- ID:
- ivo://CDS.VizieR/J/MNRAS/392/1265
- Title:
- Faint red galaxies in Coma cluster spectroscopy
- Short Name:
- J/MNRAS/392/1265
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the stellar populations in a sample of 89 faint red galaxies in the Coma cluster, using high signal-to-noise ratio (S/N) spectroscopy from the 6.5-m MMT. Our sample is drawn from two 1{deg} fields, one centred on the cluster core and the other located 1{deg} to the south-west of the cluster centre. The target galaxies are mostly 2-4mag fainter than M*; galaxies with these luminosities have been previously studied only using small samples, or at low S/N. For a comparison sample we use published high-S/N data for red-sequence galaxies in the Shapley supercluster. We use state-of-the-art stellar population models (by R. Schiavon, Cat. <J/ApJS/171/146>) to interpret the absorption-line indices and infer the single-burst-equivalent age and metallicity (Fe/H) for each galaxy, as well as the abundances of the light elements Mg, Ca, C and N.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+AS/104/1
- Title:
- Faint ring-shaped galaxies near South Pole
- Short Name:
- J/A+AS/104/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A list of probable ring galaxies with a limiting magnitude of 17.5 has been prepared based on visual inspection of the film copies of the J SRC/ESO survey. About 88% of the sample of 125 selected objects seem to be new, hitherto unrecognized as ring galaxies. The candidate objects have been classified following the ring structure and the nucleus appearance.
- ID:
- ivo://CDS.VizieR/J/ApJ/714/1170
- Title:
- Faraday rotation at high Galactic latitude
- Short Name:
- J/ApJ/714/1170
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the vertical magnetic field of the Milky Way toward the Galactic poles, determined from observations of Faraday rotation toward more than 1000 polarized extragalactic radio sources at Galactic latitudes |b|>=77{deg}, using the Westerbork Radio Synthesis Telescope and the Australia Telescope Compact Array. We find median rotation measures (RMs) of 0.0+/-0.5rad/m^2^ and +6.3+/-0.7rad/m^2^ toward the north and south Galactic poles, respectively, demonstrating that there is no coherent vertical magnetic field in the Milky Way at the Sun's position. If this is a global property of the Milky Way's magnetism, then the lack of symmetry across the disk rules out pure dipole or quadrupole geometries for the Galactic magnetic field. The angular fluctuations in RM seen in our data show no preferred scale within the range ~0.1{deg} to ~25{deg}. The observed standard deviation in RM of ~9rad/m^2^ then implies an upper limit of ~1uG on the strength of the random magnetic field in the warm ionized medium at high Galactic latitudes.
- ID:
- ivo://CDS.VizieR/J/ApJ/795/63
- Title:
- Faraday rotation from magnesium II absorbers
- Short Name:
- J/ApJ/795/63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Strong singly ionized magnesium (Mg II) absorption lines in quasar spectra typically serve as a proxy for intervening galaxies along the line of sight. Previous studies have found a correlation between the number of these Mg II absorbers and the Faraday rotation measure (RM) at ~5 GHz. We cross-match a sample of 35752 optically identified non-intrinsic Mg II absorption systems with 25649 polarized background radio sources for which we have measurements of both the spectral index and RM at 1.4 GHz. We use the spectral index to split the resulting sample of 599 sources into flat-spectrum and steep-spectrum subsamples. We find that our flat-spectrum sample shows significant (~3.5{sigma}) evidence for a correlation between Mg II absorption and RM at 1.4 GHz, while our steep-spectrum sample shows no such correlation. We argue that such an effect cannot be explained by either luminosity or other observational effects, by evolution in another confounding variable, by wavelength-dependent polarization structure in an active galactic nucleus, by the Galactic foreground, by cosmological expansion, or by partial coverage models. We conclude that our data are most consistent with intervenors directly contributing to the Faraday rotation along the line of sight, and that the intervening systems must therefore have coherent magnetic fields of substantial strength (B{bar}=1.8+/-0.4{mu}G). Nevertheless, the weak nature of the correlation will require future high-resolution and broadband radio observations in order to place it on a much firmer statistical footing.
- ID:
- ivo://CDS.VizieR/J/ApJ/707/114
- Title:
- Faraday rotation in Cen A
- Short Name:
- J/ApJ/707/114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of an Australia Telescope Compact Array 1.4GHz spectropolarimetric aperture synthesis survey of 34deg^2^ centered on Centaurus A-NGC 5128. A catalog of 1005 extragalactic compact radio sources in the field to a continuum flux density of 3mJy/beam is provided along with a table of Faraday rotation measures (RMs) and linear polarized intensities for the 28% of sources with high signal to noise in linear polarization. We use the ensemble of 281 background polarized sources as line-of-sight probes of the structure of the giant radio lobes of Centaurus A. This is the first time such a method has been applied to radio galaxy lobes and we explain how it differs from the conventional methods that are often complicated by depth and beam depolarization effects. Assuming a magnetic field strength in the lobes of 1.3B1uG, where B1=1 is implied by equipartition between magnetic fields and relativistic particles, the upper limit we derive on the maximum possible difference between the average RM of 121 sources behind Centaurus A and the average RM of the 160 sources along sightlines outside Centaurus A implies an upper limit on the volume-averaged thermal plasma density in the giant radio lobes of <ne><5x10^-5^B1^-1^cm^-3^. We use an RM structure function analysis and report the detection of a turbulent RM signal, with rms=17rad/m^2^ and scale size 0.3deg, associated with the southern giant lobe. We cannot verify whether this signal arises from turbulent structure throughout the lobe or only in a thin skin (or sheath) around the edge, although we favor the latter. The RM signal is modeled as possibly arising from a thin skin with a thermal plasma density equivalent to the Centaurus intragroup medium density and a coherent magnetic field that reverses its sign on a spatial scale of 20kpc. For a thermal density of n1 10^-3^cm^-3^, the skin magnetic field strength is 0.8n1^-1^uG.
- ID:
- ivo://CDS.VizieR/J/ApJ/869/4
- Title:
- Far-infrared SED measurements of massive galaxies
- Short Name:
- J/ApJ/869/4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Massive Population II galaxies undergoing the first phase of vigorous star formation after the initial Population III stage should have high energy densities and silicate-rich interstellar dust. We have modeled the resulting far-infrared spectral energy distributions (SEDs), demonstrating that they are shifted substantially to bluer ("warmer") wavelengths relative to the best fitting ones at z~3, and with strong outputs in the 10-40{mu}m range. When combined with a low level of emission by carbon dust, their SEDs match that of Haro 11, a local moderately low-metallicity galaxy undergoing a very young and vigorous starburst that is likely to approximate the relevant conditions in young Population II galaxies. We expect to see similar SEDs at high redshifts (z>~5) given the youth of galaxies at this epoch. In fact, we find a progression with redshift in observed galaxy SEDs, from those resembling local ones at 2<~z<4 to a closer resemblance with Haro 11 at 5<~z<7. In addition to the insight on conditions in high-redshift galaxies, this result implies that estimates of the total infrared luminosities at z~6 based on measurements near {lambda}~1mm can vary by factors of 2-4, depending on the SED template used. Currently popular modified blackbodies or local templates can result in significant underestimates compared with the preferred template based on the SED of Haro 11.
- ID:
- ivo://CDS.VizieR/J/other/PBeiO/18.7
- Title:
- Far infrared Seyfert galaxies
- Short Name:
- J/other/PBeiO/18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Confusing sources of Seyfert and HII galaxies in IRAS point source catalogue may be caused by companion objects of those galaxies. Comparison between confused galaxies and non-confused galaxies have been made. The preliminary comparison shows that confused galaxies are fainter than nonconfused galaxies generally, and colour diagrams illustrate that confused Seyferts are separated from nonconfused Seyferts obviously.
- ID:
- ivo://CDS.VizieR/J/ApJ/703/1672
- Title:
- Far-IR and H{alpha} fluxes in galaxies
- Short Name:
- J/ApJ/703/1672
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We combine H{alpha} emission-line and infrared (IR) continuum measurements of two samples of nearby galaxies to derive dust attenuation-corrected star formation rates (SFRs). We use a simple energy balance based method that has been applied previously to HII regions in the Spitzer Infrared Nearby Galaxies Survey, and extend the methodology to integrated measurements of galaxies. We find that our composite H{alpha}+IR based SFRs are in excellent agreement with attenuation-corrected SFRs derived from integrated spectrophotometry, over the full range of SFRs (0.01-80M_{sun}_/yr) and attenuations (0-2.5mag) studied. The calibrations differ significantly from those obtained for HII regions, with the difference attributable to a more evolved population of stars heating the dust. Our results are consistent with a significant component of diffuse dust (the "IR cirrus" component) that is heated by a non-star-forming population.
- ID:
- ivo://CDS.VizieR/J/MNRAS/428/1880
- Title:
- Far-IR properties of VCC galaxies
- Short Name:
- J/MNRAS/428/1880
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Herschel Virgo Cluster Survey (HeViCS) is the deepest, confusion-limited survey of the Virgo Cluster at far-infrared (FIR) wavelengths. The entire survey at full depth covers ~55deg^2^ in five bands (100-500um), encompassing the areas around the central dominant elliptical galaxies (M87, M86 and M49) and extends as far as the NW cloud, the W cloud and the Southern extension. The survey extends beyond this region with lower sensitivity so that the total area covered is 84 deg2. In this paper we describe the data, the data acquisition techniques and present the detection rates of the optically selected Virgo Cluster Catalogue (VCC). We detect 254 (34%) of 750 VCC galaxies found within the survey boundary in at least one band and 171 galaxies are detected in all five bands. For the remainder of the galaxies we have measured strict upper limits for their FIR emission.
- ID:
- ivo://CDS.VizieR/J/ApJ/714/1256
- Title:
- Far-IR star formation rate indicators
- Short Name:
- J/ApJ/714/1256
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spitzer data at 24, 70, and 160um and ground-based H{alpha} images are analyzed for a sample of 189 nearby star-forming and starburst galaxies to investigate whether reliable star formation rate (SFR) indicators can be defined using the monochromatic infrared dust emission centered at 70 and 160um. We compare recently published recipes for SFR measures using combinations of the 24um and observed H{alpha} luminosities with those using 24um luminosity alone. From these comparisons, we derive a reference SFR indicator for use in our analysis. Linear correlations between SFR and the 70um and 160um luminosity are found for L(70)>~1.4x10^42^erg/s and L(160)>~2x10^42^erg/s, corresponding to SFR>~0.1-0.3M_{sun}_/yr, and calibrations of SFRs based on L(70) and L(160) are proposed. Below those two luminosity limits, the relation between SFR and 70um (160um) luminosity is nonlinear and SFR calibrations become problematic. A more important limitation is the dispersion of the data around the mean trend, which increases for increasing wavelength.