- ID:
- ivo://CDS.VizieR/J/MNRAS/465/501
- Title:
- APOGEE N-rich stars in inner Galaxy
- Short Name:
- J/MNRAS/465/501
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Formation of globular clusters (GCs), the Galactic bulge, or galaxy bulges in general is an important unsolved problem in Galactic astronomy. Homogeneous infrared observations of large samples of stars belonging to GCs and the Galactic bulge field are one of the best ways to study these problems. We report the discovery by APOGEE (Apache Point Observatory Galactic Evolution Experiment) of a population of field stars in the inner Galaxy with abundances of N, C, and Al that are typically found in GC stars. The newly discovered stars have high [N/Fe], which is correlated with [Al/Fe] and anticorrelated with [C/Fe]. They are homogeneously distributed across, and kinematically indistinguishable from, other field stars within the same volume. Their metallicity distribution is seemingly unimodal, peaking at [Fe/H]~-1, thus being in disagreement with that of the Galactic GC system. Our results can be understood in terms of different scenarios. N-rich stars could be former members of dissolved GCs, in which case the mass in destroyed GCs exceeds that of the surviving GC system by a factor of ~8. In that scenario, the total mass contained in so-called 'first-generation' stars cannot be larger than that in 'second-generation' stars by more than a factor of ~9 and was certainly smaller. Conversely, our results may imply the absence of a mandatory genetic link between 'second-generation' stars and GCs. Last, but not least, N-rich stars could be the oldest stars in the Galaxy, the by-products of chemical enrichment by the first stellar generations formed in the heart of the Galaxy.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/903/55
- Title:
- APOGEE parameters through 83 open clusters
- Short Name:
- J/ApJ/903/55
- Date:
- 15 Mar 2022
- Publisher:
- CDS
- Description:
- The chemical homogeneity of surviving stellar clusters contains important clues about interstellar medium (ISM) mixing efficiency, star formation, and the enrichment history of the Galaxy. Existing measurements in a handful of open clusters suggest homogeneity in several elements at the 0.03dex level. Here we present (I) a new cluster member catalog based only on APOGEE radial velocities and Gaia-DR2 proper motions, (II) improved abundance uncertainties for APOGEE cluster members, and (III) the dependence of cluster homogeneity on Galactic and cluster properties, using abundances of eight elements from the APOGEE survey for 10 high-quality clusters. We find that cluster homogeneity is uncorrelated with Galactocentric distance, |Z|, age, and metallicity. However, velocity dispersion, which is a proxy for cluster mass, is positively correlated with intrinsic scatter at relatively high levels of significance for [Ca/Fe] and [Mg/Fe]. We also see a possible positive correlation at a low level of significance for [Ni/Fe], [Si/Fe], [Al/Fe], and [Fe/H], while [Cr/Fe] and [Mn/Fe] are uncorrelated. The elements that show a correlation with velocity dispersion are those that are predominantly produced by core-collapse supernovae (CCSNe). However, the small sample size and relatively low correlation significance highlight the need for follow-up studies. If borne out by future studies, these findings would suggest a quantitative difference between the correlation lengths of elements produced predominantly by Type Ia SNe versus CCSNe, which would have implications for Galactic chemical evolution models and the feasibility of chemical tagging.
- ID:
- ivo://CDS.VizieR/J/ApJS/134/77
- Title:
- ASCA Galactic Plane Survey faint X-ray sources
- Short Name:
- J/ApJS/134/77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The X-ray emission from the central region of the Galactic plane, |l|<~45{deg} and |b|<~0.4{deg}, was studied in the 0.710keV energy band with a spatial resolution of ~3' with the Advanced Satellite for Cosmology and Astrophysics (ASCA) observatory. We developed a new analysis method for the ASCA data to resolve discrete sources from the extended Galactic ridge X-ray emission (GRXE). We successfully resolved 163 discrete sources with an X-ray flux down to 10^-12.5^ergs/cm^2^/s and determined the intensity variations of the GRXE as a function of the Galactic longitude with a spatial resolution of about 1{deg}.
- ID:
- ivo://CDS.VizieR/J/ApJ/725/331
- Title:
- Astrometry in the Galactic Center
- Short Name:
- J/ApJ/725/331
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present significantly improved proper motion measurements of the Milky Way's central stellar cluster. These improvements are made possible by refining our astrometric reference frame with a new geometric optical distortion model for the W. M. Keck II 10m telescope's adaptive optics camera (NIRC2) in its narrow field mode. For the first time, this distortion model is constructed from on-sky measurements and is made available to the public in the form of FITS files. When applied to widely dithered images, it produces residuals in the separations of stars that are a factor of ~3 smaller compared with the outcome using previous models. By applying this new model, along with corrections for differential atmospheric refraction, to widely dithered images of SiO masers at the Galactic center (GC), we improve our ability to tie into the precisely measured radio Sgr A*-rest frame. The resulting infrared reference frame is ~2-3 times more accurate and stable than earlier published efforts. In this reference frame, Sgr A* is localized to within a position of 0.6mas and a velocity of 0.09mas/yr, or ~3.4km/s at 8kpc (1{sigma}). Also, proper motions for members of the central stellar cluster are more accurate, although less precise, due to the limited number of these wide field measurements. We define a reference frame with SiO masers and this reference frame's stability should improve steadily with future measurements of the SiO masers in this region ({propto}t^-3/2^). This is essential for achieving the necessary reference frame stability required to detect the effects of general relativity and extended mass on short-period stars at the GC.
- ID:
- ivo://CDS.VizieR/J/A+A/544/A146
- Title:
- ATLASGAL cold high-mass clumps with NH_3_
- Short Name:
- J/A+A/544/A146
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The APEX Telescope Large Area Survey: The Galaxy (ATLASGAL) is an unbiased continuum survey of the inner Galactic disk at 870 micron. It covers +/-60{deg} in Galactic longitude and aims to find all massive clumps at various stages of high-mass star formation in the inner Galaxy, particularly the earliest evolutionary phases. We aim to determine properties such as the gas kinetic temperature and dynamics of new massive cold clumps found by ATLASGAL. Most importantly, we derived their kinematical distances from the measured line velocities. We observed the ammonia (J,K)=(1,1) to (3,3) inversion transitions toward 862 clumps of a flux-limited sample of submm clumps detected by ATLASGAL and extracted ^13^CO(1-0) spectra from the Galactic Ring Survey (GRS). We determined distances for a subsample located at the tangential points (71 sources) and for 277 clumps whose near/far distance ambiguity is resolved. Most ATLASGAL clumps are cold with rotational temperatures from 10-30K with a median of 17K. They have a wide range of NH_3_ linewidths (1-7km/s with 1.9km/s as median, which by far exceeds the thermal linewidth, as well as a broad distribution of high column densities from 10^14^ to 10^16^cm^-2^ (median of 2x10^15^cm^-2^) with an NH_3_ abundance in the range of 5 to 30x10^-8^. ATLASGAL sources are massive, >100M_{sun}_, and a fraction of clumps with a broad linewidth is in virial equilibrium. We found an enhancement of clumps at Galactocentric radii of 4.5 and 6kpc. The comparison of the NH_3_ lines as high-density probes with the GRS ^13^CO emission as low-density envelope tracer yields broader linewidths for ^13^CO than for NH_3_. The small differences in derived clump velocities between NH_3_ (representing dense core material) and ^13^CO (representing more diffuse molecular cloud gas) suggests that the cores are essentially at rest relative to the surrounding giant molecular cloud. The high detection rate (87%) confirms ammonia as an excellent probe of the molecular content of the massive, cold clumps revealed by ATLASGAL. A clear trend of increasing rotational temperatures and linewidths with evolutionary stage is seen for source samples ranging from 24 micron dark clumps to clumps with embedded HII regions. The survey provides the largest ammonia sample of high-mass star forming clumps and thus presents an important repository for the characterization of statistical properties of the clumps and the selection of subsamples for detailed, high-resolution follow-up studies.
- ID:
- ivo://CDS.VizieR/J/A+A/568/A41
- Title:
- ATLASGAL Compact Source Catalog: 280<l<60
- Short Name:
- J/A+A/568/A41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) is the largest and most sensitive systematic survey of the inner Galactic plane in the submillimetre wavelength regime. The observations were carried out with the Large APEX Bolometer Camera (LABOCA), an array of 295 bolometers observing at 870um (345GHz). In this research note we present the compact source catalogue for the 280{deg}<l<330{deg}and 21{deg}<l<60{deg}regions of this survey. The construction of this catalogue was made with the source extraction routine SExtractor using the same input parameters and procedures as used to analyse the inner Galaxy region presented in an earlier publication (i.e., 330{deg}<l<21{deg}). We have identified 3523 compact sources and present a catalogue of their properties. When combined with the regions already published (see Contreras et al., 2013, Cat. J/A+A/549/A45), this provides a comprehensive and unbiased database of ~10163 massive, dense clumps located across the inner Galaxy.
- 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/ApJS/211/29
- Title:
- Atlas of HI absorption toward HII regions in SGPS I
- Short Name:
- J/ApJS/211/29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a complete catalog of H I emission and absorption spectrum pairs, toward H II regions, detectable within the boundaries of the Southern Galactic Plane Survey (SGPS I), a total of 252 regions. The catalog is presented in graphical, numerical, and summary formats. We demonstrate an application of this new data set through an investigation of the locus of the Near 3kpc Arm.
