- ID:
- ivo://CDS.VizieR/J/A+A/396/397
- Title:
- Deep cluster survey in Chandra archival data
- Short Name:
- J/A+A/396/397
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- I present the first results of a search for clusters of galaxies in Chandra ACIS pointed observations at high galactic latitude with exposure times larger than 10ks. The survey is being carried out using the Voronoi Tessellation and Percolation technique, which is particularly suited for the detection and accurate quantification of extended and/or low surface brightness emission in X-ray imaging observations. A new catalogue of 36 cluster candidates has been created from 5.55deg^2^ of surveyed area. Five of these candidates have already been associated to visible enhancements of the projected galaxy distribution in low deepness DSS-II fields and are probably low-to moderate redshift systems. Three of the candidates have been identified in previous ROSAT-based surveys. I show that a significative fraction (30-40%) of the candidate clusters are probably intermediate to high redshift systems. In this paper I publish the catalogue of these first candidate clusters. I also derive the number counts of clusters and compare it with the results of deep ROSAT-based cluster surveys.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/190/43
- Title:
- Deep GALEX observations of the Coma cluster
- Short Name:
- J/ApJS/190/43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a source catalog from a deep 26ks Galaxy Evolution Explorer (GALEX) observation of the Coma cluster in the far-UV (FUV; 1530{AA}) and near-UV (NUV; 2310{AA}) wavebands. The observed field is centered ~0.9{deg} (1.6Mpc) southwest of the Coma core in a well-studied region of the cluster known as "Coma-3". The entire field is located within the apparent virial radius of the Coma cluster, and has optical photometric coverage with Sloan Digital Sky Survey (SDSS) and deep spectroscopic coverage to r~21. We detect GALEX sources to NUV=24.5 and FUV=25.0, which corresponds to a star formation rate of ~10^-3^M_{sun}_/yr for galaxies at the distance of Coma. We have assembled a catalog of 9700 galaxies with GALEX and SDSS photometry, including 242 spectroscopically confirmed Coma member galaxies (in fig. 1) that span a large range of galaxy types from giant spirals and elliptical galaxies to dwarf irregular and early-type galaxies. The full multi-wavelength catalog (cluster plus background galaxies) is ~80% complete to NUV=23 and FUV=23.5. The GALEX images presented here are very deep and include detections of many resolved cluster members superposed on a dense field of unresolved background galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/612/A26
- Title:
- Deep HI observations of Leo T with WSRT
- Short Name:
- J/A+A/612/A26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Leo T is the lowest mass gas-rich galaxy currently known and studies of its gas content help us understand how such marginal galaxies survive and form stars. We present deep neutral hydrogen (HI) observations from the Westerbork Synthesis Radio Telescope in order to understand its HI distribution and potential for star formation. We find a larger HI line flux than the previously accepted value, resulting in a 50% larger HI mass of 4.1x10^5^M_{sun}_. The additional HI flux is from low surface brightness emission that was previously missed; with careful masking this emission can be recovered even in shallower data.We perform a Gaussian spectral decomposition to find a cool neutral medium component (CNM) with a mass of 3.7x10^4^M_{sun}_, or almost 10% of the total HI mass. Leo T has no HI emission extending from the main HI body, but there is evidence of interaction with the Milky Way circumgalactic medium in both a potential truncation of the HI body and the offset of the peak HI distribution from the optical center. The CNM component of Leo T is large when compared to other dwarf galaxies, even though Leo T is not currently forming stars and has a lower star formation efficiency than other gas-rich dwarf galaxies. However, the HI column density associated with the CNM component in Leo T is low. One possible explanation is the large CNM component is not related to star formation potential but rather a recent, transient phenomenon related to the interaction of Leo T with the Milky Way circumgalactic medium.
- ID:
- ivo://CDS.VizieR/J/ApJ/518/69
- Title:
- Deep Optical Catalog of galaxy systems
- Short Name:
- J/ApJ/518/69
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We assemble and observe a sample of poor galaxy systems that is suitable for testing N-body simulations of hierarchical clustering and other dynamical halo models. We (1) determine the parameters of the density profile {Rho}(r) and the velocity dispersion profile {sigma}_p_(R), (2) separate emission-line galaxies from absorption-line galaxies, examining the model parameters, {beta}, and as a function of spectroscopic type, and (3) for the best-behaved subsample, constrain the velocity anisotropy parameter, {beta}, which determines the shapes of the galaxy orbits. Our sample consists of 20 systems, 12 of which have extended X-ray emission in the ROSAT All-Sky Survey. We measure the 877 optical spectra of galaxies brighter than m_R_~15.4 within 1.5h^-1^Mpc of the system centers (we take H_0_=100h*km/s/Mpc). Thus, we sample the system membership to a radius typically three times larger than other recent optical group surveys. The average system population is 30 galaxies, and the average line-of-sight velocity dispersion is ~300km/s. The Navarro, Frenk, & White universal profile and the Hernquist model both provide good descriptions of the spatial data. In most cases an isothermal sphere is ruled out. Systems with declining {sigma}_p_(R) are well-matched by theoretical profiles in which the star-forming galaxies have predominantly radial orbits ({beta}>0); many of these galaxies are probably falling in for the first time. There is significant evidence for spatial segregation of the spectroscopic classes regardless of {sigma}_p_(R).
- ID:
- ivo://CDS.VizieR/J/MNRAS/458/1590
- Title:
- Deep spectroscopy of Abell 85
- Short Name:
- J/MNRAS/458/1590
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new deep spectroscopic catalogue for Abell 85, within 3.0x2.6Mpc^2^ and down to M_r_~M_r_^*^+6. Using the Visible Multi-Object Spectrograph at the Very Large Telescope and the AutoFiber 2 at the William Herschel Telescope, we obtained almost 1430 new redshifts for galaxies with m_r_<=21mag and <{mu}_e,r_><=24mag/arcsec^2^. These redshifts, together with Sloan Digital Sky Survey Data Release 6 and NASA/IPAC Extragaalctic Database spectroscopic information, result in 460 confirmed cluster members. This data set allows the study of the luminosity function (LF) of the cluster galaxies covering three orders of magnitudes in luminosities. The total and radial LFs are best modelled by a double Schechter function. The normalized LFs show that their bright (M_r_<=-21.5) and faint (M_r_>=-18.0) ends are independent of clustercentric distance and similar to the field LFs unlike the intermediate luminosity range (-21.5<=M_r_<=-18.0). Similar results are found for the LFs of the dominant types of galaxies: red, passive, virialized and early-infall members. On the contrary, the LFs of blue, star forming, non-virialized and recent-infall galaxies are well described by a single Schechter function. These populations contribute to a small fraction of the galaxy density in the innermost cluster region. However, in the outskirts of the cluster, they have similar densities to red, passive, virialized and early-infall members at the LF faint end. These results confirm a clear dependence of the colour and star formation of Abell 85 members in the cluster centric distance.
- ID:
- ivo://CDS.VizieR/J/A+A/593/A30
- Title:
- Detection of fast HI outflow in Mrk231
- Short Name:
- J/A+A/593/A30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the detection, performed with the Westerbork Synthesis Radio Telescope (WSRT) and the Karl Jansky Very Large Array (VLA), of a fast HI 21-cm outflow in the ultra-luminous infrared galaxy Mrk 231. The outflow is observed as shallow HI absorption blueshifted ~1300 km/s with respect to the systemic velocity and located against the inner kpc of the radio source. The outflowing gas has an estimated column density between 5 and 15x10^18^Tspin.cm^-2^. We derive the Tspin to lie in the range 400-2000 K and the corresponding HI densities are n_HI_~10-100cm^-3^. We also obtained deeper continuum images than previously available. They confirm the complex structure of the radio continuum originating both from the AGN and star formation. At the resolution obtained with the VLA (~1-arcsec) we do not see a kpc-scale jet. Instead, we detect a plateau of emission, likely due to star formation, surrounding the bright nuclear region. We also detect a poorly collimated bridge which may represent the channel feeding the southern lobe. The unprecedented depth of the low-resolution WSRT image reveals radio emission extending 50-arcsec (43kpc) to the south and 20arcsec (17kpc) to the north.
- ID:
- ivo://CDS.VizieR/J/MNRAS/329/87
- Title:
- 2dF Galaxy Redshift Survey: galaxy clusters
- Short Name:
- J/MNRAS/329/87
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have carried out a study of known clusters within the 2dF Galaxy Redshift Survey (2dFGRS, Cat. <VII/226>) observed areas and have identified 431 Abell, 173 APM and 343 EDCC clusters. Precise redshifts, velocity dispersions and new centroids have been measured for the majority of these objects, and this information is used to study the completeness of these catalogues, the level of contamination from foreground and background structures along the cluster's line of sight, the space density of the clusters as a function of redshift, and their velocity dispersion distributions. We find that the Abell and EDCC catalogues are contaminated at the level of about 10 per cent, whereas the APM catalogue suffers only 5 per cent contamination. If we use the original catalogue centroids, the level of contamination rises to approximately 15 per cent for the Abell and EDCC catalogues, showing that the presence of foreground and background groups may alter the richness of clusters in these catalogues. There is a deficiency of clusters at z~0.05 hat may correspond to a large underdensity in the Southern hemisphere. From the cumulative distribution of velocity dispersions for these clusters, we derive a space density of {sigma}>1000km/s clusters of 3.6x10^-6^h^3^/Mpc^3^. This result is used to constrain models for structure formation; our data favour low-density cosmologies, subject to the usual assumptions concerning the shape and normalization of the power spectrum.
- ID:
- ivo://CDS.VizieR/J/MNRAS/348/866
- Title:
- 2dFGRS Percolation-Inferred Galaxy Group (2PIGG)
- Short Name:
- J/MNRAS/348/866
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The construction of a catalogue of galaxy groups from the Two-degree Field Galaxy Redshift Survey (2dFGRS) is described. Groups are identified by means of a friends-of-friends percolation algorithm which has been thoroughly tested on mock versions of the 2dFGRS generated from cosmological N-body simulations. The tests suggest that the algorithm groups all galaxies that it should be grouping, with an additional 40 per cent of interlopers. About 55 per cent of the ~190000 galaxies considered are placed into groups containing at least two members of which ~29000 are found. Of these, ~7000 contain at least four galaxies, and these groups have a median redshift of 0.11 and a median velocity dispersion of 260km/s. This 2dFGRS Percolation-Inferred Galaxy Group (2PIGG) catalogue represents the largest available homogeneous sample of galaxy groups.
- ID:
- ivo://CDS.VizieR/J/MNRAS/463/2653
- Title:
- 8620 DIB equivalent width and extinction
- Short Name:
- J/MNRAS/463/2653
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The young stellar cluster Westerlund 1 (Wd 1: l=339.6, b=-0.4) is one of the most massive in the local Universe, but accurate parameters are pending on better determination of its extinction and distance. Based on our photometry and data collected from other sources, we have derived a reddening law for the cluster line-of-sight representative of the Galactic plane (-5{deg}<b<+5{deg}) in the window 0.4-4.8um. The power-law exponent alpha=2.13+/-0.08 is much steeper than those published a decade ago (1.6-1.8) and our index RV=2.50+/-0.04 also differs from them, but in very good agreement with recent works based on deep surveys in the inner Galaxy. As a consequence, the total extinction AKs=0.74+/-0.08 (AV=11.40+/-2.40) is substantially smaller than previous results (0.91-1.13), part of which (AKs=0.63 or AV=9.66) is from the interstellar medium. The extinction in front of the cluster spans a range of AV~8.7 with a gradient increasing from SW to NE across the cluster face, following the same general trend of warm dust distribution. The map of the J-Ks colour index also shows a trend of reddening in this direction. We measured the equivalent width of the diffuse interstellar band at 8620 A (the 'GAIA DIB') for Wd 1 cluster members and derived the relation AKs=0.612EW-0.191EW^2^. This extends the Munari et al. relation, valid for E(B-V)<1, to the non-linear regime (AV>4).
- ID:
- ivo://CDS.VizieR/J/ApJ/726/108
- Title:
- Dispersion-supported stellar systems
- Short Name:
- J/ApJ/726/108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We examine scaling relations of dispersion-supported galaxies over more than eight orders of magnitude in luminosity by transforming standard fundamental plane parameters into a space of mass, radius, and luminosity. The radius variable r_1/2_ is the deprojected (three-dimensional) half-light radius, the mass variable M_1/2_ is the total gravitating mass within this radius, and L_1/2_ is half the luminosity. We find that from ultra-faint dwarf spheroidals to giant cluster spheroids, dispersion-supported galaxies scatter about a one-dimensional "fundamental curve" through this MRL space.
