共查询到20条相似文献,搜索用时 31 毫秒
1.
A composite sample of NIR-selected galaxies having extended multicolor coverage has been used to probe the cosmological evolution
of the blue luminosity function and of the stellar mass function. The bright fraction of the sample has spectroscopic redshifts,
and the remaining fraction well-calibrated photometric redshifts. The resulting blue luminosity function shows an increasing
brightening with redshift respect to the local luminosity function. Hierarchical CDM models predictions are in agreement only
at low and intermediate redshifts but fail to reproduce the observed brightening at high redshifts (z ∼ 2–3). This brightening marks the epoch where starburst activity triggered by galaxy interactions could be an important
physical mechanism for the galaxy evolution. At the same time the NIR galaxy sample has been used to trace the evolution of
the cosmological stellar mass density up to ∼3. A clear decrease of the average mass density is apparent with a fraction ∼15%
of the local value at z ∼ 3. UV bright star-forming galaxies are substancial contributors to the evolution of the stellar mass density. Although
these results are globally consistent with Λ–CDM scenarios, they tend to underestimate the mass density produced by more massive
galaxies present at z > 2. 相似文献
2.
Renato Falomo 《Astrophysics and Space Science》2004,294(1-2):57-61
Near-IR images, obtained at the ESO-VLT during excellent seeing conditions, of a sample of 17 radio-loud and radio-quiet quasars
in the redshift range 1 < z < 2 are presented. The host galaxies of both types of quasars appear to follow the expected trend in luminosity of massive
ellipticals undergoing simple passive evolution. We find a systematic difference by a factor ∼2 in the host luminosity between
RLQs and RQQs that does not change significantly from z = 2 to the present epoch. Quasar hosts appear thus to be already well formed at z ∼ 2 and similar to massive inactive spheroids. These findings are in disagreement with the predictions of models for the
joint formation and evolution of galaxies and active nuclei based on the hierarchical structure formation scenario. 相似文献
3.
A. Fritz B.L. Ziegler R.G. Bower I. Smail R.L. Davies 《Astrophysics and Space Science》2003,285(1):61-66
We explore the evolution of the early-type galaxy population in the rich cluster Abell 2390 at z=0.23. For this purpose, we have obtained spectroscopic data of 51 elliptical and lenticular galaxies with MOSCA at the 3.5
m telescope on Calar Alto Observatory. As our investigation spans both a broad range in luminosity (–22.3≤MB≤–:19.3)and a wide field of view (10′×10′), the environmental dependence of different formation scenarios can be analysed
in detail as a function of radius from the cluster center. In this paper, we present first results on the Faber-Jackson relation
and, for a subsample of 14 galaxies with morphological and structural parameters from HST, we also investigate the evolution
of the Kormendy relation and the Fundamental Plane. We find a mild luminosity evolution of the early-type galaxies in Abell
2390: our objects are on average brighter by m
B∼0.4 mag.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
4.
D. Bettoni P. Kjrgaard B. Milvang‐Jensen M. D'Onofrio A. Moretti B.M. Poggianti G. Fasano M. Moles 《Astronomische Nachrichten》2011,332(3):299-300
We present the first results of our X‐shooter observations for a sample of dwarf (–17 < MB < –15) galaxies in nearby (0.04 < z < 0.07) galaxy clusters. This luminosity range is fundamental to trace the evolution of higher‐z star‐forming cluster galaxies down to the present day, and to explore the galaxy scaling relations of early‐type galaxies over a broad mass range. Thanks to high resolution and availability of several lines we can derive the velocity dispersion of the galaxies in this range of luminosities and we begin the construction of the fundamental plane of faint early‐type galaxies (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
5.
Understanding the formation and evolution of massive galaxies provides important keys to constrain the baryon assembly processes
in the ΛCDM hierarchical scenario. We review the main results obtained so far with the K20 and other recent near-IR surveys
on the redshift distribution, the evolution of the luminosity function and luminosity density, the nature of old and dusty
EROs, the evolution of the galaxy stellar mass function and the nature of luminous starbursts at z∼2 which may be the progenitors of the present-day massive spheroidal galaxies. 相似文献
6.
Samples of spiral galaxies from two catalogues of 21 cm line observations and a catalogue of near-infrared observations of
nearby galaxies have been used in conjunction with Infrared Astronomical Satellite data to study correlations involving MG, the dynamic mass of the galaxies, the luminosities in theH band (1.6Μm), the blue band and the far infrared bands and the mass of atomic hydrogen, it is found that both the blue and the far-IR
luminosities which are indicators of star formation averaged over ∼3 × l09 and ∼107 years respectively, have a linear dependence onM
G On the other hand, theH luminosity which is a measure of star formation averaged over the lifetime of galaxies, has a steeper power law dependence
onM
G. The correlations observed do not have significant dependence on the morophological type of the galaxies There is a poor correlation
between the far-infrared luminosity and the mass of atomic hydrogen. The mass of atomic hydrogen has a dependence of the formM
G. Because of the decrease in the mean mass for later morphological types and due to differences in power law dependences of
luminosities in different bands onM
G, the mean value of luminosity-to-mass ratio is a constant for blue and far-IR bands, decreases for theH band and the gas-to-mass ratio increases as morphological type increases. 相似文献
7.
The Eridanus galaxies follow the well-known radio—FIR correlation. The majority (70%) of these galaxies have their star formation
rates below that of the Milky Way. The galaxies that have a significant excess of radio emission are identified as low luminosity
AGNs based on their radio morphologies obtained from the GMRT observations. There are no powerful AGNs (L
20cm > 1023 W Hz−1) in the group. The two most far-infrared and radio luminous galaxies in the group have optical and HI morphologies suggestive
of recent tidal interactions. The Eridanus group also has two far-infrared luminous but radio-deficient galaxies. It is believed
that these galaxies are observed within a few Myr of the onset of an intense star formation episode after being quiescent
for at least a 100 Myr. The upper end of the radio luminosity distribution of the Eridanus galaxies (L
20cm ∼ 1022 W Hz−1) is consistent with that of the field galaxies, other groups, and late-type galaxies in nearby clusters. 相似文献
8.
A. Cimatti 《Astrophysics and Space Science》2003,285(1):231-246
The problem of the formation and evolution of field massive galaxies is briefly reviewed from an observational perspective.
The motivations and the characteristics of the K20 survey are outlined. The redshift distribution of K
s<20 galaxies, the evolution of the rest-frame K
s-band luminosity function and luminosity density to z∼ 1.5, the nature and the role of the red galaxy population are presented. Such results are compared with the predictions
of models of galaxy evolution.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
9.
Nicola Menci 《Astrophysics and Space Science》2004,294(1-2):15-22
10.
Paolo Tozzi 《Astrophysics and Space Science》2004,294(1-2):45-50
The study of X-ray clusters of galaxies, started 30 years ago, has revealed an increasing complexity in the thermodynamics
of the X-ray emitting intracluster medium (ICM) as long as the sensitivity and the resolution of the X-ray satellites increased.
At the same time, deep surveysdetected several, unexpected, high-z clusters. Here we focus on the Chandra observations of the most distant X-ray selected clusters (0.3 < z < 1.3), in order to constrain their thermodynamic evolution. The X-ray scaling properties show hints of negative evolution
in the luminosity–temperature and M
gas–temperature relations, and a positive evolution in the entropy–temperature relation. We find that the mean iron abundance
at 〈z〉 = 0.8 is Z
Fe = 0.25+0.04
−0.06
Z
⊙, and at 〈z〉 ∼ 1.2 is Z
Fe = 0.35+0.06
−0.05
Z
⊙, both measures consistent with no evolution with respect to the local value Z
Fe≃ 0.3 Z
⊙. These results can provide interesting constraints on the thermodynamics of the ICM at large look back times, pointing towards
a redshift z ≳ 2 for the onset of non-gravitational processes. 相似文献
11.
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
12.
We discuss the prospects for detecting faint intermediate-mass black holes, such as those predicted to exist in the cores
of globular clusters and dwarf spheroidal galaxies. We briefly summarize the difficulties of stellar dynamical searches, then
show that recently discovered relations between black hole mass, X-ray luminosity and radio luminosity imply that in most
cases, these black holes should be more easily detected in the radio than in the X-rays. Finally, we show upper limits from
some radio observations of globular clusters, and discuss the possibility that the radio source in the core of the Ursa Minor
dwarf spheroidal galaxy might be a ∼10,000–100,000 M⊙ black hole. 相似文献
13.
We present results of an investigation of clustering evolution of field galaxies between a redshift of z ∼ 1 and the present epoch. The current analysis relies on a sample of ∼ 14000 galaxies in two fields of the COMBO 17 survey.
The redshift distribution extends to z ∼ 1. The amplitude of the three-dimensional correlation function can be estimated by means of the projected correlation function
w(r
p
). The validity of the deprojection was tested on the Las Campanas Redshift Survey (LCRS). In a flat cosmology with non-zero
cosmological constant for bright galaxies (M
B ≤-18) the clustering growth is proportional to (1+z)
-2. However, the measured clustering evolution clearly depends on Hubble type. While locally the clustering strength of early
type galaxies is equal to that of the bright galaxies, at high redshifts they are much stronger clustered, and thus the clustering
has to evolve much more slowly.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
14.
To investigate the environmental dependence of u ‐, g ‐, r ‐, i ‐, and z ‐band luminosities, we perform comparative studies of luminosity distributions between galaxy members of compact groups (CGs) and isolated galaxies. It is found that for the r, i, and z bands isolated galaxies have a higher proportion of faint galaxies and a lower proportion of luminous galaxies than galaxy members of CGs, but for the u band an opposite trend is observed. The correlation between the g ‐band luminosity and the environment has different trends in different luminosity regions (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
15.
Andrea Merloni Sebastian Heinz Tiziana Di Matteo 《Astrophysics and Space Science》2005,300(1-3):45-53
We examine the disc-jet connection in stellar mass and supermassive black holes by investigating the properties of their compact
emission in the hard X-ray and radio bands. We compile a sample of ∼100 active galactic nuclei with measured mass, 5 GHz core
emission, and 2–10 keV luminosity, together with eight galactic black holes with a total of ∼50 simultaneous observations
in the radio and X-ray bands. Using this sample, we study the correlations between the radio (LR) and the X-ray (LX) luminosity and the black hole mass (M). We find that the radio luminosity is correlated with both M and LX, at a highly significant level. We show how this result can be used to extend the standard unification by orientation scheme
to encompass unification by mass and accretion rate. 相似文献
16.
In the framework of ‘microscopic’ theory of black holes (J. Phys. Soc. Jpn. Suppl. B 70, 84, 2001; Astrophys. USSR 4, 659, 1996; 35, 335, 1991, 33, 143, 1990, 31, 345, 1989a; Astrophys. Space Sci. 1, 1992; Dokl. Akad. Nauk USSR 309, 97, 1989b), and references therein, we address the ‘pre-radiation time’ (PRT) of neutrinos from black holes, which implies the lapse
of time from black hole’s birth till radiation of an extremely high energy neutrinos. For post-PRT lifetime, the black hole
no longer holds as a region of spacetime that cannot communicate with the external universe. We study main features of spherical
accretion onto central BH and infer a mass accretion rate onto it, and, further, calculate the resulting PRT versus bolometric
luminosity due to accretion onto black hole. We estimate the PRTs of AGN black holes, with the well-determined masses and
bolometric luminosities, collected from the literature by Woo Jong-Hak and Urry (Astrophys. J. 579, 530, 2002) on which this paper is partially based. The simulations for the black holes of masses M
BH
≃(1.1⋅106
÷4.2⋅109) M
⊙ give the values of PRTs varying in the range of about T
BH
≃(4.3⋅105
÷5.6⋅1011) yr. The derived PRTs for the 60 AGN black holes are longer than the age of the universe (∼13.7 Gyr) favored today. At present,
some of remaining 174 BHs may radiate neutrinos. However, these results would be underestimated if the reservoir of gas for
accretion in the galaxy center is quite modest, and no obvious way to feed the BHs with substantial accretion. 相似文献
17.
The nature of Ultraluminous X-ray Sources – X-ray sources which exceed the Eddington luminosity for a ∼10 M
⊙ black hole – remains a mystery. One possible explanation is an inhomogeneous accretion disk around a solar mass black hole
where photon transport through radiation-pressure dominated “photon bubbles” can lead to super-Eddington accretion. While
previous studies of this model have focused primarily on its radiation-hydrodynamics aspects, here we explore some observational
implications of such a model with a Monte Carlo–Fokker Planck radiation transport code. 相似文献
18.
The first set of supermassive black hole mass estimates, published from 1977 to 1984 by E.A. Dibai, are shown to be in excellent
agreement with recent reverberation-mapping estimates. Comparison of the masses of 17 AGNs covering a mass range from about
106 to 109
M
⊙ shows that the Dibai mass estimates agree with reverberation-mapping mass estimates to significantly better than ±0.3 dex
and were, on average, only 0.14 dex (∼40%) systematically lower than masses obtained from reverberation mapping. This surprising
agreement with the results of over a quarter of a century ago has important implication for the structure and kinematics of
AGNs and implies that type-1 AGNs are very similar. Our results give strong support to the use of the single-epoch-spectrum
(Dibai) method for investigating the co-evolution of supermassive black holes and their host galaxies.
The article was translated by the authors. 相似文献
19.
C. L. Carilli F. Walter R. Wang A. Wootten K. Menten F. Bertoldi E. Schinnerer P. Cox A. Beelen A. Omont 《Astrophysics and Space Science》2008,313(1-3):307-311
We discuss observations of the first galaxies, within cosmic reionization, at centimeter and millimeter wavelengths. We present
a summary of current observations of the host galaxies of the most distant QSOs (z∼6). These observations reveal the gas, dust, and star formation in the host galaxies on kpc-scales. These data imply an enriched
ISM in the QSO host galaxies within 1 Gyr of the big bang, and are consistent with models of coeval supermassive black hole
and spheroidal galaxy formation in major mergers at high redshift. Current instruments are limited to studying truly pathologic
objects at these redshifts, meaning hyper-luminous infrared galaxies (L
FIR
∼1013
L
⊙). ALMA will provide the one to two orders of magnitude improvement in millimeter astronomy required to study normal star
forming galaxies (i.e. Ly-α emitters) at z∼6. ALMA will reveal, at sub-kpc spatial resolution, the thermal gas and dust—the fundamental fuel for star formation—in galaxies
into cosmic reionization. 相似文献
20.
Daniel Thomas Ralf Bender Ulrich Hopp Claudia Maraston Laura Greggio 《Astrophysics and Space Science》2003,284(2):599-602
We present kinematics and stellar population properties of 17 dwarf early-type galaxies in the luminosity range -14 ≥ M
B ≥ -19. Our sample fills the gap between the intensively studied giant elliptical and Local Group dwarf spheroidal galaxies.
The dwarf ellipticals of the present sample have constant velocity dispersion profiles within their effective radii and do
not show significant rotation, hence are clearly anisotropic. The dwarf lenticulars, instead, rotate faster and are, at least
partially, supported by rotation. From optical Lick absorption indices, we derive metallicities and element abundances. Combining
our sample with literature data of the Local Group dwarf spheroidals and giant ellipticals, we find a surprisingly tight linear
correlation between metallicity and luminosity over a wide range: -8 ≥ M
B ≥ -22. The α/Fe ratios of our dwarf ellipticals are significantly lower than the ones of giant elliptical galaxies, which
is in agreement with spectroscopy of individual stars in Local Group dwarf spheroidals. Our results suggest the existence
of a clear kinematic and stellar population dichotomy between dwarf and giant elliptical galaxies. This result is important
for theories of galaxy formation, because it implies that present-day dwarf ellipticals are not the fossiled building blocks
of giant ellipticals.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献