- ID:
- ivo://CDS.VizieR/J/AJ/154/96
- Title:
- Groups of galaxies from from SDSS-DR7
- Short Name:
- J/AJ/154/96
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the dependence of stellar population properties of galaxies on group dynamical stage for a subsample of the Yang catalog. We classify groups according to their galaxy velocity distribution into Gaussian (G) and Non-Gaussian (NG). Using two totally independent approaches, we have shown that our measurement of Gaussianity is robust and reliable. Our sample covers Yang's groups in the redshift range 0.03{<=}z{<=}0.1, with mass {>=}10^14^M_{Sun}_. The new method, called Hellinger Distance, to determine whether a group has a velocity distribution Gaussian or NG is very effective in distinguishing between the two families. NG groups present halo masses higher than the G ones, confirming previous findings. Examining the skewness and kurtosis of the velocity distribution of G and NG groups, we find that faint galaxies in NG groups are mainly infalling, for the first time, into the groups. We show that considering only faint galaxies in the outskirts; those in NG groups are older and more metal-rich than those in G groups. Also, examining the Projected Phase Space of cluster galaxies, we see that bright and faint galactic systems in G groups are in dynamical equilibrium-which does not seem to be the case in NG groups. These findings suggest that NG systems have a higher infall rate, assembling more galaxies that have experienced preprocessing before entering the group.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/513/A21
- Title:
- GRS 1915+105 timing analysis
- Short Name:
- J/A+A/513/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- GRS 1915+105 was observed by BeppoSAX for about 10 days in October 2000. For about 80% of the time, the source was in the variability class rho, characterised by a series of recurrent bursts. We describe the results of the timing analysis performed on the MECS (1.6-10keV) and PDS (15-100keV) data. The X-ray count rate from GRS 1915+105 showed an increasing trend with different characteristics in the various energy bands: in the bands (1.6-3keV) and (15-100keV), it was nearly stable in the first part of the pointing and increased in a rather short time by about 20%, while in the energy range (3-10keV) the increase had a smoother trend.
- ID:
- ivo://CDS.VizieR/J/other/NatAs/4.1072
- Title:
- HaloSat survey of southern Galactic halo
- Short Name:
- J/other/NatAs/4.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Milky Way galaxy is surrounded by a circumgalactic medium (CGM) that may play a key role in galaxy evolution as the source of gas for star formation and a repository of metals and energy produced by star formation and nuclear activity. The CGM may also be a repository for baryons seen in the early universe, but undetected locally. The CGM has an ionized component at temperatures near 2x10^6^K studied primarily in the soft X-ray band. Here we report a survey of the southern Galactic sky with a soft X-ray spectrometer optimized to study diffuse soft X-ray emission. The X-ray emission is best fit with a disc-like model based on the radial profile of the surface density of molecular hydrogen, a tracer of star formation, suggesting that the X-ray emission is predominantly from hot plasma produced via stellar feedback. Strong variations in the X-ray emission on angular scales of ~10 degrees indicate that the CGM is clumpy. Addition of an extended, and possibly massive, halo component is needed to match the halo density inferred from other observations.
- ID:
- ivo://CDS.VizieR/J/ApJ/884/162
- Title:
- HaloSat targets to study the hot Galactic halo
- Short Name:
- J/ApJ/884/162
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- HaloSat is a small satellite (CubeSat) designed to map soft X-ray oxygen line emission across the sky in order to constrain the mass and spatial distribution of hot gas in the Milky Way. The goal of HaloSat is to help determine if hot gas gravitationally bound to individual galaxies makes a significant contribution to the cosmological baryon budget. HaloSat was deployed from the International Space Station in 2018 July and began routine science operations in 2018 October. We describe the goals and design of the mission, the on-orbit performance of the science instrument, and initial observations.
- ID:
- ivo://CDS.VizieR/J/A+A/406/535
- Title:
- Hamburg/RASS Cat. of optical ident. V3.0
- Short Name:
- J/A+A/406/535
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the Hamburg/RASS Catalogue (HRC) of optical identifications of X-ray sources at high-galactic latitude. The HRC includes all X-ray sources from the ROSAT Bright Source Catalogue (RASS-BSC) with galactic latitude |b|>=30{deg} and declination DE>=0{deg}. In this part of the sky covering ~10 000 deg^2^ the RASS-BSC contains 5341 X-ray sources. For the optical identification we used blue Schmidt prism and direct plates taken for the northern hemisphere Hamburg Quasar Survey (HQS) which are now available in digitized form. The limiting magnitudes are 18.5 and 20, respectively. For 82% of the selected RASS-BSC an identification could be given. For the rest either no counterpart was visible in the error circle or a plausible identification was not possible. With ~42% AGN represent the largest group of X-ray emitters, ~31% have a stellar counterpart, whereas galaxies and cluster of galaxies comprise only ~4% and ~5%, respectively. In ~3% of the RASS-BSC sources no object was visible on our blue direct plates within 40" around the X-ray source position. The catalogue is used as a source for the selection of (nearly) complete samples of the various classes of X-ray emitters.
- ID:
- ivo://CDS.VizieR/J/A+A/466/823
- Title:
- Hard 2-10kev X-ray selected sources
- Short Name:
- J/A+A/466/823
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Chandra and Spitzer data for the 186, extragalactic, hard 2-10keV X-ray selected sources, which lie in the central part of the Chandra Deep Field South (CDFS). For the vast majority of sources (99.5%), there is a spectroscopic or photometric redshift available. We classify 17 sources as X-ray obscured QSOs, strictly according to X-ray criteria, i.e. defined as having large hydrogen column densities (NH>10^22cm^-2^) and luminosities (LX>10^44^erg/s). The surface density of X-ray obscured QSOs is ~210{deg}^-2^. We find 18 candidate Compton-thick NH>10^24^cm^-2^ sources, of which three have QSO luminosities (LX>10^44^erg/s). The X-ray obscured QSO comprise a mixed bag of objects, covering the redshift range z=1.3-4.3. Eight of these show narrow-line optical spectra, two show no obscuration in their optical spectra that present broad lines, while for the other seven there is only a photometric redshift available. About half of the X-ray obscured QSOs show high X-ray to optical flux ratios, X/O>1, and red colours, I-3.6{mu}m>4. Combining the X-ray with the mid-IR 8{mu}m or 24{mu}m flux can be used as an additional diagnostic to sift out the heavily obscured AGN. All X-ray selected QSOs present red mid-IR colours and can be easily separated among mid-IR sources, demonstrating that mid-IR selection provides a powerful tool for detecting obscured QSOs.
- ID:
- ivo://CDS.VizieR/J/MNRAS/318/1073
- Title:
- Hard spectrum ROSAT sources. I.
- Short Name:
- J/MNRAS/318/1073
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalogue of 147 serendipitous X-ray sources selected to have hard spectra ({alpha}<0.5) from a survey of 188 ROSAT fields. Such sources must be the dominant contributors to the X-ray background at faint fluxes. We have used Monte Carlo simulations to verify that our technique is very efficient at selecting hard sources: the survey has >=10 times as much effective area for hard sources as it has for soft sources above a 0.5-2keV flux level of 10^-14^erg/cm^2^/s. The distribution of best-fitting spectral slopes of the hard sources suggests that a typical ROSAT hard source in our survey has a spectral slope {alpha}~0. The hard sources have a steep number flux relation (dN/dS_{mu}_S^-{gamma}^ with a best-fitting value of {gamma}=2.72+/-0.12) and make up about 15 per cent of all 0.5-2keV sources with S>10^-14^erg/cm^2^/s. If their N(S) continues to fainter fluxes, the hard sources will comprise ~40 per cent of sources with 5x10^-15^<S<10^-14^erg/cm^2^/s. The population of hard sources can therefore account for the harder average spectra of ROSAT sources with S<10^-14^erg/cm^2^/s. They probably make a strong contribution to the X-ray background at faint fluxes and could be the solution to the X-ray background spectral paradox.
- ID:
- ivo://CDS.VizieR/J/PAZh/37/651
- Title:
- Hard X-ray bursts by INTEGRAL in 2003-2009
- Short Name:
- J/PAZh/37/651
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To find X-ray bursts from sources within the field of view of the IBIS/INTEGRAL telescope, we have analyzed all the archival data of the telescope available at the time of writing the paper (the observations from January 2003 to April 2009). We have detected 834 hard (15-25keV) X-ray bursts, 239 of which were simultaneously recorded by the JEM-X/INTEGRAL telescope in the standard X-ray energy range. More than 70% of all bursts (587 events) have been recorded from the well-known X-ray burster GX 354-0. We have found upper limits on the distances to their sources by assuming that the Eddington luminosity limit was reached at the brightness maximum of the brightest bursts.
- ID:
- ivo://CDS.VizieR/J/PAZh/32/508
- Title:
- Hard X-ray Bursts by INTEGRAL in 2003-2004
- Short Name:
- J/PAZh/32/508
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- All of the observations performed with the IBIS telescope onboard the INTEGRAL observatory during the first one and a half years of its in-orbit operation (from February 10, 2003, through July 2, 2004) have been analyzed to find X-ray bursts. The time history of the IBIS/ISGRI total count rate in the energy range 15-25keV revealed 1077 bursts of durations from 5 to 500s with a high statistical significance (over the entire period of observations, only one event could be detected by chance with a probability of 20%). A part from the events associated with cosmic gamma-ray bursts (detected in the field of view or passed through the IBIS shield), solar flares, and activity of the soft gamma repeater SGR 1806-20, we were able to localize 105 bursts and, with one exception, to identify them with previously known persistent or transient X-ray sources (96 were identified with known X-ray bursters). In one case, the burst source was a new burster in a low state that received the name IGR J17364-2711. Basic parameters of the localized bursts and their identifications are presented in the catalog of bursts. Curiously enough, 61 bursts were detected from one X-ray burster, GX 354-0. The statistical distributions of bursts in duration, maximum flux, and recurrence time have been analyzed for this source. Some of the bursts observed with the IBIS/ISGRI telescope were also detected by the JEM-X telescope onboard the INTEGRAL observatory in the standard X-ray energy range 3-20keV.
- ID:
- ivo://CDS.VizieR/J/PAZh/30/589
- Title:
- Hard X-ray catalog of Sagittarius arm
- Short Name:
- J/PAZh/30/589
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The images of the Sagittarius arm tangent obtained with the IBIS telescope of the INTEGRAL observatory in the energy range 18-120keV during their observations in the spring of 2003 are analyzed.