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2551. Chamaeleon I star-forming region census
ID:
ivo://CDS.VizieR/J/ApJ/602/816
Title:
Chamaeleon I star-forming region census
Short Name:
J/ApJ/602/816
Date:
21 Oct 2021
Publisher:
CDS
Description:
I present a new census of the members of the Chamaeleon I star-forming region. Optical spectroscopy has been obtained for 179 objects that have been previously identified as possible members of the cluster, that lack either accurate spectral types or clear evidence of membership, and that are optically visible (I<~18). I have used these spectroscopic data and all other available constraints to evaluate the spectral classifications and membership status of a total sample of 288 candidate members of Chamaeleon I that have appeared in published studies of the cluster. The latest census of Chamaeleon I now contains 158 members, eight of which are later than M6 and thus are likely to be brown dwarfs. I find that many of the objects identified as members of Chamaeleon I in recent surveys are actually field stars. Meanwhile, seven of nine candidates discovered by Carpenter and coworkers are confirmed as members, one of which is the coolest known member of Chamaeleon I at a spectral type of M8 (~0.03M_{sun}_). I have estimated extinctions, luminosities, and effective temperatures for the members and used these data to construct an H-R diagram for the cluster. Chamaeleon I has a median age of ~2Myr according to evolutionary models and hence is similar in age to IC 348 and is slightly older than Taurus (~1Myr). The measurement of an initial mass function for Chamaeleon I from this census is not possible because of the disparate methods with which the known members were originally selected and must await an unbiased, magnitude-limited survey of the cluster.
2552. Chamaeleon I 870um sources
ID:
ivo://CDS.VizieR/J/A+A/527/A145
Title:
Chamaeleon I 870um sources
Short Name:
J/A+A/527/A145
Date:
21 Oct 2021
Publisher:
CDS
Description:
Chamaeleon I is the most active region in terms of star formation in the Chamaeleon molecular cloud complex. Although it is one of the nearest low-mass star forming regions, its population of prestellar and protostellar cores is not known and a controversy exists concerning its history of star formation. Our goal is to search for prestellar and protostellar cores and characterize the earliest stages of star formation in this cloud.
2553. Chamaeleon-MMS1 NH_3_ (1,1) and (2,2) maps
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.
2554. Cha-MMS1 CO 3-2 and ^13^CO 3-2 datacubes
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.
2555. CHAMP (Chandra Multiwavelength Project) Hard X-Ray Emitting AGN
ID:
ivo://nasa.heasarc/champhxagn
Title:
CHAMP (Chandra Multiwavelength Project) Hard X-Ray Emitting AGN
Short Name:
CHAMPHXAGN
Date:
28 Feb 2025
Publisher:
NASA/GSFC HEASARC
Description:
This table contains the results from an X-ray and optical analysis of 188 active galactic nuclei (AGN) identified from 497 hard X-ray (observed flux in the (2.0 - 8.0 keV) band &gt; 2.7 x 10&lt;sup&gt;-15&lt;/sup&gt; erg/cm&lt;sup&gt;2&lt;/sup&gt;/s) sources in 20 Chandra fields (1.5 square degrees) forming part of the Chandra Multiwavelength Project (ChaMP). These medium-depth X-ray observations enable the detection of a representative subset of those sources responsible for the bulk of the 2 - 8 keV cosmic X-ray background. Brighter than the survey&#39;s optical spectroscopic limit, the authors achieve a reasonable degree of completeness (77% of X-ray sources with counterparts r&#39; &lt; 22.5 have been classified): broad emission-line AGNs (62%), narrow emission-line galaxies (24%), absorption-line galaxies (7%), stars (5%), or clusters (2%). To construct a pure AGN sample, the authors required the rest-frame 2.0-8.0 keV luminosity (uncorrected for intrinsic absorption) to exceed 10&lt;sup&gt;42&lt;/sup&gt; erg s&lt;sup&gt;-1&lt;/sup&gt;, thereby excluding any sources that may contain a significant stellar or hot ISM component. The most luminous known star-forming or elliptical galaxies attain at most L&lt;sub&gt;X&lt;/sub&gt; = 10&lt;sup&gt;42&lt;/sup&gt; erg s&lt;sup&gt;-1&lt;/sup&gt;. Since many of the traditional optical AGN signatures are not present in obscured sources, high X-ray luminosity becomes the authors&#39; single discriminant for supermassive black hole accretion. They believe that almost all of the NELGs and ALGs harbor accreting SMBHs based on their X-ray luminosity. They find that 90% of the identified ChaMP sources have luminosities above this threshold. These selection criteria yield a sample of 188 AGNs from 20 Chandra fields with f(2-8 keV) &gt; 2.7 x 10&lt;sup&gt;-15&lt;/sup&gt; erg cm&lt;sup&gt;-2&lt;/sup&gt; s&lt;sup&gt;-1&lt;/sup&gt;, r&#39; &lt; 22.5, and L&lt;sub&gt;X&lt;/sub&gt; &gt; 10&lt;sup&gt;42&lt;/sup&gt; erg s&lt;sup&gt;-1&lt;/sup&gt;. The authors removed five objects identified as clusters based on their extended X-ray emission. This table was created by the HEASARC in March 2007 based on the CDS table J/ApJ/618/123, file table4.dat. This is a service provided by NASA HEASARC .
2556. ChaMP extended stellar survey (ChESS)
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.
2557. ChaMP Extended Stellar Survey (ChESS) X-Ray Catalog
ID:
ivo://nasa.heasarc/chesscat
Title:
ChaMP Extended Stellar Survey (ChESS) X-Ray Catalog
Short Name:
CHESSCAT
Date:
28 Feb 2025
Publisher:
NASA/GSFC HEASARC
Description:
The ChaMP Extended Stellar Survey (ChESS) X-ray catalog contains 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). The authors used morphological star/galaxy separation, matching to an SDSS quasar catalog, an optical color-magnitude cut, and X-ray data-quality tests to create this catalog, from a sample of 2121 matched ChaMP/SDSS sources. Their 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 their final catalog are previously identified stellar X-ray emitters. For 42 catalog members, spectroscopic classifications are available in the literature. New spectral classifications and H-alpha measurements are presented for an additional 79 stars. The catalog is dominated by main-sequence stars; the authors estimate the fraction of giants in ChESS to be ~10%. They identify seven giant stars (including a possible Cepheid and an RR Lyrae star) as ChaMP sources, as well as three cataclysmic variables. They derive distances from ~10 to 2000 pc for the stars in the catalog using photometric parallax relations appropriate for dwarfs on the main sequence and calculate their X-ray and bolometric luminosities. These stars lie in a unique space in the L&lt;sub&gt;X&lt;/sub&gt;-distance plane, filling the gap between the nearby stars identified as counterparts to sources in the ROSAT All Sky Survey and the more distant stars detected in deep Chandra and XMM-Newton surveys. For 36 newly identified X-ray-emitting M stars, the authors calculated L&lt;sub&gt;H-alpha&lt;/sub&gt;/L&lt;sub&gt;bol&lt;/sub&gt;. The quantities L&lt;sub&gt;H-alpha&lt;/sub&gt;/L&lt;sub&gt;bol&lt;/sub&gt; and L&lt;sub&gt;X&lt;/sub&gt;/L&lt;sub&gt;bol&lt;/sub&gt; are linearly related below L&lt;sub&gt;X&lt;/sub&gt;/L&lt;sub&gt;bol&lt;/sub&gt; ~ 3 x 10&lt;sup&gt;-4&lt;/sup&gt;, while L&lt;sub&gt;H-alpha&lt;/sub&gt;/L&lt;sub&gt;bol&lt;/sub&gt; appears to turn over at larger L&lt;sub&gt;X&lt;/sub&gt;/L&lt;sub&gt;bol&lt;/sub&gt; values. Stars with reliable SDSS photometry have an ~0.1 mag blue excess in u-g, likely due to increased chromospheric continuum emission. Photometric metallicity estimates suggest that the sample is evenly split between the young and old disk populations of the Galaxy; the lowest activity sources belong to the old disk population, a clear signature of the decay of magnetic activity with age. This table was created by the HEASARC in January 2009 based on the electronic version of Tables 2 and 3 from the reference paper which were obtained from the ApJ web site. This is a service provided by NASA HEASARC .
2558. ChaMP. I. First X-ray source catalog
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.
2559. ChaMPlane deep galactic bulge survey. I.
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.
2560. ChaMPlane Galactic Bulge and Center X-Ray Source Catalog
ID:
ivo://nasa.heasarc/champlanex
Title:
ChaMPlane Galactic Bulge and Center X-Ray Source Catalog
Short Name:
CHAMPLANEX
Date:
28 Feb 2025
Publisher:
NASA/GSFC HEASARC
Description:
This table contains the Chandra Multiwavelength Plane (ChaMPlane) Survey catalog of X-ray point sources in the window and four Galactic bulge fields, specifically all source detections with net counts &gt;= 1 in the 0.3-8 keV broad band. In the reference paper, the authors present the log N-log S and spatial distributions of X-ray point sources in seven Galactic bulge (GB) fields within 4 degrees of the Galactic center (GC). They compare the properties of 1159 X-ray point sources discovered in their deep (100 ks) Chandra observations of three low extinction Window fields near the GC with the X-ray sources in the other GB fields centered around Sgr B2, Sgr C, the Arches Cluster, and Sgr A* using Chandra archival data. To reduce the systematic errors induced by the uncertain X-ray spectra of the sources coupled with field-and-distance-dependent extinction, they classify the X-ray sources using quantile analysis and estimate their fluxes accordingly. The result indicates that the GB X-ray population is highly concentrated at the center, more heavily than the stellar distribution models. It extends out to more than 1.4 degrees from the GC, and the projected density follows an empirical radial relation inversely proportional to the offset from the GC. They also compare the total X-ray and infrared surface brightness using the Chandra and Spitzer observations of the regions. The radial distribution of the total infrared surface brightness from the 3.6-micron band images appears to resemble the radial distribution of the X-ray point sources better than that predicted by the stellar distribution models. Assuming a simple power-law model for the X-ray spectra, the closer to the GC, the intrinsically harder the X-ray spectra appear, but adding an iron emission line at 6.7 keV in the model allows the spectra of the GB X-ray sources to be largely consistent across the region. This implies that the majority of these GB X-ray sources can be of the same or similar type. Their X-ray luminosity and spectral properties support the idea that the most likely candidate is magnetic cataclysmic variables (CVs), primarily intermediate polars (IPs). Their observed number density is also consistent with the majority being IPs, provided the relative CV to star density in the GB is not smaller than the value in the local solar neighborhood. This table was created by the HEASARC in January 2010, based on the electronic version of Table 2 from the reference paper, which was obtained from the Astrophysical Journal web site. This is a service provided by NASA HEASARC .

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