A Study of Three Groups of Galaxies: Plausible Explanation of the Virial Mass Discrepancy

AbstractFrom the volume-limited MAIN galaxy sample of the SDSS Data Release 6 (SDSS6), we have identified 1298 compact groups of galaxies (CGs) at the neighbourhood radius of R = 1.2 Mpc by three-dimensional cluster analysis. In order to compile the CG catalog, we also estimated velocity dispersion, virial radius, virial mass and crossing time of CGs. In addition, our results show that properties of galaxies may not correlate with merging frequencies.

Download Full-text

Biases in Mass Estimates of Groups of Galaxies

Symposium - International Astronomical Union ◽

10.1017/s0074180900150004 ◽

1987 ◽

Vol 117 ◽

pp. 114-114

Author(s):

Gary A. Mamon

Keyword(s):

Dark Matter ◽

Small Groups ◽

Mass Density ◽

Groups Of Galaxies ◽

Virial Mass ◽

Mass Segregation ◽

The Masses

The knowledge of the masses of small groups of galaxies is important, because the timescales for collapse and virialization of groups depend on their mass-density. While the large inefficiency of the virial mass statistic is well known (Bahcall and Tremaine 1981, hereafter BT, and references therein), biases in the virial mass may produce wrong evolution timescales for small groups. These biases originate from group contamination by interlopers, and from the different galaxy and dark matter distributions inside the groups (caused by mass segregation). This second bias was first studied by Smith (1980, 1984) although already implicit in the work of Limber (1959). It formally arises because the ratio 2T/C where C = ΣFα·Rα (the Clausius virial) is not the same for the luminous and global matter distributions. We illustrate here some quantitative aspects of this Limber bias from the output of N-body simulations of groups of 8 galaxies described elsewhere (Mamon 1986).

Download Full-text

Virial Mass Determinations of Bound and Unstable Groups of Galaxies.

The Astrophysical Journal ◽

10.1086/151324 ◽

1972 ◽

Vol 172 ◽

pp. 17 ◽

Cited By ~ 26

Author(s):

Sverre J. Aarseth ◽

William C. Saslaw

Keyword(s):

Groups Of Galaxies ◽

Virial Mass

Download Full-text

Triple Galaxies and a Hidden Mass Problem

International Astronomical Union Colloquium ◽

10.1017/s0252921100004978 ◽

1990 ◽

Vol 124 ◽

pp. 115-127

Author(s):

I.D. Karachentsev ◽

V.E. Karachentseva ◽

V.S. Lebedev

Keyword(s):

Velocity Dispersion ◽

Absolute Magnitude ◽

Mass Excess ◽

Homogeneous Sample ◽

Groups Of Galaxies ◽

Triple Systems ◽

Crossing Time ◽

Dynamical Parameters ◽

Virial Mass ◽

Harmonic Radius

AbstractWe consider a homogeneous sample of 84 triple systems of galaxies with components brighter than m = 15.7, located in the northern sky and satisfying an isolation criterion with respect to neighboring galaxies in projection. The distributions of basic dynamical parameters for triplets have median values as follows: radial velocity dispersion 133 km/s, mean harmonic radius 63 kpc, absolute magnitude of galaxies MB = —20.38, crossing time τ = 0.04 H−1. For different ways of estimation the median mass-to-luminosity ratio is (20 – 30)f⊙.A comparison of the last value with the ones for single and binary galaxies shows the presence of a virial mass excess for triplets by a factor 4. The mass-to-luminosity ratio is practically uncorrelated with linear size of triplets or with morphological types of their components.We note that a significant part of the virial excess may be explained by the presence of nonisolated triple configurations in the sample, which are produced by debris of more populous groups of galaxies.

Download Full-text

The role of AGN activity in the building up of the BCG at z ∼ 1.6

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320003105 ◽

2019 ◽

Vol 15 (S356) ◽

pp. 280-284

Author(s):

Angela Bongiorno ◽

Andrea Travascio

Keyword(s):

Galaxy Cluster ◽

Cluster Galaxy ◽

X Ray ◽

Groups Of Galaxies ◽

Star Forming ◽

The Core ◽

The Galaxy ◽

Multi Wavelength

AbstractXDCPJ0044.0-2033 is one of the most massive galaxy cluster at z ∼1.6, for which a wealth of multi-wavelength photometric and spectroscopic data have been collected during the last years. I have reported on the properties of the galaxy members in the very central region (∼ 70kpc × 70kpc) of the cluster, derived through deep HST photometry, SINFONI and KMOS IFU spectroscopy, together with Chandra X-ray, ALMA and JVLA radio data.In the core of the cluster, we have identified two groups of galaxies (Complex A and Complex B), seven of them confirmed to be cluster members, with signatures of ongoing merging. These galaxies show perturbed morphologies and, three of them show signs of AGN activity. In particular, two of them, located at the center of each complex, have been found to host luminous, obscured and highly accreting AGN (λ = 0.4−0.6) exhibiting broad Hα line. Moreover, a third optically obscured type-2 AGN, has been discovered through BPT diagram in Complex A. The AGN at the center of Complex B is detected in X-ray while the other two, and their companions, are spatially related to radio emission. The three AGN provide one of the closest AGN triple at z > 1 revealed so far with a minimum (maximum) projected distance of 10 kpc (40 kpc). The discovery of multiple AGN activity in a highly star-forming region associated to the crowded core of a galaxy cluster at z ∼ 1.6, suggests that these processes have a key role in shaping the nascent Brightest Cluster Galaxy, observed at the center of local clusters. According to our data, all galaxies in the core of XDCPJ0044.0-2033 could form a BCG of M* ∼ 1012Mȯ hosting a BH of 2 × 108−109Mȯ, in a time scale of the order of 2.5 Gyrs.

Download Full-text

NIHAO – XXV. Convergence in the cusp-core transformation of cold dark matter haloes at high star formation thresholds

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3028 ◽

2020 ◽

Vol 499 (2) ◽

pp. 2648-2661

Author(s):

Aaron A Dutton ◽

Tobias Buck ◽

Andrea V Macciò ◽

Keri L Dixon ◽

Marvin Blank ◽

...

Keyword(s):

Dark Matter ◽

Star Formation ◽

Galaxy Formation ◽

Cold Dark Matter ◽

Dwarf Galaxies ◽

Dwarf Galaxy ◽

Good Description ◽

Good Match ◽

Virial Mass ◽

Density Threshold

ABSTRACT We use cosmological hydrodynamical galaxy formation simulations from the NIHAO project to investigate the response of cold dark matter (CDM) haloes to baryonic processes. Previous work has shown that the halo response is primarily a function of the ratio between galaxy stellar mass and total virial mass, and the density threshold above which gas is eligible to form stars, n[cm−3]. At low n all simulations in the literature agree that dwarf galaxy haloes are cuspy, but at high n ≳ 100 there is no consensus. We trace halo contraction in dwarf galaxies with n ≳ 100 reported in some previous simulations to insufficient spatial resolution. Provided the adopted star formation threshold is appropriate for the resolution of the simulation, we show that the halo response is remarkably stable for n ≳ 5, up to the highest star formation threshold that we test, n = 500. This free parameter can be calibrated using the observed clustering of young stars. Simulations with low thresholds n ≤ 1 predict clustering that is too weak, while simulations with high star formation thresholds n ≳ 5, are consistent with the observed clustering. Finally, we test the CDM predictions against the circular velocities of nearby dwarf galaxies. Low thresholds predict velocities that are too high, while simulations with n ∼ 10 provide a good match to the observations. We thus conclude that the CDM model provides a good description of the structure of galaxies on kpc scales provided the effects of baryons are properly captured.

Download Full-text

A new catalogue of multiple galaxies in the Local Supercluster

International Astronomical Union Colloquium ◽

10.1017/s0252921100054725 ◽

2000 ◽

Vol 174 ◽

pp. 40-45

Author(s):

D. I. Makarov ◽

I. D. Karachentsev

Keyword(s):

New Approach ◽

Galaxy Groups ◽

Closed Orbits ◽

Crossing Time ◽

Local Supercluster ◽

Virial Mass ◽

Nearby Galaxies ◽

The Individual ◽

Group Member ◽

Harmonic Radius

AbstractA new approach is suggested which makes use of the individual properties of galaxies, for the identification of small galaxy groups in the Local Supercluster. The criterion is based on the assumption of closed orbits of the companions around the dominating group member within a zero velocity sphere.The criterion is applied to a sample of 6321 nearby galaxies with radial velocities V0 ≤ 3000 km s−1. These 3472 galaxies have been assigned to 839 groups that include 55% of the sample considered. For the groups identified by the new algorithm (with k ≥ 5 members) the median velocity dispersion is 86 km s−1, the median harmonic radius is 247 kpc, the median crossing time is 0.08(1/H), and the median virial-mass-to-light ratio is 56 M⊙/L⊙.

Download Full-text

The Dark Matter Halo Density Profile, Spiral Arm Morphology, and Supermassive Black Hole Mass of M33

ISRN Astronomy and Astrophysics ◽

10.5402/2011/725697 ◽

2011 ◽

Vol 2011 ◽

pp. 1-8 ◽

Cited By ~ 6

Author(s):

Marc S. Seigar

Keyword(s):

Black Hole ◽

Dark Matter ◽

Density Profile ◽

Pitch Angle ◽

Rotation Curve ◽

Dark Matter Halo ◽

Black Hole Mass ◽

Supermassive Black Hole ◽

Virial Mass ◽

Spiral Arm

We investigate the dark matter halo density profile of M33. We find that the HI rotation curve of M33 is best described by an NFW dark matter halo density profile model, with a halo concentration of and a virial mass of . We go on to use the NFW concentration of M33, along with the values derived for other galaxies (as found in the literature), to show that correlates with both spiral arm pitch angle and supermassive black hole mass.

Download Full-text

Poor Groups Around Strong Gravitational Lenses

Proceedings of the International Astronomical Union ◽

10.1017/s174392130600634x ◽

2006 ◽

Vol 2 (S235) ◽

pp. 230-230

Author(s):

Ivelina Momcheva ◽

Kurtis Williams ◽

Ann Zabludoff ◽

Charles Keeton

Keyword(s):

Galaxy Evolution ◽

Velocity Dispersion ◽

Gravitational Lenses ◽

Local Universe ◽

Groups Of Galaxies ◽

Hot Gas ◽

Gas Kinematics ◽

The Galaxy ◽

Group Centroid ◽

Group Galaxy

AbstractPoor groups are common and interactive environments for galaxies, and thus are important laboratories for studying galaxy evolution. Unfortunately, little is known about groups at z ≥ 0.1, because of the difficulty in identifying them in the first place. Here we present results from our ongoing survey of the environments of strong gravitational lenses, in which we have so far discovered six distant (z ≥ 0.5) groups of galaxies. As in the local Universe, the highest velocity dispersion groups contain a brightest member spatially coincident with the group centroid, whereas lower-dispersion groups tend to have an offset brightest group galaxy. This suggests that higher-dispersion groups are more dynamically relaxed than lower-dispersion groups and that at least some evolved groups exist by z ~ 0.5. We also compare the galaxy and hot gas kinematics with those of similarly distant clusters and of nearby groups.

Download Full-text

Environmental Effects in Galaxy Clusters: Infalling Groups in Abell 85 and 1367

Proceedings of the International Astronomical Union ◽

10.1017/s1743921311022976 ◽

2010 ◽

Vol 6 (S277) ◽

pp. 296-299

Author(s):

H. Bravo-Alfaro ◽

T. C. Scott ◽

E. Brinks ◽

L. Cortese ◽

P. Granados ◽

...

Keyword(s):

Galaxy Clusters ◽

Environmental Effects ◽

Compact Groups ◽

Late Type ◽

Gravitational Effects ◽

Groups Of Galaxies ◽

Preliminary Results ◽

Nir Imaging ◽

Gaseous Component ◽

Global Cluster

AbstractWe are carrying out a multifrequency survey of late type galaxies in nearby clusters with the aim to investigate the effects exerted by both the very local and the global cluster environments. We report new VLA-HI images of galaxies in Abell 1367 and study the evolution of their gaseous component. In Abell 85 we perform a deep NIR imaging survey of the brightest spirals projected up to 1.0 Abell radius with the aim of unveiling possible gravitational effects on their stellar disks. Here we show preliminary results of these projects, mainly focused on infalling compact groups of galaxies moving towards their respective cluster centers.

Download Full-text