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16771. Velocity distributions in galaxy clusters
ID:
ivo://CDS.VizieR/J/other/NewA/27.41
Title:
Velocity distributions in galaxy clusters
Short Name:
J/other/NewA/27.
Date:
21 Oct 2021
Publisher:
CDS
Description:
We study 416 galaxy systems with more than 7 members selected from the 2MASS catalog. We applied five well known normality tests to the velocity distributions of these systems to distinguish Gaussian and non-Gaussian clusters. Using controlled samples, we estimated type I and II errors for each test. We verified that individual tests minimize the chances of classifying a Gaussian system as non-Gaussian, while the Fisher's meta-analysis method, a procedure to combine p-values from several statistical tests, minimizes the chances of classifying a non-Gaussian system as Gaussian. Taking the positive elements of each method and also including a modality analysis of the velocity distribution, we defined objective criteria to split up the sample into Gaussian and non-Gaussian clusters. Our analysis indicates that 50-58% of groups have Gaussian distribution, a lower fraction than that we found using individual normality tests, 71-87%. We also found that some properties of galaxy clusters are significantly different between Gaussian and non-Gaussian systems. For instance, non-Gaussian clusters have larger radii and contain more galaxies than Gaussian clusters. Finally, we discussed the importance of choosing the adequate methodology to classify galaxy systems from their velocity distributions and also the dependence of the results on the criteria used to identify clusters in galaxy surveys.
16772. Velocity field in the Local Group
ID:
ivo://CDS.VizieR/J/A+A/393/57
Title:
Velocity field in the Local Group
Short Name:
J/A+A/393/57
Date:
21 Oct 2021
Publisher:
CDS
Description:
Pratton, Melott and McKee (1997ApJ...479L..15P) showed that the velocity field around clusters could generate an apparent distortion that appears as tangential structures or radial filaments. In the present paper we determine the parameters of the Peebles' model (1976ApJ...205..318P) describing infall of galaxies onto clusters with the aim of testing quantitatively the amplitude of this distortion. The distances are determined from the concept of sosie galaxies (Paturel, 1994A&A...289..711P) using 21 calibrators for which the distances were recently calculated from two independent Cepheid calibrations. We use both B and I-band magnitudes.
16773. Velocity field of the Lyra complex
ID:
ivo://CDS.VizieR/J/A+A/633/A108
Title:
Velocity field of the Lyra complex
Short Name:
J/A+A/633/A108
Date:
02 Nov 2021 11:15:00
Publisher:
CDS
Description:
The formation of cosmic structures culminates with the assembly of galaxy clusters, a process that is quite different from cluster to cluster. We present the study of the structure and dynamics of the Lyra complex, consisting of the two clusters RXC J1825.3+3026 and CIZA J1824.1+3029, which was very recently studied by using both X-ray and radio data. This is the first analysis based on the kinematics of member galaxies. New spectroscopic data for 285 galaxies were acquired at the Italian Telescopio Nazionale Galileo and were used in combination with PanSTARRS photometry. The result of our member selection is a sample of 198 galaxies. For RXCJ1825 and CIZAJ1824 we report the redshifts, z=0.0645 and z=0.0708, the first estimates of velocity dispersion, sigma_v_=995_-125_^+131^km/s and sigma_v_=700+/-50km/s, and of dynamical mass, M_200_=1.1+/-0.4x10^15^M_[sun}_ and M_200_=4+/-0.110^14^M_{sun}_. The past assembly of RXCJ1825 is traced by the two dominant galaxies, which are both aligned with the major axis of the galaxy distribution along the east-west direction, and by a minor northeast substructure. We also detect a quite peculiar high velocity field in the southwest region of the Lyra complex. This feature is likely related to a very luminous galaxy, which is characterized by a high velocity. This galaxy is suggested to be the central galaxy of a group that is in interaction with RXCJ1825 according to very recent studies based on X-ray and radio data. The redshift of the whole Lyra complex is z=0.067. Assuming that the redshift difference between RXCJ1825 and CIZAJ1824 is due to the relative kinematics, the projected distance between the cluster centers is D~1.3Mpc and the line-of-sight velocity difference is ~1750km/s. A dynamical analysis of the system shows that the two clusters are likely to be gravitationally bound in a pre-merger phase, and that CIZAJ1824 is moving toward RXCJ1825. Our results corroborate a picture where the Lyra region is the place of a very complex scenario of cluster assembly.
16774. Velocity gradient and brightness in disc galaxies
ID:
ivo://CDS.VizieR/J/MNRAS/433/L30
Title:
Velocity gradient and brightness in disc galaxies
Short Name:
J/MNRAS/433/L30
Date:
21 Oct 2021
Publisher:
CDS
Description:
For disc galaxies, a close relation exists between the distribution of light and the shape of the rotation curve. We quantify this relation by measuring the inner circular-velocity gradient d_R_V(0) for spiral and irregular galaxies with high-quality rotation curves. We find that d_R_V(0) correlates with the central surface brightness {mu}_0_ over more than two orders of magnitude in d_R_V(0) and four orders of magnitudes in {mu}_0_. This is a scaling relation for disc galaxies. It shows that the central stellar density of a galaxy closely relates to the inner shape of the potential well, also for low-luminosity and low-surface-brightness galaxies that are expected to be dominated by dark matter.
16775. Velocity measurements in Segue 1
ID:
ivo://CDS.VizieR/J/ApJ/733/46
Title:
Velocity measurements in Segue 1
Short Name:
J/ApJ/733/46
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of a comprehensive Keck/DEIMOS spectroscopic survey of the ultra-faint Milky Way satellite galaxy Segue 1. We have obtained velocity measurements for 98.2% of the stars within 67pc (10', or 2.3 half-light radii) of the center of Segue 1 that have colors and magnitudes consistent with membership, down to a magnitude limit of r=21.7. Based on photometric, kinematic, and metallicity information, we identify 71 stars as probable Segue 1 members, including some as far out as 87pc. After correcting for the influence of binary stars using repeated velocity measurements, we determine a velocity dispersion of 3.7^+1.4^_-1.1_km/s. The mass within the half-light radius is 5.8^+8.2^_-3.1_x10^5^M_{sun}_. The stellar kinematics of Segue 1 require very high mass-to-light ratios unless the system is far from dynamical equilibrium, even if the period distribution of unresolved binary stars is skewed toward implausibly short periods. With a total luminosity less than that of a single bright red giant and a V-band mass-to-light ratio of 3400M_{sun}_/L_{sun}_, Segue 1 is the darkest galaxy currently known.
16776. Velocity of eight RASSCALS galaxy groups
ID:
ivo://CDS.VizieR/J/ApJ/622/187
Title:
Velocity of eight RASSCALS galaxy groups
Short Name:
J/ApJ/622/187
Date:
21 Oct 2021
Publisher:
CDS
Description:
We study the distribution of gas pressure and entropy in eight groups of galaxies belonging to the ROSAT All-Sky Survey/Center for Astrophysics Loose Systems (RASSCALS, Cat. <J/ApJ/534/114>). We use archival and proprietary XMM-Newton observations, supplementing the X-ray data with redshifts derived from the literature; we also list 125 new redshifts measured with the Gemini North telescope.
16777. Velocity precision in the Gaia-ESO Survey
ID:
ivo://CDS.VizieR/J/A+A/580/A75
Title:
Velocity precision in the Gaia-ESO Survey
Short Name:
J/A+A/580/A75
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Gaia-ESO Survey (GES) is a large public spectroscopic survey at the European Southern Observatory Very LargeTelescope. A key aim is to provide precise radial velocities (RVs) and projected equatorial velocities (vsini) for representative samples of Galactic stars, which will complement information obtained by the Gaia astrometry satellite. We present an analysis to empirically quantify the size and distribution of uncertainties in RV and vsini using spectra from repeated exposures of the same stars. We show that the uncertainties vary as simple scaling functions of signal-to-noise ratio (S/N) and vsini, that the uncertainties become larger with increasing photospheric temperature, but that the dependence on stellar gravity, metallicity and age is weak. The underlying uncertainty distributions have extended tails that are better represented by Students t-distributions than by normal distributions. Parametrised results are provided, which enable estimates of the RV precision for almost all GES measurements, and estimates of the vsini precision for stars in young clusters, as a function of S/N, vsini and stellar temperature. The precision of individual high S/N GES RV measurements is 0.22-0.26km/s, dependent on instrumental configuration.
16778. Velocity Vectors of B and A stars
ID:
ivo://CDS.VizieR/V/30
Title:
Velocity Vectors of B and A stars
Short Name:
V/30
Date:
21 Oct 2021
Publisher:
CDS
Description:
A compilation of proper motions, radial velocities, and apparent magnitudes of B and A stars is combined with the absolute magnitudes and colour excesses from the "Catalogue of estimated astrophysical parameters" by Philip and Egret (at. V/14).
16779. VERA 22GHz Fringe Search Survey
ID:
ivo://CDS.VizieR/J/AJ/133/2487
Title:
VERA 22GHz Fringe Search Survey
Short Name:
J/AJ/133/2487
Date:
21 Oct 2021
Publisher:
CDS
Description:
This paper presents results of a survey search for bright compact radio sources at 22GHz with the VERA radio interferometer. Each source from a list of 2494 objects was observed in one scan for 2 minutes. The purpose of this survey was to find compact extragalactic sources bright enough at 22GHz to be useful as phase calibrators. Observed sources were either (1) within 6{deg} of the Galactic plane, or (2) within 11{deg} of the Galactic center, or (3) within 2{deg} of known water masers. Among the observed sources, 549 were detected, including 180 extragalactic objects that were not previously observed with the very long baseline interferometry technique. Estimates of the correlated flux densities of the detected sources are presented. It was found that the probability of detecting a 200mJy source with 120s of integration time is 60%.
16780. VERITAS gamma-ray TeV LCs of 6 blazars
ID:
ivo://CDS.VizieR/J/ApJ/833/117
Title:
VERITAS gamma-ray TeV LCs of 6 blazars
Short Name:
J/ApJ/833/117
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a targeted search for blazar flux-correlated high-energy ({epsilon}_{nu}_>~1TeV) neutrinos from six bright northern blazars, using the public database of northern hemisphere neutrinos detected during "IC40" 40-string operations of the IceCube neutrino observatory (2008 April to 2009 May). Our six targeted blazars are subjects of long-term monitoring campaigns by the VERITAS TeV {gamma}-ray observatory. We use the publicly available VERITAS light curves to identify periods of excess and flaring emission. These predefined intervals serve as our "active temporal windows" in a search for an excess of neutrinos, relative to Poisson fluctuations of the near-isotropic atmospheric neutrino background, which dominates at these energies. After defining the parameters of an optimized search, we confirm the expected Poisson behavior with Monte Carlo simulations prior to testing for excess neutrinos in the actual data. We make two searches: one for excess neutrinos associated with the bright flares of Mrk 421 that occurred during the IC40 run, and one for excess neutrinos associated with the brightest emission periods of five other blazars (Mrk 501, 1ES 0806+524, 1ES 1218+304, 3C 66A, and W Comae), all significantly fainter than the Mrk 421 flares. We find no significant excess of neutrinos from the preselected blazar directions during the selected temporal windows. We derive 90% confidence upper limits on the number of expected flux-associated neutrinos from each search. These limits are consistent with previous point-source searches and Fermi GeV flux-correlated searches. Our upper limits are sufficiently close to the physically interesting regime that we anticipate that future analyses using already-collected data will either constrain models or yield discovery of the first blazar-associated high-energy neutrinos.

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