- ID:
- ivo://CDS.VizieR/J/MNRAS/500/4849
- Title:
- GALAH emission-line stars
- Short Name:
- J/MNRAS/500/4849
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a neural network autoencoder structure that is able to extract essential latent spectral features from observed spectra and then reconstruct a spectrum from those features. Because of the training with a set of unpeculiar spectra, the network is able to reproduce a spectrum of high signal-to-noise ratio that does not show any spectral peculiarities, even if they are present in an observed spectrum. Spectra generated in this manner were used to identify various emission features among spectra acquired by multiple surveys using the HERMES spectrograph at the Anglo-Australian telescope. Emission features were identified by a direct comparison of the observed and generated spectra. Using the described comparison procedure, we discovered 10364 candidate spectra with varying intensities (from partially filled-in to well above the continuum) of the H{alpha}/H{beta} emission component, produced by different physical mechanisms. A fraction of these spectra belong to the repeated observation that shows temporal variability in their emission profile. Among the emission spectra, we find objects that feature contributions from a nearby rarefied gas (identified through the emission of [NII] and [SII] lines) that was identified in 4004 spectra, which were not all identified as having H{alpha} emission. The positions of identified emission-line objects coincide with multiple known regions that harbour young stars. Similarly, detected nebular emission spectra coincide with visually prominent nebular clouds observable in the red all-sky photographic composites.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/other/RAA/11.245
- Title:
- Galaxies in the field of RX J0054.0-2823
- Short Name:
- J/other/RAA/11.2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present galactic spectroscopic data from a pencil beam of 10.75'x7.5' centered on the X-ray cluster RXJ0054.0-2823 at z=0.29. We study the spectral evolution of galaxies from z=1 down to the cluster redshift in a magnitude-limited sample at R<=23, for which the statistical properties of the sample are well understood. We divide emission-line galaxies into star-forming galaxies, Low Ionization Nuclear Emission line Regions (LINERs), and Seyferts by using emission-line ratios of [OII],H{beta}, and [OIII], and derive stellar fractions from population synthesis models. We focus our analysis on absorption and low-ionization galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/640/A30
- Title:
- Galaxies in the Perseus cluster field
- Short Name:
- J/A+A/640/A30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the galaxies brighter than B~20 in the field of the Perseus cluster. The galaxies were selected on Schmidt CCD images in B and Halpha in combination with SDSS images. The survey field roughly covers the virial radius of the cluster. The galaxy sample is used for analysing cluster properties, such as radial profiles, indications of sub-structure, virial mass, and viral radius and is applied for a study of the cluster galaxy population with an emphasis on morphological types and peculiarities, star formation rates and active galactic nuclei.
- ID:
- ivo://CDS.VizieR/J/ApJ/742/125
- Title:
- Galaxies in X-ray groups. I. COSMOS memberships
- Short Name:
- J/ApJ/742/125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Understanding the mechanisms that lead dense environments to host galaxies with redder colors, more spheroidal morphologies, and lower star formation rates than field populations remains an important problem. As most candidate processes ultimately depend on host halo mass, accurate characterizations of the local environment, ideally tied to halo mass estimates and spanning a range in halo mass and redshift, are needed. In this work, we present and test a rigorous, probabilistic method for assigning galaxies to groups based on precise photometric redshifts and X-ray-selected groups drawn from the COSMOS field. The groups have masses in the range 10^13^<~M_200c_/M_{sun}_<~10^14^ and span redshifts 0<z<1. We characterize our selection algorithm via tests on spectroscopic subsamples, including new data obtained at the Very Large Telescope, and by applying our method to detailed mock catalogs. We find that our group member galaxy sample has a purity of 84% and completeness of 92% within 0.5R_200c_. We measure the impact of uncertainties in redshifts and group centering on the quality of the member selection with simulations based on current data as well as future imaging and spectroscopic surveys. As a first application of our new group member catalog which will be made publicly available, we show that member galaxies exhibit a higher quenched fraction compared to the field at fixed stellar mass out to z~1, indicating a significant relationship between star formation and environment at group scales. We also address the suggestion that dusty star-forming galaxies in such groups may impact the high-l power spectrum of the cosmic microwave background and find that such a population cannot explain the low power seen in recent Sunyaev-Zel'dovich measurements.
- ID:
- ivo://CDS.VizieR/J/ApJ/853/95
- Title:
- Galaxies probing galaxies in PRIMUS. I.
- Short Name:
- J/ApJ/853/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The spectroscopy of background QSO sightlines passing close to foreground galaxies is a potent technique for studying the circumgalactic medium (CGM). However, QSOs are effectively point sources, limiting their potential to constrain the size of circumgalactic gaseous structures. Here we present the first large Keck/Low-resolution Imaging Spectrometer (LRIS) and Very Large Telescope (VLT)/Focal Reducer/Low-dispersion Spectrograph 2 (FORS2) spectroscopic survey of bright (B_AB_<22.3) background galaxies whose lines of sight probe MgII{lambda}{lambda}2796,2803 absorption from the CGM around close projected foreground galaxies at transverse distances 10kpc<R_{perp}_<150kpc. Our sample of 72 projected pairs, drawn from the PRIsm MUlti-object Survey, includes 48 background galaxies that do not host bright active galactic nuclei, and both star-forming and quiescent foreground galaxies with stellar masses of 9.0<logM_*_/M_{sun}_<11.2 at redshifts of 0.35<z_f/g_<0.8. We detect MgII absorption associated with these foreground galaxies with equivalent widths of 0.25{AA}<W_2796_<2.6{AA} at >2{sigma} significance in 20 individual background sightlines passing within R_{perp}_<50kpc and place 2{sigma} upper limits on W_2796_ of <~0.5{AA} in an additional 11 close sightlines. Within R_{perp}_<50kpc, W_2796_ is anticorrelated with R_{perp}_, consistent with analyses of Mg ii absorption detected along background QSO sightlines. Subsamples of these foreground hosts divided at logM_*_/M_{sun}_=9.9 exhibit statistically inconsistent W_2796_ distributions at 30kpc<R_{perp}_<50kpc, with the higher-M* galaxies yielding a larger median W_2796_ by 0.9{AA}. Finally, we demonstrate that foreground galaxies with similar stellar masses exhibit the same median W_2796_ at a given R_{perp}_ to within <0.2{AA} toward both background galaxies and toward QSO sightlines drawn from the literature. Analysis of these data sets constraining the spatial coherence scale of circumgalactic MgII absorption is presented in a companion paper.
- ID:
- ivo://CDS.VizieR/J/AJ/138/873
- Title:
- Galaxies with H{alpha} emission in A2151
- Short Name:
- J/AJ/138/873
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents the first results of an H{alpha} imaging survey of galaxies in the central regions of the A2151 cluster. A total of 50 sources were detected in H{alpha}, from which 41 were classified as secure members of the cluster and 2 as likely members based on spectroscopic and photometric redshift considerations. The remaining seven galaxies were classified as background contaminants and thus excluded from our study on the H{alpha} properties of the cluster.
- ID:
- ivo://CDS.VizieR/J/AJ/131/2018
- Title:
- Galaxies with large velocity dispersions
- Short Name:
- J/AJ/131/2018
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe the results of a search for galaxies with large (350>=km/s) velocity dispersions. The largest systems we have found appear to be the extremes of the early-type galaxy population: compared to other galaxies with similar luminosities, they have the largest velocity dispersions and the smallest sizes.
- ID:
- ivo://CDS.VizieR/J/ApJS/246/2
- Title:
- Galaxy cluster cat. from SDSS-DR13 (GalWCat19)
- Short Name:
- J/ApJS/246/2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Utilizing the SDSS-DR13 spectroscopic data set, we create a new publicly available catalog of 1800 galaxy clusters (GalWeight cluster catalog, GalWCat19) and a corresponding catalog of 34,471 identified member galaxies. The clusters are identified from overdensities in redshift phase space. The GalWeight technique introduced by Abdullah+ (2018ApJ...861...22A) is then applied to identify cluster members. The completeness of the cluster catalog (GalWCat19) and the procedure followed to determine cluster mass are tested on the Bolshoi N-body simulations. The 1800 GalWCat19 clusters range in redshift between 0.01 and 0.2 and have masses in the range of (0.4-14)x10^14^h^-1^M_{sun}_. The cluster catalog provides a large number of cluster parameters, including sky position, redshift, membership, velocity dispersion, and mass at overdensities {Delta}=500, 200, 100, and 5.5. The 34471 member galaxies are identified within the radius at which the density is 200 times the critical density of the universe. The galaxy catalog provides the coordinates of each galaxy and the ID of the cluster that the galaxy belongs to. The cluster velocity dispersion scales with mass as log({sigma}_200_)=log(946+/-52km/s)+ (0.349+/-0.142)log[h(z)M_200_/10^1 5^M_{sun}], with a scatter of {delta}log{sigma}=0.06+/-0.04.
- ID:
- ivo://CDS.VizieR/J/ApJ/774/40
- Title:
- Galaxy clusters aligned with quasars. III.
- Short Name:
- J/ApJ/774/40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Gemini/GMOS-S multi-object spectroscopy of 31 galaxy cluster candidates at redshifts between 0.2 and 1.0 and centered on QSO sight lines taken from Lopez et al. (Paper I, J/ApJ/679/1144). The targets were selected based on the presence of an intervening MgII absorption system at a similar redshift to that of a galaxy cluster candidate lying at a projected distance <2h_71_^-1^Mpc from the QSO sight line (a "photometric hit"). The absorption systems span rest-frame equivalent widths between 0.015 and 2.028{AA}. The general population of our confirmed absorbing galaxies have luminosities L_B_~L_B_^*^ and mean rest-frame colors (R_c_-z') typical of S_cd_ galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/551/A8
- Title:
- Galaxy clusters in XMM field within CFHT-LS D4
- Short Name:
- J/A+A/551/A8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The XMM-Newton Distant Cluster Project (XDCP) aims at the identification of a well defined sample of X-ray selected clusters of galaxies at redshifts z>0.8. As part of this project, we analyse the deep XMM-Newton exposure covering one of the CFHTLS deep fields to quantify the cluster content. We validate the optical follow-up strategy as well as the X-ray selection function. We search for extended X-ray sources in archival XMM-Newton EPIC observations. Multi-band optical imaging is performed to select high redshift cluster candidates among the extended X-ray sources. Here we present a catalogue of the extended sources in one the deepest LBQS ~250ks XMM-Newton fields targeting LBQS J2212-1759 covering ~0.2 square degrees. The cluster identification is based, among others, on deep imaging with the ESO VLT and from the CFHT legacy survey. The confirmation of cluster candidates is done by VLT/FORS2 multi-object spectroscopy. Photometric redshifts from the CFHTLS D4 are utilized to confirm the effectiveness of the X-ray cluster selection method. The survey sensitivity is computed with extensive Monte-Carlo simulations. At a flux limit of S(0.5-2.0keV)~2.5e-15erg/s/cm2 we achieve a completeness level higher than 50% in an area of ~0.13 square degrees. We detect six galaxy clusters above this limit with optical counterparts, of which 5 are new spectroscopic discoveries. Two newly discovered X-ray luminous galaxy clusters are at z>1.0, another two at z=0.41 and one at z=0.34. For the most distant X-ray selected cluster in this field at z=1.45 we find additional (active) member galaxies from both X-ray and spectroscopic data. Additionally, we find evidence of large scale structures at moderate redshifts of z=0.41 and z=0.34. The quest for distant clusters in archival XMM-Newton data has led to the detection of six clusters in a single field, making XMM-Newton an outstanding tool for cluster surveys. Three of these clusters are at z>1, which emphasises the valuable contribution of small, yet deep surveys to cosmology. Beta-models are appropriate descriptions for the cluster surface brightness to perform cluster detection simulations in order to compute the X-ray selection function. The constructed log N-log S tends to favour a scenario where no evolution in the cluster X-ray luminosity function (XLF) takes place.
