- 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.
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- 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.
- ID:
- ivo://CDS.VizieR/J/A+A/644/A160
- Title:
- ATLASGAL-selected massive clumps. Chemistry of PDR
- Short Name:
- J/A+A/644/A160
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study ten molecular transitions obtained from an unbiased 3mm molecular line survey using the IRAM 30m telescope toward 409 compact dust clumps identified by the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) to better understand the photodissociation regions (PDRs) associated with these clumps. The main goal of this study is to investigate whether the abundances of the selected molecules show any variations resulting from the PDR chemistry in different clump environments. We selected HCO, HOC^+^, C_2_H, c-C_3_H_2_, CN, H^13^CN, HC^15^N, and HN^13^C as PDR tracers, and H^13^CO^+^ and C^18^O as dense gas tracers. By using estimated optical depths of C_2_H and H^13^CN and assuming optically thin emission for other molecular transitions, we derived the column densities of those molecules and their abundances. To assess the influence of the presence and strength of ultra- violet radiation, we compare abundances of three groups of the clumps: HII regions, infrared bright non-HII regions, and infrared dark non-HII regions. We detected C^18^O, H^13^CO^+^, C_2_H, c-C_3_H_2_, CN, and HN^13^C toward most of the observed dust clumps (detection rate >94%), and H^13^CN is also detected with a detection rate of 75%. On the other hand, HCO and HC^15^N show detection rates of 32% and 39%, respectively, toward the clumps, which are mostly associated with HII region sources: Detection rates of HCO and HC^15^N toward the HII regions are 66% and 79%. We find that the abundances of HCO, CN, C_2_H, and c-C_3_H_2_ decrease as the H_2_ column density increases, indicating high visual extinction, while those of high-density tracers (i.e., H^13^CO^+^ and HC^15^N) are constant. In addition, N(HCO)/N(H^13^CO^+^) ratios significantly decrease as H_2_ column density increases, and, in particular, 82 clumps have X(HCO)>=10^-10^ and N(HCO)/N(H^13^CO^+^)>~1, which are indications of far-ultraviolet (FUV) chemistry. This suggests the observed HCO abundances are likely associated with FUV radiation illuminating the PDRs. We also find that high N(c-C_3_H_2_)/N(C_2_H) ratios found for HII regions that have high HCO abundances (>~10^-10^) are associated with more evolved clumps with high L_bol_/M_clump_. This trend might be associated with gain-surface processes, which determine the initial abundances of these molecules, and time-dependent effects in the clumps corresponding to the envelopes around dense PDRs and HII regions. In addition, some fraction of the measured abundances of the small hydrocarbons of the HII sources may be the result of the photodissociation of PAH molecules.
- ID:
- ivo://CDS.VizieR/J/MNRAS/441/2555
- Title:
- ATLAS 1.4GHz Data Release 2
- Short Name:
- J/MNRAS/441/2555
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the first of two papers describing the second data release (DR2) of the Australia Telescope Large Area Survey at 1.4GHz, which comprises deep wide-field observations in total intensity, linear polarization, and circular polarization over the Chandra Deep Field-South and European Large Area Infrared Space Observatory Survey-South 1 regions. DR2 improves upon the first data release by maintaining consistent data reductions across the two regions, including polarization analysis, and including differential number counts in total intensity and linear polarization. Typical DR2 sensitivities across the mosaicked multipointing images are 30{mu}Jy/beam at approximately 12"x6" resolution over a combined area of 6.4deg^2^. In this paper we present detailed descriptions of our data reduction and analysis procedures, including corrections for instrumental effects such as positional variations in image sensitivity, bandwidth smearing with a non-circular beam, and polarization leakage, and application of the BLOBCAT source extractor. We present the DR2 images and catalogues of components (discrete regions of radio emission) and sources (groups of physically associated radio components). We describe new analytic methods to account for resolution bias and Eddington bias when constructing differential number counts of radio components.
- ID:
- ivo://CDS.VizieR/J/MNRAS/453/4020
- Title:
- ATLAS 1.4GHz Data Release 3
- Short Name:
- J/MNRAS/453/4020
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the third data release from the Australia Telescope Large Area Survey. These data combine the observations at 1.4GHz before and after upgrades to the Australia Telescope Compact Array reaching a sensitivity of 14{mu}Jy/beam in 3.6 deg^2^ over the Chandra Deep Field South (CDFS) and of 17{mu}Jy/beam in 2.7 deg^2^ over the European Large Area ISO Survey South 1 (ELAIS-S1). We used a variety of array configurations to maximize the uv coverage resulting in a resolution of 16 by 7-arcsec in CDFS and of 12 by 8-arcsec in ELAIS-S1. After correcting for peak bias and bandwidth smearing, we find a total of 3034 radio source components above 5{sigma} in CDFS, of which 514 (17 per cent) are considered to be extended. The number of components detected above 5{sigma} in ELAIS-S1 is 2084, of which 392 (19 per cent) are classified as extended. The catalogues include reliable spectral indices ({Delta}{alpha}<0.2) between 1.40 and 1.71GHz for ~350 of the brightest components.
- ID:
- ivo://CDS.VizieR/J/A+A/544/A38
- Title:
- ATLAS 2.3GHz observations of ELAIS-S1 and CDF-S
- Short Name:
- J/A+A/544/A38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Australia Telescope Large Area Survey (ATLAS) aims to image a 7deg^2^ region centred on the European Large Area ISO Survey - South 1 (ELAIS-S1) field and the Chandra Deep Field South (CDF-S) at 1.4GHz with high sensitivity (up to {sigma}~10uJy) to study the evolution of star-forming galaxies (SFGs) and Active Galactic Nuclei (AGN) over a wide range of cosmic time. We present here ancillary radio observations at a frequency of 2.3GHz obtained with the Australia Telescope Compact Array (ATCA). The main goal of this is to study the radio spectra of an unprecedented large sample of sources (~2000 observed, ~600 detected in both frequencies).
- ID:
- ivo://CDS.VizieR/J/MNRAS/426/2342
- Title:
- ATLAS 5.5GHz survey of Chandra Deep Field South
- Short Name:
- J/MNRAS/426/2342
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Star-forming galaxies are thought to dominate the sub-mJy radio population, but recent work has shown that low-luminosity active galactic nuclei (AGNs) can still make a significant contribution to the faint radio source population. Spectral indices are an important tool for understanding the emission mechanism of the faint radio sources. We have observed the extended Chandra Deep Field South at 5.5GHz using a mosaic of 42 pointings with the Australia Telescope Compact Array. Our image reaches an almost uniform sensitivity of ~12Jy rms over 0.25deg^2^ with a restoring beam of 4.9"x2.0", making ATLAS 5.5GHz survey one of the deepest 6cm surveys to date. We present the 5.5GHz catalogue and source counts from this field. We take advantage of the large amount of ancillary data in this field to study the 1.4 to 5.5GHz spectral indices of the sub-mJy population.
- ID:
- ivo://CDS.VizieR/J/A+A/397/1035
- Title:
- Atlas of B6-A2 hyper- and supergiants
- Short Name:
- J/A+A/397/1035
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an atlas of spectra of 5 emission-line stars: the low-luminosity luminous blue variables (LBVs) HD 168625 and HD 160529, the white hypergiants (and LBV candidates) HD 168607 and AS 314, and the supergiant HD 183143. The spectra were obtained with 2 echelle spectrometers at the 6-m telescope of the Russian Academy of Sciences in the spectral range 4800 to 6700{AA}, with a resolution of 0.4{AA}. We have identified 380 spectral lines and diffuse interstellar bands within the spectra. Specific spectral features of the objects are described.
- ID:
- ivo://CDS.VizieR/VIII/54
- Title:
- Atlas of Galactic Neutral Hydrogen
- Short Name:
- VIII/54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Leiden/Dwingeloo HI survey mapped the 21-cm spectral line emission over the entire sky above declinations of -30 degrees using a grid spacing of ~ 0.5 degree and a velocity sampling of ~ 1.03 km/s. The useful velocity (V_lsr) range is from -450 to +400 km/s. The Atlas presents calibrated spectra in units of brightness temperature. Using interpolation and averaging, the authors have placed their data on an evenly-spaced grid in Galactic coordinates (l,b). A detailed discussion of the instrument and calibration procedures is provided in the published Atlas. The average sensitivity level of the survey is 0.07 K (1-sigma, rms). This sensitivity level depends critically on the success of the stray-radiation correction as discussed in Hartmann et al. (1996A&AS..119..115H). In that discussion, several caveats are offered regarding the removal of stray radiation, in particular that component which might be due to reflection from the ground. Some instances have been found where there are residuals which are clearly larger than the mean accuracy quoted as representative of the Leiden/Dwingeloo survey. Users of the data are reminded that the stray-radiation correction was applied conservatively, ensuring that no overestimate was calculated and removed, thereby yielding spurious negative intensities. A specific example of remaining spurious emission is evident towards the North Galactic Pole, a direction notoriously difficult to observe. All spectra taken towards b=+90 degrees should, of course, be identical, no matter the longitude or the orientation of the telescope with respect to the ground or to the meridian. Because the sky was sampled in 5x5 degree boxes, a spectrum was recorded at b=+90 degrees for every Nx5 degrees (N=0..72) in longitude. The spectra in the final dataset were interpolated between these measured spectra to yield a 0.5x0.5 degree grid. So, only every 10th spectrum at this extreme latitude corresponds to an observed spectrum. Comparing all spectra at b=+90 reveals differences which are larger than expected. The origin of this discrepancy is currently unknown. There is also an instrumental effect which reveals itself as correlated noise, showing a pattern which alternates sign at adjacent channels when the very lowest levels of intensity are examined. This effect is due to an offset in the DAS autocorrelator used as the backend in the Leiden/Dwingeloo survey. The presence of this artifact becomes noticeable only after averaging 50 or more spectra. Although a Hanning convolution of the data would eliminate this effect, it would also degrade the velocity resolution; as the correlated noise is noticeable only at very low levels (about 15 mK), well below the mean rms sensitivity of the survey itself, the original spectra have not been Hanning smoothed. Excepted are those spectra which suffered from sinc interference. These spectra were Hanning smoothed to enable the elimination of the interference spike. Dr. Lloyd Higgs has compared the HI spectra made with the DRAO 26-m telescope in support of the Canadian Galactic Plane Survey with those of the Leiden Dwingeloo Survey, and has pointed out what are evidently calibration problems in a small number of isolated LDS spectra. Either Hartmann, Burton, or Higgs could provide additional information. The Leiden/Dwingeloo HI survey is intended primarily for studies of the interstellar gas associated with our own Galaxy. There are, however, a small number of spectra in which 'contaminating' signatures from known external galaxies are present. Detections of roughly 50 such external galaxies were made; refer to table 4 of the Atlas for a list. The HI spectra from the Leiden/Dwingeloo survey are archived as 721 files. Each file is in FITS image format, and maps the 21-cm brightness temperature at a fixed Galactic longitude for an evenly-spaced rectangular grid of (Galactic latitude, velocity) points. There is one FITS file for every 0.5 degree in Galactic longitude in the "fits" subdirectory. In addition to the 721 (b,v) FITS files, there is an (l,b) FITS image named TOTAL_HI.FIT, which contains the integrated intensity map over the velocity range -450 km/s <= V_lsr <= +400 km/s. The map units are in [K.km/s] and the FITS header contains comments regarding the conversion to column densities. Included as a visual aid is the GIF image file total_hi.gif, which depicts the velocity-integrated map. The data were originally distributed on a CD-ROM enclosed with the Atlas of Galactic Neutral Hydrogen (reference given above). The CD also contains animations of velocity slices through the data cube.
