNR is an excellent example of remnant in which detached clumps of ejecta are visible as X-ray emitting bullets that have been observed and studied in great detail. We aim at modelling the evolution of ejecta shrapnel in the Vela SNR, investigating the role of their initial parameters (position and density) and addressing the effects of thermal conduction and radiative losses. We performed a set of 2D hydrodynamic simulations describing the evolution of a density inhomogeneity in the ejecta profile. We explored different initial setups. We found that the final position of the shrapnel is very sensitive to its initial position within the ejecta, while the dependence on the initial density contrast is weaker. Our model also shows that moderately overdense knots can reproduce the detached features observed in the Vela SNR. Efficient thermal conduction produces detectable effects by determining an efficient mixing of the ejecta knot with the surrounding medium and shaping a characteristic elongated morphology in the clump. [ABSTRACT FROM AUTHOR]

LL Orionis-type objects (LL objects) are hyperbolic bowshocks visible around young stars in the outer Orion nebula, many of which are also associated with curved, highly collimated jets. The bowshocks are clearly due to the supersonic interaction between an outflow from the young star and an environmental flow from the core of the nebula, but the exact nature of these flows has not yet been established. We present the first high-resolution optical spectra of two of these objects, LL 1 and LL 2, together with their associated Herbig-Haro (HH) jets, HH 888 and HH 505.We combine multiple long-slit echelle spectra in the Ha 6563Å and [N II] 6584Å lines to produce velocity maps of the two objects at a resolution of 4 arcsec × 2 arcsec × 11 km s-1. The gas motions within both stellar bowshocks are of rather low velocity (10-20 km s-1), but there are important differences between the two objects. LL 1 shows a high degree of symmetry, whereas LL 2 has very asymmetric kinematics that seem to follow velocity gradients in the surrounding nebula. We also measure the line-of-sight velocity for multiple knots in the HH 888 and HH 505 jets, and combine our spectroscopy with new and existing proper-motion measurements to reconstruct the three-dimensional kinematics of the jets. The knot motions in both jets are very similar: both flows are inclined at 40° to 60° from the plane of the sky, with exclusively redshifted knots to the north and exclusively blueshifted knots to the south. In both cases, one also sees a deceleration along the length of the jets, from >200 km s-1 close to the respective stars down to 100 km s-1 farther out. The marked contrasts that we find between the kinematics of the jets and the kinematics of the stellar bowshocks are evidence that the two phenomena are not causally related. Regular patterns in the dynamic ages of the HH 505 knots imply periodic ejections on three different time-scales: 50, 12 and 4 yr. We use line ratios and photometry to measure electron densities and excitation/ionization conditions in the stellar bowshocks and jet knots. The LL 1 bowshock has a bright inner shell with density 3000 cm-3 (compared with a local nebula density of 1000 cm-3) and line ratios that are consistent with equilibrium photoionization models. The bowshock also has a fainter outer rim, where the line ratios show evidence of shock excitation. Many of the jet knots also show evidence for a shock contribution to their excitation and have densities from 1000 to 8000 cm-3. [ABSTRACT FROM AUTHOR]

W28 is one of the archetypal supernova remnants (SNRs) interacting with molecular clouds (MCs). HESS observation found four TeV sources which are coincident with the MCs around W28, but Fermi LAT detected no prominent GeV counterparts for two of them. An accumulative diffusion model is established in this Letter, and the energetic protons colliding with the nearby MCs are considered to be an accumulation of the diffusive protons escaping from the shock front throughout the history of the SNR expansion. We have fitted the γ-ray spectra of the four sources and naturally explained the GeV spectral break of the north-eastern source (source N) and the non-significant GeV emission of southern sources A and C. The distances of sources A and C from the SNR centre are found to be much larger than those of sources N and B, which may be the basic reason for the faint GeV γ-rays of the two former sources. [ABSTRACT FROM AUTHOR]

We present a census of molecular outflows across four active regions of star formation in the Perseus molecular cloud (NGC 1333, IC348/HH211, L1448 and L1455), totalling an area of over 1000 arcmin. This is one of the largest surveys of outflow evolution in a single molecular cloud published to date. We analyse large-scale, sensitive CO data sets from the James Clerk Maxwell Telescope, including new data towards NGC 1333. Where possible we make use of our complementary CO and CO data to correct for the CO optical depth and measure ambient cloud properties. Of the 65 submillimetre cores in our fields, we detect outflows towards 45. 24 of these are marginal detections where the outflow's shape is unclear or could be confused with the other outflows. We compare various parameters between the outflows from Class 0 and I protostars, including their mass, momentum, energy and momentum flux. Class 0 outflows are longer, faster, more massive and have more energy than Class I outflows. The dynamical time-scales we derive from these outflows are uncorrelated to the age of the outflow driving source, computed from the protostar's bolometric temperature. We confirm the results of Bontemps et al. that outflows decrease in force as they age. There is a decrease in momentum flux from the Class 0 to I stage: compared to M km s yr, suggesting a decline in the mass accretion rate assuming the same entrainment fraction for both classes of outflow. If is the flux expected in radiation from the central source, then and . Furthermore, we confirm there are additional sources of mass loss from protostars. If a core's mass is only lost from outflows at the current rate, cores would endure a few million years, much longer than current estimates for the duration of the protostellar stage. Finally, we note that the total energy contained in outflows in NGC 1333, L1448 and L1455 is greater than the estimated turbulent energy in the respective regions, which may have implications for the regions' evolution. [ABSTRACT FROM AUTHOR]

We present photometry and images (3.6, 4.5, 5.8 and 8.0 μm) from the Spitzer Infrared Array Camera (IRAC) of the star-forming region Messier 8 (M8). The IRAC photometry reveals ongoing star formation in the M8 complex, with 64 class 0/I and 168 class II sources identified in several locations in the vicinity of submm gas cores/clumps. Nearly 60 per cent of these young stellar objects (YSOs) occur in about seven small clusters. The spatial surface density of the clustered YSOs is determined to be about 10–20 YSOs pc−2. Fresh star formation by the process of ‘collect and collapse’ might have been triggered by the expanding H ii regions and winds from massive stars. IRAC ratio images are generated and studied in order to identify possible diagnostic emission regions in M8. The image of 4.5/8.0 μm reveals a Brα counterpart of the optical Hourglass H ii region, while the ratio 8.0/4.5 μm indicates PAH emission in a cavity-like structure to the east of the Hourglass. The ratio maps of 3.6/4.5, 5.8/4.5 and 8.0/4.5 μm seem to identify PAH emission regions in the sharp ridges and filamentary structures seen east to west and north-east to south-west in the M8 complex. [ABSTRACT FROM AUTHOR]

HH 110 is a rather peculiar HerbigHaro object in Orion that originates due to the deflection of another jet (HH 270) by a dense molecular clump, instead of being directly ejected from a young stellar object. Here we present new results on the kinematics and physical conditions of HH 110 based on Integral Field Spectroscopy. The 3D spectral data cover the whole outflow extent (∼4.5 arcmin, ≃0.6 pc at a distance of 460 pc) in the spectral range 6500–7000 Å. We built emission-line intensity maps of Hα, [N ii] and [S ii] and of their radial velocity channels. Furthermore, we analysed the spatial distribution of the excitation and electron density from [N ii]/Hα, [S ii]/Hα and [S ii] 6716/6731 integrated line-ratio maps, as well as their behaviour as a function of velocity, from line-ratio channel maps. Our results fully reproduce the morphology and kinematics obtained from previous imaging and long-slit data. In addition, the integral field spectroscopy (IFS) data revealed, for the first time, the complex spatial distribution of the physical conditions (excitation and density) in the whole jet, and their behaviour as a function of the kinematics. The results here derived give further support to the more recent model simulations that involve deflection of a pulsed jet propagating in an inhomogeneous ambient medium. The IFS data give richer information than that provided by current model simulations or laboratory jet experiments. Hence, they could provide valuable clues to constrain the space parameters in future theoretical works. [ABSTRACT FROM AUTHOR]

The Cygnus Loop is interacting with a protrusion of the cavity wall in its eastern edge (the XA region), where the X-ray emission is very bright. The complexity of the environment and the non-linear physical processes of the shock–cloud interaction make the origin of the X-ray emission still not well understood. Our purpose is to understand the physical origin of the X-ray emission in the XA region, addressing, in particular, the role of thermal conduction in the interaction process. We analysed two XMM–Newton data sets, performing image analysis and spatially resolved spectral analysis on a set of homogeneous regions. We applied a recently developed diagnostic tool to compare spectral analysis results with predictions of theoretical models, and to estimate the efficiency of thermal conduction on the X-ray-emitting shocked plasma. We found that the inhomogeneous cavity wall contains both large clumps (the protrusion) and small isolated clumps with different densities. A large indentation bent over to the south is detected. The abundance of the surrounding interstellar medium is ∼0.2 times solar value. We confirmed the important role of thermal conduction in the evolution of X-ray-emitting plasma during shock–cloud interaction. [ABSTRACT FROM AUTHOR]

We present high-sensitivity arcmin2 maps of the J= 2→1 rotational lines of SiO, CO, 13CO and C18O, observed towards the filamentary infrared dark cloud (IRDC) G 00.33. Single-pointing spectra of the SiO J= 2→1 and J= 3→2 lines towards several regions in the filament are also reported. The SiO images reveal that SiO is widespread along the IRDC (size ≥2 pc), showing two different components: one bright and compact arising from three condensations (N, E and S) and the other weak and extended along the filament. While the first component shows broad lines (linewidths of ∼4–7 km s−1) in both SiO J= 2→1 and SiO J= 3→2, the second one is only detected in SiO J= 2→1 and has narrow lines (∼0.8 km s−1). The maps of CO and its isotopologues show that low-density filaments are intersecting the IRDC and appear to merge towards the densest portion of the cloud. This resembles the molecular structures predicted by flow-driven, shock-induced and magnetically-regulated cloud formation models. As in outflows associated with low-mass star formation, the excitation temperatures and fractional abundances of SiO towards N, E and S increase with velocity from ∼6 to 40 K and from ∼10−10 to , respectively, over a velocity range of ∼7 km s−1. Since 8 μm and 24 μm sources and/or extended m emission are detected in N, E and S, broad SiO is likely produced in outflows associated with high-mass protostars. The excitation temperatures and fractional abundances of the narrow SiO lines, however, are very low (∼9 K and ∼10−11, respectively), and consistent with the processing of interstellar grains by the passage of a shock with km s−1. This emission could be generated (i) by a large-scale shock, perhaps remnant of the IRDC formation process, (ii) by decelerated or recently processed gas in large-scale outflows driven by 8- and 24-μm sources or (iii) by an undetected and widespread population of lower mass protostars. High-angular-resolution observations are needed to disentangle between these three scenarios. [ABSTRACT FROM AUTHOR]

Abstract: Using the 13.7-m millimeter wave telescope of Purple Mountain Observatory, we for the first time observed in C18O(J=1−0), the northwest region (size 16′ × 25′) of the molecular cloud W31. We constructed contour maps in different velocity ranges (grid separation 1′). Three compact molecular clumps are identified and their physical parameters are derived from the observed temperature and line width; they are found to be rather young and stable. We discuss their distribution with respect to the associated HII regions, in regard to star formation. [Copyright &y& Elsevier]