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741. CFHT ugi photometry of globular clusters in M85
ID:
ivo://CDS.VizieR/J/ApJ/872/202
Title:
CFHT ugi photometry of globular clusters in M85
Short Name:
J/ApJ/872/202
Date:
21 Oct 2021
Publisher:
CDS
Description:
We survey globular clusters (GCs) in M85 using ugi-band images of a 1{deg}x1{deg} field obtained with the MegaCam at the 3.6m Canada-France-Hawaii Telescope. We identify 1318 GC candidates with 20.0mag<g_0_<23.5mag in the entire survey region. Their radial number density profile is well fit by a Sersic profile with n=2.58_-0.33_^+0.43^ and effective radius R_e,GCS_=4.14' (=22kpc), showing that the candidates at R<20' are mostly genuine GCs in M85. We estimate the total number of GCs, N(total)=1216_-50_^+82^, and the specific frequency, S_N_=1.41_-0.06_^+0.10^. The overall color distribution of the GCs in M85 is bimodal, but the GCs in the central region at R<2' do not show a bimodal distribution clearly. The radial number density profile and surface number density map of the blue GCs (BGCs) show more extended structures than those of the red GCs (RGCs). The spatial distributions of both BGCs and RGCs are elongated, similar to that of the galaxy stellar light. The number fraction of the RGCs in the central region is much smaller compared to those in other early-type galaxies of similar luminosity. The mean (g-i)_0_ color of the RGCs in M85 is about 0.1mag bluer than typical values for other Virgo early-type galaxies of similar luminosity, indicating that a significant fraction of the RGCs in M85 may be younger than typical GCs. These results indicate that M85 might have undergone a major wet merger recently.
742. CGS. V. Statistical study of bars and buckled bars
ID:
ivo://CDS.VizieR/J/ApJ/845/87
Title:
CGS. V. Statistical study of bars and buckled bars
Short Name:
J/ApJ/845/87
Date:
21 Oct 2021
Publisher:
CDS
Description:
Simulations have shown that bars are subject to a vertical buckling instability that transforms thin bars into boxy or peanut-shaped structures, but the physical conditions necessary for buckling to occur are not fully understood. We use the large sample of local disk galaxies in the Carnegie-Irvine Galaxy Survey to examine the incidence of bars and buckled bars across the Hubble sequence. Depending on the disk inclination angle (i), a buckled bar reveals itself as either a boxy/peanut-shaped bulge (at high i) or as a barlens structure (at low i). We visually identify bars, boxy/peanut-shaped bulges, and barlenses, and examine the dependence of bar and buckled bar fractions on host galaxy properties, including Hubble type, stellar mass, color, and gas mass fraction. We find that the barred and unbarred disks show similar distributions in these physical parameters. The bar fraction is higher (70%-80%) in late-type disks with low stellar mass (M*<10^10.5^M_{sun}_) and high gas mass ratio. In contrast, the buckled bar fraction increases to 80% toward massive and early-type disks (M*>10^10.5^M_{sun}_), and decreases with higher gas mass ratio. These results suggest that bars are more difficult to grow in massive disks that are dynamically hotter than low-mass disks. However, once a bar forms, it can easily buckle in the massive disks, where a deeper potential can sustain the vertical resonant orbits. We also find a probable buckling bar candidate (ESO506-G004) that could provide further clues to understand the timescale of the buckling process.
743. 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.
744. ChaMPlane X-ray sources in the Galactic bulge
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.
745. Chandra and AAOmega observations of Abell 2744
ID:
ivo://CDS.VizieR/J/ApJ/728/27
Title:
Chandra and AAOmega observations of Abell 2744
Short Name:
J/ApJ/728/27
Date:
21 Oct 2021
Publisher:
CDS
Description:
New Chandra X-ray data and extensive optical spectroscopy, obtained with AAOmega on the 3.9m Anglo-Australian Telescope, are used to study the complex merger taking place in the galaxy cluster Abell 2744. Combining our spectra with data from the literature provides a catalog of 1237 redshifts for extragalactic objects lying within 15' of the cluster center. From these, we confirm 343 cluster members projected within 3Mpc of the cluster center. Combining positions and velocities, we identify two major substructures, corresponding to the remnants of two major subclusters. The new data are consistent with a post-core-passage, major merger taking place along an axis that is tilted well out of the plane of the sky, together with an interloping minor merger. Supporting this interpretation, the new X-ray data reveal enriched, low entropy gas from the core of the approaching, major subcluster, lying ~2' north of the cluster center, and a shock front to the southeast of the previously known bright, compact core associated with the receding subcluster. The X-ray morphology of the compact core is consistent with a Bullet-like cluster viewed from within ~45{deg} of the merger axis. An X-ray peak ~3' northwest of the cluster center, with an associated cold front to the northeast and a trail of low entropy gas to the south, is interpreted as the remnant of an interloping minor merger taking place roughly in the plane of the sky. We infer approximate paths for the three merging components.
746. Chandra deep protocluster survey
ID:
ivo://CDS.VizieR/J/MNRAS/400/299
Title:
Chandra deep protocluster survey
Short Name:
J/MNRAS/400/299
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present X-ray point-source catalogues for a deep ~400ks Chandra ACIS-I (Advanced CCD Imaging Spectrometer) exposure of the SSA22 field. The observations are centred on a z=3.09 protocluster, which is populated by Lyman break galaxies (LBGs), Ly{alpha} emitters (LAEs) and extended Ly{alpha}-emitting blobs (LABs). The survey reaches ultimate (3 count) sensitivity limits of ~5.7x10^-17^ and ~3.0x10^-16^erg/cm^2^/s for the 0.5-2 and 2-8keV bands, respectively (corresponding to L_2-10keV_~5.7x10^42^erg/s and L_10-30keV_~2.0x10^43^erg/s at z=3.09, respectively, for an assumed photon index of {GAMMA}=1.4). These limits make SSA22 the fourth deepest extragalactic Chandra survey yet conducted, and the only one focused on a known high-redshift structure. In total, we detect 297 X-ray point sources and identify one obvious bright extended X-ray source over a ~330arcmin^2^ region. In addition to our X-ray catalogues, we provide all available optical spectroscopic redshifts and near-infrared and mid-infrared photometry available for our sources.
747. Chandra Galactic Bulge Survey
ID:
ivo://CDS.VizieR/J/MNRAS/458/4530
Title:
Chandra Galactic Bulge Survey
Short Name:
J/MNRAS/458/4530
Date:
21 Oct 2021
Publisher:
CDS
Description:
As part of the Chandra Galactic Bulge Survey (GBS), we present a catalogue of optical sources in the GBS footprint. This consists of two regions centered at Galactic latitude b=1.5{deg} above and below the Galactic Centre, spanning (lxb)=(6{deg}x1{deg}). The catalogue consists of 2 or more epochs of observations for each line of sight in r', i' and H{alpha} filters. The catalogue is complete down to r'=20.2 and i'=19.2mag; the mean 5{sigma} depth is r'=22.5 and i'=21.1mag. The mean root-mean-square residuals of the astrometric solutions is 0.04-arcsec. We cross-correlate this optical catalogue with the 1640 unique X-ray sources detected in Chandra observations of the GBS area, and nd candidate optical counterparts to 1480 X-ray sources. We use a false alarm probability analysis to estimate the contamination by interlopers, and expect ~10 0 per cent of optical counterparts to be chance alignments. To determine the most likely counterpart for each X-ray source, we compute the likelihood ratio for all optical sources within the 4{sigma} X-ray error circle. This analysis yields 1480 potential counterparts (~90 per cent of the sample). 584 counterparts have saturated photometry (r'<=17, i'<=16), indicating these objects are likely foreground sources and the real counterparts. 171 candidate counterparts are detected only in the i' -band. These sources are good qLMXB and CV candidates as they are X-ray bright and likely located in the Bulge.
748. Chandra multi-epoch study of the spiral gal. NGC7331
ID:
ivo://CDS.VizieR/J/ApJ/879/112
Title:
Chandra multi-epoch study of the spiral gal. NGC7331
Short Name:
J/ApJ/879/112
Date:
21 Oct 2021
Publisher:
CDS
Description:
X-ray point sources in galaxies are dominated by X-ray binaries (XRBs) that are variables or transients, and whether their variability would alter the X-ray luminosity functions (XLFs) is still in debate. Here we report on NGC 7331 as an example to test this with seven Chandra observations. Their detection limit is 7x10^37^erg/s in the energy range 0.3-8.0keV by assuming a power-law (PL) spectral model with a photon index of 1.7. We detected 55 X-ray sources. Thirteen of them are variables, of which three are transients, and some of the sources possess a bimodal feature in their luminosity-hardness ratio, which is often observed among XRBs. Nine more ultraluminous X-ray sources are found in comparison with previous studies and eight are likely to be low-mass or high-mass XRBs. Twenty-one optical counterpart candidates are found based on the Hubble Space Telescope images, but we cannot rule out the possibility of positional coincidence. The spectral analysis of SN 2014C shows a trend of increasing soft photons and decreasing hydrogen column densities as its outer shell expands. We fit the seven incompleteness-corrected XLFs to both a PL and a PL with an exponential cut-off (PLC) model using the Bayesian method, which is used for the first time in XLF fitting. The hierarchical PLC model can describe the XLF of NGC 7331 best with a slope of ~0.5 and a luminosity cut-off around 8x10^38^erg/s. This study proves that multi-epoch observations decrease the deviation due to the variable luminous sources in XLFs.
749. CHANDRA observations of NGC 2264
ID:
ivo://CDS.VizieR/J/AJ/127/2659
Title:
CHANDRA observations of NGC 2264
Short Name:
J/AJ/127/2659
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results of a Chandra observation of a field in NGC 2264. The observations were taken with the ACIS-I camera with an exposure time of 48.1ks. We present a catalog of 263 sources, which includes X-ray luminosity, optical and infrared photometry, and X-ray variability information. We found 41 variable sources, 14 of which have a flarelike light curve, and two of which have a pattern of a steady increase or decrease over a 10-hr period. The optical and infrared photometry for the stars identified as X-ray sources are consistent with most of these objects being premain-sequence stars with ages younger than 3Myr.
750. Chandra observations of 2106 radio-quiet QSOs
ID:
ivo://CDS.VizieR/J/MNRAS/492/719
Title:
Chandra observations of 2106 radio-quiet QSOs
Short Name:
J/MNRAS/492/719
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present Chandra observations of 2106 radio-quiet quasars in the redshift range 1.7<=z<=2.7 from the Sloan Digital Sky Survey (SDSS), through data release fourteen (DR14, 2018ApJS..235...42A), that do not contain broad absorption lines (BAL) in their rest-frame UV spectra. This sample adds over a decade worth of SDSS and Chandra observations to our previously published sample of 139 quasars from SDSS DR5 which is still used to correlate X-ray and optical/UV emission in typical quasars. We fit the SDSS spectra for 753 of the quasars in our sample that have high-quality (large exposure time and small off-axis observation angle) X-ray observations, and analyze their X-ray properties (aox and daox) with respect to the measured CIV and MgII emission-line rest-frame equivalent width (EW) and the CIV emission-line blueshift. We find significant correlations (at the >=99.99% level) between aox and these emission-line parameters, as well as between daox and CIV EW. Slight correlations are found between daox and CIV blueshift, MgII EW, and the ratio of CIV EW to MgII EW. The best-fit trend in each parameter space is used to compare the X-ray weakness (daox) and optical/UV emission properties of typical quasars and weak-line quasars (WLQs). The WLQs clearly deviate from the expectation for every relationship, typically exhibiting much weaker X-ray emission than predicted by the typical quasar relationships. The best-fit relationships for our typical quasars are consistent with predictions from the disk-wind quasar model. The behavior of the WLQs with respect to our typical quasars can be explained by an X-ray shielding model.