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1.
We report the results of study of the A1569 cluster (12
h
36m.3, +16°35′) and the neighboring A1589 cluster (12
h
41m.3, +18°34′), making up a pair (a supercluster) with a projected size of about 10Mpc. This study is done within the framework
of our program for investigating the galaxy clusters with bimodal velocity distributions (i.e., clusters where the velocities
of subsystems differ by more than Δcz ∼ 3000 km/s). In the A1569 cluster we have identified two subsystems: A1569A (cz = 20613 km/s) and A1569B (cz = 23783 km/s). These subsystems have the line-of-sight velocity dispersions of 484 km/s and 493 km/s, and dynamic masses
within the R
200 radius equal to 1.8 × 1014 and 2.0 × 1014
M
⊙, respectively. We directly estimate the distances to these subsystems using three methods applied to earlytype galaxies:
the Kormendy relation, photometric plane, and fundamental plane. To this end, we use the results of our observations made
with the 1-m telescope of the SAO RAS and the data adopted from the SDSS DR7 catalog. We found that A1569 consists of two
independent clusters. The A1569B cluster is located at the Hubble distance corresponding to its radial velocity. The A1569A
cluster has a peculiar velocity of −1290 ± 630 km/s, which can be explained by the effect of the more massive A1589 cluster
(with a mass of 7.9 × 1014
M
⊙) and of the supercluster where it resides. In all the four bimodal clusters that we studied within the framework of our program,
A1035, A1775, A1831, and A1569, the subsystems are independent clusters lying close to the Hubble relation between redshift
and distance. 相似文献
2.
Kormendy’s relation (μe-logR e) is used to investigate the structure of the compact Ursa Major supercluster of galaxies (11h30m+55°, cz=18 000 km s?1); this relation allows the distances of early-type galaxies to be estimated. The relative distances of 13 clusters in the supercluster and their peculiar velocities are determined with a mean statistical accuracy of 6%. In general, the supercluster obeys the Hubble relation between radial velocity and distance. However, there is reason to suggest that the supercluster consists of two subsystems with mean radial velocities of 16 200 and 19 700 km s?1. For a velocity dispersion in the subsystems of ～1100 km s?1, the fact that each of them is gravitationally bound is not ruled out. 相似文献
3.
We analyze the structure of the cluster of galaxies Abell 1775 (α = 13 h 42 m , δ = +26°22′, cz ≈ 21000 km/s), which exhibits a bimodal distribution of radial velocities of the containing galaxies. The difference of the subcluster radial velocities is ΔV ≈ 2900 km/s. We use the results of our photometric observations made with the 1-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences and the spectroscopic and photometric data from the SDSS DR6 catalog to determine independent distances to the subclusters via three different methods: the Kormendy relation, photometric plane, and fundamental plane. We find that the A1775 cluster consists of two independent clusters, A1775A (cz = 19664 km/s) and A1775B (cz = 22576 km/s), each located at its own Hubble distance and having small peculiar velocities. Given the velocity dispersions of 324 km/s and 581 km/s and the dynamic masses within the R 200 radius equal to 0.6 × 1014 and 3.3 × 1014 M ⊙, the A1775A and A1775B clusters have the K-band luminosity-to-mass ratios of 29 and 61, respectively. A radio galaxy with an extended tail belongs to the A1775B cluster. 相似文献
4.
Available data on the distances and radial velocities of galaxies are systematized in order to study the distribution of peculiar
velocities in neighborhoods of the Local cosmic void lying in the direction of the Aquila and Hercules constellations. A sample
of 1056 galaxies is used, with distances measured in terms of the luminosity of the tip of the red giant branch (TRGB), the
luminosity of the cepheids, the luminosity of type 1a supernovae, surface brightness fluctuations (SBF), and the Tully-Fisher
relation. The amplitude of the outflow velocity of the galaxies is found to be ∼300 km/s. The average number density of galaxies
inside the void is roughly a factor of five lower than the average outside it. The Local void population is characterized
by lower luminosities and later morphological types, with medians of M
B
= − 15m.7 and T=8 (Sdm), respectively. 相似文献
5.
We present the results of a search for companions around the isolated galaxies from the 2MIG catalog. Among 3227 2MIG galaxies
we detected 125 objects with a total of 214 neighbors having radial velocity differences of ΔV < 500 km/s and projected separations of R
p
< 500 kpc relative to the 2MIG galaxies. The median luminosity of the companions is 1/25 of the luminosity of catalog galaxies,
which has little effect on the dynamic isolation of the latter. The median ratio of the orbital mass to the K-luminosity determined from 60 companions of E and S0 2MIG galaxies, 63M
⊙/L
⊙, is significantly greater than that found from the spiral galaxy companions (17M
⊙/L
⊙). We note that a fraction of 2MIG galaxies with companions may be a part of low-contrast diffuse structures: clouds and filaments. 相似文献
6.
We analyze the properties of galaxy clusters in the region of the Leo supercluster using observational data from the SDSS
and 2MASS catalogs. We have selected 14 galaxy clusters with a total dynamical mass of 1.77 × 1015
M
⊙ in the supercluster region 130 by 60 Mpc in the plane of the sky (z ≃ 0.037). The composite luminosity function of the supercluster is described by a Schechter function with parameters that,
within the error limits, correspond to field galaxies and does not differ from the luminosity function of the richer Ursa
Major (UMa) supercluster for the same luminosity range (the bright end). The luminosity functions of early-type and late-type
galaxies in Leo at the faint end are characterized by a sharp decrease (α = −0.60±0.08) and a steep increase (α = −1.44± 0.10) in the number of galaxies, respectively. In the virialized cluster regions, the fraction of early-type galaxies
selected by the u-r color, bulge contribution, and concentration index among the galaxies brighter than M
K
* + 1 is, on average, 62%. This fraction is smaller than that in the UMa supercluster at a 2–3σ level. The near-infrared luminosities of galaxy clusters down to a fixed absolute magnitude correlate with their masses almost
in the same way as for other samples of galaxy clusters (L
200,K
∝ M
2000.63±0.11)). 相似文献
7.
The structure of the A1035 cluster of galaxies (10h32m + 40°13′, cz ～ 22000 kms?1), which exhibits a bimodal distribution of galaxy radial velocities (ΔV ≈ 3000 kms?1), is analyzed using three methods of determining the relative distances to clusters from early-type galaxies: the Kormendy relation corrected for the dependence of residuals on galaxy magnitude, the photometric plane, and the fundamental plane. We use the data obtained with the l-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences and SDSS (DR5) data to show that A1035 consists of two gravitationally unbound independent clusters. These clusters with the velocity dispersions of 566 km s?1 and 610 km s?1 and masses within R 200 equal to 2.7 · 1014 and 3.5 · 1014 M ⊙, respectively, obey the Hubble law. 相似文献
8.
David G. Russell 《Journal of Astrophysics and Astronomy》2009,30(2):93-118
The value of Hubble parameter (H0) is determined using the morphologically type dependent Ks-band Tully-Fisher Relation (K-TFR). The slope and zero point are
determined using 36 calibrator galaxies with ScI morphology. Calibration distances are adopted from direct Cepheid distances,
and group or companion distances derived with the Surface Brightness Fluctuation Method or Type Ia Supernova. It is found
that a small morphological type effect is present in the K-TFR such that ScI galaxies are more luminous at a given rotational
velocity than Sa/Sb galaxies and Sbc/Sc galaxies of later luminosity classes. Distances are determined to 16 galaxy clusters
and 218 ScI galaxies with minimum distances of 40.0 Mpc. From the 16 galaxy clusters a weighted mean Hubble parameter of H0 = 84.2 ± 6 km s−1 Mpc−1 is found. From the 218 ScI galaxies a Hubble parameter of H0 = 83.4 ± 8 km s−1 Mpc−1 is found. When the zero point of K-TFR is corrected to account for recent results that find a Large Magellanic Cloud distance
modulus of 18.39±0.05, a Hubble parameter of 88.0 ± 6 km s−1 Mpc−1 is found. Effects from Malmquist bias are shown to be negligible in this sample as galaxies are restricted to a minimum rotational
velocity of 150 km s−1. It is also shown that the results of this study are negligibly affected by the adopted slope for the K-TFR, inclination
binning, and distance binning. A comparison with the results of the Hubble Key Project (Freedman et al. 2001) is made. Discrepancies between the K-TFR distances and the HKP I-TFR distances are discussed. Implications for Λ-CDM
cosmology are considered with H0 = 84 km s−1 Mpc−1. It is concluded that it is very difficult to reconcile the value of H0 found in this study with ages of the oldest globular
clusters and matter density of the universe derived from galaxy clusters in the context of Λ-CDM cosmology. 相似文献
9.
We report a catalog of 168 galaxy triplets with line-of-sight velocities V LG < 3500 km/s identified using a percolation criterion, which takes individual properties of galaxies into account. The catalog contains the line-of-sight velocities, K-band magnitudes, and morphological types of galaxies. Our sample of galaxy triplets is characterized by the median values of the line-of-sight velocity dispersion, projected harmonic radius, and crossing time of 40 km/s, 155 kpc, and 3 Gyr, respectively. The median projectedmass and K-band luminosity of our triplets are equal to 5 × 1011 M ⊙ and 15M ⊙/L ⊙, respectively, with the uncertainty of these parameters due mostly to the errors of radial-velocity measurements. The basic properties of triple systems in the Local Supercluster are compared to those of more distant isolated triplets from the KTG and KTS samples. The fraction of triplet members among all galaxies is found be more than 5%. 相似文献
10.
A radio survey, using the Very Large Array at 20 and 90 cm λ has been carried out in the direction of 46 distant Abell clusters
(0.1 ≲ z ≲ 0.3) dominated by a cD galaxy (clusters classified to be Bautz-Morgan I type). A radio source coincident with the
cD galaxy was detected in 16 clusters. We find that the radio luminosity function of the cD galaxies at 20cm λ, and below
the luminosityP
1.4ghz ≲ 1024.5 W Hz-1, is similar to that of brightest ellipticals in less clustered environments. Above this luminosity, the cDs seem to have
a higher probability of becoming radio sources. The effect of optical brightness on radio emission is shown to be the same
for the two classes. No significantly large population of very-steep-spectrum sources with spectral index α >1.2 (flux density
∝ frequency-α) was found to be associated with cD galaxies. A significant negative correlation is found between the radio luminosity of
the cD galaxy and the cooling-time of the intra cluster medium near the galaxy. We also present evidence that the probability
of radio emission from first-ranked galaxies is dependent upon their location relative to the geometrical centres of clusters
and thus related to the morphological class and the evolutionary state of the clusters. We argue that both these effects are
primarily caused by the dynamical evolution of these distant clusters of galaxies. 相似文献
11.
The local expansion field (v
220 <1200 km s-1) and the cosmic expansion field out to 30 000 km s-1 are characterized by H
0 = 58 [km s-1 Mpc-1]. While the random error of this determination is small (± 2 units), it may still be affected by systematic errors as large
as ±10%>. The local expansion is outlined by Cepheids and by Cepheid-calibrated TF distances of a complete sample of field
galaxies and by nearby groups and clusters; the cosmic expansion is defined by Cepheid-calibrated SNe Ia. The main source
of systematic errors are therefore the shape and the zero point of the P-L relation of Cepheids and its possible dependence
on metallicity. GAIA will essentially eliminate these systematic error sources. Another source of systematic error is due
to the homogenization of SNe Ia as to decline rate Δm
15 and color (B-V). GAIA will discover most of the 1100 SNe Ia within 10 000 km s-1, which will occur during its four-year lifetime. If their photometric parameters can be determined from the ground, they
will fix the dependence of the SNe Ia luminosity on Δ m
15 and (B-V) with high accuracy. At the same time they will yield exquisite distances to an equal number of field galaxies. – GAIA will
also revolutionize the very local distance scale by determining fundamental distances of the companion galaxies of the Milky
Way and even of some spirals in- and possibly outside the Local Group from their rotation curves seen in radial velocities
and proper motions. Moreover, GAIA will obtain trigonometric parallaxes of RR Lyrae stars, of red giants defining the TRGB,
of stars on the ZAMS, of White Dwarf defining their cooling sequence, and of globular clusters, and determine the metallicity
dependence of these distance indicators. It will thus establish a self-controlling network of distance indicators within the
Local Group and beyond.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
12.
We have investigated the peculiar motions of clusters of galaxies in the Ursa Major (UMa) supercluster and its neighborhood. Based on SDSS (Sloan Digital Sky Survey) data, we have compiled a sample of early-type galaxies and used their fundamental plane to determine the cluster distances and peculiar velocities. The samples of early-type galaxies in the central regions (within R 200) of 12 UMa clusters of galaxies, in three main subsystems of the supercluster—the filamentary structures connecting the clusters, and in nine clusters from the nearest UMa neighborhood have similar parameters. The fairly high overdensity (3 by the galaxy number and 15 by the cluster number) suggests that the supercluster as a whole is gravitationally bound, while no significant peculiar motions have been found: the peculiar velocities do not exceed the measurement errors by more than a factor of 1.5–2. The mean random peculiar velocities of clusters and the systematic deviations from the overall Hubble expansion in the supercluster are consistent with theoretical estimates. For the possible approach of the three UMa subsystems to be confirmed, the measurement accuracy must be increased by a factor of 2–3. 相似文献
13.
Data from the H I Parkes All-Sky Survey (HIPASS) of the southern sky in the neutral hydrogen line are used to determine the radial velocities and widths of the H I line for flat spiral galaxies of the Revised Flat-Galaxy Catalog (RFGC) seen edge-on. The sample of 103 flat galaxies detected in HIPASS is characterized by a median radial velocity of +2037 km/sec and a median width of the H I line at the level of 50% of maximum of 242 km/sec. For RFGC galaxies the 50% detection level in HIPASS corresponds to an apparent magnitude B
t = 14
m
.5 or an angular diameter a = 2.9. The relative number of detected galaxies increases from 2% for the morphological types Sbc and Sc to 41% for the type Sm. The median value of the ratio of hydrogen mass to total mass for RFGC galaxies is 0.079. With allowance for the average internal extinction for edge-on galaxies, <B
t< = 0
m
.75, the median ratio of hydrogen mass to luminosity, M
H I/L
B = 0.74 M
/L
, is typical for late-type spirals. Because of its small depth, HIPASS reveals only a few RFGC galaxies with previously unknown velocities and line widths. 相似文献
14.
We present R-band galaxy luminosity functions (GLFs) from aspectroscopic sample of six nearby rich galaxy clusters. In addition
to individual cluster GLFs, extending to, in one case, M
R=–14, we also present composite GLFs for cluster and field galaxies toM
R=–17. All six cluster samples are consistent with the composite GLF, but there is evidence that the GLF of the quiescent population
in clusters is not universal. Furthermore, the GLF of quiescent galaxies is significantly steeper in clusters than in the
field. The overall GLF in clusters is consistent with that of field galaxies, except for the luminous tip, which is enhanced
in clusters versus the field.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
15.
A sample of 145 galaxies having radial velocities relative to the centroid of the Local Group V
LG < 500 km/sec and estimated photometric distances D < 8 Mpc is considered. The field of peculiar velocities of these galaxies is estimated using the tensor of the local value of the Hubble constant H
ij
, with principal values of 81:62:48 in km/sec·Mpc, which have a standard error of 4 km/sec·Mpc. The minor axis of the Hubble ellipsoid is oriented almost along the polar axis of the Local Supercluster, while the major axis forms an angle = (29 ± 5)° with the direction toward the center of the Virgo Cluster. Such a configuration of the peculiar-velocity field shows unsatisfactory agreement with the model of a spherically symmetric flow of galaxies toward the Virgo Cluster. Rotation of the Local Supercluster may be one reason for this difference. The peculiar velocities of galaxies within a volume with D < 8 Mpc are characterized by a dispersion
V
= 74 km/sec, a considerable part of which is due to the virial motions of galaxies in groups and to distance errors. For field galaxies, located in a layer of 1 < D < 3 Mpc around the Local Group, the radial-velocity dispersion does not exceed 25 km/sec. The velocity—distance relation, constructed from the 20 closest galaxies around the Local Group with D < 3 Mpc and with errors (D) < 0.2 Mpc, exhibits the expected effect of gravitational deceleration. Using the estimate of R
0 = (0.96 ± 0.05) Mpc for the observed radius of the zero-velocity sphere, we determined the total mass of the Local Group to be (1.2 ± 0.2)·1012
M
, which agrees well with the sum of the virial masses of the subgroups of galaxies around the Local Group and M31. The ratio of the Local Group's total mass (within R
0) to its luminosity is M/L = (23 ± 4) M
/L
, which does not require the existence of supermassive dark halos around our Galaxy and M31. 相似文献
16.
We present a list of 75 isolated dwarf galaxies of later types which have no neighbors with a relative radial velocity difference
of less than 500 km/s or projected distances of less than 500 kpc. These were selected from ~2000 dwarf galaxies with radial
velocities VLG<3500 km/s within the volume of the local supercluster. In terms of their sizes, luminosities, and the amplitudes of their
internal motions, the isolated dwarf galaxies do not differ significantly from gas-rich dwarf galaxies in groups and clusters.
However, the median mass of neutral hydrogen per unit luminosity for the isolated galaxies is a factor of two greater than
for the galaxies of later types in groups. We have also identified 10 presumably isolated spheroidal dwarf galaxies. The discovery
of isolated dwarf galaxies populated exclusively by old stars is of great interest for modern cosmological scenarios of galaxy
formation. 相似文献
17.
We report a catalog of 509 pairs identified among 10403 nearby galaxies with line-of-sight velocities V LG < 3500 km/s. We selected binary systems in accordance with two criteria (“bounding” and “temporal”), which require the physical pair of galaxies to have negative total energy and its components to be located inside the zero-velocity surface. We assume that individual galaxy masses are proportional to their total K-band luminosities, M = L K × 6M ⊙/L ⊙. The catalog gives the magnitudes and morphological types of galaxies and also the projected (orbital) masses and pair isolation indices. The component line-of-sight velocity differences and projected distances of the binary systems considered have power-law distributions with the median values of 35 km/s and 123 kpc, respectively. The median mass-to-K-band luminosity ratio is equal to 11M ⊙/L ⊙, and its uncertainty is mostly due to the errors of measured velocities. Our sample of binary systems has a typical density contrast of δρ/ρ c ～ 500 and a median crossing time of about 3.5 Gyr. We point out the substantial fraction of binary systems consisting of late-type dwarf galaxies, where the luminosities of both components are lower than that of the Small Magellanic Cloud. The median projected distance for 41 such pairs is only 30 kpc, and the median difference of their line-ofsight velocities is equal to 14 km/s which is smaller than the typical error for radial-velocity (30 km/s). This specific population of gas-rich dwarf binary galaxies such as I Zw 18 may be at the stage immediately before merging of its components. Such objects, which are usually lost in flux-limited (and not distance-limited) samples deserve a thorough study in the HI radio line with high spatial and velocity resolution. 相似文献
18.
We have studied the pitch angles of spiral arms for 31 distant galaxies at z ∼ 0.7 from three Hubble Deep Fields (HDF-N, HDF-S, HUDF). Using the pitch angle-rotation velocity relation calibrated from
nearby galaxies, we have estimated the rotation velocities of galaxies from the deep fields. These estimates have a low accuracy
(∼50 km s−1), but they allow low-mass and giant galaxies to be distinguished. The Tully-Fisher relation constructed using our velocity
estimates shows satisfactory agreement with the actually observed relations for distant galaxies and provides evidence for
the luminosity evolution of spiral galaxies. 相似文献
19.
Cross correlations between observed and synthetic spectra are used to discover yet another satellite of BM Ori with the following
characteristics: effective temperature Teff = 4000 K, radius R = 16R⊙, mass M = 1.8M⊙, spectral type K7 III, absolute bolometric stellar magnitude Mb = + 4m·0, axial rotation velocity V sini = 85 km/s, and relative luminosity 0.005 near the V band.
__________
Translated from Astrofizika, Vol. 49, No. 1, pp. 111–120 (February 2006). 相似文献
20.
P. Amram C. Mendes de Oliveira H. Plana C. Balkowski M. Bolte 《Astrophysics and Space Science》2002,281(1-2):397-400
We present kinematics and photometric evidence for the presence of seven candidate tidal dwarf galaxies in Stephan's Quintet.
The central regions of the two most probable parent galaxies, NGC 7319 and NGC 7318B, contain little or no gas whereas the
intragroup medium and, in particular, the optical tails that seem to be associated with NGC 7318B are rich in cold and ionized
gas. Two tidal dwarf candidates may be located at the edge of a tidal tail, another located within a tail, and for the four
others there is no obvious stellar/gaseous bridge between them and the parent galaxy. Two of the candidates are associated
with H I clouds, one of which is, in addition, associated with a CO cloud. All seven regions have low continuum fluxes and
high Hα luminosity densities [F(Hα) = (1-60) × 10-14 ergs s-1 cm-2]. Their magnitudes (MB = –16.1 to –12.6), sizes (∼ 3.5 h75
-1 kpc), colors (typically B – R = 0.7), and gas velocity gradients (∼ 8 –26 h75 km s-1 kpc-1) are typical for tidal dwarf galaxies. In addition, the ratios between their star formation rates determined from Hα and
from the B-band luminosity are typical of other tidal dwarf galaxies. The masses of the tidal dwarf galaxies in Stephan's
Quintet range from ∼ 2 × 108 to 1010 M⊙, and the median value for their inferred mass-to-light ratios is 7 (M/L)⊙. At least two of the systems may survive possible ‘fallbacks’ or disruption by the parent galaxies and may already be, or
turn into, self-gravitating dwarf galaxies, new members of the group.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献