共查询到20条相似文献，搜索用时 46 毫秒
1.
I. D. Karachentsev D. I. Makarov V. E. Karachentseva O. V. Melnyk 《Astrophysical Bulletin》2011,66(1):1-27
We present a catalog of 520 most isolated nearby galaxies with angular velocities V
LG
< 3500 km/s, covering the entire sky. This population of “space orphans” makes up 4.8% among 10 900 galaxies with measured
radial velocities. We describe the isolation criterion used to select our sample, called the “Local Orphan Galaxies”(LOG),
and discuss their basic optical and HI properties. A half of the LOG catalog is occupied by the Sdm, Im and Ir morphological
type galaxies without a bulge. The median ratio M
gas/M
star in the LOG galaxies exceeds 1. The distribution of the catalog galaxies on the sky looks uniform with some signatures of
a weak clustering on the scale of about 0.5 Mpc. The LOG galaxies are located in the regions where the mean local density
of matter is approximately 50 times lower than the mean global density. We indicate a number of LOG galaxies with distorted
structures, which may be the consequence of interaction of isolated galaxies with massive dark objects. 相似文献
2.
3.
The procedure of the construction of a sample of distant (z > 0.3) radio galaxies using NED, SDSS, and CATS databases for further application in statistical tests is described. The sample is assumed to be cleaned from objects with quasar properties. Primary statistical analysis of the list is performed and the regression dependence of the spectral index on redshift is found. 相似文献
4.
A. M. Mickaelian 《Astrophysics》2000,43(3):309-321
A fifth list of objects from the BIG (Byurakan-IRAS galaxies) sample is given: 89 galaxies identified with 59 point sources
from the IRAS Point Source Catalog. The identifications were based on the Digital Sky Survey (DSS), the First Byurakan Survey,
blue and red maps from the Palomar Observatory Sky Survey, and infrared fluxes at 12, 25, 60, and 100 mm in the region of+65°
≤ δ ≤69δ and 5h10m ≤ α ≤9h 15m with an area of 96 deg2. For the identified galaxies the optical coordinates, their departures from the IR coordinates, and the stellar V magnitudes,
morphological types, angular sizes, and position angles were determined. The objects have optical magnitudes in the range
of 14m. 1-21m.5 and angular sizes in the range of 2″-47″. The galaxies are mainly spiral in morphology. Compact galaxies and Seyfert candidates,
interacting pairs, “mergers,” galaxies with companions and superassociations, groups of galaxies (including compact ones),
and others are encountered, which shows the importance of these objects for the study of the relationships among the phenomena
of star formation, activity, and interactions. Finder charts from the DSS are given for these objects. New designations and
numbering are introduced for galaxies in the studied sample.
Translated from Astrofizika, Vol. 43, No. 3, pp. 425-441, July– September, 2000.
The NASA/IPAC Extragalactic Database (NED), operated by the Jet Propulsion Laboratory, California Institute of Technology,
under contract with NASA. 相似文献
5.
A sample of 230 galaxies has been compiled based on their IRAS FSC fluxes to study their multiwavelength properties and carry
out comparative analyses with other similar samples. To understand the nature of these galaxies, a comparison with a sample
of bright ULIRGs having fluxes at 60 μm fν > 1 Jy and 14 optically faint IRAS FSC galaxies is presented. This comparison shows that galaxies found by IRAS are not always
strong infrared sources and that the objects from the sample of ULIRGs represent a sample of extreme galaxies, which are very
powerful infrared sources. We have confirmed the consistency between Star Formation Rates (SFRs) calibrated based on luminosities
of the PAH feature at 7.7 μm and radio 1.4 GHz flux densities. We have estimated the extinction for our 230 objects using
SFRs calibrated from the PAH feature compared to ultraviolet flux, which shows that only 1% of the ultraviolet continuum typically
escapes extinction by dust within a starburst. 相似文献
6.
We study the possibility of quasar outflows in clusters and groups of galaxies heating the intracluster gas in order to explain
the recent observation of excess entropy in this gas. We show that radio galaxies alone cannot provide the energy required
to explain the observations but the inclusion of Broad Absorption Line (BAL) outflows can do so, and that in this scenario
most of the heating takes place atz ∼ 1–4, the “preheating” epoch being at a lower redshift for lower mass clusters. 相似文献
7.
A.A. Ubachukwu 《Astrophysics and Space Science》2002,279(3):251-259
We have carried out some statistical tests of relativistic beaming and radio source orientation scenarios using the core dominance
parameter Rand linear size D of a recent sample of double-lobed quasars and radio galaxies as orientation indicators. Our results show that the maximum
Doppler boosting occurs within a cone angle of ∼ 13°corresponding to an optimum Lorentz factor of ∼ 5. On the average, quasar cores appear to be boosted by a factor of ∼ 10 relative
to those of radio galaxies. In general, we found that quasars lie at closer angles to the line of sight than radio galaxies
with median values of 28° and 51°respectively, implying a relative foreshortening factor of ∼ 2. These results are consistent with the simple relativistic
beaming and orientation-based unification hypotheses in which quasars are the beamed counterparts of powerful radio galaxies
which form the isotropic parent population. The results show a strong evidence that orientation of source axis with respect
to the line of sight is a crucial parameter in the classification schemes for radio sources.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
R. A. Kandalian 《Astrophysics》1995,38(3):225-231
We have compiled a sample of galaxies whose flux density is higher at 12 microns (f12) than at 25 microns (f25). It is argued thatf12 >f25 effectively selects quiescent galaxies which are less active in infrared, radio, and optical bands than other types of normal galaxies. Moreover galaxies withf12 >f25 do not exhibit the well-known relations that normal galaxies show between far-infrared parameters, for example, the negative correlation betweenf12/f25 andf60/f100. These galaxies also show different far-infrared and radio properties. In our opinion this sample of quiescent galaxies is suitable for use as a control sample when properties of more active galaxies are discussed. It may also be used in modeling galaxies with active star formation or an active nucleus.Translated fromAstrofizika, Vol. 38, No. 3, 1995. 相似文献
9.
Summary. Due to the foreground extinction of the Milky Way, galaxies appear increasingly fainter the closer they lie to the Galactic
Equator, creating a “zone of avoidance” of about 25% in the distribution of optically visible galaxies. A “whole-sky” map
of galaxies is essential, however, for understanding the dynamics in our local Universe, in particular the peculiar velocity
of the Local Group with respect to the Cosmic Microwave Background and velocity flow fields such as in the Great Attractor
region.
Various dynamically important structures behind the Milky Way have only recently been made “visible” through dedicated deep
surveys at various wavelengths. The wide range of observational searches (optical, near infrared, far infrared, radio and
X-ray) for galaxies in the Zone of Avoidance are reviewed, including a discussion on the limitations and selection effects
of these partly complementary approaches. The uncovered and suspected large-scale structures are summarized. Reconstruction
methods of the density field in the Zone of Avoidance are described and the resulting predictions compared with observational
evidence. The comparison between reconstructed density fields and the observed galaxy distribution allow derivations of the
density and biasing parameters and b.
Received 4 April 2000 / Published online 18 July 2000 相似文献
10.
For 2442 galaxies of the catalog, compiled based on the NED, SDSS, and CATS survey data with redshifts z, > 0.3 we conducted an analysis of the amplitude of temperature fluctuations in the cosmic microwave background (CMB) in
the points, corresponding to the direction to these objects. To this end, we used the ILC map from the WMAP mission seven-year
data release. We have estimated the dipole component of the background and tested the hypothesis of Kashlinsky on the existence
of a “dark bulk flow”, determined for the estimated dipole component of the CMB WMAP by the value of the CMB anisotropy in
the direction to the clusters of galaxies. We show that the amplitude of this dipole T
max
= 0.012mK is located within the σ interval, estimated by Monte Carlo simulations for the Gaussian fluctuations of the CMB signal in the ΛCDM model. The low
amplitude of the dipole indicates that it is impossible to confirm this hypothesis from the WMAP data. In addition, we studied
the statistics of the fluctuation amplitude of the microwave signal in the direction to radio galaxies. A weakening of the
absolute value of the mean signal in the corresponding fields was discovered. 相似文献
11.
Giant radio galaxies are the most extended radio sources in the universe having the sizes of groups and clusters of galaxies
(about 1 Mpc). Their total number is comparable with the amount of clusters, revealing the Zeldovich-Sunyaev effect, which
may lead to a biased estimation of the angular power spectrum for the ZS effect. To assess a possible contribution to the
power spectrum, we need to collect the data on all the observed giant radio galaxies. We propose an algorithm for the selection
of large sources (sized over 4′) from the NVSS survey catalog, using the parameters of possible components of radio sources,
cataloged as compact objects. As a result of the first stage of our work, we have selected 61 new giant radio galaxy candidates,
of which 35 have a pronounced morphological type FRII, and 26 galaxies—the FRI type. 相似文献
12.
The distance modulus of the Virgo cluster has been reexamined based on the Tully-Fisher relation between fully corrected B.
1
0
values and 21 cm velocity width derived from RC3 catalogue for spiral galaxies of Sbc-Sdm types, belonging to the “low-velocity”
Virgo subcluster, singled out according to the statistical method proposed by Anosova, and led to the value μ = 31.15 ± 0.57
mag. A strong dependence of the intrinsic scatter in the Tully-Fisher relation on the apparent axes ratio of galaxies has
been found, with a value of 0.4 mag for strongly flattened, highly inclined galaxies and galaxies with small inclinations
and a value of 0.72 mag for objects with intermediate values of axes ratio. The restriction to samples only with galaxies
with photoelectric observations does not lead to a considerable change of amplitude of scatter and decreases the value the
of distance modulus.
Published in Astrofizika, Vol. 42, No. 1, pp. 37–46, January–March, 1999. 相似文献
13.
Hardcastle Alexander Pooley & Riley 《Monthly notices of the Royal Astronomical Society》1998,296(2):445-462
In previous papers we have discussed high-resolution observations of a large sample of powerful radio galaxies with z < 0.3. Jets are detected in up to 80 per cent of the sample, and radio cores in nearly all the objects; in addition, we are able to resolve the hotspots in most sources. In this paper we present measurements of the radio properties of these components. The prominences of the jets detected do not appear to be a function of radio luminosity, providing the clearest evidence yet that the reported low detection rate of jets in radio galaxies has been an artefact of low-sensitivity observations. We find a positive correlation between the total source length and core prominence in the narrow-line radio galaxies. We have found evidence for a relationship between hotspot size and total source size, but few other significant relationships between hotspot properties and those of the jets or lobes. We compare our measurements with those of Bridle et al., based on observations of a sample of quasars, and argue that the results are consistent with a modification of the unified model in which the broad-line radio galaxies are the low-luminosity counterparts of quasars, although the situation is complicated by contamination with low-excitation radio galaxies which appear to have radio properties different from the high-excitation objects. We discuss the classes of empirical model that can be fitted to the data set. 相似文献
14.
E. H. Nikogossian 《Astrophysics》2000,43(1):32-39
The hierarchical structure of the clusters of galaxies A 999, A 1016, and A 1142, which are part of one supercluster, is investigated.
The HTree method is used to determine that A 999 and A 1016 are a single, dynamically bound system consisting of two “cores”
and a common field of galaxies. The composition of the “cores” includes almost all the E and S0 galaxies, the luminosity function
of which is very nearly Gaussian. It is also established that the cluster A 1142 has a nonuniform structure, both in density
distribution and in radial velocity distribution. The location of the maxima in density and in the radial velocity distribution
correlates with the galaxies that are sources of radio and x-ray emission.
Translated from Astrofizika, Vol. 43, No. 1, pp. 45-54, January–March, 2000. 相似文献
15.
In this study we attempt to assess the possibility of detection of variable sources using the data of the 7.6-cm wavelength surveys carried out on the RATAN-600 radio telescope in the period from 1980 through 1994. Objects selected according to certain criteria from the RCR catalog are used to construct the calibration curves and to estimate the accuracy of the resulting calibration curves and determine the r.m.s. errors for the measured source flux densities. To check the calibration sources for the presence of variable objects, quantitative estimates are performed for a number of parameters that characterize variability, in particular, for the long-term variability index V and the χ 2 (chi-square) probability p. The long-term variability index was found to be positive for 14 out of approximately 80 calibration sources, possibly indicating that these sources are variable. The most likely candidate variables are the three sources with the χ 2 probability p > 0.95. Five sources have χ 2 probabilities in the 0.85 < p < 0.95 interval, and the remaining six in the 0.6 < p < 0.8 interval. Nine out of 14 objects are possibly variable in the optical range. The light curves and spectra are determined for possible variable sources and a number of “non-variable” objects. We plan to use the results of this study in our future searches for variable radio sources using the data of the “Cold” surveys. 相似文献
16.
V. E. Karachentseva S. N. Mitronova O. V. Melnyk I. D. Karachentsev 《Astrophysical Bulletin》2010,65(1):1-17
We search for isolated galaxies based on the automatic identification of isolated sources from the Two Micron All-Sky Survey
(2MASS) followed by a visual inspection of their surroundings. We use the modified Karachentseva criterion to compile a catalog
of 3227 isolated galaxies (2MIG), which contains 6% of 2MASS Extended Sources Catalog (or 2MASX) sources brighter than K
s = 12
m
with angular diameters a
K
≥ 30″. The catalog covers the entire sky and has an effective depth of z ∼ 0.02. The 2493 very isolated objects of the catalog, which we include into the 2MVIG catalog, can be used as a reference
sample to investigate the effects of the environment on the structure and evolution of galaxies located in regions with extremely
low density of matter. 相似文献
17.
Matt J. Jarvis Steve Rawlings Steve Eales Katherine M. Blundell rew J. Bunker Steve Croft Ross J. McLure Chris J. Willott 《Monthly notices of the Royal Astronomical Society》2001,326(4):1585-1600
In this paper, the third and final of a series, we present complete K -band imaging and some complementary I -band imaging of the filtered 6C* sample. We find no systematic differences between the K – z relation of 6C* radio galaxies and those from complete samples, so the near-infrared properties of luminous radio galaxies are not obviously biased by the additional 6C* radio selection criteria (steep spectral index and small angular size). The 6C* K – z data significantly improve delineation of the K – z relation for radio galaxies at high redshift ( z >2) . Accounting for non-stellar contamination, and for correlations between radio luminosity and stellar mass, we find little support for previous claims that the underlying scatter in the stellar luminosity of radio galaxies increases significantly at z >2 . In a particular spatially flat universe with a cosmological constant (ΩM =0.3 and ΩΛ =0.7) , the most luminous radio sources appear to be associated with galaxies with a luminosity distribution with a high mean (≈5 L *), and a low dispersion ( σ ∼0.5 mag) which formed their stars at epochs corresponding to z ≳2.5 . This result is in line with recent submillimetre studies of high-redshift radio galaxies and the inferred ages of extremely red objects from faint radio samples. 相似文献
18.
J. R. Martirosian 《Astrophysics》2007,50(3):301-310
This is a statistical study of galaxies with a UV excess. A sample of 702 Kazarian galaxies (KG) is used. The KGs are identified
with objects from the MAPS, IRAS FSC, IRAS PSC, and NVSS catalogs. The O and E magnitudes are known for more than 92% of the
KGs. It is shown that the KG sample is complete up to 16m.0 in the blue and to 16m.5 in the red. More than 36% of the KGs
are identified with infrared (IR) sources at wavelengths of 12, 25, 60, and 100 m. Calculations of the far IR (FIR) luminosities
show that 4% of the KGs are strong FIR emitters (LFIR ≥ 1011 L⊙). More than 32% of the KGs have been identified as radio sources at a frequency of 1.4 GHz. A determination of the radio
luminosities shows that the sample of KGs with known radial velocities include one powerful, LR ≥ 1025 W/Hz, radio object (Kaz 273) which is a BL Lac object. A close correlation (r=0.93) is bound between the FIR and radio luminosities
for galaxies with a UV excess. An examination of the relationship between the FIR and radio luminosities for galaxies in different
spectral classes shows that the correlation coefficient is higher (r=0.99) and the slope of the fit curve is larger (a=1.18)
for Seyfert galaxies. Calculations of the logarithm of the ratio of the FIR and radio fluxes indicate that the sample includes
4 KGs with a radio excess, while there are none with an IR excess.
__________
Translated from Astrofizika, Vol. 50, No. 3, pp. 369–379 (August 2007). 相似文献
19.
We present and discuss in this paper the rest frame radio spectra (1–25 GHz) of a sample of fourteen radio galaxies atz >2 from the newly defined MRC/1Jy complete sample of 558 radio sources. These galaxies are among the most powerful radio sources
known and range in luminosity from 1028-1028·8 watt Hz-1 at 1 GHz. We find that the median rest frame spectral index of this
sample of galaxies atz >2 is significantly steeper than that of a matched luminosity sample of 3CRR galaxies which are at a much lower redshift (0.85
<z < 1.7). This indicates that spectral index correlates primarily with redshift, at least in the luminosity range considered
here. The difference between the distributions of rest frame spectral curvatures for the two samples does not appear to be
statistically significant.
We suggest a new explanation for the steeper spectra of radio galaxies at high redshift involving steeper electron energy
spectra at injection. Electron energy spectra are expected to steepen in a first-order Fermi acceleration process, at both
non-relativistic and relativistic shock fronts, as the upstream fluid velocity decreases. This may well be the case at high
redshifts: the hotter and denser circum-galactic medium at high redshifts could result in slower speeds for the hotspot and
the jet material behind it. The smaller sizes of radio sources at higher redshifts provide support to this scenario.
Since deceased. 相似文献
20.
Katherine M.Blundell SteveRawlings Stephen A.Eales Gregory B.Taylor Alistair D.Bradley 《Monthly notices of the Royal Astronomical Society》1998,295(2):265-279
We describe the selection of a sample of 34 radio sources from the 6C survey from a region of sky covering 0.133 sr. The selection criteria for this sample, hereafter called 6C*, were chosen to optimize the chances of finding radio galaxies at redshift z > 4. Optical follow-up observations have already led to the discovery of the most distant known radio galaxy at z = 4.41. We present VLA radio maps and derive radio spectra for all the 6C* objects. 相似文献