- ID:
- ivo://CDS.VizieR/J/MNRAS/473/1059
- Title:
- Complete sample of Galactic clump properties
- Short Name:
- J/MNRAS/473/1059
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) is an unbiased 870um submillimetre survey of the inner Galactic plane (|l|<60{deg} with |b|<1.5{deg}). It is the largest and most sensitive ground-based submillimetre wavelength Galactic survey to date and has provided a large and systematic inventory of all massive, dense clumps in the Galaxy (>=1000M_{sun}_ at a heliocentric distance of 20kpc) and includes representative samples of all of the earliest embedded stages of high-mass star formation. Here, we present the first detailed census of the properties (velocities, distances, luminosities and masses) and spatial distribution of a complete sample of ~8000 dense clumps located in the Galactic disc (5{deg}<|l|<60{deg}). We derive highly reliable velocities and distances to ~97 per cent of the sample and use mid- and far-infrared survey data to develop an evolutionary classification scheme that we apply to the whole sample. Comparing the evolutionary subsamples reveals trends for increasing dust temperatures, luminosities and linewidths as a function of evolution indicating that the feedback from the embedded protoclusters is having a significant impact on the structure and dynamics of their natal clumps. We find that the vast majority of the detected clumps are capable of forming a massive star and 88 per cent are already associated with star formation at some level. We find the clump mass to be independent of evolution suggesting that the clumps form with the majority of their mass in situ. We estimate the statistical lifetime of the quiescent stage to be ~5x10^4^yr for clump masses >1000M_{sun}_ decreasing to ~1x10^4^yr for clump masses >10000M_{sun}_. We find a strong correlation between the fraction of clumps associated with massive stars and peak column density. The fraction is initially small at low column densities, but reaching 100 per cent for column densities above 10^23^cm^x2^; there are no clumps with column densities above this value that are not already associated with massive star formation. All of the evidence is consistent with a dynamic view of star formation wherein the clumps form rapidly and are initially very unstable so that star formation quickly ensues.
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Search Results
- ID:
- ivo://CDS.VizieR/VIII/39
- Title:
- Composite CO Survey of the Milky Way
- Short Name:
- VIII/39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This survey consists of CO(J=1-0) (115 GHz) spectra for the entire Galactic plane. The latitude coverage varies with longitude and in some regions extends from -25 degrees to +25 degrees. The observations were made with the Columbia/GISS 1.2m telescope in New York City, and a twin telescope on Cerro Tololo in Chile. The angular resolution of the survey is 30' (square), the velocity resolution is 1.3km/s and the sensitivity ranges from about 0.1K/chan to 0.35K/chan. The survey is presented as 720 latitude-velocity maps in FITS format, one for each 30' of longitude from -180.0 deg to +179.5 deg, and one velocity-integrated map covering the entire plane. The velocity range of each file is -300 km/s to +300 km/s. The survey has been updated to include some additional data, more careful reprojections of the regions that were originally mapped in equatorial coordinates, and improved estimates of the absolute calibration of the CO intensities (Digel and Dame 1995, unpublished).
- ID:
- ivo://CDS.VizieR/J/A+A/562/A24
- Title:
- Cool carbon stars in the halo and Fornax dSph
- Short Name:
- J/A+A/562/A24
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The population of cool carbon (C) stars located far from the galactic plane is probably made of debris of small galaxies such as the Sagittarius dwarf spheroidal galaxy (Sgr), which are disrupted by the gravitational field of the Galaxy. We aim to know this population better through spectroscopy, 2MASS photometric colours, and variability data. When possible, we compared the halo results to C star populations in the Fornax dwarf spheroidal galaxy, Sgr, and the solar neighbourhood. We first present a few new discoveries of C stars in the halo and in Fornax. The number of spectra of halo C stars is now 125. Forty percent show H{alpha} in emission. The narrow location in the JHK diagram of the halo C stars is found to differ from that of similar C stars in the above galaxies. The light curves of the Catalina and LINEAR variability databases were exploited to derive the pulsation periods of 66 halo C stars. A few supplementary periods were obtained with the TAROT telescopes. We confirm that the period distribution of the halo strongly resembles that of Fornax, and we found that it is very different from the C stars in the solar neighbourhood. There is a larger proportion of short-period Mira/SRa variables in the halo than in Sgr, but the survey for C stars in this dwarf galaxy is not complete, and the study of their variability needs to be continued to investigate the link between Sgr and the cool halo C stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/892/112
- Title:
- CTIO/DECam LCs for Galactic bulge variable stars
- Short Name:
- J/ApJ/892/112
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- With the advent of the Legacy Survey of Space and Time, time-domain astronomy will be faced with an unprecedented volume and rate of data. Real-time processing of variables and transients detected by such large-scale surveys is critical to identifying the more unusual events and allocating scarce follow-up resources efficiently. We develop an algorithm to identify these novel events within a given population of variable sources. We determine the distributions of magnitude changes (dm) over time intervals (dt) for a given passband f, p_f_^(dm|dt)^, and use these distributions to compute the likelihood of a test source being consistent with the population or being an outlier. We demonstrate our algorithm by applying it to the DECam multiband time-series data of more than 2000 variable stars identified by Saha+ (2019, J/ApJ/874/30) in the Galactic Bulge that are largely dominated by long-period variables and pulsating stars. Our algorithm discovers 18 outlier sources in the sample, including a microlensing event, a dwarf nova, and two chromospherically active RS CVn stars, as well as sources in the blue horizontal branch region of the color-magnitude diagram without any known counterparts. We compare the performance of our algorithm for novelty detection with the multivariate Kernel Density Estimator and Isolation Forest on the simulated PLAsTiCC data set. We find that our algorithm yields comparable results despite its simplicity. Our method provides an efficient way for flagging the most unusual events in a real-time alert-broker system.
- ID:
- ivo://CDS.VizieR/J/ApJ/766/14
- Title:
- Deep Chandra bulge field X-ray point sources
- Short Name:
- J/ApJ/766/14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Apparently diffuse X-ray emission has been known to exist along the central quarter of the Galactic Plane since the beginning of X-ray astronomy; this is referred to as the Galactic Ridge X-ray emission (GRXE). Recent deep X-ray observations have shown that numerous X-ray point sources account for a large fraction of the GRXE in the hard band (2-8keV). However, the nature of these sources is poorly understood. Using the deepest X-ray observations made in the Chandra bulge field, we present the result of a coherent photometric and spectroscopic analysis of individual X-ray point sources for the purpose of constraining their nature and deriving their fractional contributions to the hard-band continuum and Fe K line emission of the GRXE. Based on the X-ray color-color diagram, we divided the point sources into three groups: A (hard), B (soft and broad spectrum), and C (soft and peaked spectrum). The group A sources are further decomposed spectrally into thermal and non-thermal sources with different fractions in different flux ranges. From their X-ray properties, we speculate that the group A non-thermal sources are mostly active galactic nuclei and the thermal sources are mostly white dwarf (WD) binaries such as magnetic and non-magnetic cataclysmic variables (CVs), pre-CVs, and symbiotic stars, whereas the group B and C sources are X-ray active stars in flares and quiescence, respectively. In the log N-log S curve of the 2-8 keV band, the group A non-thermal sources are dominant above {approx}10^-14^erg/cm2/s, which is gradually taken over by Galactic sources in the fainter flux ranges. The Fe K{alpha} emission is mostly from the group A thermal (WD binaries) and the group B (X-ray active stars) sources.
- ID:
- ivo://CDS.VizieR/J/MNRAS/465/1807
- Title:
- Deep OB star population in Carina
- Short Name:
- J/MNRAS/465/1807
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Massive OB stars are critical to the ecology of galaxies, and yet our knowledge of OB stars in the Milky Way, fainter than V~12, remains patchy. Data from the VST Photometric H-alpha Survey (VPHAS+) permit the construction of the first deep catalogues of blue excess-selected OB stars, without neglecting the stellar field. A total of 14900 candidates with 2MASS cross-matches are blue-selected from a 42 square-degree region in the Galactic longitude range 282{deg}<l<293{deg} Spectral energy distribution fitting is performed on these candidates' combined VPHAS+ u/g/r/i and 2MASS J/H/K magnitudes. This delivers: effective temperature constraints, statistically separating O from early-B stars; high-quality extinction parameters, A_0_ and R_V_ (random errors typically <0.1). The high confidence O-B2 candidates number 5915 and a further 5170 fit to later B spectral type. Spectroscopy of 276 of the former confirms 97% of them. The fraction of emission line stars among all candidate B stars is 7-8%. Greyer (R_V_>3.5) extinction laws are ubiquitous in the region, over the distance range 2.5-3kpc to ~10kpc. Near prominent massive clusters, R_V_ tends to rise, with particularly large and chaotic excursions to R_V_~5 seen in the Carina Nebula. The data reveal a hitherto unnoticed association of 108 O-B2 stars around the O5If+ star LSS 2063 (l=289.77{deg}, b=-1.22{deg}). Treating the OB star scale-height as a constant within the thin disk, we find an orderly mean relation between extinction (A_0_) and distance in the Galactic longitude range, 287.6{deg}<l< 293.5{deg}, and infer the subtle onset of thin-disk warping. A halo around NGC 3603, roughly a degree in diameter, of ~500 O-B2 stars with 4<A_0_(mag)<7 is noted.
- ID:
- ivo://CDS.VizieR/J/MNRAS/443/2907
- Title:
- 3D extinction map of northern Galactic plane
- Short Name:
- J/MNRAS/443/2907
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a three dimensional map of extinction in the Northern Galactic Plane derived using photometry from the IPHAS survey. We construct the map using a method based on a hierarchical Bayesian model as previously described by Sale (2012MNRAS.427.2119S). In addition to mean extinction, we also measure differential extinction, which arises from the fractal nature of the ISM. The method applied also furnishes us with photometric estimates of the distance, extinction, effective temperature, surface gravity, and mass for ~38 million stars. Further details about the data as well as additional formats and data products are available via http://www.iphas.org/extinction.
- ID:
- ivo://CDS.VizieR/J/AJ/138/1380
- Title:
- Dust clumps in the Galactic Plane
- Short Name:
- J/AJ/138/1380
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present imaging observations of continuum emission from interstellar dust at 850 and 1200um of a section of the Galactic Plane covering 2deg^2^ centered at l=44{deg}. Complementary jiggle-mapping and fast-scanning techniques were used, respectively, at these two wavelengths. The mapped area includes the well-known star formation regions W49 and G45.1/45.5. Using an automated clump-finding routine, we identify 132 compact 850um emission features within the region above a completeness level of about 200mJy/beam. The positions of the latter objects were used to determine fluxes from the 1200um image. Spectral line data were subsequently obtained with the same observing beamwidth as at 850um for almost half of the objects; these were either imaged in the ^13^CO (3-2) line, or basic characteristics determined using the ^12^CO (3-2) transition. We use these data, supplemented by existing ^13^CO (1-0) and HI survey data, to determine distances and hence derive masses for the dust clump ensemble, assuming a uniform dust temperature of 15K. From these data we find that the number-mass relationship for clumps in the field is similar to that found for individual star-forming regions.
- ID:
- ivo://CDS.VizieR/IX/15
- Title:
- Einstein EMSS Survey
- Short Name:
- IX/15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Einstein Extended Medium Sensitivity Survey (EMSS) consists of 835 serendipitous X-ray sources detected at or above 4 times the rms level in 1435 IPC fields with their centers located away from the galactic plane. Their limiting sensitivities range from ~5*10-14 to to ~ 3*10-12 erg.cm-2.s-1 in the 0.3-3.5keV band. A total area of 778 square degrees of the high galactic latitude sky (|b|>20) has been covered. The analysis has been performed using data from the Rev 1 processing system at the CfA. The resulting EMSS catalog is a flux-limited and homogeneous sample of astronomical objects that can be used for statistical studies. Here we present the table listing all the sources taken from the publication referenced below and the optical identifications. At present over 96% of the 835 X-ray sources have been successfully identified in the following proportions: active galactic nuclei (QSO's, quasars and Seyfert), 51.1%; BL Lacertae objects, 4.3%; clusters of galaxies, 12.2%; normal galaxies, 2.1%; cooling flow galaxies, 0.6%; Galactic stars 25.8%; and unidentified, 3.9%. Most of the individual optical counterparts are previously unknown objects and so constitute large statistical samples independent of previously selection methods. The contents of the table is described below. The sky coverage computed for a specific assumed source spectrum is also given under "Additional Information" below. For further details please see the published articles: Gioia et al. 1990, Stocke et al. 1991.
- ID:
- ivo://CDS.VizieR/J/A+A/515/A51
- Title:
- Extended red(dened) regions in 2MASS
- Short Name:
- J/A+A/515/A51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The aim of this paper is to identify extended red regions in the outer galactic plane based on reddening of stars in the near-infrared. We argue that these regions appear reddened mainly due to extinction caused by molecular clouds and young stellar objects. The work presented here is used as a basis for identifying star forming regions and in particular the very early stages. An accompanying paper describes the cross-identification of the identified regions with existing data, uncovering more on the nature of the reddening.
