CG 12 Chandra X-Ray Point Source Catalog

CG 12 Chandra X-Ray Point Source Catalog CG12CXO ivo://nasa.heasarc/cg12cxo NASA/GSFC HEASARC Getman et al. 2026-10-09 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov Survey Source The mysterious high Galactic latitude cometary globule CG 12 has been observed with the ACIS detector on board the Chandra X-Ray Observatory. 128 X-ray sources are detected, of which half are likely young stars formed within the globule's head. This new population of >~ 50 T Tauri stars and one new embedded protostar is far larger than the previously reported few intermediate-mass and two protostellar members of the cloud. Most of the newly discovered stars have masses of 0.2-0.7 Msolar, and 9% - 15% have K-band excesses from inner protoplanetary disks. X-ray properties provide an independent distance estimate consistent with the unusual location of CG 12 >~200 pc above the Galactic plane. The star formation efficiency in CG 12 appears to be 15% - 35%, far above that seen in other triggered molecular globules. The median photometric age found for the T Tauri population, assuming Siess et al. (2000, A&A, 358, 593) isochrones, is ~4 Myr with a large spread of <1 - 20 Myr and ongoing star formation in the molecular cores. The stellar age and spatial distributions are inconsistent with a simple radiation-driven implosion (RDI) model and suggest either that CG 12 is an atypically large shocked globule or that it has been subject to several distinct episodes of triggering and ablation. In their paper the authors report a previously unnoticed group of B-type stars northwest of CG 12 that may be the remnants of an OB association that produced multiple supernova explosions that could have shocked and ablated the cloud over a 15 - 30 Myr period. HD 120958 (B3e), the most luminous member of the group, may be currently driving an RDI shock into the CG 12 cloud. The current project combines four X-ray observations of the globule: <pre> Field ObsID Start Time Expo. R.A. Decl. Roll Angle (UT) (ks) (J2000.0) (deg) I.... 6423 2006 Apr 15 16:19:17 30.8 13 57 44.52 39 58 48.31 11.5 II... 6424 2006 Jun 02 07:25:09 3.1 13 57 42.87 39 43 01.76 285.0 III.. 6425 2006 Apr 13 08:44:08 3.1 13 56 19.40 39 42 47.94 14.7 IV... 6426 2006 Apr 15 12:54:20 3.1 13 56 19.40 39 58 48.09 11.1 </pre> where the units of right ascension are hours, minutes, and seconds, and the units of declination are degrees, arcminutes, and arcseconds, ObsID values are from the Chandra Observation Catalog, exposure times are the sum of Good Time Intervals (GTIs) for the CCD at the telescope aim point (CCD3) minus 1.3% to account for CCD readouts, and the aim points and roll angles are obtained from the satellite aspect solution before astrometric correction was applied. There is one primary field (I in Fig. 1 of the reference paper) with ~31 ks exposure directed at the globule's core and three secondary fields (II, III, and IV in Fig. 1) with ~3 ks exposures positioned contiguously to the north and west of the core. The primary pointing is intended to detect the population of pre-main sequence (PMS) stars forming in the molecular head of the globule. The secondary pointings are designed to locate an older population of stars expected if the present cloud is only the ablated remnant of a larger cloud that experienced sequential star formation triggering events, similar to the sequence of stars found in the authors' Chandra study of IC 1396N (Getman et al. 2007, ApJ, 654, 316, available in Browse as the IC1396NCXO table). Source searching was performed with data images and exposure maps constructed at three spatial resolutions (0.5", 1.0", and 1.4" pixel-1) using the CIAO wavdetect tool. The authors ran wavdetect with a low threshold P = 10-5, which is highly sensitive but permits false detections at this point in the analysis. This was followed by visual examination to locate other candidate sources, mainly close doubles and candidate sources near the detection threshold. Using ACIS Extract, photons were extracted within polygonal contours of ~90% encircled energy using position-dependent models of the PSF. The background was measured locally in source-free regions. Due to the very low, spatially invariant ACIS-I background in the Chandra observations of CG 12, there is a one-to-one correspondence between a source's significance and net counts. Following the procedure of Getman et al. (2007, ApJ, 654, 316), the list of candidate sources ws trimmed to omit sources with fewer than ~5 estimated source net counts, net full-band counts/PSF fraction <~ 4.5. In the case of the CG 12 observations, the above criterion is equivalent to accepting sources with a source significance of >~ 1.1. Thus, most of the statistically insignificant source candidates found during the wavdetect step were eliminated by the application of these source existence criteria. For Chandra sources with > 20 net counts, the authors performed spectral analysis with the XSPEC spectral fitting package version 12.2. The unbinned source and background spectra were fitted with one-temperature APEC plasma emission models using the maximum likelihood method. They assumed 0.3 times solar elemental abundances previously suggested as typical for young stellar objects (YSOs) in other star-forming regions. Solar abundances were taken from Anders & Grevesse (1989, Geochim. Cosmochim. Acta, 53, 197). X-ray absorption was modeled using the atomic cross sections of Morrison & McCammon (1983, ApJ, 270, 119). For absorbed thermal spectra characteristics of PMS stars, the absorption NH can be estimated to roughly a factor of 2 precision for 20 count sources. This table was created by the HEASARC in October 2010 based on the electronic versions of Tables 2, 3 and 4 from the paper which were obtained from the CDS (their catalog J/ApJ/673/331). This is a service provided by NASA HEASARC . 2008ApJ...673..331G https://heasarc.gsfc.nasa.gov/W3Browse/all/cg12cxo.html Catalog Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=cg12cxo& GET text/xml 180 99999 true 209.3667 -40.146102 0.0166666666666667 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=cg12cxo GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_cg12cxo&Action=More+Options&Action=Parameter+Search&ConeAdd=1 CHANDRA 0.0166666666666667 Infrared Optical X-ray public cg12cxo CG 12 Chandra X-Ray Point Source Catalog name Source Designation (CXOU JHHMMSS.dd+DDMMSS.s) meta.id;meta.main char nullable alt_name Alternative Catalog-Based Source Designation meta.id char nullable ra Right Ascension degree pos.eq.ra;meta.main double nullable dec Declination degree pos.eq.dec;meta.main double nullable error_radius Positional Uncertainty arcsec stat.error;pos double nullable counts Estimated Net Counts from Extracted Area in Total Energy Band 0.5-8.0keV ct phot;em.X-ray double nullable counts_error RMS Uncertainty for Estimated Net Counts in Total Energy Band ct stat.error;phot;em.X-ray double nullable rmag R Magnitude mag phot.mag;em.opt.R double nullable rmag_error RMS Uncertainty on R Magnitude mag stat.error;phot.mag;em.opt.R double nullable jmag 2MASS J Magnitude mag phot.mag;em.IR.J double nullable jmag_error RMS Uncertainty on Jmag mag stat.error;phot.mag;em.IR.J double nullable "__x_ra_dec" System unit vector column double nullable "__y_ra_dec" System unit vector column double nullable "__z_ra_dec" System unit vector column double nullable "__row" System index column char nullable twomass_name 2MASS Source Designation (2MASS JHHMMSSss+DDMMSSs) meta.id.assoc char nullable psf_fraction Fraction of PSF at Fiducial Energy of 1.497keV Enclosed within Extracted Area instr.det.psf double nullable best_pm_dec Best Proper Motion Along Declination mas/yr pos.pm;pos.eq.dec double nullable exposure Source Effective Exposure (s) s time.duration;obs.exposure double nullable snr Source Significance in Sigma stat.snr;phot;em.X-ray double nullable log_nh Best-Fit Value of the Column Density log(cm^-2) phys.columnDensity double nullable best_pm_dec_error RMS Uncertainty for Best Proper Motion in Declination mas/yr stat.error;pos.pm;pos.eq.dec double nullable log_hb_lx_obs_error RMS Uncertainty for Logarithm of Hard Band (2-8keV) X-Ray Luminosity log(erg/s) stat.error;phys.luminosity;em.X-ray.medium double nullable mmb2004b_name Source Identifier from Maheswar et al. (2004, Cat. <J/MNRAS/355/1272>) meta.id.assoc char nullable lii Galactic Longitude degree pos.galactic.lon double nullable apec_kt Best-Fit Value for Plasma Temperature keV phys.temperature double nullable log_hb_lx_obs Logarithm of Hard Band (2-8keV) X-Ray Luminosity log(erg/s) phys.luminosity;em.X-ray.medium double nullable log_lx_obs_error RMS Uncertainty for Logarithm of Total Band (-0.5-8keV) X-Ray Luminosity log(erg/s) stat.error;phys.luminosity;em.X-ray double nullable hb_counts Estimated Net Counts from Extracted Area in Hard Energy Band 2-8keV ct phot;em.X-ray.medium double nullable var_flag Flag [abc] Indicates Variability Characterization Based on K-S Statistics meta.code;src.var char nullable cxo_nomad_offset Chandra-NOMAD Positional Offset arcsec pos.angDistance;em.X-ray;em.opt double nullable nomad_name NOMAD Source Identification (NOMAD1 NNNN-NNNNNNN) meta.id.assoc char nullable best_pm_ra_error RMS Uncertainty for Best Proper Motion in RA mas/yr stat.error;pos.pm;pos.eq.ra double nullable log_hb_lx Logarithm of Hard Band (2-8keV) Absorption-Corrected X-Ray Luminosity log(erg/s) phys.luminosity;em.X-ray.medium double nullable apec_kt_pos_err Upper Error on kT keV stat.error;phys.temperature double nullable log_bck_prob Logarithm of K-S Probability That Background and Source Spectra Are Same stat.probability double nullable ks_mag_error RMS Uncertainty on Ks Magnitude mag stat.error;phot.mag;em.IR.K double nullable source_flags Flags [ge] Indicate Source Anomalies char nullable source_number Sequential Identification Number for Each Source in Field meta.id;src short nullable log_lx Logarithm of Total Band (-0.5-8keV) Absorption-Corrected X-Ray Luminosity log(erg/s) phys.luminosity;em.X-ray double nullable off_axis Off-Axis Angle arcmin instr.offset double nullable median_energy Background-Corrected Median Photon Energy in the Total 0.5-8keV Energy Band keV phys.energy double nullable vmag_error RMS Uncertainty on V Magnitude mag stat.error;phot.mag;em.opt.V double nullable best_pm_ra Best Proper Motion in RA (pmRA*cosDE) mas/yr pos.pm;pos.eq.ra double nullable vmag V Magnitude mag phot.mag;em.opt.V double nullable twomass_flags Flags Indicates 2MASS Photometry Quality and Confusion-Contamination meta.code char nullable bii Galactic Latitude degree pos.galactic.lat double nullable ks_mag 2MASS Ks Magnitude mag phot.mag;em.IR.K double nullable cxo_2mass_offset Chandra-2MASS Positional Offset arcsec pos.angDistance;em.X-ray;em.IR double nullable log_nh_neg_err Lower Error on Log_NH log(cm^-2) stat.error;phys.columnDensity double nullable apec_kt_neg_err Lower Error on kT keV stat.error;phys.temperature double nullable log_nh_pos_err Upper Error on Log_NH log(cm^-2) stat.error;phys.columnDensity double nullable hmag 2MASS H Magnitude mag phot.mag;em.IR.H double nullable field_code Chandra ACIS-I Field Surveyed in the CG 12 Region meta.id;obs.field char nullable log_hb_lx_error RMS Uncertainty for Log of Hard Band Absorption-Corrected X-Ray Luminosity log(erg/s) stat.error;phys.luminosity;em.X-ray.medium double nullable log_lx_obs Logarithm of Total Band (-0.5-8keV) X-Ray Luminosity log(erg/s) phys.luminosity;em.X-ray double nullable log_lx_error RMS Uncertainty for Total Band (-0.5-8keV) Absorption-Corrected X-Ray Luminosity log(erg/s) stat.error;phys.luminosity;em.X-ray double nullable hmag_error RMS Uncertainty on Hmag mag stat.error;phot.mag;em.IR.H double nullable bck_counts Estimated Background Counts from Extracted Area in Total Energy Band ct phot;instr.background;em.X-ray double nullable