- ID:
- ivo://CDS.VizieR/J/MNRAS/344/283
- Title:
- 100-Mpc-scale structures of radio galaxies
- Short Name:
- J/MNRAS/344/283
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present unequivocal evidence for a huge (~80x100x100Mp^3^) superstructure at redshift z=0.27 in the three-dimensional distribution of radio galaxies from the Texas-Oxford NVSS Structure 08h region (TONS08) sample, confirming tentative evidence for such a structure from the 7C redshift survey (7CRS). A second, newly discovered superstructure is also found less securely at redshift 0.35 (of dimensions ~100x100x100Mpc^3^). We present full observational details on the TONS08 sample which was constructed to probe structures in the redshift range 0<z<0.5 by matching NVSS sources with objects in APM catalogues to obtain a sample of optically bright (E~R<=19.83), radio-faint (1.4GHz flux density S_1.4_>=3mJy) radio galaxies in the same 25deg^2^ area as part II of the 7CRS.
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2322. M31 PHAT star clusters
- ID:
- ivo://CDS.VizieR/J/A+A/602/A112
- Title:
- M31 PHAT star clusters
- Short Name:
- J/A+A/602/A112
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This study is the fifth of a series that investigates the degeneracy and stochasticity problems present in the determination of physical parameters such as age, mass, extinction, and metallicity of partially resolved or unresolved star cluster populations in external galaxies when using HST broad-band photometry. In this work we aim to derive parameters of star clusters using models with fixed and free metallicity based on the HST WFC3+ACS photometric system. The method is applied to derive parameters of a subsample of 1363 star clusters in the Andromeda galaxy observed with the HST. Following Paper III (de Meulenaer et al., 2015A&A...574A..66D), we derive the star cluster parameters using a large grid of stochastic models that are compared to the six observed integrated broad-band WFC3+ACS magnitudes of star clusters. We show that the age, mass, and extinction of the M31 star clusters, derived assuming fixed solar metallicity, are in agreement with previous studies. We also demonstrate the ability of the WFC3+ACS photometric system to derive metallicity of star clusters older than ~1 Gyr. We show that the metallicity derived using broad-band photometry of 36 massive M31 star clusters is in good agreement with the metallicity derived using spectroscopy.
- ID:
- ivo://CDS.VizieR/J/ApJ/786/117
- Title:
- M31 PHAT star clusters ages and masses
- Short Name:
- J/ApJ/786/117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present ages and masses for 601 star clusters in M31 from the analysis of the six filter integrated light measurements from near-ultraviolet to near-infrared wavelengths, made as part of the Panchromatic Hubble Andromeda Treasury (PHAT). We derive the ages and masses using a probabilistic technique, which accounts for the effects of stochastic sampling of the stellar initial mass function. Tests on synthetic data show that this method, in conjunction with the exquisite sensitivity of the PHAT observations and their broad wavelength baseline, provides robust age and mass recovery for clusters ranging from ~10^2^ to 2x10^6^ M_{sun}_. We find that the cluster age distribution is consistent with being uniform over the past 100 Myr, which suggests a weak effect of cluster disruption within M31. The age distribution of older (>100 Myr) clusters falls toward old ages, consistent with a power-law decline of index -1, likely from a combination of fading and disruption of the clusters. We find that the mass distribution of the whole sample can be well described by a single power law with a spectral index of -1.9+/-0.1 over the range of 10^3^-3x10^5^ M_{sun}_. However, if we subdivide the sample by galactocentric radius, we find that the age distributions remain unchanged. However, the mass spectral index varies significantly, showing best-fit values between -2.2 and -1.8, with the shallower slope in the highest star formation intensity regions. We explore the robustness of our study to potential systematics and conclude that the cluster mass function may vary with respect to environment.
- ID:
- ivo://CDS.VizieR/J/ApJ/582/170
- Title:
- M51 Planetary Nebula Candidates
- Short Name:
- J/ApJ/582/170
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of a radial velocity survey of planetary nebulae (PNe) located in the tidal features of the well-known interacting system NGC 5194/95 (M51). We find clear kinematic evidence that M51's northwestern tidal debris consists of two discrete structures that overlap in projection - NGC 5195's own tidal tail and diffuse material stripped from NGC 5194. We compare these kinematic data to a new numerical simulation of the M51 system and show that the data are consistent with the classic "single-passage" model for the encounter, with a parabolic satellite trajectory and a 2:1 mass ratio. We also comment on the spectra of two unusual objects: a high-velocity PN that may be associated with NGC 5194's halo and a possible interloping high-redshift galaxy.
- ID:
- ivo://CDS.VizieR/J/MNRAS/369/97
- Title:
- M31 planetary nebulae velocities
- Short Name:
- J/MNRAS/369/97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present radial velocities for a sample of 721 planetary nebulae in the disc and bulge of M31, measured using the WYFFOS fibre spectrograph on the William Herschel Telescope. Velocities are determined using the [OIII] {lambda}5007 emission line. Rotation and velocity dispersion are measured to a radius of 50arcmin (11.5kpc), the first stellar rotation curve and velocity dispersion profile for M31 to such a radius. Our kinematics are consistent with rotational support at radii well beyond the bulge effective radius of 1.4kpc, although our data beyond a radius of 5kpc are limited. We present tentative evidence for kinematic substructure in the bulge of M31 to be studied fully in a later work. This paper is part of an ongoing project to constrain the total mass, mass distribution and velocity anisotropy of the disc, bulge and halo of M31.
- ID:
- ivo://CDS.VizieR/J/A+A/571/A61
- Title:
- M31 polarization & magnetic structure
- Short Name:
- J/A+A/571/A61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Andromeda Galaxy (M31) is the nearest grand-design spiral galaxy. Thus far, most studies in the radio regime concentrated on the 10kpc ring. The central region of M31 has significantly different properties than the outer parts: The star formation rate is low, and inclination and position angle are largely different from the outer disk. The existing model of the magnetic field in the radial range 6<=r<=14kpc is extended to the innermost part r<=0.5kpc to ultimately achieve a picture of the entire magnetic field in M 31. We combined observations taken with the VLA at 3.6cm and 6.2cm with data from the Effelsberg 100-m telescope to fill the missing spacings of the synthesis data. The resulting polarization maps were averaged in sectors to analyse the azimuthal behaviour of the polarized intensity (PI), rotation measure (RM), and apparent pitch angle ({phi}_obs_). We developed a simplified 3D model for the magnetic field in the central region to explain the azimuthal behaviour of the three observables. Our 3D model of a quadrupolar or dipolar dynamo field can explain the observed patterns in PI, RM, and {phi}_obs_, while a 2D configuration is not sufficient to explain the azimuthal behaviour. In addition and independent of our model, the RM pattern shows that the spiral magnetic field in the inner 0.5kpc points outward, which is opposite to that in the outer disk, and has a pitch angle of =~33{deg}, which is much larger than that of 8{deg}-19{deg} in the outer disk. The physical conditions in the central region differ significantly from those in the 10kpc ring. In addition, the orientation of this region with respect to the outer disk is completely different. The opposite magnetic field directions suggest that the central region is decoupled from the outer disk, and we propose that an independent dynamo is active in the central region.
- ID:
- ivo://CDS.VizieR/J/A+A/588/A114
- Title:
- M101 radio polarization & magnetic structure
- Short Name:
- J/A+A/588/A114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We observed total and polarized radio continuum emission from the spiral galaxy M 101 at {lambda}{lambda}6.2cm and 11.1cm with the Effelsberg telescope. The angular resolutions are 2.5' (=5.4kpc) and 4.4' (=9.5kpc), respectively. We use these data to study various emission components in M 101 and properties of the magnetic field. Separation of thermal and non-thermal emission shows that the thermal emission is closely correlated with the spiral arms, while the non-thermal emission is more smoothly distributed indicating di ff usion of cosmic ray electrons away from their places of origin. The radial distribution of both emissions has a break near R=16kpc (=7.4'), where it steepens to an exponential scale length of L=~5kpc, which is about 2.5 times smaller than at R<16kpc. The distribution of the polarized emission has a broad maximum near R=12kpc and beyond R=16kpc also decreases with L=~5kpc. It seems that near R=16kpc a major change in the structure of M 101 takes place, which also a ff ects the distributions of the strength of the random and ordered magnetic field. Beyond R=16kpc the radial scale length of both fields is about 20kpc, which implies that they decrease to about 0.3uG at R=70kpc, which is the largest optical extent. The equipartition strength of the total field ranges from nearly 10uG at R<2kpc to 4uG at R=22-24kpc. As the random field dominates in M 101 (B_ran_/B_ord_=~2.4), wavelength-independent polarization is the main polarization mechanism. We show that energetic events causing H i shells of mean diameter <625pc could partly be responsible for this. At radii <24kpc, the random magnetic field depends on the star formation rate/area, {Sigma}_SFR_, with a power-law exponent of b=0.28+/-0.02. The ordered magnetic field is generally aligned with the spiral arms with pitch angles that are about 8{deg} larger than those of HI filaments.
- ID:
- ivo://CDS.VizieR/J/MNRAS/431/1107
- Title:
- M82 radio sources flux density variations
- Short Name:
- J/MNRAS/431/1107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents the results of the 2009-2010 monitoring sessions of the starburst galaxy M82, obtained with the Multi-Element Radio-Linked Interferometer Network (MERLIN) at 5GHz and e-MERLIN at 6GHz. Combining several 5GHz MERLIN epochs to form a map with 33.0{mu}Jy/bm noise level, 52 discrete sources, mostly supernova remnants and HII regions, are identified. These include three objects which were not detected in the 2002 5GHz MERLIN monitoring session: supernova SN2008iz, the transient source 43.78+59.3, and a new supernova remnant shell. Flux density variations, in the long (1981 to 2010), medium (2002 to 2010) and short (2009 to 2010) term are investigated. We find that flux densities of supernova remnants (SNRs) in M82 stay constant in most of the sample (~95 per cent), although the distributions of flux density variations show an offset from zero. This is consistent with a slight statistical reduction in flux density of the source distribution. In addition, aside from SN2008iz and the well-known variable source 41.95+57.5, two sources display tentative evidence for short- and medium-term variations over the period 2009-2010. These sources are amongst the most compact SNR in M82. These flux density variations could be due to changes in the circumstellar and interstellar medium in which the shocks travel.
- ID:
- ivo://CDS.VizieR/J/ApJS/107/19
- Title:
- MRC/1Jy Radio source survey. I.
- Short Name:
- J/ApJS/107/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the first in a series of papers discussing the properties of a complete set of radio sources selected near S408=1Jy. We present optical or infrared identifications for a sample of 452 radio galaxies. The sources were selected from the 408MHz Molonglo Reference Catalog, restricted only by flux density and position on the sky, as follows: S408>0.95Jy and -30<decl.(1950)<-20, and 9h20m<R.A.(1950)<14h4m or 20h20m<R.A.(1950)<6h14m. This complete sample, the MRC/1 Jy survey, contains 558 radio galaxies or quasars, of which six are occulted by bright stars or galaxies and two are multiple confused sources. Of the remaining 550 sources, 527, or 96%, are identified to an r magnitude of 25, and eight additional sources are identified to K=19. Of the 17 unocculted objects that remain unidentified, 15 are sources for which we have either poor radio maps or inadequate optical/IR images. This paper presents finding charts and astrometric positions for the 452 sources that are not identified as either quasars or BL Lacertae objects. Magnitudes in the r passband accurate to typically 0.1mag are given for 353 of the radio galaxy identifications. Redshifts for 268 of the galaxies are also listed; these have been derived from 450 spectroscopic observations. The radio observations, quasar and BL Lac identifications, spectroscopy, and near-IR images will be presented in subsequent papers in this series.
- ID:
- ivo://CDS.VizieR/J/MNRAS/381/341
- Title:
- MRCR-SUMSS Ultra-steep-spectrum (USS) sample
- Short Name:
- J/MNRAS/381/341
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper introduces a new program to find high-redshift radio galaxies in the Southern hemisphere through ultra-steep spectrum (USS) selection. We define a sample of 234 USS radio sources with spectral indices {alpha}^843^_408_<=-1.0 (S_{nu}_{prop.to}{nu}^alpha^) and flux densities S_408_>=200mJy in a region of 0.35sr, chosen by cross-correlating the revised 408MHz Molonglo Reference Catalogue, the 843MHz Sydney University Molonglo Sky Survey and the 1400MHz NRAO VLA Sky Survey in the overlap region -40{deg}<DE<-30{deg}. We present Australia Telescope Compact Array (ATCA) high-resolution 1384 and 2368MHz radio data for each source, which we use to analyse the morphological, spectral index and polarization properties of our sample. We find that 85 per cent of the sources have observed-frame spectral energy distributions that are straight over the frequency range 408-2368MHz, and that, on average, sources with smaller angular sizes have slightly steeper spectral indices and lower fractional linear polarization. Fractional polarization is anticorrelated with flux density at both 1400 and 2368MHz. We also use the ATCA data to determine observed-frame Faraday rotation measures for half of the sample.