- ID:
- ivo://CDS.VizieR/J/MNRAS/448/3731
- Title:
- Local Group dSph radio survey with ATCA
- Short Name:
- J/MNRAS/448/3731
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Dwarf spheroidal (dSph) galaxies are key objects in near-field cosmology, especially in connection to the study of galaxy formation and evolution at small scales. In addition, dSphs are optimal targets to investigate the nature of dark matter. However, while we begin to have deep optical photometric observations of the stellar population in these objects, little is known so far about their diffuse emission at any observing frequency, and hence on thermal and non-thermal plasma possibly residing within dSphs. In this paper, we present deep radio observations of six local dSphs performed with the Australia Telescope Compact Array (ATCA) at 16cm wavelength. We mosaicked a region of radius of about 1{deg} around three 'classical' dSphs, Carina, Fornax, and Sculptor, and of about half of degree around three 'ultrafaint' dSphs, BootesII, Segue2, and Hercules. The rms noise level is below 0.05 mJy for all the maps. The restoring beams full width at half-maximum ranged from 4.2"x2.5" to 30.0"x2.1" in the most elongated case. A catalogue including the 1392 sources detected in the six dSph fields is reported. The main properties of the background sources are discussed, with positions and fluxes of brightest objects compared with the FIRST, NVSS, and SUMSS observations of the same fields. The observed population of radio emitters in these fields is dominated by synchrotron sources. We compute the associated source number counts at 2GHz down to fluxes of 0.25mJy, which prove to be in agreement with AGN count models.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/657/A54
- Title:
- Local Group Gaia eDR3 systemic motions
- Short Name:
- J/A+A/657/A54
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We perform a comprehensive determination of the systemic proper motions of 74 dwarf galaxies and dwarf galaxy candidates in the Local Group based on Gaia early data release 3. The outputs of the analysis for each galaxy, including probabilities of membership, will be made publicly available. The analysis is augmented by a determination of the orbital properties of galaxies within 500kpc. We adopt a flexible Bayesian methodology presented in the literature, which takes into account the location of the stars on the sky, on the colour-magnitude diagram, and on the proper motion plane. We applied some modifications, in particular to the way the colour-magnitude diagram and spectroscopic information are factored in, for example, by including stars in several evolution phases. The bulk motions were integrated in three gravitational potentials: two where the Milky Way was treated in isolation and has a mass 0.9 & 1.6x10^12^M_{sun}_, and a time-varying potential, which includes the infall of a massive Large Magellanic Cloud (LMC). We were able to determine bulk proper motions for 73 systems, and we consider 66 to be reliable measurements. For the first time, systemic motions are presented for galaxies out to a distance of 1.4Mpc in the NGC 3109 association. The inclusion of the infall of a massive LMC significantly modifies the orbital trajectories of the objects, with respect to orbit integration in static Milky-Way-only potentials, and this leads to six galaxies likely being associated with the LMC, three possibly being associated with it, and one recently captured object. We discuss the results of the orbit integration in the context of the relation of the galaxies to the system of Milky Way satellites, implications for the too-big-to-fail problem, the impact on star formation histories, and tidal disruption.
1993. Local hosts of SNe Ia
- ID:
- ivo://CDS.VizieR/J/ApJ/707/1449
- Title:
- Local hosts of SNe Ia
- Short Name:
- J/ApJ/707/1449
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use multi-wavelength, matched aperture, integrated photometry from the Galaxy Evolution Explorer (GALEX), the Sloan Digital Sky Survey, and the RC3 to estimate the physical properties of 166 nearby galaxies hosting 168 well-observed Type Ia supernovae (SNe Ia). The ultraviolet (UV) imaging of local SN Ia hosts from GALEX allows a direct comparison with higher-redshift hosts measured at optical wavelengths that correspond to the rest-frame UV. Our data corroborate well-known features that have been seen in other SN Ia samples. Specifically, hosts with active star formation produce brighter and slower SNe Ia on average, and hosts with luminosity-weighted ages older than 1Gyr produce on average more faint, fast, and fewer bright, slow SNe Ia than younger hosts. New results include that in our sample, the faintest and fastest SNe Ia occur only in galaxies exceeding a stellar mass threshold of ~10^10^M_{sun}_, leading us to conclude that their progenitors must arise in populations that are older and/or more metal rich than the general SN Ia population.
- ID:
- ivo://CDS.VizieR/J/MNRAS/438/796
- Title:
- Local radio-galaxy population at 20GHz
- Short Name:
- J/MNRAS/438/796
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have made the first detailed study of the high-frequency radio-source population in the local Universe, using a sample of 202 radio sources from the Australia Telescope 20GHz (AT20G) survey identified with galaxies from the 6dF Galaxy Survey (6dFGS). The AT20G-6dFGS galaxies have a median redshift of z=0.058 and span a wide range in radio luminosity, allowing us to make the first measurement of the local radio luminosity function at 20GHz. Our sample includes some classical Fanaroff-Riley type I (FR I) and FR II radio galaxies, but most of the AT20G-6dFGS galaxies host compact (FR 0) radio active galactic nuclei which appear to lack extended radio emission even at lower frequencies. Most of these FR 0 sources show no evidence for relativistic beaming, and the FR 0 class appears to be a mixed population which includes young compact steep-spectrum and gigahertz peaked-spectrum radio galaxies. We see a strong dichotomy in the Wide-field Infrared Survey Explorer (WISE) mid-infrared colours of the host galaxies of FR I and FR II radio sources, with the FR I systems found almost exclusively in WISE 'early-type' galaxies and the FR II radio sources in WISE 'late-type' galaxies. The host galaxies of the flat- and steep-spectrum radio sources have a similar distribution in both K-band luminosity and WISE colours, though galaxies with flat-spectrum sources are more likely to show weak emission lines in their optical spectra. We conclude that these flat-spectrum and steep-spectrum radio sources mainly represent different stages in radio-galaxy evolution, rather than beamed and unbeamed radio-source populations.
- ID:
- ivo://CDS.VizieR/J/A+A/343/93
- Title:
- Local radio luminosity function of galaxies. II.
- Short Name:
- J/A+A/343/93
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using new extensive radio continuum surveys at 1.4GHz (FIRST and NVSS), we derive the distribution of the radio/optical and radio/NIR luminosity (RLF) of late-type (Sa-Irr) galaxies (m_p_<15.7) in 5 nearby clusters of galaxies: A262, Cancer, A1367, Coma and Virgo. With the aim of discussing possible environmental dependences of the radio properties, we compare these results with those obtained for relatively isolated objects in the Coma supercluster. We find that the RLF of Cancer, A262 and Virgo are consistent with that of isolated galaxies. Conversely we confirm earlier claims that galaxies in A1367 and Coma have their radio emissivity enhanced by a factor ~5 with respect to isolated objects. We discuss this result in the framework of the dynamical pressure suffered by galaxies in motion through the intra-cluster gas (ram-pressure). We find that the radio excess is statistically larger for galaxies in fast transit motion. This is coherent with the idea that enhanced radio continuum activity is associated with magnetic field compression. The X-ray luminosities and temperatures of Coma and A1367 imply that these two clusters have significantly larger intracluster gas density than the remaining three studied ones, providing a clue for explaining the higher radio continuum luminosities of their galaxies. Multiple systems in the Coma supercluster bridge (with projected separations smaller than 300kpc) have radio luminosities significantly larger than isolated galaxies.
- ID:
- ivo://CDS.VizieR/J/MNRAS/457/2703
- Title:
- Local SDSS galaxies in Herschel Stripe 82
- Short Name:
- J/MNRAS/457/2703
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study a set of 3319 galaxies in the redshift interval 0.04<z<0.15 Herschel/SPIRE 250{mu}m band. Total infrared (TIR) luminosities derived from HerS and Wide-field Infrared Survey Explorer (WISE) photometry allow us to compare infrared and optical estimates of SFR with unprecedented statistics for diverse classes of galaxies. We find excellent agreement between TIR-derived and emission line-based SFRs for H ii galaxies. Other classes, such as active galaxies and evolved galaxies, exhibit systematic discrepancies between optical and TIR SFRs. We demonstrate that these offsets are attributable primarily to survey biases and the large intrinsic uncertainties of the D_n_4000- and colour-based optical calibrations used to estimate the SDSS SFRs of these galaxies. Using a classification scheme which expands upon popular emission-line methods, we demonstrate that emission-line galaxies with uncertain classifications include a population of massive, dusty, metal-rich star-forming systems that are frequently neglected in existing studies. We also study the capabilities of infrared selection of star-forming galaxies. FIR selection reveals a substantial population of galaxies dominated by cold dust which are missed by the long-wavelength WISE bands. Our results demonstrate that Herschel large-area surveys offer the means to construct large, relatively complete samples of local star-forming galaxies with accurate estimates of SFR that can be used to study the interplay between nuclear activity and star formation.
- ID:
- ivo://CDS.VizieR/J/AJ/153/6
- Title:
- Local Tully-Fisher relation for dwarf galaxies
- Short Name:
- J/AJ/153/6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study different incarnations of the Tully-Fisher (TF) relation for the Local Volume (LV) galaxies taken from Updated Nearby Galaxy Catalog. The UNGC sample contains 656 galaxies with W_50_ HI-line-width estimates, mostly belonging to low-mass dwarfs. Of them, 296 objects have distances measured with accuracies better than 10%. For the sample of 331 LV galaxies having baryonic masses logM_bar_>5.8logM_{Sun}_, we obtain a relation logM_bar_=2.49logW_50_+3.97 with an observed scatter of 0.38dex. The largest factors affecting the scatter are observational errors in K-band magnitudes and W_50_ line widths for the tiny dwarfs, as well as uncertainty of their inclinations. We find that accounting for the surface brightness of the LV galaxies or their gas fraction, specific star-formation rate, or isolation index does not essentially reduce the observed scatter on the baryonic TF diagram. We also notice that a sample of 71 dSph satellites of the Milky Way and M31 with a known stellar velocity dispersion {sigma}* tends to follow nearly the same bTF relation, having slightly lower masses than that of late-type dwarfs.
- ID:
- ivo://CDS.VizieR/J/MNRAS/478/1611
- Title:
- Local Volume H I Survey (LVHIS)
- Short Name:
- J/MNRAS/478/1611
- Date:
- 19 Jan 2022 11:54:59
- Publisher:
- CDS
- Description:
- The 'Local Volume HI Survey' (LVHIS) comprises deep HI spectral line and 20-cm radio continuum observations of 82 nearby, gas-rich galaxies, supplemented by multiwavelength images. Our sample consists of all galaxies with Local Group velocities v_LG_<550km/s or distances D<10Mpc that are detected in the HI Parkes All Sky Survey (HIPASS). Using full synthesis observations in at least three configurations of the Australia Telescope Compact Array (ATCA), we obtain detailed HI maps for a complete sample of gas-rich galaxies with {delta}~-30{deg}. Here we present a comprehensive LVHIS galaxy atlas, including the overall gas distribution, mean velocity field, velocity dispersion, and position-velocity diagrams, together with a homogeneous set of measured and derived galaxy properties. Our primary goal is to investigate the HI morphologies, kinematics, and environment at high resolution and sensitivity. LVHIS galaxies represent a wide range of morphologies and sizes; our measured HI masses range from ~10^7^ to 10^10^M_{sun}_, based on independent distance estimates.
- ID:
- ivo://CDS.VizieR/J/MNRAS/463/2997
- Title:
- Lockman Hole low-frequency radio sources
- Short Name:
- J/MNRAS/463/2997
- Date:
- 02 Nov 2021 11:21:03
- Publisher:
- CDS
- Description:
- The Lockman Hole is a well-studied extragalactic field with extensive multi-band ancillary data covering a wide range in frequency, essential for characterizing the physical and evolutionary properties of the various source populations detected in deep radio fields (mainly star-forming galaxies and AGNs). In this paper, we present new 150-MHz observations carried out with the LOw-Frequency ARray (LOFAR), allowing us to explore a new spectral window for the faint radio source population. This 150-MHz image covers an area of 34.7 square degrees with a resolution of 18.6x14.7-arcsec and reaches an rms of 160{mu}Jy/beam at the centre of the field. As expected for a low-frequency selected sample, the vast majority of sources exhibit steep spectra, with a median spectral index of {alpha}_150_^1400^=-0.78+/-0.015. The median spectral index becomes slightly flatter (increasing from {alpha}_150_^1400^=-0.84 to {alpha}_150_^1400^=-0.75) with decreasing flux density down to S_150_ ~10mJy before flattening out and remaining constant below this flux level. For a bright subset of the 150-MHz selected sample, we can trace the spectral properties down to lower frequencies using 60-MHz LOFAR observations, finding tentative evidence for sources to become flatter in spectrum between 60 and 150MHz. Using the deep, multi-frequency data available in the Lockman Hole, we identify a sample of 100 ultra-steep-spectrum sources and 13 peaked-spectrum sources. We estimate that up to 21 per cent of these could have z>4 and are candidate high-z radio galaxies, but further follow-up observations are required to confirm the physical nature of these objects.
- ID:
- ivo://CDS.VizieR/J/ApJ/793/82
- Title:
- LOFAR Bootes and 3C295 field sources
- Short Name:
- J/ApJ/793/82
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Low Frequency Array (LOFAR) Low Band observations of the Bootes and 3C 295 fields. Our images made at 34, 46, and 62 MHz reach noise levels of 12, 8, and 5 mJy/beam, making them the deepest images ever obtained in this frequency range. In total, we detect between 300 and 400 sources in each of these images, covering an area of 17-52 deg^2^. From the observations, we derive Euclidean-normalized differential source counts. The 62 MHz source counts agree with previous GMRT 153 MHz and Very Large Array 74 MHz differential source counts, scaling with a spectral index of -0.7. We find that a spectral index scaling of -0.5 is required to match up the LOFAR 34 MHz source counts. This result is also in agreement with source counts from the 38 MHz 8C survey, indicating that the average spectral index of radio sources flattens toward lower frequencies. We also find evidence for spectral flattening using the individual flux measurements of sources between 34 and 1400 MHz and by calculating the spectral index averaged over the source population. To select ultra-steep spectrum ({alpha}<-1.1) radio sources that could be associated with massive high-redshift radio galaxies, we compute spectral indices between 62 MHz, 153 MHz, and 1.4 GHz for sources in the Bootes field. We cross-correlate these radio sources with optical and infrared catalogs and fit the spectral energy distribution to obtain photometric redshifts. We find that most of these ultra-steep spectrum sources are located in the 0.7<~z<~2.5 range.
