- ID:
- ivo://CDS.VizieR/J/A+A/564/A99
- Title:
- Chamaeleon-MMS1 NH_3_ (1,1) and (2,2) maps
- Short Name:
- J/A+A/564/A99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The aim of this study is to investigate the structure and kinematics of the nearby candidate first hydrostatic core Cha-MMS1. Cha-MMS1 was mapped in the NH_3_(1,1) line and the 1.2cm continuum using the Australia Telescope Compact Array, ATCA. The angular resolution of the ATCA observations is 7" (~1000AU), and the velocity resolution is 50m/s. The core was also mapped with the 64-m Parkes telescope in the NH_3_(1,1) and (2,2) lines. Observations from Herschel Space Observatory and Spitzer Space telescope were used to help interpretation. The ammonia spectra were analysed using Gaussian fits to the hyperfine structure. A two-layer model was applied in the central parts of the core where the ATCA spectra show signs of self-absorption.
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- ID:
- ivo://CDS.VizieR/J/A+A/633/A126
- Title:
- Cha-MMS1 CO 3-2 and ^13^CO 3-2 datacubes
- Short Name:
- J/A+A/633/A126
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- On the basis of its low luminosity, its chemical composition, and the absence of a large-scale outflow, the dense core Cha-MMS1 located in the Chamaeleon I molecular cloud was proposed as a first hydrostatic core (FHSC) candidate a decade ago. Our goal is to test this hypothesis by searching for a slow, compact outflow driven by Cha-MMS1 that would match the predictions of MHD simulations for this short phase of star formation. We use the Atacama Large Millimeter/submillimeter Array (ALMA) to map Cha-MMS1 at high angular resolution in CO 3-2 and ^13^CO 3-2 as well as in continuum emission. We report the detection of a bipolar outflow emanating from the central core, along a (projected) direction roughly parallel to the filament in which Cha-MMS1 is embedded and perpendicular to the large-scale magnetic field. The morphology of the outflow indicates that its axis lies close to the plane of the sky. We measure velocities corrected for inclination of more than 90km/s which is clearly incompatible with the expected properties of a FHSC outflow. Several properties of the outflow are determined and compared to previous studies of Class 0 and Class I protostars. The outflow of Cha-MMS1 has a much smaller momentum force than the outflows of other Class0 protostars. In addition, we find a dynamical age of 200-3000yr indicating that Cha-MMS1 might be one of the youngest ever observed Class 0 protostars. While the existence of the outflow suggests the presence of a disk, no disk is detected in continuum emission and we derive an upper limit of 55au to its radius. We conclude that Cha-MMS1 has already gone through the FHSC phase and is a young Class 0 protostar, but it has not brought its outflow to full power yet.
- ID:
- ivo://CDS.VizieR/J/ApJS/178/339
- Title:
- ChaMP extended stellar survey (ChESS)
- Short Name:
- J/ApJS/178/339
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 348 X-ray-emitting stars identified from correlating the Extended Chandra Multiwavelength Project (ChaMP), a wide-area serendipitous survey based on archival X-ray images, with the Sloan Digital Sky Survey (SDSS-DR6). We use morphological star/galaxy separation, matching to an SDSS quasar catalog, an optical color-magnitude cut, and X-ray data-quality tests to create our catalog, the ChaMP Extended Stellar Survey (ChESS), from a sample of 2121 matched ChaMP/SDSS sources. Our cuts retain 92% of the spectroscopically confirmed stars in the original sample while excluding 99.6% of the 684 spectroscopically confirmed extragalactic sources. Fewer than 3% of the sources in our final catalog are previously identified stellar X-ray emitters. For 42 catalog members, spectroscopic classifications are available in the literature. We present new spectral classifications and H{alpha} measurements for an additional 79 stars. The catalog is dominated by main-sequence stars; we estimate the fraction of giants in ChESS is ~10%. We identify seven giant stars (including a possible Cepheid and an RR Lyrae star) as ChaMP sources, as well as three cataclysmic variables. Future papers will present analyses of source variability and comparisons of this catalog to models of stellar activity in the Galactic disk.
- ID:
- ivo://CDS.VizieR/J/ApJS/150/19
- Title:
- ChaMP. I. First X-ray source catalog
- Short Name:
- J/ApJS/150/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Chandra Multiwavelength Project (ChaMP) is a wide-area (~14deg^2^) survey of serendipitous Chandra X-ray sources, aiming to establish fair statistical samples covering a wide range of characteristics (such as absorbed active galactic nuclei, high-z clusters of galaxies) at flux levels (fX~10^-15^ to 10^-14^erg/s/cm^2^) ) intermediate between the Chandra deep surveys and previous missions. We present the first ChaMP catalog, which consists of 991 near on-axis, bright X-ray sources obtained from the initial sample of 62 observations. The data have been uniformly reduced and analyzed with techniques specifically developed for the ChaMP and then validated by visual examination. To assess source reliability and positional uncertainty, we perform a series of simulations and also use Chandra data to complement the simulation study. The false source detection rate is found to be as good as or better than expected for a given limiting threshold. On the other hand, the chance of missing a real source is rather complex, depending on the source counts, off-axis distance (or PSF), and background rate. The positional error (95% confidence level) is usually less than 1" for a bright source, regardless of its off-axis distance, while it can be as large as 4" for a weak source (~20counts) at a large off-axis distance (Doff-axis>8'). We have also developed new methods to find spatially extended or temporary variable sources, and those sources are listed in the catalog.
- ID:
- ivo://CDS.VizieR/J/ApJ/700/1702
- Title:
- ChaMPlane deep galactic bulge survey. I.
- Short Name:
- J/ApJ/700/1702
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have carried out a deep X-ray and optical survey with Chandra and HST of low-extinction regions in the Galactic bulge. Here we present the results of a search for low-luminosity (L_X_<~10^34^erg/s) accreting binaries among the Chandra sources in the region closest to the Galactic center, at an angular offset of 1.4{deg}, that we have named the Limiting Window (LW). Based on their blue optical colors, excess H{alpha} fluxes, and high X-ray-to-optical flux ratios, we identify three likely accreting binaries; these are probably white dwarfs accreting from low-mass companions (cataclysmic variables; CVs) although we cannot exclude that they are quiescent neutron-star or black-hole low-mass X-ray binaries. Distance estimates put these systems farther than >~2kpc. Based on their H{alpha}-excess fluxes and/or high X-ray-to-optical flux ratios, we find 22 candidate accreting binaries; however, the properties of some can also be explained if they are dMe stars or active galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/685/463
- Title:
- ChaMPlane X-ray sources in the Galactic bulge
- Short Name:
- J/ApJ/685/463
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have carried out optical and X-ray spectral analyses on a sample of 136 candidate optical counterparts of X-ray sources found in five Galactic bulge fields included in our Chandra Multiwavelength Plane Survey. We use a combination of optical spectral fitting and quantile X-ray analysis to obtain the hydrogen column density toward each object, and a three-dimensional dust model of the Galaxy to estimate the most probable distance in each case. We present the discovery of a population of stellar coronal emission sources, likely consisting of pre-main-sequence, young main-sequence, and main-sequence stars, as well as a component of active binaries of RS CVn or BY Dra type. We identify one candidate quiescent low-mass X-ray binary with a subgiant companion; we note that this object may also be an RS CVn system. We report the discovery of three new X-ray-detected cataclysmic variables (CVs) in the direction of the Galactic center (at distances <~2kpc). This number is in excess of predictions made with a simple CV model based on a local CV space density of <~10^-5^pc^-3^, and a scale height ~200pc. We discuss several possible reasons for this observed excess.
- ID:
- ivo://CDS.VizieR/J/ApJ/645/955
- Title:
- ChaMP serendipitous galaxy cluster survey
- Short Name:
- J/ApJ/645/955
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a survey of serendipitous extended X-ray sources and optical cluster candidates from the Chandra Multiwavelength Project (ChaMP). Our main goal is to make an unbiased comparison of X-ray and optical cluster detection methods. In 130 archival Chandra pointings covering 13deg^2^, we use a wavelet decomposition technique to detect 55 extended sources, of which 6 are nearby single galaxies. Our X-ray cluster catalog reaches a typical flux limit of about 10^-14^ergs/cm^2^/s, with a median cluster core radius of 21". For 56 of the 130 X-ray fields, we use the ChaMP's deep NOAO 4m MOSAIC g', r', and i' imaging to independently detect cluster candidates using a Voronoi tessellation and percolation (VTP) method. Red-sequence filtering decreases the galaxy fore- and background contamination and provides photometric redshifts to z~0.7. From the overlapping 6.1deg^2^ X-ray/optical imaging, we find 115 optical clusters (of which 11% are in the X-ray catalog) and 28 X-ray clusters (of which 46% are in the optical VTP catalog).
- ID:
- ivo://CDS.VizieR/J/ApJS/169/401
- Title:
- ChaMP X-ray point source catalog
- Short Name:
- J/ApJS/169/401
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the Chandra Multiwavelength Project (ChaMP) X-ray point source catalog with ~6800 X-ray sources detected in 149 Chandra observations covering ~10deg^2^. The full ChaMP catalog sample is 7 times larger than the initial published ChaMP catalog. The exposure time of the fields in our sample ranges from 0.9 to 124ks, corresponding to a deepest X-ray flux limit of f_0.5-8.0_=9x10^-16^ergs/cm^2^/s. The ChaMP X-ray data have been uniformly reduced and analyzed with ChaMP-specific pipelines and then carefully validated by visual inspection. The ChaMP catalog includes X-ray photometric data in eight different energy bands as well as X-ray spectral hardness ratios and colors. To best utilize the ChaMP catalog, we also present the source reliability, detection probability, and positional uncertainty.
- ID:
- ivo://CDS.VizieR/J/ApJS/192/10
- Title:
- Chandra ACIS survey in 383 nearby galaxies. I.
- Short Name:
- J/ApJS/192/10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- By 2007 December 14, 383 galaxies within 40Mpc with isophotal major axis above 1arcmin had been observed by 626 public Chandra/ACIS observations, most of which were for the first time analyzed by this survey to study the X-ray point sources. Uniform data analysis procedures are applied to the 626 ACIS observations and lead to the detection of 28099 point sources, which belong to 17599 independent sources. These include 8700 sources observed twice or more and 1000 sources observed 10 times or more, providing us a wealth of data to study the long-term variability of these X-ray sources. Cross-correlation of these sources with galaxy isophotes led to 8519 sources within the D_25_ isophotes of 351 galaxies, 3305 sources between the D_25_ and 2D_25_ isophotes of 309 galaxies, and additionally 5735 sources outside 2D_25_ isophotes of galaxies. This survey has produced a uniform catalog, by far the largest, of 11824 X-ray point sources within 2D_25_ isophotes of 380 galaxies. Contamination analysis using the log N-log S relation shows that 74% of sources within 2D_25_ isophotes above 10^39^erg/s, 71% of sources above 10^38^erg/s, 63% of sources above 10^37^erg/s, and 56% of all sources are truly associated with galaxies. Meticulous efforts have identified 234 X-ray sources with galactic nuclei of nearby galaxies. This archival survey leads to 300 ultraluminous X-ray sources (ULXs) with L_X_(0.3-8keV)>=2x10^39^erg/s within D_25_ isophotes, 179 ULXs between D_25_ and 2D_25_ isophotes, and a total of 479 ULXs within 188 host galaxies, with about 324 ULXs truly associated with host galaxies based on the contamination analysis.
- ID:
- ivo://CDS.VizieR/J/ApJ/829/20
- Title:
- Chandra ACIS survey in nearby galaxies. II
- Short Name:
- J/ApJ/829/20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on the recently completed Chandra/ACIS survey of X-ray point sources in nearby galaxies, we study the X-ray luminosity functions (XLFs) for X-ray point sources in different types of galaxies and the statistical properties of ultraluminous X-ray sources (ULXs). Uniform procedures are developed to compute the detection threshold, to estimate the foreground/background contamination, and to calculate the XLFs for individual galaxies and groups of galaxies, resulting in an XLF library of 343 galaxies of different types. With the large number of surveyed galaxies, we have studied the XLFs and ULX properties across different host galaxy types, and confirm with good statistics that the XLF slope flattens from lenticular ({alpha}{\sim}1.50{\pm}0.07) to elliptical ({\sim}1.21{\pm}0.02), to spirals ({\sim}0.80{\pm}0.02), to peculiars ({\sim}0.55{\pm}0.30), and to irregulars ({\sim}0.26{\pm}0.10). The XLF break dividing the neutron star and black hole binaries is also confirmed, albeit at quite different break luminosities for different types of galaxies. A radial dependency is found for ellipticals, with a flatter XLF slope for sources located between D_25_ and 2D_25_, suggesting the XLF slopes in the outer region of early-type galaxies are dominated by low-mass X-ray binaries in globular clusters. This study shows that the ULX rate in early-type galaxies is 0.24{\pm}0.05 ULXs per surveyed galaxy, on a 5{sigma} confidence level. The XLF for ULXs in late-type galaxies extends smoothly until it drops abruptly around 4x10^40^erg/s, and this break may suggest a mild boundary between the stellar black hole population possibly including 30M{\sun} black holes with super-Eddington radiation and intermediate mass black holes.
