- ID:
- ivo://CDS.VizieR/J/A+A/642/A85
- Title:
- RX J0603.3+4214 LOFAR 58GHz images
- Short Name:
- J/A+A/642/A85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Ultra-low frequency observations (<100MHz) are particularly challenging because they are usually performed in a low signal-to-noise ratio regime due to the high sky temperature and because of ionospheric disturbances whose effects are inversely proportional to the observing frequency. Nonetheless, these observations are crucial for studying the emission from low-energy populations of cosmic rays. We aim to obtain the first thermal-noise limited (~1.5mJy/beam) deep continuum radio map using the Low Frequency Array's Low Band Antenna (LOFAR LBA) system. Our demonstration observation targeted the galaxy cluster RX J0603.3+4214 (known as the Toothbrush cluster). We used the resulting ultra-low frequency (39-78MHz) image to study cosmic-ray acceleration and evolution in the post shock region considering the presence of a radio halo. We describe the data reduction we used to calibrate LOFAR LBA observations. The resulting image was combined with observations at higher frequencies (LOFAR 150MHz and VLA 1500MHz) to extract spectral information.Results.We obtained the first thermal-noise limited image from an observation carried out with the LOFAR LBA system using allDutch stations at a central frequency of 58MHz. With eight hours of data, we reached an rms noise of 1.3mJy/beam at a resolution of 18"x11". The procedure we developed is an important step towards routine high-fidelity imaging with the LOFAR LBA. Theanalysis of the radio spectra shows that the radio relic extends to distances of 800kpc downstream from the shock front, larger than what is allowed by electron cooling time. Furthermore, the shock wave started accelerating electrons already at a projected distance of <300kpc from the crossing point of the two clusters. These results may be explained by electrons being re-accelerated down stream by background turbulence, possibly combined with projection effects with respect to the radio halo.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/592/A108
- Title:
- RXJ1257.2+4738 morphological properties
- Short Name:
- J/A+A/592/A108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Studying the evolution of the morphological distribution of galaxies in different environments can provide important information about the effects of the environment and the physical mechanisms responsible for the morphological transformations. As part of a complete analysis of the young cluster RXJ 1257+4738 at z~0.9, in this work we study the morphological properties of its galaxies. We used non-parametric methods of morphological classification, as implemented in the galSVM code. The classification with the applied method was possible even using ground-based observations, as the r'-band imaging from OSIRIS/GTC. We defined very conservative probability limits, taking into account the probability errors, to obtain a trustworthy classification. In this way we were able to classify ~30% of all cluster members and to separate between late-type (LT) and early-type (ET) galaxies. Additionally, when analysing the colour-magnitude diagram, we observed a significant population of blue ET galaxies among the classified ones. We discussed possible explanations for finding this population. Moreover, we studied different physical properties of LT, ET, and blue ET galaxies. They turn out to be comparable, with the exception of the stellar mass that shows that the red ET population is more massive. We also analysed the morphology-density and morphology-radius relations observing that, only when considering the morphological separation between ET and LT galaxies, a mild classical behaviour is obtained. RXJ 1257+4738 is a young galaxy cluster, showing a clumpy structure, which is still in the process of formation, and which could explain the lack of some of the standard morphological relations. This makes this cluster a very attractive case for obtaining higher resolution data and for studying the morphological properties of the entire cluster in more detail and their relation to the environment.
- ID:
- ivo://CDS.VizieR/J/A+A/642/A153
- Title:
- SAGAN. I. New sample & multi-wavelength studies
- Short Name:
- J/A+A/642/A153
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first results of a project called SAGAN, which is dedicated solely to the studies of relatively rare megaparsec-scale radio galaxies in the Universe, called giant radio galaxies (GRGs). We have identified 162 new GRGs primarily from the NVSS with sizes ranging from ~0.71Mpc to 2.82Mpc in the redshift range of ~0.03-0.95, of which 23 are hosted by quasars (giant radio quasars, GRQs). As part of the project SAGAN, we have created a database of all known GRGs, the GRG catalogue, from the literature (including our new sample); it includes 820 sources. For the first time, we present the multi-wavelength properties of the largest sample of GRGs. Our results establish that the distributions of the radio spectral index and the black hole mass of GRGs do not differ from the corresponding distributions of normal-sized radio galaxies (RGs). However, GRGs have a lower Eddington ratio (ER) than RGs. Using the mid-infrared data, we classified GRGs in terms of their accretion mode: either a high-power radiatively efficient high-excitation state, or a radiatively inefficient low-excitation state. We find that GRGs in high-excitation state statistically have larger sizes, stronger radio power, jet kinetic power, and higher ER than those in low-excitation state. Our analysis reveals a strong correlation between the ER and the scaled jet kinetic power, which suggests a disc-jet coupling. Our environmental study reveals that ~10% of all GRGs may reside at the centres of galaxy clusters, in a denser galactic environment, while the majority appears to reside in a sparse environment. We find that the probability of BCG as a GRG is quite low. We present new results for GRGs that range from black hole mass to large-scale environment properties. We discuss their formation and growth scenarios, highlighting the key physical factors that cause them to reach their gigantic size.
- ID:
- ivo://CDS.VizieR/J/MNRAS/449/4010
- Title:
- SALT galaxy clusters detected by ACT
- Short Name:
- J/MNRAS/449/4010
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Southern African Large Telescope follow-up observations of seven massive clusters detected by the Atacama Cosmology Telescope (ACT) on the celestial equator using the Sunyaev-Zel'dovich (SZ) effect. We conducted multi-object spectroscopic observations with the Robert Stobie Spectrograph in order to measure galaxy redshifts in each cluster field, determine the cluster line-of-sight velocity dispersions, and infer the cluster dynamical masses. We find that the clusters, which span the redshift range 0.3<z<0.55, range in mass from (5-20)x10^14^M_{sun}_ (M_200c_). Their masses, given their SZ signals, are similar to those of Southern hemisphere ACT clusters previously observed using Gemini and the VLT. We note that the brightest cluster galaxy in one of the systems studied, ACT-CL J0320.4+0032 at z=0.38, hosts a type II quasar. Only a handful of such systems are currently known, and therefore ACT-CL J0320.4+0032 may be a rare example of a very massive halo in which quasar-mode feedback is actively taking place.
- ID:
- ivo://CDS.VizieR/J/ApJ/875/60
- Title:
- SAMI Galaxy Survey: early-type gal. in A119 & A168
- Short Name:
- J/ApJ/875/60
- Date:
- 08 Mar 2022 13:03:14
- Publisher:
- CDS
- Description:
- We investigate the kinematic alignments of luminous early-type galaxies (M_r_<=-19.5mag) in A119 and A168 using the kinematic position angles (PA_kin_) from the Sydney-AAO Multi-object Integral-field spectrograph (SAMI) survey data, motivated by the implication of the galaxy spin alignment in a cosmological context. To increase the size of our sample for statistical significance, we also use the photometric position angles (PA_phot_) for galaxies that have not been observed by SAMI, if their ellipticities are higher than 0.15. Our luminous early-type galaxies tend to prefer the specific position angles in both clusters, confirming the results of Kim+ (2018ApJ...860L...3K), who recently found the kinematic alignment of early-type galaxies in the Virgo cluster based on the ATLAS3D integral-field spectroscopic data. This alignment signal is more prominent for galaxies in the projected phase-space regions dominated by infalling populations. Furthermore, the alignment angles are closely related to the directions of the filamentary structures around clusters. The results lead us to conclude that many cluster early-type galaxies are likely to be accreted along filaments while maintaining their spin axes, which are predetermined before cluster infall.
856. SAMI Pilot Survey
- ID:
- ivo://CDS.VizieR/J/MNRAS/454/2050
- Title:
- SAMI Pilot Survey
- Short Name:
- J/MNRAS/454/2050
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the SAMI Pilot Survey, consisting of integral field spectroscopy of 106 galaxies across three galaxy clusters, Abell 85, Abell 168 and Abell 2399. The galaxies were selected by absolute magnitude to have Mr<-20.25mag. The survey, using the Sydney-AAO Multi-object Integral field spectrograph (SAMI), comprises observations of galaxies of all morphological types with 75 per cent of the sample being early-type galaxies (ETGs) and 25 per cent being late-type galaxies (LTGs). Stellar velocity and velocity dispersion maps are derived for all 106 galaxies in the sample. The {lambda}_R_ parameter, a proxy for the specific stellar angular momentum, is calculated for each galaxy in the sample. We find a trend between {lambda}_R_ and galaxy concentration such that LTGs are less concentrated higher angular momentum systems, with the fast-rotating ETGs (FRs) more concentrated and lower in angular momentum. This suggests that some dynamical processes are involved in transforming LTGs to FRs, though a significant overlap between the {lambda}_R_ distributions of these classes of galaxies implies that this is just one piece of a more complicated picture. We measure the kinematic misalignment angle, {Psi}, for the ETGs in the sample, to probe the intrinsic shapes of the galaxies. We find the majority of FRs (83 per cent) to be aligned, consistent with them being oblate spheroids (i.e. discs). The slow rotating ETGs (SRs), on the other hand, are significantly more likely to show kinematic misalignment (only 38 per cent are aligned). This confirms previous results that SRs are likely to be mildly triaxial systems.
- ID:
- ivo://CDS.VizieR/J/MNRAS/423/2690
- Title:
- Sample of Compact Group (CG) galaxies
- Short Name:
- J/MNRAS/423/2690
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We construct a sample of 75863 star-forming galaxies with robust metallicity and star formation rate (SFR) measurements from the Sloan Digital Sky Survey Data Release 7, from which we select a clean sample of compact group (CG) galaxies. The CGs are defined to be close configurations of at least four galaxies that are otherwise apparently isolated. Our selection results in a sample of 112 spectroscopically identified CG galaxies, which can be further divided into groups that are either embedded within a larger structure, such as a cluster or large group, or truly isolated systems. The CGs then serve as a probe into the influence of large-scale environment on a galaxy's evolution, while keeping the local density fixed at high values. W
- ID:
- ivo://CDS.VizieR/J/AJ/129/1237
- Title:
- SARS galaxy luminosity profiles
- Short Name:
- J/AJ/129/1237
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have analyzed CCD images of 14 Abell clusters in the R filter of the Southern Abell Clusters Redshifts Survey (SARS) with cz<40,000km/s. We have obtained the luminosity profiles for 507 galaxies, of which 232 (46%) have known redshifts. In order to fit the luminosity profiles, we used the de Vaucouleurs law for bulge systems and an exponential profile for disk systems, and we also fitted the Sersic's law (r^n^) to all galaxy profiles.
- ID:
- ivo://CDS.VizieR/VII/251
- Title:
- SBS/Zwicky cluster relation
- Short Name:
- VII/251
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the same area covered by Second Byurakan Survey and CGCG, there are 1677 SBS galaxies, of which 892 are positioned inside the contours of Zwicky clusters. Data on these galaxies and respective clusters are presented in different tables, according to whether they are galaxies which are members of clusters or their substructures, probable or possible members. Projection cases are considered separately.
- ID:
- ivo://CDS.VizieR/J/AJ/130/968
- Title:
- SDSS-C4 cluster catalog
- Short Name:
- J/AJ/130/968
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the C4 Cluster Catalog, a new sample of 748 clusters of galaxies identified in the spectroscopic sample of the Second Data Release (DR2, 2004AJ....128..502A) of the Sloan Digital Sky Survey (SDSS). The C4 cluster-finding algorithm identifies clusters as overdensities in a seven-dimensional position and color space, thus minimizing projection effects that have plagued previous optical cluster selection. The present C4 catalog covers ~2600deg^2^ of sky and ranges in redshift from z=0.02 to 0.17. The mean cluster membership is 36 galaxies (with measured redshifts) brighter than r=17.7, but the catalog includes a range of systems, from groups containing 10 members to massive clusters with over 200 cluster members with measured redshifts. The catalog provides a large number of measured cluster properties including sky location, mean redshift, galaxy membership, summed r-band optical luminosity (L_r_), and velocity dispersion, as well as quantitative measures of substructure and the surrounding large-scale environment. We use new, multicolor mock SDSS galaxy catalogs, empirically constructed from the {Lambda}CDM Hubble Volume (HV) Sky Survey output, to investigate the sensitivity of the C4 catalog to the various algorithm parameters (detection threshold, choice of passbands, and search aperture), as well as to quantify the purity and completeness of the C4 cluster catalog.
