- ID:
- ivo://CDS.VizieR/J/A+A/649/A21
- Title:
- ATLASGAL deuteration of ammonia
- Short Name:
- J/A+A/649/A21
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Deuteration has been used as a tracer of the evolutionary phases of low- and high-mass star formation. The APEX Telescope Large Area Survey (ATLASGAL) provides an important repository for a detailed statistical study of massive star-forming clumps in the inner Galactic disc at different evolutionary phases. We study the amount of deuteration using NH_2_D in a representative sample of high-mass clumps discovered by the ATLASGAL survey covering various evolutionary phases of massive star formation. The deuterium fraction of NH_3_ is derived from the NH_2_D 1_11_-1_01_ortho transition at ~86GHz and NH_2_D 1_11_-1_01_para line at ~110GHz. This is refined for the first time by measuring the NH_2_D excitation temperature directly with the NH_2_D 2_12_-2_02_para transition at ~74GHz. Any variation of NH_3_ deuteration and ortho-to-para ratio with the evolutionary sequence is analysed. Unbiased spectral line surveys at 3mm were conducted towards ATLASGAL clumps between 85 and 93GHz with the Mopra telescope and from 84 to 115GHz using the IRAM 30m telescope. A subsample was followed up in the NH_2_D transition at 74GHz with the IRAM 30m telescope. We determined the deuterium fractionation from the column density ratio of NH_2_D and NH_3_ and measured the NH_2_D excitation temperature for the first time from the simultaneous modelling of the 74 and 110GHz line using MCWeeds. We searched for trends in NH_3_ deuteration with the evolutionary sequence of massive star formation. We derived the column density ratio from the 86 and 110GHz transitions as an estimate of the NH_2_D ortho-to-para ratio. We find a large range of the NH_2_D to NH_3_ column density ratio up to 1.6+/-0.7 indicating a high degree of NH_3_ deuteration in a subsample of the clumps. Our analysis yields a clear difference between NH_3_ and NH_2_D rotational temperatures for a fraction. We therefore advocate observation of the NH_2_D transitions at 74 and 110GHz simultaneously to determine the NH_2_D temperature directly. We determine a median ortho-to-para column density ratio of 3.7+/-1.2. The high detection rate of NH_2_D confirms a high deuteration previously found in massive star-forming clumps. Using the excitation temperature of NH_2_D instead of NH_3_ is needed to avoid an overestimation of deuteration. We measure a higher detection rate of NH_2_D in sources at early evolutionary stages. The deuterium fractionation shows no correlation with evolutionary tracers such as the NH_3_ (1,1) line width, or rotational temperature.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/565/A75
- Title:
- ATLASGAL: dust condensations in Galactic plane
- Short Name:
- J/A+A/565/A75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The formation processes and the evolutionary stages of high-mass stars are poorly understood compared to low-mass stars. Large-scale surveys are needed to provide an unbiased census of high column density sites which can potentially host precursors to high-mass stars. The ATLASGAL survey covers 420 sq. degree of the Galactic plane, between -80{deg}<l<+60{deg} at 870um. Here we identify the population of embedded sources throughout the inner Galaxy. With this catalog we first investigate the general statistical properties of dust condensations in terms of their observed parameters, such as flux density and angular size. Then using mid-IR surveys we aim to investigate their star-formation activity and the Galactic distribution of star-forming and quiescent clumps. Our ultimate goal is to determine the statistical properties of quiescent and star-forming clumps within the Galaxy and to constrain the star-formation processes. We optimized the source extraction method, referred to as MRE-GCL, for the ATLASGAL maps in order to generate a catalog of compact sources. This technique is based on a multi-scale filtering to remove extended emission from clouds to better determine the parameters corresponding to the embedded compact sources. In a second step we extract the sources by fitting 2D Gaussians with the Gaussclumps algorithm.
- ID:
- ivo://CDS.VizieR/J/MNRAS/431/1752
- Title:
- ATLASGAL 6.7GHz methanol masers
- Short Name:
- J/MNRAS/431/1752
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the 870um APEX Telescope large area survey of the Galaxy, we have identified 577 submillimetre continuum sources with masers from the methanol multibeam survey in the region 280{deg}<l<20{deg}; |b|<1.5{deg}. 94 per cent of methanol masers in the region are associated with submillimetre dust emission. We estimate masses for ~450 maser-associated sources and find that methanol masers are preferentially associated with massive clumps. These clumps are centrally condensed, with envelope structures that appear to be scale-free, the mean maser position being offset from the peak column density by 0+/-4 arcsec. Assuming a Kroupa initial mass function and a star formation efficiency of ~30 per cent, we find that over two-thirds of the clumps are likely to form clusters with masses >20M_{sun}_. Furthermore, almost all clumps satisfy the empirical mass-size criterion for massive star formation. Bolometric luminosities taken from the literature for ~100 clumps range between ~100 and 10^6^L_{sun}_. This confirms the link between methanol masers and massive young stars for 90 per cent of our sample. The Galactic distribution of sources suggests that the star formation efficiency is significantly reduced in the Galactic Centre region, compared to the rest of the survey area, where it is broadly constant, and shows a significant drop in the massive star formation rate density in the outer Galaxy.
- ID:
- ivo://CDS.VizieR/J/A+A/579/A91
- Title:
- ATLASGAL inner Galaxy massive cold dust clumps
- Short Name:
- J/A+A/579/A91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The formation of high mass stars and clusters occurs in giant molecular clouds. Objects in evolved stages of massive star formation such as protostars, hot molecular cores, and ultracompact HII regions have been studied in more detail than earlier, colder objects. Further progress thus requires the analysis of the time before massive protostellar objects can be probed by their infrared emission. With this in mind, the APEX Telescope Large Area Survey of the whole inner Galactic plane at 870{mu}m (ATLASGAL) has been carried out to provide a global view of cold dust and star formation at submillimetre wavelengths. We derive kinematic distances to a large sample of massive cold dust clumps from their measured line velocities. We estimate masses and sizes of ATLASGAL sources, for which the kinematic distance ambiguity is resolved. The ATLASGAL sample is divided into groups of sources, which are located close together, mostly within a radius of 2pc, and have velocities in a similar range with a median velocity dispersion of ~1km/s. We use NH_3_, N_2_H^+^, and CS velocities to calculate near and far kinematic distances to those groups. We obtain 296 groups of ATLASGAL sources in the first quadrant and 393 groups in the fourth quadrant, which are coherent in space and velocity. We analyse HI self-absorption and HI absorption to resolve the kinematic distance ambiguity to 689 complexes of submm clumps. They are associated with ^12^CO emission probing large-scale structure and ^13^CO (1-0) line as well as the 870{mu}m dust continuum on a smaller scale. We obtain a scale height of ~28+/-2pc and displacement below the Galactic midplane of ~-7+/-1pc. Within distances from 2 to 18kpc ATLASGAL clumps have a broad range of gas masses with a median of 1050M_{sun}_ as well as a wide distribution of radii with a median of 0.4pc. Their distribution in galactocentric radii is correlated with spiral arms. Using a statistically significant ATLASGAL sample we derive a power-law exponent of -2.2+/-0.1 of the clump mass function. This is consistent with the slope derived for clusters and with that of the stellar initial mass function. Examining the power-law index for different galactocentric distances and various source samples shows that it is independent of environment and evolutionary phase. Fitting the mass-size relationship by a power law gives a slope of 1.76+/-0.01 for cold sources such as IRDCs and warm clumps associated with HII regions.
- ID:
- ivo://CDS.VizieR/J/A+A/570/A65
- Title:
- ATLASGAL massive clumps CO depletion
- Short Name:
- J/A+A/570/A65
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the low-mass regime, molecular cores have spatially resolved temperature and density profiles allowing a detailed study of their chemical properties. It is found that the gas-phase abundances of C-bearing molecules in cold starless cores rapidly decrease with increasing density. Here the molecules tend to stick to the grains, forming ice mantles. We study CO depletion in a large sample of massive clumps, and investigate its correlation with evolutionary stage and with the physical parameters of the sources. Moreover, we study the gradients in [^12^C]/[^13^C] and [^18^O]/[^17^O] isotopic ratios across the inner Galaxy, and the virial stability of the clumps. From the ATLASGAL 870{mu}m survey we selected 102 clumps, which have masses in the range ~10^2^-3x10^4^M_{sun}_, sampling different evolutionary stages. We use low-J emission lines of CO isotopologues and the dust continuum emission to infer the depletion factor f_D_. RATRAN one-dimensional models were also used to determine f_D_ and to investigate the presence of depletion above a density threshold. The isotopic ratios and optical depth were derived with a Bayesian approach. We find a significant number of clumps with a high degree of CO depletion, up to ~20. Larger values are found for colder clumps, thus for earlier evolutionary phases. For massive clumps in the earliest stages of evolution we estimate the radius of the region where CO depletion is important to be a few tenths of a pc. The value of the [^12^C]/[^13^C] ratio is found to increase with distance from the Galactic centre, with a value of ~66+/-12 for the solar neighbourhood. The [^18^O]/[^17^O] ratio is approximately constant (~4) across the inner Galaxy between 2kpc and 8kpc, albeit with a large range (~2-6). Clumps are found with total masses derived from dust continuum emission up to ~20 times higher than M_vir_, especially among the less evolved sources. These large values may in part be explained by the presence of depletion: if the CO emission comes mainly from the low-density outer layers, the molecules may be subthermally excited, leading to an overestimate of the dust masses. CO depletion in high-mass clumps seems to behave as in the low-mass regime, with less evolved clumps showing larger values for the depletion than their more evolved counterparts, and increasing for denser sources. The ratios [^12^C]/[^13^C] and [^18^O]/[^17^O] are consistent with previous determinations, and show a large intrinsic scatter.
- ID:
- ivo://CDS.VizieR/J/A+A/599/A139
- Title:
- ATLASGAL massive clumps dust characterization
- Short Name:
- J/A+A/599/A139
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ATLASGAL survey provides an ideal basis for detailed studies of large numbers of massive star forming clumps covering the whole range of evolutionary stages. The ATLASGAL Top100 is a sample of clumps selected from their infrared and radio properties to be representative for the whole range of evolutionary stages. The ATLASGAL Top100 sources are the focus of a number of detailed follow-up studies that will be presented in a series of papers. In the present work we use the dust continuum emission to constrain the physical properties of this sample and identify trends as a function of source evolution. We determine flux densities from mid-infrared to submm wavelength (8-870micron) images and use these values to fit their spectral energy distributions (SEDs) and determine their dust temperature and flux. Combining these with recent distances from the literature including maser parallax measurements we determine clump masses, luminosities and column densities. We find trends for increasing temperature, luminosity and column density with the proposed evolution sequence, confirming that this sample is representative of different evolutionary stages of massive star formation. We show that most of the sample has the ability to form massive stars (including the most massive O-type stars) and that the majority is gravitationally unstable and hence likely to be collapsing. The highest column density ATLASGAL sources presented cover the whole range of evolutionary stages from the youngest to the most evolved high-mass star forming clumps. Their study provides a unique starting point for more in-depth research on massive star formation in four distinct evolutionary stages whose well defined physical parameters afford more detailed studies. As most of the sample is closer than 5kpc, these sources are also ideal for follow-up observations with high spatial resolution.
- ID:
- ivo://CDS.VizieR/J/A+A/611/A6
- Title:
- ATLASGAL massive clumps H_2_CO data
- Short Name:
- J/A+A/611/A6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Formaldehyde (H_2_CO) is a reliable tracer to accurately measure the physical parameters of dense gas in star-forming regions. We aim to determine directly the kinetic temperature and spatial density with formaldehyde for the ~100 brightest ATLASGAL-selected clumps (the TOP100 sample) at 870um representing various evolutionary stages of high-mass star formation. Ten transitions (J=3-2 and 4-3) of ortho- and para-H2CO near 211, 218, 225, and 291GHz were observed with the Atacama Pathfinder EXperiment (APEX) 12m telescope.
- ID:
- ivo://CDS.VizieR/J/A+A/601/A60
- Title:
- ATLASGAL: Massive cluster progenitors sample
- Short Name:
- J/A+A/601/A60
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The progenitors of high-mass stars and clusters are still challenging to recognise. Only unbiased surveys, sensitive to compact regions of high dust column density, can unambiguously reveal such a small population of particularly massive and cold clumps. Here we use the ATLASGAL survey to identify a sample of candidate progenitors of massive clusters in the inner Galaxy. We characterise a flux limited sample of compact sources selected from the ATLASGAL survey. Sensitive mid-infrared data at 21-24um from the WISE and MIPSGAL surveys were explored to search for embedded objects, and complementary spectroscopic data were used to investigate their stability and their star formation activity. We identify an unbiased sample of infrared-quiet massive clumps in the Galaxy that potentially represent the earliest stages of massive cluster formation. An important fraction of this sample consists of sources that have not been studied in detail before. We first find that clumps hosting more evolved embedded objects and infrared-quiet clumps exhibit similar physical properties in terms of mass and size, suggesting that the sources are not only capable of forming high-mass stars, but likely also follow a single evolutionary track leading to the formation of massive clusters. The majority of the clumps are likely not in virial-equilibrium, suggesting collapse on the clump scale.
- ID:
- ivo://CDS.VizieR/J/MNRAS/443/1555
- Title:
- ATLASGAL massive star forming clumps sample
- Short Name:
- J/MNRAS/443/1555
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- By matching infrared-selected, massive young stellar objects (MYSOs) and compact HII regions in the Red MSX Source survey to massive clumps found in the submillimetre ATLASGAL (APEX Telescope Large Area Survey of the Galaxy) survey, we have identified ~1000 embedded young massive stars between 280{deg}<l<350{deg} and 10{deg}<l<60{deg} with |b|<1.5{deg}. Combined with an existing sample of radio-selected methanol masers and compact HII regions, the result is a catalogue of ~1700 massive stars embedded within ~1300 clumps located across the inner Galaxy, containing three observationally distinct subsamples, methanol-maser, MYSO and HII-region associations, covering the most important tracers of massive star formation, thought to represent key stages of evolution.
- ID:
- ivo://CDS.VizieR/J/MNRAS/435/400
- Title:
- ATLASGAL. Properties of compact HII regions
- Short Name:
- J/MNRAS/435/400
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a complete sample of molecular clumps containing compact and ultracompact HII (UC HII) regions between l=10{deg} and 60{deg} and |b|<1{deg}, identified by combining the APEX Telescope Large Area Survey of the Galaxy submm and CORNISH radio continuum surveys with visual examination of archival infrared data. Our sample is complete to optically thin, compact and UC HII regions driven by a zero-age main-sequence star of spectral type B0 or earlier embedded within a 1000M_{sun}_ clump. In total we identify 213 compact and UC HII regions, associated with 170 clumps. Unambiguous kinematic distances are derived for these clumps and used to estimate their masses and physical sizes, as well as the Lyman continuum fluxes and sizes of their embedded HII regions.
