- ID:
- ivo://CDS.VizieR/J/A+A/607/A131
- Title:
- Abell 520 galaxies redshifts
- Short Name:
- J/A+A/607/A131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The mergers of galaxy clusters are the most energetic events in the universe after the Big Bang. An ever increasing fraction of local clusters exhibit signs of recent or past mergers. Our goal is to probe how these mergers affect the evolution and content of their member galaxies. We specifically aim to answer the following questions: Is the quenching of star formation in merging clusters enhanced when compared with relaxed clusters? Is the quenching accompanied by a (short lived) burst of star formation? We obtained optical spectroscopy of $>400$ galaxies in the field of the merging cluster Abell 520. We combine these observations with archival data to get a comprehensive picture of the state of star formation in the members of this merging cluster. Finally, we compare these observations with a control sample of 10 non-merging clusters at the same redshift from The Arizona Cluster Redshift Survey (ACReS). We split the member galaxies in passive, star forming or recently quenched depending on their spectra. The core of the merger shows a decreased fraction of star-forming galaxies compared to clusters in the non-merging sample. This region, dominated by passive galaxies, is extended along the axis of the merger. We find evidence of rapid quenching of the galaxies during the core passage with no signs of a star burst on the time scales of the merger. Additionally, we report the tentative discovery of an infalling group along the main filament feeding the merger, currently at ~2.5Mpc from the merger centre. This group contains a high fraction of star forming galaxies as well as ~2/3 of all the recently quenched galaxies in our survey.
« Previous |
1 - 10 of 234
|
Next »
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/468/703
- Title:
- Abell 168 ultra-diffuse galaxies distribution
- Short Name:
- J/MNRAS/468/703
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Taking advantage of the Sloan Digital Sky Survey Stripe82 data, we have explored the spatial distribution of ultra-diffuse galaxies (UDGs) within an area of 8x8Mpc^2^ centred around the galaxy cluster Abell 168 (z=0.045). This intermediate massive cluster ({sigma}=550km/s) is surrounded by a complex large-scale structure. Our work confirms the presence of UDGs in the cluster and in the large-scale structure that surrounds it, and it is the first detection of UDGs outside clusters. Approximately 50 per cent of the UDGs analysed in the selected area inhabit the cluster region (~11+/-5 per cent in the core and ~39+/-9 per cent in the outskirts), whereas the remaining UDGs are found outside the main cluster structure (~50+/-11 per cent). The colours and the spatial distribution of the UDGs within this large-scale structure are more similar to dwarf galaxies than to L* galaxies, suggesting that most UDGs could be bona fide dwarf galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/723/1632
- Title:
- Abundance spreads in Bootes I and Segue 1
- Short Name:
- J/ApJ/723/1632
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an AAOmega spectroscopic study of red giants in the ultra-faint dwarf galaxy Bootes I (M_V_~-6) and the Segue 1 system (M_V_~-1.5), either an extremely low luminosity dwarf galaxy or an unusually extended globular cluster. Both Bootes I and Segue 1 have significant abundance dispersions in iron and carbon. Bootes I has a mean abundance of [Fe/H]=-2.55+/-0.11 with an [Fe/H] dispersion of {sigma}=0.37+/-0.08, and abundance spreads of {Delta}[Fe/H]=1.7 and {Delta}[C/H]=1.5. Segue 1 has a mean of [Fe/H]=-2.7+/-0.4 with [Fe/H] dispersion of {sigma}=0.7+/-0.3, and abundances spreads of {Delta}[Fe/H]=1.6 and {Delta}[C/H]=1.2. Moreover, Segue 1 has a radial-velocity member at four half-light radii that is extremely metal-poor and carbon-rich, with [Fe/H]=-3.5, and [C/Fe]=+2.3. Modulo an unlikely non-member contamination, the [Fe/H] abundance dispersion confirms Segue 1 as the least-luminous ultra-faint dwarf galaxy known.
- ID:
- ivo://CDS.VizieR/J/A+A/445/765
- Title:
- A Catalog of Edge-on Disk Galaxies
- Short Name:
- J/A+A/445/765
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spiral galaxies range from bulge-dominated early-type galaxies to late types with little or no bulge. Cosmological models do not predict the formation of disk-dominated, essentially bulgeless galaxies, yet these objects exist. A particularly striking and poorly understood example of bulgeless galaxies are flat or superthin galaxies with large axis ratios. We therefore embarked on a study aimed at a better understanding of these enigmatic objects, starting by compiling a statistically meaningful sample with well-defined properties. The disk axis ratios can be most easily measured when galaxies are seen edge-on. We used data from the Sloan Digital Sky Survey (SDSS) in order to identify edge-on galaxies with disks in a uniform, reproducible, automated fashion. In the five-color photometric database of the SDSS Data Release 1 (DR1, http://www.sdss.org/dr1) (2099 deg^2) we identified 3169 edge-on disk galaxies, which we subdivided into disk galaxies with bulge, intermediate types, and simple disk galaxies without any obvious bulge component. We subdivided these types further into subclasses: Sa(f), Sb(f), Sc(f), Scd(f), Sd(f), Irr(f), where the (f) indicates that these galaxies are seen edge-on. Here we present our selection algorithm and the resulting catalogs of the 3169 edge-on disk galaxies including the photometric, morphological, and structural parameters of our targets. A number of incompleteness effects affect our catalog, but it contains almost a factor of four more bulgeless galaxies with prominent simple disks (flat galaxies) within the area covered here than optical previous catalogs, which were based on the visual selection from photographic plates (Karachentsev et al. 1999, see Cat. VII/219). We find that approximately 15% of the edge-on disk galaxies in our catalog are flat galaxies, demonstrating that these galaxies are fairly common, especially among intermediate- mass star-forming galaxies. Bulgeless disks account for roughly one third of our galaxies when also puffy disks and edge-on irregulars are included. Our catalog provides a uniform database for a multitude of follow-up studies of bulgeless galaxies in order to constrain their intrinsic and environmental properties and their evolutionary status.
- ID:
- ivo://CDS.VizieR/J/MNRAS/437/968
- Title:
- AGN automatic photometric classification
- Short Name:
- J/MNRAS/437/968
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we discuss an application of machine-learning-based methods to the identification of candidate active galactic nucleus (AGN) from optical survey data and to the automatic classification ofAGNs in broad classes. We applied four different machine-learning algorithms, namely the Multi Layer Perceptron, trained, respectively, with the Conjugate Gradient, the Scaled Conjugate Gradient, the Quasi Newton learning rules and the Support Vector Machines, Q4 to tackle the problem of the classification of emission line galaxies in different classes, mainly AGNs versus non-AGNs, obtained using optical photometry in place of the diagnostics based on line intensity ratios which are classically used in the literature. Using the same photometric features, we discuss also the behaviour of the classifiers on finer AGN classification tasks, namely Seyfert I versus Seyfert II, and Seyfert versus LINER. Furthermore, we describe the algorithms employed, the samples of spectroscopically classified galaxies used to train the algorithms, the procedure followed to select the photometric parameters and the performances of our methods in terms of multiple statistical indicators. The results of the experiments show that the application of self-adaptive data mining algorithms trained on spectroscopic data sets and applied to carefully chosen photometric parameters represents a viable alternative to the classical methods that employ time-consuming spectroscopic observations.
- ID:
- ivo://CDS.VizieR/J/ApJ/737/101
- Title:
- AGN pairs from SDSS-DR7. I.
- Short Name:
- J/ApJ/737/101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Galaxy-galaxy mergers and close interactions have long been regarded as a viable mechanism for channeling gas toward the central supermassive black holes (SMBHs) of galaxies which are triggered as active galactic nuclei (AGNs). AGN pairs, in which the central SMBHs of a galaxy merger are both active, are expected to be common from such events. We conduct a systematic study of 1286 AGN pairs at \bar{z}~0.1 with line-of-sight velocity offsets {Delta}v<600km/s and projected separations r_p_<100h^-1^_70_kpc, selected from the Seventh Data Release of the Sloan Digital Sky Survey (SDSS, Cat. II/294). This AGN pair sample was drawn from 138070 AGNs optically identified based on diagnostic emission line ratios and/or line widths. The fraction of AGN pairs with 5h^-1^_70_kpc<~r_p_<100h^-1^_70_kpc among all spectroscopically selected AGNs at 0.02<z<0.16 is 3.6% after correcting for SDSS spectroscopic incompleteness; ~30% of these pairs show morphological tidal features in their SDSS images, and the fraction becomes >~80% for pairs with the brightest nuclei.
- ID:
- ivo://CDS.VizieR/J/AJ/142/170
- Title:
- ALFALFA survey: the {alpha}.40 HI source catalog
- Short Name:
- J/AJ/142/170
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a current catalog of 21cm HI line sources extracted from the Arecibo Legacy Fast Arecibo L-band Feed Array (ALFALFA) survey over ~2800deg^2^ of sky: the {alpha}.40 catalog. Covering 40% of the final survey area, the {alpha}.40 catalog contains 15855 sources in the regions 07h30m<RA<16h30m, +04{deg}<DEC<+16{deg}, and +24{deg}<DEC<+28{deg} and 22h<RA<03h, +14{deg}<DEC<+16{deg}, and +24{deg}<DEC<+32{deg}. Of those, 15041 are certainly extragalactic, yielding a source density of 5.3 galaxies per deg^2^, a factor of 29 improvement over the catalog extracted from the HI Parkes All-Sky Survey. In addition to the source centroid positions, HI line flux densities, recessional velocities, and line widths, the catalog includes the coordinates of the most probable optical counterpart of each HI line detection, and a separate compilation provides a cross-match to identifications given in the photometric and spectroscopic catalogs associated with the Sloan Digital Sky Survey Data Release 7. Fewer than 2% of the extragalactic HI line sources cannot be identified with a feasible optical counterpart; some of those may be rare OH megamasers at 0.16<z<0.25. A detailed analysis is presented of the completeness, width-dependent sensitivity function and bias inherent of the {alpha}.40 catalog. The impact of survey selection, distance errors, current volume coverage, and local large-scale structure on the derivation of the HI mass function is assessed.
- ID:
- ivo://CDS.VizieR/J/A+A/608/A15
- Title:
- ALMA survey of submm galaxies in COSMOS field
- Short Name:
- J/A+A/608/A15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We carried out targeted ALMA observations of 129 fields in the COSMOS region at 1.25mm, detecting 152 galaxies at S/N>=5 with an average continuum RMS of 150 {mu}Jy. These fields represent a S/N-limited sample of AzTEC/ASTE sources with 1.1mm S/N>=4 over an area of 0.72 square degrees. Given ALMA's fine resolution and the exceptional spectroscopic and multiwavelength photometric data available in COSMOS, this survey allows us unprecedented power in identifying submillimeter galaxy counterparts and determining their redshifts through spectroscopic or photometric means. In addition to 30 sources with prior spectroscopic redshifts, we identified redshifts for 113 galaxies through photometric methods and an additional nine sources with lower limits, which allowed a statistically robust determination of the redshift distribution. We have resolved 33 AzTEC sources into multi-component systems and our redshifts suggest that nine are likely to be physically associated. Our overall redshift distribution peaks at z~2.0 with a high-redshift tail skewing the median redshift to z^~^=2.48+/-0.05. We find that brighter millimeter sources are preferentially found at higher redshifts. Our faintest sources, with S_1.25mm_<1.25mJy, have a median redshift of z^~^=2.18+/-0.09, while the brightest sources, S_1.25mm_>1.8mJy, have a median redshift of z^~^=3.08+/-0.17. After accounting for spectral energy distribution shape and selection effects, these results are consistent with several previous submillimeter galaxy surveys, and moreover, support the conclusion that the submillimeter galaxy redshift distribution is sensitive to survey depth.
- ID:
- ivo://CDS.VizieR/J/ApJS/212/18
- Title:
- An atlas of UV-to-MIR galaxy SEDs
- Short Name:
- J/ApJS/212/18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an atlas of 129 spectral energy distributions for nearby galaxies, with wavelength coverage spanning from the ultraviolet to the mid-infrared. Our atlas spans a broad range of galaxy types, including ellipticals, spirals, merging galaxies, blue compact dwarfs, and luminous infrared galaxies. We have combined ground-based optical drift-scan spectrophotometry with infrared spectroscopy from Spitzer and Akari with gaps in spectral coverage being filled using Multi-wavelength Analysis of Galaxy Physical Properties spectral energy distribution models. The spectroscopy and models were normalized, constrained, and verified with matched-aperture photometry measured from Swift, Galaxy Evolution Explorer, Sloan Digital Sky Survey, Two Micron All Sky Survey, Spitzer, and Wide-field Infrared Space Explorer images. The availability of 26 photometric bands allowed us to identify and mitigate systematic errors present in the data. Comparison of our spectral energy distributions with other template libraries and the observed colors of galaxies indicates that we have smaller systematic errors than existing atlases, while spanning a broader range of galaxy types. Relative to the prior literature, our atlas will provide improved K-corrections, photometric redshifts, and star-formation rate calibrations.
- ID:
- ivo://CDS.VizieR/J/ApJ/871/129
- Title:
- A redshift catalog of the galaxy cluster A2029
- Short Name:
- J/ApJ/871/129
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explore the structure of galaxy cluster A2029 and its surroundings based on intensive spectroscopy along with X-ray and weak lensing observations. The redshift survey includes 4376 galaxies (1215 spectroscopic cluster members) within 40' of the cluster center; the redshifts are included here. Two subsystems, A2033 and a southern infalling group (SIG), appear in the infall region based on the spectroscopy, as well as on the weak lensing and X-ray maps. The complete redshift survey of A2029 also identifies at least 12 foreground and background systems (10 are extended X-ray sources) in the A2029 field; we include a census of their properties. The X-ray luminosities (L_X_)-velocity dispersions ({sigma}_cl_) scaling relations for A2029, A2033, SIG, and the foreground/background systems are consistent with the known cluster scaling relations. The combined spectroscopy, weak lensing, and X-ray observations provide a robust measure of the masses of A2029, A2033, and SIG. The total mass of the infalling groups (A2033 and SIG) is ~60% of the M200 of the primary cluster, A2029. Simple dynamical considerations suggest that A2029 will accrete these subsystems in the next few Gyr. In agreement with simulations and other clusters observed in a similar redshift range, the total mass in the A2029 infall region is comparable to the A2029 M200 and will mostly be accreted in the long-term future.