- ID:
- ivo://CDS.VizieR/VII/257
- Title:
- 2MASS-selected Isolated Galaxies (2MIG)
- Short Name:
- VII/257
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We undertook searches for isolated galaxies based on automatic selection of infrared sources from the Two Micron All-Sky Survey (2MASS, Cat. II/246) followed by a visual inspection of their surrounding. Using a modified criterion by Karachentseva (1973SoSAO...8....3K), we compiled a catalog of 3227 isolated galaxies (2MIG) containing 6% of 2MASS Extended Sources (2MASX, Cat. VII/233) brighter than K_s_=12mag with angular diameters a_K_<=30". The most isolated 2493 galaxies among them enter in the 2MASS Very Isolated Galaxy Catalog, 2MVIG. Being situated in the regions of extremely low mass density, the 2MVIG galaxies can serve as a reference sample for investigation the influence of environment on structure and evolution of galaxies.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/516/693
- Title:
- Mass-to-light ratio of binary galaxies
- Short Name:
- J/ApJ/516/693
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the mass-to-light ratio determination based on a newly selected binary galaxy sample, which includes a large number of pairs whose separations exceed a few hundred kpc. The probability distributions of the projected separation and the velocity difference have been calculated considering the contamination of optical pairs, and the mass-to-light (M/L) ratio has been determined based on the maximum likelihood method. The best estimate of the M/L in the B band for 57 pairs is found to be 28 - 36 depending on the orbital parameters and the distribution of optical pairs (solar unit: H_o_ = 50 km s^-1^ Mpc^-1^). The best estimate of the M/L for 30 pure spiral pairs is found to be 12 - 16. These results are relatively smaller than those obtained in previous studies but are consistent with each other within the errors. Although the number of pairs with large separation is significantly increased compared with previous samples, the M/L does not show any tendency of increase but is found to be almost independent of the separation of pairs beyond 100 kpc. The constancy of the M/L beyond 100 kpc may indicate that the typical halo size of spiral galaxies is less than 100 kpc.
- ID:
- ivo://CDS.VizieR/J/ApJ/850/15
- Title:
- Mass-to-light ratios in low-mass early-type gal.
- Short Name:
- J/ApJ/850/15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present dynamical measurements of the central mass-to-light ratio (M/L) of a sample of 27 low-mass early-type ATLAS^3D^ galaxies. We consider all ATLAS^3D^ galaxies with 9.7<log(M*/M_{sun}_)<10.5 in our analysis, selecting out galaxies with available high-resolution Hubble Space Telescope (HST) data, and eliminating galaxies with significant central color gradients or obvious dust features. We use the HST images to derive mass models for these galaxies and combine these with the central velocity dispersion values from ATLAS^3D^ data to obtain a central dynamical M/L estimate. These central dynamical M/Ls are higher than dynamical M/Ls derived at larger radii and stellar population estimates of the galaxy centers in ~80% of galaxies, with a median enhancement of ~14% and a statistical significance of 3.3{sigma}. We show that the enhancement in the central M/L is best described either by the presence of black holes in these galaxies or by radial initial mass function variations. Assuming a black hole model, we derive black hole masses for the sample of galaxies. In two galaxies, NGC 4458 and NGC 4660, the data suggest significantly overmassive black holes, while in most others only upper limits are obtained. We also show that the level of M/L enhancements we see in these early-type galaxy nuclei are consistent with the larger enhancements seen in ultracompact dwarf galaxies (UCDs), supporting the scenario where massive UCDs are created by stripping galaxies of these masses.
- ID:
- ivo://CDS.VizieR/J/ApJ/756/74
- Title:
- 2MASS view of Sgr dSph. VII. Kinematics
- Short Name:
- J/ApJ/756/74
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have assembled a large-area spectroscopic survey of giant stars in the Sagittarius (Sgr) dwarf galaxy core. Using medium resolution (R~15000), multifiber spectroscopy we have measured velocities of these stars, which extend up to 12{deg} from the galaxy's center (3.7 core radii or 0.4 times the King limiting radius). From these high-quality spectra we identify 1310 Sgr members out of 2296 stars surveyed, distributed across 24 different fields across the Sgr core. Additional slit spectra were obtained of stars bridging from the Sgr core to its trailing tail. Our systematic, large-area sample shows no evidence for significant rotation, a result at odds with the ~20km/s rotation required as an explanation for the bifurcation seen in the Sgr tidal stream; the observed small (<=4km/s) velocity trend primarily along the major axis is consistent with models of the projected motion of an extended body on the sky with no need for intrinsic rotation. The Sgr core is found to have a flat velocity dispersion (except for a kinematically colder center point) across its surveyed extent and into its tidal tails, a property that matches the velocity dispersion profiles measured for other Milky Way dwarf spheroidal (dSph) galaxies. We comment on the possible significance of this observed kinematical similarity for the dynamical state of the other classical Milky Way dSphs in light of the fact that Sgr is clearly a strongly tidally disrupted system.
- ID:
- ivo://CDS.VizieR/J/ApJ/847/18
- Title:
- Mass, Z, dust attenuation, and SFR relations
- Short Name:
- J/ApJ/847/18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze the optical continuum of star-forming galaxies in the Sloan Digital Sky Survey by fitting stacked spectra with stellar population synthesis models to investigate the relation between stellar mass, stellar metallicity, dust attenuation, and star formation rate. We fit models calculated with star formation and chemical evolution histories that are derived empirically from multi-epoch observations of the stellar mass-star formation rate and the stellar mass-gas-phase metallicity relations, respectively. We also fit linear combinations of single-burst models with a range of metallicities and ages. Star formation and chemical evolution histories are unconstrained for these models. The stellar mass-stellar metallicity relations obtained from the two methods agree with the relation measured from individual supergiant stars in nearby galaxies. These relations are also consistent with the relation obtained from emission-line analysis of gas-phase metallicity after accounting for systematic offsets in the gas-phase metallicity. We measure dust attenuation of the stellar continuum and show that its dependence on stellar mass and star formation rate is consistent with previously reported results derived from nebular emission lines. However, stellar continuum attenuation is smaller than nebular emission line attenuation. The continuum-to-nebular attenuation ratio depends on stellar mass and is smaller in more massive galaxies. Our consistent analysis of stellar continuum and nebular emission lines paves the way for a comprehensive investigation of stellar metallicities of star-forming and quiescent galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/872/148
- Title:
- 2MASX/NVSS galaxies brighter than K_20fe_=12.25
- Short Name:
- J/ApJ/872/148
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We identified 15658 NRAO VLA Sky Survey (NVSS) radio sources among the 55288 2 Micron All-Sky Survey eXtended (2MASX) galaxies brighter than k_20fe_=12.25 at {lambda}=2.16{mu}m and covering the {Omega}=7.016sr of sky defined by J2000 {delta}>-40{deg} and |b|>20{deg}. The complete sample of 15043 galaxies with 1.4GHz flux densities S>=2.45mJy contains a 99.9% spectroscopically complete subsample of 9517 galaxies with k_20fe_<=11.75. We used only radio and infrared data to quantitatively distinguish radio sources powered primarily by recent star formation from those powered by active galactic nuclei. The radio sources with log[L(W/Hz)]>19.3 that we used to derive the local spectral luminosity and power-density functions account for >99% of the total 1.4GHz spectral power densities U_SF_=(1.54+/-0.20)x10^19^W/Hz/Mpc^3^ and U_AGN_=(4.23+/-0.78)x10^19^W/Hz/Mpc^3^ in the universe today, and the spectroscopic subsample is large enough that the quoted errors are dominated by cosmic variance. The recent comoving star formation rate density indicated by USF is {psi}~0.015M_{sun}_/yr/Mpc^3^.
- ID:
- ivo://CDS.VizieR/J/AJ/137/42
- Title:
- Matched SDSS and FIRST Sample
- Short Name:
- J/AJ/137/42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The question as to whether the distribution of radio loudness in active galactic nuclei (AGNs) is actually bimodal has been discussed extensively in the literature. Furthermore, there have been claims that radio loudness depends on black hole mass (M_BH_) and Eddington ratio (L_bol_/L_Edd_).We investigate these claims using the low- redshift broad line AGN sample of Greene & Ho (2007ApJ...667..131G), which consists of 8434 objects at z<0.35 from the Sloan Digital Sky Survey Fourth Data Release (SDSS DR4). We obtained radio fluxes from the Very Large Array Faint Images of the Radio Sky at Twenty-centimeters (FIRST) survey for the SDSS AGN. Out of the 8434 SDSS AGNs, 821 have corresponding observed radio fluxes in the FIRST survey.
- ID:
- ivo://CDS.VizieR/J/MNRAS/506/5494
- Title:
- MATLAS dwarfs structure and morphology
- Short Name:
- J/MNRAS/506/5494
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We present a photometric study of the dwarf galaxy population in the low to moderate density environments of the MATLAS (Mass Assembly of early-Type gaLAxies with their fine Structures) deep imaging survey. The sample consists of 2210 dwarfs, including 508 nucleated. We define a nucleus as a compact source that is close to the galaxy photocentre (within 0.5Re) which is also the brightest such source within the galaxy's effective radius. The morphological analysis is performed using a 2D surface brightness profile modelling on the g-band images of both the galaxies and nuclei. Our study reveals that, for similar luminosities, the MATLAS dwarfs show ranges in the distribution of structural properties comparable to cluster (Virgo and Fornax) dwarfs and a range of sizes comparable to the Local Group and Local Volume dwarfs. Colour measurements using the r- and i-band images indicate that the dwarfs in low and moderate density environments are as red as cluster dwarfs on average. The observed similarities between dwarf ellipticals in vastly different environments imply that dEs are not uniquely the product of morphological transformation due to ram-pressure stripping and galaxy harassment in high density environments. We measure that the dwarf nuclei are located predominantly in massive, bright and round dwarfs and observe fewer nuclei in dwarfs with a faint centre and a small size. The colour of the galaxy nucleus shows no clear relation to the colour of the dwarf, in agreement with the migration and wet migration nucleus formation scenarios. The catalogues of the MATLAS dwarfs photometric and structural properties are provided.
- ID:
- ivo://CDS.VizieR/J/A+A/654/A105
- Title:
- MATLAS ultra diffuse galaxies
- Short Name:
- J/A+A/654/A105
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Recent advances in deep dedicated imaging surveys over the past decade have uncovered a surprisingly large number of extremely faint low surface brightness galaxies with large physical sizes called ultra diffuse galaxies (UDGs) in clusters and, more recently, in lower density environments. As part of the Mass Assembly of early-Type GaLAxies with their fine Structures (MATLAS) survey, a deep imaging large program at the Canada-France-Hawaii Telescope (CFHT), our team has identified 2210 dwarf galaxies, 59 (~3%) of which qualify as UDGs. Averaging over the survey area, we find ~0.4 UDG per square degree. They are found in a range of low to moderate density environments, although 61% of the sample fall within the virial radii of groups. Based on a detailed analysis of their photometric and structural properties, we find that the MATLAS UDGs do not show significant differences from the traditional dwarfs, except from the predefined size and surface brightness cut. Their median color is as red as the one measured in galaxy clusters, albeit with a narrower color range. The majority of the UDGs are visually classified as dwarf ellipticals with log stellar masses of 6.5-8.7. The fraction of nucleated UDGs (~34%) is roughly the same as the nucleated fraction of the traditional dwarfs. Only five (~8%) UDGs show signs of tidal disruption and only two are tidal dwarf galaxy candidates. A study of globular cluster (GC) candidates selected in the CFHT images finds no evidence of a higher GC specific frequency S_N for UDGs than for classical dwarfs, contrary to what is found in most clusters. The UDG halo-to-stellar mass ratio distribution, as estimated from the GC counts, peaks at roughly the same value as for the traditional dwarfs, but spans the smaller range of ~10-2000. We interpret these results to mean that the large majority of the field-to-group UDGs do not have a different formation scenario than traditional dwarfs.
- ID:
- ivo://CDS.VizieR/J/A+A/651/A98
- Title:
- M31 C-band (6.6GHz) Sardinia radio tel. map
- Short Name:
- J/A+A/651/A98
- Date:
- 17 Jan 2022 11:45:00
- Publisher:
- CDS
- Description:
- The Andromeda galaxy is the best known large galaxy besides our own Milky Way. Several images and studies exist at all wavelengths from radio to hard X-ray. Nevertheless, only few observations are available in the microwave range where its average radio emission reaches the minimum. In this paper we want to study the radio morphology of the galaxy, decouple thermal from non-thermal emission and extract the star formation rate. We also aim to derive a complete catalogue of radio sources for the mapped patch of sky. We have observed the Andromeda galaxy with the Sardinia Radio Telescope at 6.6 GHz with very high sensitivity and angular resolution, and an unprecedented sky coverage. Using new 6.6GHz data and Effelsberg radio telescope ancillary data, we confirm that, globally, the spectral index assumes a value of ~0.7-0.8, while in the star forming regions it decreases to ~0.5. By disentangling (gas) thermal and non-thermal emission, we found that at 6.6GHz, thermal emission follows the distribution of HII regions around the ring. Non-thermal emission, within the ring, appears to be more uniform and smooth than thermal emission, due to the diffusion of the cosmic ray electrons away from their birthplaces. Hence the magnetic fields are nearly constant in intensity. Based on the thermal emission map, we have calculated a star formation rate map. Integrating within a radius of R_max_=15kpc, we obtained a total star formation rate of 0.19+/-0.01M*/yr in agreement with previous results in literature. Finally, we correlated our radio data with Infrared images of the Andromeda galaxy. We found an unexpected high correlation between non-thermal and MIR data in the central region, with a correlation parameter r=0.93. Finally, by computing the logarithmic 24um/21cm ratio q_24um_, we found a decreasing trend with increasing galactocentric distance and an increasing dispersion. The logarithmic FIR/radio ratio is found to be 2.41+/-0.04.
