- ID:
- ivo://CDS.VizieR/J/A+A/542/A16
- Title:
- X-ray detection of radio-selected SF galaxies
- Short Name:
- J/A+A/542/A16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- X-ray surveys contain sizable numbers of star forming galaxies, beyond the AGN which usually make the majority of detections. Many methods to separate the two populations are used in the literature, based on X-ray and multiwavelength properties. We aim at a detailed test of the classification schemes and to study the X-ray properties of the resulting samples. We build on a sample of galaxies selected at 1.4GHz in the VLA-COSMOS survey, classified by Smolcic et al. (2008ApJS..177...14S) according to their optical colours and observed with Chandra. A similarly selected control sample of AGN is also used for comparison. We review some X-ray based classification criteria and check how they affect the sample composition. The efficiency of the classification scheme devised by Smolcic et al. (2008ApJS..177...14S) is such that ~30% of composite/misclassified objects are expected because of the higher X-ray brightness of AGN with respect to galaxies. The latter fraction is actually 50% in the X-ray detected sources, while it is expected to be much lower among X-ray undetected sources. Indeed, the analysis of the stacked spectrum of undetected sources shows, consistently, strongly different properties between the AGN and galaxy samples. X-ray based selection criteria are then used to refine both samples. The radio/X-ray luminosity correlation for star forming (SF) galaxies is found to hold with the same X-ray/radio ratio valid for nearby galaxies. Some evolution of the ratio may be possible for sources at high redshift or high luminosity, tough it is likely explained by a bias arising from the radio selection. Finally, we discuss the X-ray number counts of star forming galaxies from the VLA- and C-COSMOS surveys according to different selection criteria, and compare them to the similar determination from the Chandra Deep Fields. The classification scheme proposed here may find application in future works and surveys.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/721/1368
- Title:
- X-ray emission from the Sombrero galaxy
- Short Name:
- J/ApJ/721/1368
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of discrete X-ray sources in and around the bulge-dominated, massive Sa galaxy, Sombrero (M104), based on new and archival Chandra observations with a total exposure of ~200ks. With a detection limit of L_X_~10^37^erg/s and a field of view covering a galactocentric radius of ~30kpc (11.5'), 383 sources are detected. Cross-correlation with Spitler et al.'s catalog of Sombrero globular clusters (GCs) (Cat. J/AJ/132/1593) identified from HST/ACS observations reveals 41 X-ray sources in GCs, presumably low-mass X-ray binaries (LMXBs). We quantify the differential luminosity functions (LFs) for both the detected GC and field LMXBs, whose power-law indices (~1.1 for the GC-LF and ~1.6 for field-LF) are consistent with previous studies for elliptical galaxies. With precise sky positions of the GCs without a detected X-ray source, we further quantify, through a fluctuation analysis, the GC-LF at fainter luminosities down to 10^35^erg/s. We also detect 101 sources in the halo of Sombrero. The presence of these sources cannot be interpreted as galactic LMXBs whose spatial distribution empirically follows the starlight. Their number is also higher than the expected number of cosmic active galactic nuclei (52+/-11 [1{sigma}]) whose surface density is constrained by deep X-ray surveys.
- ID:
- ivo://CDS.VizieR/J/MNRAS/376/960
- Title:
- X-ray emission from the Sombrero galaxy (NGC 4594)
- Short Name:
- J/MNRAS/376/960
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an X-ray study of the massive edge-on Sa galaxy, Sombrero (M 104; NGC 4594), based on XMM-Newton and Chandra observations. A list of 62 XMM-Newton and 175 Chandra discrete X-ray sources is provided, the majority of which are associated with the galaxy. Spectral analysis is carried out for relatively bright individual sources and for an accumulated source spectrum.
- ID:
- ivo://CDS.VizieR/J/ApJ/706/810
- Title:
- X-ray emitters in the Groth-Westphal strip
- Short Name:
- J/ApJ/706/810
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Groth field is one of the sky regions that will be targeted by the OSIRIS Tunable Filter Emission Line Object survey in the optical 820nm and 920nm atmospheric windows. In the present paper, public Chandra X-ray data with total exposure time of 200ks are analyzed and combined with optical broadband data of the Groth field, in order to study a set of optical structural parameters of the X-ray emitters and its relation with X-ray properties. To this aim, we processed the raw, public X-ray data using the Chandra Interactive Analysis of Observations, and determined and analyzed different structural parameters, in order to produce a morphological classification of X-ray sources. We present the morphology of 340 X-ray emitters with optical counterpart detected. Objects have been classified by X-ray type using a diagnostic diagram relating X-ray-to-optical ratio (X/O) to hardness ratio. We did not find any clear correlation between X-ray and morphological types. We analyzed the angular clustering of X-ray sources with optical counterpart using two-point correlation functions. A significant positive angular clustering was obtained from a preliminary analysis of four subsamples of the X-ray sources catalog. The clustering signal of the optically extended counterparts is similar to that of strongly clustered populations like red and very red galaxies, suggesting that the environment plays an important role in active galactic nuclei phenomena. Finally, we combined optical structural parameters with other X-ray and optical properties, and we confirmed an anticorrelation between the X/O ratio and the Abraham concentration index, which might suggest that early-type galaxies have lower Eddington rates than those of late-type galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/435/799
- Title:
- X-ray emitting normal galaxies from BMW-HRI
- Short Name:
- J/A+A/435/799
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We obtained a sample of 143 normal galaxies with X-ray luminosity in the range 10^38^-10^43^erg/s from the cross-correlation of the ROSAT HRI Brera Multi-scale Wavelet (BMW-HRI) Catalogue with the Lyon-Meudon Extragalactic Database (LEDA). We find that the average X-ray properties of this sample are in good agreement with those of other samples of galaxies in the literature. We selected a complete flux limited serendipitous sample of 32 galaxies from which we derived the logN-logS distribution of normal galaxies in the flux range 1.1-110x10^-14^erg/cm^2^/s. The resulting distribution is consistent with the Euclidean -1.5 slope. Comparisons with other samples, such as the Extended Medium Sensitivity Survey, the ROSAT All Sky Survey, the XMM-Newton/2dF survey, and the Chandra Deep Field Survey indicate that the logN-logS distribution of normal galaxies is consistent with a Euclidean slope over a flux range of about 6 decades. Description:
- ID:
- ivo://CDS.VizieR/J/ApJ/790/16
- Title:
- X-ray ETGs properties in the Chandra COSMOS survey
- Short Name:
- J/ApJ/790/16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study a sample of 69 X-ray detected early-type galaxies (ETGs), selected from the Chandra COSMOS survey, to explore the relation between the X-ray luminosity of hot gaseous halos (L_X, gas_) and the integrated stellar luminosity (L_K_) of the galaxies, in a range of redshift extending out to z = 1.5. In the local universe, a tight, steep relationship has been established between these two quantities (L_x.gas_ ~ L_K_^4.5^), suggesting the presence of largely virialized halos in X-ray luminous systems. We use well-established relations from the study of local universe ETGs, together with the expected evolution of the X-ray emission, to subtract the contribution of low-mass X-ray binary populations from the X-ray luminosity of our sample. Our selection minimizes the presence of active galactic nuclei (AGNs), yielding a sample representative of normal passive COSMOS ETGs; therefore, the resulting luminosity should be representative of gaseous halos, although we cannot exclude other sources such as obscured AGNs or enhanced X-ray emission connected with embedded star formation in the higher-z galaxies. We find that most of the galaxies with estimated L_X_< 10^42^ erg/s and z < 0.55 follow the L_X, gas_-L_K_ relation of local universe ETGs. For these galaxies, the gravitational mass can be estimated with a certain degree of confidence from the local virial relation. However, the more luminous (10^42^ erg/s <L_X_< 10^43.5^ erg/s) and distant galaxies present significantly larger scatter; these galaxies also tend to have younger stellar ages. The divergence from the local L_X, gas_-L_K_relation in these galaxies implies significantly enhanced X-ray emission up to a factor of 100 larger than predicted from the local relation. We discuss the implications of this result for the presence of hidden AGNs, and the evolution of hot halos, in nuclear and star formation feedback.
- ID:
- ivo://CDS.VizieR/J/ApJ/765/117
- Title:
- X-ray group of galaxies in AEGIS
- Short Name:
- J/ApJ/765/117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a search for extended X-ray sources and their corresponding galaxy groups from 800ks Chandra coverage of the All-wavelength Extended Groth Strip International Survey (AEGIS). This yields one of the largest X-ray-selected galaxy group catalogs from a blind survey to date. The red-sequence technique and spectroscopic redshifts allow us to identify 100% of reliable sources, leading to a catalog of 52 galaxy groups. These groups span the redshift range z~0.066-1.544 and virial mass range M_200_~1.3-13.3x10^13^^M_{sun}_. For the 49 extended sources that lie within DEEP2 and DEEP3 Galaxy Redshift Survey coverage, we identify spectroscopic counterparts and determine velocity dispersions. We select member galaxies by applying different cuts along the line of sight or in projected spatial coordinates. A constant cut along the line of sight can cause a large scatter in scaling relations in low-mass or high-mass systems depending on the size of the cut. A velocity-dispersion-based virial radius can cause a larger overestimation of velocity dispersion in comparison to an X-ray-based virial radius for low-mass systems. There is no significant difference between these two radial cuts for more massive systems. Independent of radial cut, an overestimation of velocity dispersion can be created in the case of the existence of significant substructure and compactness in X-ray emission, which mostly occur in low-mass systems. We also present a comparison between X-ray galaxy groups and optical galaxy groups detected using the Voronoi-Delaunay method for DEEP2 data in this field.
- 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.
- 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.
- ID:
- ivo://CDS.VizieR/J/A+A/533/A52
- Title:
- X-ray monitoring of M31 novae
- Short Name:
- J/A+A/533/A52
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Context. Classical novae (CNe) represent the major class of supersoft X-ray sources (SSSs) in the central region of the galaxy M31. We performed a dedicated monitoring of the M31 central region with XMM-Newton and Chandra between Nov 2007 and Feb 2008 and between Nov 2008 and Feb 2009, respectively, to find SSS counterparts of CNe, determine the duration of their SSS phase, and derive physical outburst parameters. We systematically searched our data for X-ray counterparts of CNe, determined their X-ray light curves and characterised their spectra using blackbody fits and white dwarf (WD) atmosphere models. Additionally, we determined luminosity upper limits for all previously known X-ray emitting novae that are not detected any more and for all CNe in our field of view with optical outbursts between one year before the start of the X-ray monitoring (Oct 2006) and its end (Feb 2009).