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2721. Chandra X-ray sources in NGC 2362
ID:
ivo://CDS.VizieR/J/A+A/460/133
Title:
Chandra X-ray sources in NGC 2362
Short Name:
J/A+A/460/133
Date:
21 Oct 2021
Publisher:
CDS
Description:
We observed the young cluster NGC 2362 in X-rays with Chandra ACIS-I, and detected 387 point X-ray sources, most of which are shown to be cluster members. We report here the list of all detected X-ray sources and their basic X-ray properties, and report separately their identifications with optical stars, using data from Moitinho et al. (2001ApJ...563L..73M; UBVRI photometry) and Dahm (2005, Cat. <J/AJ/130/1805>; H{alpha} data). We include in the second table a classification of optically-identified X-ray sources, based on position in the HR diagram, which helps to separate rather clearly cluster members from field objects.
2722. Chandra X-ray sources in {omega} Cen
ID:
ivo://CDS.VizieR/J/ApJ/697/224
Title:
Chandra X-ray sources in {omega} Cen
Short Name:
J/ApJ/697/224
Date:
21 Oct 2021
Publisher:
CDS
Description:
We analyze a ~70ks Chandra Advanced CCD Imaging Spectrometer exposure of the globular cluster {omega} Cen (NGC 5139). The ~17'x17' field of view fully encompasses three core radii and almost twice the half-mass radius. We detect 180 sources to a limiting flux of ~4.3x10^-16^erg/cm^2^/s (L_x_=1.2x10^30^erg/s at 4.9kpc). After accounting for the number of active galactic nuclei and possible foreground stars, we estimate that 45-70 of the sources are cluster members. Four of the X-ray sources have previously been identified as compact accreting binaries in the cluster - three cataclysmic variables (CVs) and one quiescent neutron star. Correlating the Chandra positions with known variable stars yields eight matches, of which five are probable cluster members that are likely to be binary stars with active coronae. Extrapolating these optical identifications to the remaining unidentified X-ray source population, we estimate that 20-35 of the sources are CVs and a similar number are active binaries. This likely represents most of the CVs in the cluster, but only a small fraction of all the active binaries.
2723. Chandra X-ray sources in Orion Nebula Cluster
ID:
ivo://CDS.VizieR/J/ApJ/582/382
Title:
Chandra X-ray sources in Orion Nebula Cluster
Short Name:
J/ApJ/582/382
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this first of two companion papers on the Orion Nebula Cluster (ONC), we present our analysis of a 63ks Chandra HRC-I observation that yielded 742 X-ray detections within the 30'x30' field of view. To facilitate our interpretation of the X-ray image, here we collect a multiwavelength catalog of nearly 2900 known objects in the region by combining 17 different catalogs from the recent literature. We define two reference groups: an infrared sample, containing all objects detected in the K band, and an optical sample comprising low-extinction, well-characterized ONC members. We show for both samples that field object contamination is generally low. Our X-ray sources are primarily low-mass ONC members. The detection rate for optical sample stars increases monotonically with stellar mass from zero at the brown dwarf limit to ~100% for the most massive stars but shows a pronounced dip between 2 and 10M_{sun}_. We determine L_X_ and L_X_/L_bol_ or all stars in our optical sample and utilize this information in our companion paper to study correlations between X-ray activity and other stellar parameters.
2724. Chandra X-Ray sources in the {gamma} Cyg Field
ID:
ivo://CDS.VizieR/J/ApJ/615/897
Title:
Chandra X-Ray sources in the {gamma} Cyg Field
Short Name:
J/ApJ/615/897
Date:
21 Oct 2021
Publisher:
CDS
Description:
In search of the counterpart to the brightest unidentified gamma-ray source, 3EG J2020+4017 (2CG 078+2), we report on new X-ray and radio observations of the {gamma} Cygni field with the Chandra X-Ray Observatory and with the Green Bank Telescope (GBT). We also report on reanalysis of archival ROSAT data.
2725. Chandra X-ray sources in the globular cluster 47 Tuc
ID:
ivo://CDS.VizieR/J/ApJ/876/59
Title:
Chandra X-ray sources in the globular cluster 47 Tuc
Short Name:
J/ApJ/876/59
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using archival Chandra observations with a total exposure of 510ks, we present an updated catalog of point sources for globular cluster (GC) 47 Tucanae. Our study covers an area of ~176.7'^2^ (i.e., with R<~7.5') with 537 X-ray sources. We show that the surface density distribution of X-ray sources in 47 Tuc is highly peaked in the cluster center, rapidly decreases at intermediate radii, and finally rises again at larger radii, with two distribution dips at R~100" and R~170" for the faint (L_X_>~5.0x10^30^erg/s) and bright (L_X_<~5.0x10^30^erg/s) groups of X-ray sources, respectively. These distribution features are similar to those of blue straggler stars (BSSs), where the distribution dip is located at R~200". By fitting the radial distribution of each group of sources with a "generalized King model", we estimated an average mass of 1.51+/-0.17M_{sun}_, 1.44+/-0.15M_{sun}_ and 1.16+/-0.06M_{sun}_ for the BSSs, bright X-ray sources, and faint X-ray sources, respectively. These results are consistent with the mass segregation effect of heavy objects in GCs, where more massive objects drop to the cluster center faster and their distribution dip propagates outward further. Besides, the peculiar distribution profiles of X-ray sources and BSSs are also consistent with the mass segregation model of binaries in GCs, which suggests that, in addition to the dynamical formation channel, primordial binaries are also a significant contributor to the X-ray source population in GCs.
2726. Chandra X-ray sources of NGC 1068
ID:
ivo://CDS.VizieR/J/ApJ/591/138
Title:
Chandra X-ray sources of NGC 1068
Short Name:
J/ApJ/591/138
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an analysis of the compact X-ray source population in the Seyfert 2 galaxy NGC 1068, imaged with a 50ks Chandra observation. We find a total of 84 compact sources on the S3 chip, of which 66 are located within the 25.0B-mag/arcsec^2^ isophote of the galactic disk of NGC 1068. Spectra have been obtained for the 21 sources with at least 50 counts and modeled with both multicolor disk blackbody and power-law models.
2727. Chandra X-ray sources of NGC 1399
ID:
ivo://CDS.VizieR/J/ApJ/736/90
Title:
Chandra X-ray sources of NGC 1399
Short Name:
J/ApJ/736/90
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a wide-field study of the globular cluster (GC)/low-mass X-ray binary (LMXB) connection in the giant elliptical NGC 1399. The large field of view of the Advanced Camera for Surveys/WFC, combined with Hubble Space Telescope and Chandra high resolution, allow us to constrain the LMXB formation scenarios in elliptical galaxies. We confirm that NGC 1399 has the highest LMXB fraction in GCs of all nearby elliptical galaxies studied so far, even though the exact value depends on galactocentric distance due to the interplay of a differential GC versus galaxy light distribution and the GC color dependence. In fact, LMXBs are preferentially hosted by bright, red GCs out to >5R_eff_ of the galaxy light. The finding that GCs hosting LMXBs follow the radial distribution of their parent GC population argues against the hypothesis that the external dynamical influence of the galaxy affects the LMXB formation in GCs. On the other hand, field-LMXBs closely match the host galaxy light, thus indicating that they are originally formed in situ and not inside GCs. We measure GC structural parameters, finding that the LMXB formation likelihood is influenced independently by mass, metallicity, and GC structural parameters. In particular, the GC central density plays a major role in predicting which GCs host accreting binaries. Finally, our analysis shows that LMXBs in GCs are marginally brighter than those in the field, and in particular the only color-confirmed GC with L_X_>10^39^erg/s shows no variability, which may indicate a superposition of multiple LMXBs in these systems.
2728. Chandra X-ray sources toward Galactic Center
ID:
ivo://CDS.VizieR/J/ApJ/589/225
Title:
Chandra X-ray sources toward Galactic Center
Short Name:
J/ApJ/589/225
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a catalog of 2357 point sources detected during 590ks of Chandra observations of the 17x17' field around Sgr A*. This field encompasses a physical area of 40x40pc at a distance of 8kpc. The completeness limit of the sample at the Galactic center is 10^31^erg/s (2.0-8.0keV), while the detection limit is an order of magnitude lower. The 281 sources detected below 1.5keV are mainly in the foreground of the Galactic center, while comparisons to the Chandra deep fields at high Galactic latitudes suggest that only about 100 of the observed sources are background AGNs.
2729. CHANG-ES. IV. VLA D-configuration observations
ID:
ivo://CDS.VizieR/J/AJ/150/81
Title:
CHANG-ES. IV. VLA D-configuration observations
Short Name:
J/AJ/150/81
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the first part of the observations made for the Continuum Halos in Nearby Galaxies, an EVLA Survey (CHANG-ES) project. The aim of the CHANG-ES project is to study and characterize the nature of radio halos, their prevalence as well as their magnetic fields, and the cosmic rays illuminating these fields. This paper reports observations with the compact D configuration of the Karl G. Jansky Very Large Array (VLA) for the sample of 35 nearby edge-on galaxies of CHANG-ES. With the new wide bandwidth capabilities of the VLA, an unprecedented sensitivity was achieved for all polarization products. The beam resolution is an average of 9.6" and 36" with noise levels reaching approximately 6 and 30{mu}Jy/beam for C- and L-bands, respectively (robust weighting). We present intensity maps in these two frequency bands (C and L), with different weightings, as well as spectral index maps, polarization maps, and new measurements of star formation rates (SFRs). The data products described herein are available to the public in the CHANG-ES data release available at http://www.queensu.ca/changes. We also present evidence of a trend among galaxies with larger halos having higher SFR surface density, and we show, for the first time, a radio continuum image of the median galaxy, taking advantage of the collective signal-to-noise ratio of 30 of our galaxies. This image shows clearly that a "typical" spiral galaxy is surrounded by a halo of magnetic fields and cosmic rays.
2730. CHAOS IV: NGC3184 LBT obs. & 3 other gal. abundances
ID:
ivo://CDS.VizieR/J/ApJ/893/96
Title:
CHAOS IV: NGC3184 LBT obs. & 3 other gal. abundances
Short Name:
J/ApJ/893/96
Date:
07 Mar 2022 07:28:28
Publisher:
CDS
Description:
The chemical abundances of spiral galaxies, as probed by HII regions across their disks, are key to understanding the evolution of galaxies over a wide range of environments. We present Large Binocular Telescope/Multi-Object Double Spectrographs spectra of 52 HII regions in NGC 3184 as part of the CHemical Abundances Of Spirals (CHAOS) project. We explore the direct-method gas-phase abundance trends for the first four CHAOS galaxies, using temperature measurements from one or more auroral-line detections in 190 individual HII regions. We find that the dispersion in T_e_-T_e_ relationships is dependent on ionization, as characterized by F_{lambda}5007_/F_{lambda}3727_, and so we recommend ionization-based temperature priorities for abundance calculations. We confirm our previous results that [NII] and [SIII] provide the most robust measures of electron temperature in low-ionization zones, while [OIII] provides reliable electron temperatures in high-ionization nebula. We measure relative and absolute abundances for O, N, S, Ar, and Ne. The four CHAOS galaxies marginally conform with a universal O/H gradient, as found by empirical integral field unit studies when plotted relative to effective radius. However, after adjusting for vertical offsets, we find a tight universal N/O gradient of {alpha}_N/O_=-0.33dex/R_e_ with {sigma}_tot._=0.08 for R_g_/R_e_<2.0, where N is dominated by secondary production. Despite this tight universal N/O gradient, the scatter in the N/O-O/H relationship is significant. Interestingly, the scatter is similar when N/O is plotted relative to O/H or S/H. The observable ionic states of S probe lower ionization and excitation energies than O, which might be more appropriate for characterizing abundances in metal-rich HII regions.

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