- ID:
- ivo://CDS.VizieR/J/A+A/608/A127
- Title:
- Breaks in disc galaxy abundance gradients
- Short Name:
- J/A+A/608/A127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We examine the relation between breaks in the surface brightness profiles and radial abundance gradients within the optical radius in the discs of 134 spiral galaxies from the CALIFA survey. The distribution of the radial abundance (in logarithmic scale) in each galaxy was fitted by simple and broken linear relations. The surface brightness profile was fitted assuming pure and broken exponents for the disc. We find that the maximum absolute difference between the abundances in a disc given by broken and pure linear relations is less than 0.05dex in the majority of our galaxies and exceeds the scatter in abundances for 26 out of 134 galaxies considered. The scatter in abundances around the broken linear relation is close (within a few percent) to that around the pure linear relation. The breaks in the surface brightness profiles are more prominent. The scatter around the broken exponent in a number of galaxies is lower by a factor of two or more than that around the pure exponent. The shapes of the abundance gradients and surface brightness profiles within the optical radius in a galaxy may be different. A pure exponential surface brightness profile may be accompanied by a broken abundance gradient and vise versa. There is no correlation between the break radii of the abundance gradients and surface brightness profiles. Thus, a break in the surface brightness profile does not need to be accompanied by a break in the abundance gradient.
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- ID:
- ivo://CDS.VizieR/J/A+A/625/A36
- Title:
- Breaks in surf. brightness prof. of galaxy disks
- Short Name:
- J/A+A/625/A36
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using a sample of 175 low-inclination galaxies from the S^4^G, we investigate the origins of up-bending (Type III) breaks in the 3.6{mu}m surface brightness profiles of disk galaxies. We reanalyzed a sample of previously identified Type III disk break-hosting galaxies using a new, unbiased break-finding algorithm, which uncovered many new, sometimes subtle disk breaks across the whole sample. We classified each break by its likely origin through close examination of the galaxy images across wavelengths, and compare samples of galaxies separated by their outermost identified break types in terms of their stellar populations and local environments. We find that more than half of the confirmed Type III breaks in our sample can be attributed to morphological asymmetry in the host galaxies. As these breaks are mostly an artifact of the azimuthal averaging process, their status as physical breaks is questionable. Such galaxies occupy some of the highest density environments in our sample, implying that much of this asymmetry is the result of tidal disturbance. We also find that Type III breaks related to extended spiral arms or star formation often host down-bending (Type II) breaks at larger radius which were previously unidentified. Such galaxies reside in the lowest density environments in our sample, in line with previous studies that found a lack of Type II breaks in clusters. Galaxies occupying the highest density environments most often show Type III breaks associated with outer spheroidal components. We find that Type III breaks in the outer disks of galaxies arise most often through environmental influence: either tidal disturbance (resulting in disk asymmetry) or heating through, for example, galaxy harrassment (leading to spheroidal components). Galaxies hosting the latter break types also show bimodal distributions in central g-r color and morphological type, with more than half of such galaxies classified as Sa or earlier; this suggests these galaxies may be evolving into early-type galaxies. By contrast, we find that Type III breaks related to apparently secular features (e.g., spiral arms) may not truly define their hosts' outer disks, as often in such galaxies additional significant breaks can be found at larger radius. Given this variety in Type III break origins, we recommend in future break studies making a more detailed distinction between break subtypes when seeking out, for example, correlations between disk breaks and environment, to avoid mixing unlike physical phenomena.
- ID:
- ivo://CDS.VizieR/J/ApJS/147/29
- Title:
- BRHalpha data of blue compact dwarf galaxies
- Short Name:
- J/ApJS/147/29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present B, R, and H{alpha} images for a total of 114 nearby galaxies (v_helio_<4000km/s) that, with exception of nine objects, are classified as blue compact dwarfs (BCDs). BR integrated magnitudes, H{alpha} fluxes and H{alpha} equivalent widths for all the objects in the sample are presented.
- ID:
- ivo://CDS.VizieR/J/A+A/544/A34
- Title:
- Bright AGN VLBI imaging study at 2 and 8GHz
- Short Name:
- J/A+A/544/A34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate statistical and individual astrophysical properties of active galactic nuclei (AGNs), such as parsec-scale flux density, core dominance, angular and linear sizes, maximum observed brightness temperatures of VLBI core components, spectral index distributions for core and jet components, and evolution of brightness temperature along the jets. Furthermore, we statistically compare core flux densities and brightness temperature as well as jet spectral indices of {gamma}-ray bright and weak sources. We used 19 very long baseline interferometry (VLBI) observing sessions carried out simultaneously at 2.3GHz and 8.6GHz with the participation of 10 Very Long Baseline Array (VLBA) stations and up to 10 additional geodetic telescopes. The observations span the period 1998-2003. We present here single-epoch results from high-resolution radio observations of 370 AGNs. Our VLBI images at 2.3GHz and 8.6GHz as well as Gaussian models are presented and analyzed. At least one-fourth of the cores are completely unresolved on the longest baselines of the global VLBI observations. The VLBI core components are partially opaque with the median value of spectral index of alpha_core_~0.3, while the jet features are usually optically thin alpha_jet_~-0.7. The spectral index typically decreases along the jet ridge line owing to the spectral aging, with a median value of -0.05mas^-1^. Brightness temperatures are found to be affected by Doppler boosting and reach up to ~10^13^K with a median of ~2.5x10^11^K at both frequencies. The brightness temperature gradients along the jets typically follow a power law T_b_~r^-2.2^ at both frequencies. We find that 147 sources (40%) positionally associated with gamma-ray detections from the Fermi LAT Second Source Catalog have higher core flux densities and brightness temperatures, and are characterized by the less steep radio spectrum of the optically thin jet emission.
- ID:
- ivo://CDS.VizieR/J/ApJ/853/47
- Title:
- Brightest cluster galaxies bright in 22um (W4BCGs)
- Short Name:
- J/ApJ/853/47
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Brightest cluster galaxies (BCGs) are believed to have assembled most of their stars early in time and therefore should be passively evolving at low redshifts and appear "red-and-dead." However, there have been reports that a minority of low-redshift BCGs still have ongoing star formation rates (SFRs) of a few to even ~100M_{sun}_/yr. Such BCGs are found in "cool-core" ("CC") clusters, and their star formation is thought to be fueled by "cooling flow." To further investigate the implications of low-redshift, star-forming BCGs, we perform a systematic search using the 22{mu}m data ("W4" band) from the Wide-field Infrared Survey Explorer (WISE) on the GMBCG catalog, which contains 55424 BCGs at 0.1<~z<~0.55 identified in the Sloan Digital Sky Survey (SDSS). Our sample consists of 389 BCGs that are bright in W4 ("W4BCGs"), most being brighter than 5mJy. While some (<~20%) might host active galactic nuclei, most W4BCGs should owe their strong mid-IR emissions to dust-enshrouded star formation. Their median total IR luminosity (L_IR_) is 5x10^11^L_{sun}_ (SFR~50M_{sun}_/yr), and 27% of the whole sample has L_IR_>10^12^L_{sun}_ (SFR>100M_{sun}_/yr). Using 10 W4BCGs that have Chandra X-ray data, we show that 7 of them are possibly in CC clusters. However, in most cases (five out of seven) the mass deposition rate cannot account for the observed SFR. This casts doubt on the idea that cooling flows are the cause of the star formation in non-quiescent BCGs.
- ID:
- ivo://CDS.VizieR/J/MNRAS/440/405
- Title:
- Brightest galaxies in Local Volume
- Short Name:
- J/MNRAS/440/405
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Distances and near-infrared luminosities of the brightest galaxies in the Local Volume have been re-evaluated in order to gain a fully homogeneous collection of data for elucidating the framework of the Local Sheet and its relevance to Local Group evolution. It is demonstrated that the Local Sheet is both geometrically and dynamically distinct from the Local Supercluster and that the evolution of the Sheet and Local Group were probably interconnected. The Sheet is inclined by 8{deg} with respect to the Local Supercluster, and the dispersion of giant members about the mid-plane is only 230kpc. A 'Council of Giants' with a radius of 3.75Mpc encompasses the Local Group, demarcating a clear upper limit to the realm of influence of the Local Group. The only two giant elliptical galaxies in the Sheet sit on opposite sides of the Council, raising the possibility that they have somehow shepherded the evolution of the Local Group. The position vector of the Andromeda galaxy with respect to the Milky Way deviates only 11{deg} from the Sheet plane and only 11{deg} from the projected axis of the ellipticals. The Local Group appears to be moving away from a ridge in the potential surface of the Council on a path parallel to the elliptical axis. Spin directions of the giants in the Council are distributed over the sky in a pattern which is very different from that of giants beyond, possibly in reaction to the central mass asymmetry that developed into the Local Group. By matching matter densities of Group and Council giants, the edge of the volume of space most likely to have contributed to the development of the Local Group is shown to be very close to where gravitational forces from the Local Group and the Council balance. The boundary specification reveals that the Local Sheet formed out of a density perturbation of very low amplitude (~10%), but that normal matter was incorporated into galaxies with relatively high efficiency (~40%). It appears that the development of the giants of the Local Sheet was guided by a pre-existing flattened framework of matter.
- ID:
- ivo://CDS.VizieR/J/ApJ/889/189
- Title:
- Brightest high-z galaxies in RELICS clusters
- Short Name:
- J/ApJ/889/189
- Date:
- 17 Jan 2022 00:21:16
- Publisher:
- CDS
- Description:
- Massive foreground galaxy clusters magnify and distort the light of objects behind them, permitting a view into both the extremely distant and intrinsically faint galaxy populations. We present here the z~6-8 candidate high-redshift galaxies from the Reionization Lensing Cluster Survey (RELICS), a Hubble and Spitzer Space Telescope survey of 41 massive galaxy clusters spanning an area of ~200arcmin^2^. These clusters were selected to be excellent lenses, and we find similar high-redshift sample sizes and magnitude distributions as the Cluster Lensing And Supernova survey with Hubble (CLASH). We discover 257, 57, and eight candidate galaxies at z~6, 7, and 8 respectively, (322 in total). The observed (lensed) magnitudes of the z~6 candidates are as bright as AB mag ~23, making them among the brightest known at these redshifts, comparable with discoveries from much wider, blank-field surveys. RELICS demonstrates the efficiency of using strong gravitational lenses to produce high-redshift samples in the epoch of reionization. These brightly observed galaxies are excellent targets for follow-up study with current and future observatories, including the James Webb Space Telescope.
- ID:
- ivo://CDS.VizieR/J/AJ/124/1954
- Title:
- 1000 brightest HIPASS galaxies catalog
- Short Name:
- J/AJ/124/1954
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The HI Parkes All-Sky Survey (HIPASS) is a blind 21cm survey for extragalactic neutral hydrogen, covering the whole southern sky. The HIPASS Bright Galaxy Catalog (BGC) is a subset of HIPASS and contains the 1000 HI brightest (peak flux density) galaxies. Here we present the 138 HIPASS BGC galaxies that had no redshift measured prior to the Parkes multibeam HI surveys. Of the 138 galaxies, 87 are newly catalogued. Newly catalogued is defined as having no optical (or infrared) counterpart in the NASA/IPAC Extragalactic Database. Using the Digitized Sky Survey, we identify optical counterparts for almost half of the newly catalogued galaxies, which are typically of irregular or Magellanic morphological type. Several HI sources appear to be associated with compact groups or pairs of galaxies rather than an individual galaxy. The majority (57) of the newly catalogued galaxies lie within 10{deg} of the Galactic plane and are missing from optical surveys as a result of confusion with stars or dust extinction. This sample also includes newly catalogued galaxies first discovered by Henning et al. in the HI shallow survey of the zone of avoidance. The other 30 newly catalogued galaxies escaped detection because of their low surface brightness or optical compactness. Only one of these, HIPASS J0546-68, has no obvious optical counterpart, as it is obscured by the Large Magellanic Cloud. We find that the newly catalogued galaxies with |b|>10{deg} are generally lower in HI mass and narrower in velocity width compared with the total HIPASS BGC. In contrast, newly catalogued galaxies behind the Milky Way are found to be statistically similar to the entire HIPASS BGC. In addition to these galaxies, the HIPASS BGC contains four previously unknown HI clouds. Description:
- ID:
- ivo://CDS.VizieR/J/MNRAS/216/173
- Title:
- Bright extragalactic radio sources at 2.7 GHz
- Short Name:
- J/MNRAS/216/173
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The brightest extragalactic radio sources at 2.7 GHz are catalogued. The complete sample comprises 233 sources found in the major centimeter wavelength surveys carried out at ANRAO/Parkes, NNRAO/Greenbank, and MPIfR/Bonn: the sample covers 9.81 sr and has limits S(27) = 2.0 Jy and |b| > 10{deg}. A critical reanalysis of the data shows that 227 (97 percent) have optical identifications and 171 (73 percent) have measured redshifts. The implications of the catalogue statistics for the luminosity functions of different radio-source populations are considered.
- ID:
- ivo://CDS.VizieR/VIII/5
- Title:
- Bright Extragalactic Radio Sources (1Jy)
- Short Name:
- VIII/5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The catalog is a compilation of 518 extragalactic radio sources with flux densities greater than 1 Jy at 5 GHz. It contains sources from the NRAO-MPI 5-GHz Strong Source Surveys and from re-observation at 5 GHz of sources found in the Parkes 2.7-GHz surveys. All sources were found in 9.811 sr covered by the two surveys. This is essentially the whole sky, excluding the galactic plane (latitudes less than 10 degrees) and the Magellanic Clouds. The catalog includes radio flux densities, radio positions, object classes, visual magnitudes, redshifts, and spectral indices.
