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25131. X-ray luminosities of early-type galaxies
ID:
ivo://CDS.VizieR/J/MNRAS/328/461
Title:
X-ray luminosities of early-type galaxies
Short Name:
J/MNRAS/328/461
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a catalogue of X-ray luminosities for 401 early-type galaxies, of which 136 are based on newly analysed ROSAT PSPC pointed observations (Cat. <IX/30>). The remaining luminosities are taken from the literature and converted to a common energy band, spectral model and distance scale. Using this sample we fit the L_X_/L_B_ relation for early-type galaxies and find a best-fit slope for the catalogue of ~2.2. We demonstrate the influence of group-dominant galaxies on the fit and present evidence that the relation is not well modelled by a single power-law fit. We also derive estimates of the contribution to galaxy X-ray luminosities from discrete-sources and conclude that they provide L_(discrete-source-contribution)_/L_B_~29.5erg/s/L_B{sun}_. We compare this result with luminosities from our catalogue. Lastly, we examine the influence of environment on galaxy X-ray luminosity and on the form of the L_X_/L_B_ relation. We conclude that although environment undoubtedly affects the X-ray properties of individual galaxies, particularly those in the centres of groups and clusters, it does not change the nature of whole populations.
25132. X-ray luminosities of SDSS DR7 clusters from RASS
ID:
ivo://CDS.VizieR/J/MNRAS/439/611
Title:
X-ray luminosities of SDSS DR7 clusters from RASS
Short Name:
J/MNRAS/439/611
Date:
21 Oct 2021
Publisher:
CDS
Description:
We use ROSAT All Sky Survey broad-band X-ray images and the optical clusters identified from Sloan Digital Sky Survey Data Release 7 to estimate the X-ray luminosities around ~65000 candidate clusters with masses >~10^13^h-1^M_{sun}_ based on an optical to X-ray (OTX) code we develop. We obtain a catalogue with X-ray luminosity for each cluster. This catalogue contains 817 clusters (473 at redshift z<=0.12) with signal-to-noise ratio >3 in X-ray detection. We find about 65% of these X-ray clusters have their most massive member located near the X-ray flux peak; for the rest 35%, the most massive galaxy is separated from the X-ray peak, with the separation following a distribution expected from a Navarro-Frenk-White profile. We investigate a number of correlations between the optical and X-ray properties of these X-ray clusters, and find that the cluster X-ray luminosity is correlated with the stellar mass (luminosity) of the clusters, as well as with the stellar mass (luminosity) of the central galaxy and the mass of the halo, but the scatter in these correlations is large. Comparing the properties of X-ray clusters of similar halo masses but having different X-ray luminosities, we find that massive haloes with masses >~10^14^h^-1^M_{sun}_ contain a larger fraction of red satellite galaxies when they are brighter in X-ray. An opposite trend is found in central galaxies in relative low-mass haloes with masses <~10^14^h^-1^M_{sun}_ where X-ray brighter clusters have smaller fraction of red central galaxies. Clusters with masses >~10^14^h^-1^M_{sun}_ that are strong X-ray emitters contain many more low-mass satellite galaxies than weak X-ray emitters. These results are also confirmed by checking X-ray clusters of similar X-ray luminosities but having different characteristic stellar masses. A cluster catalogue containing the optical properties of member galaxies and the X-ray luminosity is available at http://gax.shao.ac.cn/data/Group.html.
25133. X-ray luminosity functions of M37 low-mass stars
ID:
ivo://CDS.VizieR/J/ApJ/830/44
Title:
X-ray luminosity functions of M37 low-mass stars
Short Name:
J/ApJ/830/44
Date:
21 Oct 2021
Publisher:
CDS
Description:
We use a 440.5ks Chandra observation of the ~500Myr old open cluster M37 to derive the X-ray luminosity functions of its <=1.2M_{sun}_ stars. Combining detections of 162 M37 members with upper limits for 160 non-detections, we find that its G, K, and M stars have a similar median (0.5-7keV) X-ray luminosity L_X_=10^29.0^erg/s, whereas the L_X_-to-bolometric-luminosity ratio (L_X_/L_bol_) indicates that M stars are more active than G and K stars by ~1 order of magnitude at 500Myr. To characterize the evolution of magnetic activity in low-mass stars over their first ~600Myr, we consolidate X-ray and optical data from the literature for stars in six other open clusters: from youngest to oldest they are, the Orion Nebula Cluster (ONC), NGC 2547, NGC 2516, the Pleiades, NGC 6475, and the Hyades. For these, we homogenize the conversion of instrumental count rates to L_X_ by applying the same one-temperature emission model as for M37, and obtain masses using the same empirical mass-absolute magnitude relation (except for the ONC). We find that for G and K stars X-ray activity decreases ~2 orders of magnitude over their first 600Myr, and for M stars, ~1.5. The decay rate of the median L_X_ follows the relation L_X_{propto}t^b^, where b=-0.61+/-0.12 for G stars, -0.82+/-0.16 for K stars, and -0.40+/-0.17 for M stars. In L_X_/L_bol_ space, the slopes are -0.68+/-0.12, -0.81+/-0.19, and -0.61+/-0.12, respectively. These results suggest that for low-mass stars the age-activity relation steepens after ~625Myr, consistent with the faster decay in activity observed in solar analogs at t>1Gyr.
25134. X-ray luminosity-velocity dispersion relation
ID:
ivo://CDS.VizieR/J/ApJ/554/L129
Title:
X-ray luminosity-velocity dispersion relation
Short Name:
J/ApJ/554/L129
Date:
21 Oct 2021
Publisher:
CDS
Description:
We demonstrate that individual elliptical galaxies and clusters of galaxies form a continuous X-ray luminosity-velocity dispersion (L_X_-{sigma}) relation. Our samples of 280 clusters and 57 galaxies have L_X_ {prop.to}{sigma}^4.4^ and L_X_{prop.to}{sigma}^10^, respectively. This unified L_X_-{sigma} relation spans 8 orders of magnitude in L_X_ and is fully consistent with the observed and theoretical luminosity-temperature scaling laws. Our results support the notion that galaxies and clusters of galaxies are the luminous tracers of similar dark matter halos.
25135. X-ray-luminous galaxy cluster RX J0142.0+2131
ID:
ivo://CDS.VizieR/J/AJ/130/445
Title:
X-ray-luminous galaxy cluster RX J0142.0+2131
Short Name:
J/AJ/130/445
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a photometric and spectroscopic study of stellar populations in the X-ray-luminous cluster of galaxies RX J0142.0+2131 at z=0.280. This paper analyzes the results of high signal-to-noise ratio spectroscopy, as well as g'-, r'-, and i'-band imaging, using the Gemini Multi-Object Spectrograph on Gemini North.
25136. X-ray mass segregation effect in GCs. III. M28
ID:
ivo://CDS.VizieR/J/ApJ/892/16
Title:
X-ray mass segregation effect in GCs. III. M28
Short Name:
J/ApJ/892/16
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using archival Chandra observations with a total effective exposure of 323ks, we derive an updated catalog of point sources in the bulge globular cluster M28. The catalog contains 502 X-ray sources within an area of ~475arcmin^2^, and more than 90% of these sources are first detected in this cluster. We find significant dips in the radial distribution profiles of X-ray sources in M28, and the projected distance and width of the distribution dip for bright (L_X_>~4.5x10^30^erg/s) X-ray sources are larger than for faint (L_X_<~4.5x10^30^erg/s) sources. Fitting with the "generalized King model" gives a slightly larger average mass for the bright sources (1.30+/-0.15M_{sun}_) than for the faint ones (1.09+/-0.14M_{sun}_), which supports a universal delay in mass segregation between heavy objects in globular clusters. We show that the dynamical age of M28 is comparable to that of Terzan 5 and much smaller than that of 47 Tuc, but M28 is evolving faster (i.e., with a shorter two-body relaxation timescale) than 47 Tuc. These features may suggest an acceleration effect of cluster dynamical evolution by tidal shock in M28. Besides, we find an abnormal deficiency of X-ray sources in the central region (R<~1.5') of M28 compared with its outskirts, which indicates that M28 may have suffered an early phase of primordial binary disruption within its central region, and the mass segregation effect will erase such a phenomenon as clusters evolve to an older dynamical age.
25137. X-ray measurements of ChaMP-SDSS galaxies
ID:
ivo://CDS.VizieR/J/ApJ/705/1336
Title:
X-ray measurements of ChaMP-SDSS galaxies
Short Name:
J/ApJ/705/1336
Date:
21 Oct 2021
Publisher:
CDS
Description:
The combination of the Sloan Digital Sky Survey (SDSS) and the Chandra Multiwavelength Project (ChaMP; Green et al. 2004ApJS..150...43G) currently offers the largest and most homogeneously selected sample of nearby galaxies for investigating the relation between X-ray nuclear emission, nebular line emission, black hole masses, and properties of the associated stellar populations. We provide X-ray spectral fits and valid uncertainties for all the galaxies with counts ranging from 2 to 1325 (mean 76, median 19). We present here novel constraints that both X-ray luminosity L_X_ and X-ray spectral energy distribution bring to the galaxy evolutionary sequence HII->Seyfert/Transition Object->LINER->Passive suggested by optical data.
25138. X-ray & MIR AGNs in Stripe 82 with eBOSS spectra
ID:
ivo://CDS.VizieR/J/ApJ/876/50
Title:
X-ray & MIR AGNs in Stripe 82 with eBOSS spectra
Short Name:
J/ApJ/876/50
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the results of a Sloan Digital Sky Survey IV eBOSS program to target X-ray sources and mid-infrared-selected Wide-field Infrared Survey Explorer (WISE) active galactic nucleus (AGN) candidates in a 36.8deg^2^ region of Stripe 82. About half this survey (15.6deg^2^) covers the largest contiguous portion of the Stripe 82 X-ray survey. This program represents the largest spectroscopic survey of AGN candidates selected solely by their WISE colors. We combine this sample with X-ray and WISE AGNs in the field identified via other sources of spectroscopy, producing a catalog of 4847 sources that is 82% complete to r~22. Based on X-ray luminosities or WISE colors, 4730 of these sources are AGNs, with a median sample redshift of z~1. About 30% of the AGNs are optically obscured (i.e., lack broad lines in their optical spectra). BPT analysis, however, indicates that 50% of the WISE AGNs at z<0.5 have emission line ratios consistent with star-forming galaxies, so whether they are buried AGNs or star-forming galaxy contaminants is currently unclear. We find that 61% of X-ray AGNs are not selected as mid-infrared AGNs, with 22% of X-ray AGNs undetected by WISE. Most of these latter AGNs have high X-ray luminosities (Lx>10^44^erg/s), indicating that mid-infrared selection misses a sizable fraction of the highest luminosity AGNs, as well as lower luminosity sources where AGN-heated dust is not dominating the mid-infrared emission. Conversely, ~58% of WISE AGNs are undetected by X-rays, though we do not find that they are preferentially redder than the X-ray-detected WISE AGNs.
25139. X-ray & MIR luminosities of the GBT galaxies
ID:
ivo://CDS.VizieR/J/ApJ/892/18
Title:
X-ray & MIR luminosities of the GBT galaxies
Short Name:
J/ApJ/892/18
Date:
19 Jan 2022 08:55:44
Publisher:
CDS
Description:
We present an investigation of the dependence of H_2_O maser detection rates and properties on the mid-IR active galactic nucleus (AGN) luminosity, L_AGN_, and the obscuring column density, N_H_, based on mid-IR and hard X-ray photometry. Based on spectral energy distribution fitting that allows for decomposition of the black hole accretion and star formation components in the mid-infrared, we show that the megamaser (disk maser) detection rate increases sharply for galaxies with 12{mu}m AGN luminosity L_12um_^AGN^ greater than 10^42^erg/s, from <~3% (<~2%) to ~12% (~5%). By using the ratio of the observed X-ray to mid-IR AGN luminosity as an indicator of N_H_, we also find that megamaser (disk maser) detection rates are boosted to 15% (7%) and 20% (9%) for galaxies with N_H_>=10^23^/cm^2^ and N_H_>=10^24^cm^-2^, respectively. Combining these column density cuts with a constraint for high L_12um_^AGN^ (>=10^42^erg/s) predicts further increases in the megamaser (disk maser) detection rates to 19% (8%) and 27% (14%), revealing unprecedented potential increases of the megamaser and disk maser detection rates by a factor of 7-15 relative to the current rates, depending on the chosen sample selection criteria. A noteworthy aspect of these new predictions is that the completeness rates are only compromised mildly, with the rates remaining at the level of ~95% (~50%) for sources with N_H_>=10^23^/cm^2^ (N_H_>=10^24^/cm^2^). Applying these selection methods to current X-ray AGN surveys predicts the detection of >~15 new megamaser disks.
25140. X-ray monitoring of 1ES 1927+654
ID:
ivo://CDS.VizieR/J/ApJS/255/7
Title:
X-ray monitoring of 1ES 1927+654
Short Name:
J/ApJS/255/7
Date:
06 Dec 2021 19:56:23
Publisher:
CDS
Description:
1ES 1927+654 is a nearby active galactic nucleus (AGN) that underwent a changing-look event in early 2018, developing prominent broad Balmer lines that were absent in previous observations. We have followed up this object in the X-rays with an ongoing campaign that started in 2018 May and that includes 265 NICER (for a total of 678ks) and 14 Swift/XRT (26ks) observations, as well as three simultaneous XMM-Newton/NuSTAR (158/169ks) exposures. In the X-rays, 1ES 1927+654 shows a behavior unlike any previously known AGN. The source is extremely variable both in spectral shape and flux and does not show any correlation between X-ray and UV flux on timescales of hours or weeks/months. After the outburst, the power-law component almost completely disappeared, and the source showed an extremely soft continuum dominated by a blackbody component. The temperature of the blackbody increases with the luminosity, going from kT~80eV (for a 0.3-2keV luminosity of L_0.3-2_~10^41.5^erg/s) to ~200eV (for L_0.3-2_~10^44^erg/s). The spectra show evidence of ionized outflows and of a prominent feature at ~1keV, which can be reproduced by a broad emission line. The unique characteristics of 1ES 1927+654 in the X-ray band suggest that it belongs to a new type of changing-look AGN. Future X-ray surveys might detect several more objects with similar properties.

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