共查询到20条相似文献，搜索用时 31 毫秒
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P. N. Best † 《Monthly notices of the Royal Astronomical Society》2000,317(3):720-736
An analysis of the environments around a sample of 28 3CR radio galaxies with redshifts 0.6< z <1.8 is presented, based primarily upon K -band images down to K ∼20 taken using the UK Infrared Telescope (UKIRT). A net overdensity of K -band galaxies is found in the fields of the radio galaxies, with the mean excess counts being comparable to that expected for clusters of Abell Class 0 richness. A sharp peak is found in the angular cross-correlation amplitude centred on the radio galaxies that, for reasonable assumptions about the luminosity function of the galaxies, corresponds to a spatial cross-correlation amplitude between those determined for low-redshift Abell Class 0 and 1 clusters.
These data are complemented by J -band images also from UKIRT, and by optical images from the Hubble Space Telescope . The fields of the lower redshift ( z ≲0.9) radio galaxies in the sample generally show well-defined near-infrared colour–magnitude relations with little scatter, indicating a significant number of galaxies at the redshift of the radio galaxy; the relations involving colours at shorter wavelengths than the 4000 Å break show considerably greater scatter, suggesting that many of the cluster galaxies have low levels of recent or on-going star formation. At higher redshifts the colour–magnitude sequences are less prominent owing to the increased field galaxy contribution at faint magnitudes, but there is a statistical excess of galaxies with the very red infrared colours ( J − K ≳1.75) expected of old cluster galaxies at these redshifts.
Although these results are appropriate for the mean of all of the radio galaxy fields, there exist large field-to-field variations in the richness of the environments. Many, but certainly not all, powerful z ∼1 radio galaxies lie in (proto)cluster environments. 相似文献
These data are complemented by J -band images also from UKIRT, and by optical images from the Hubble Space Telescope . The fields of the lower redshift ( z ≲0.9) radio galaxies in the sample generally show well-defined near-infrared colour–magnitude relations with little scatter, indicating a significant number of galaxies at the redshift of the radio galaxy; the relations involving colours at shorter wavelengths than the 4000 Å break show considerably greater scatter, suggesting that many of the cluster galaxies have low levels of recent or on-going star formation. At higher redshifts the colour–magnitude sequences are less prominent owing to the increased field galaxy contribution at faint magnitudes, but there is a statistical excess of galaxies with the very red infrared colours ( J − K ≳1.75) expected of old cluster galaxies at these redshifts.
Although these results are appropriate for the mean of all of the radio galaxy fields, there exist large field-to-field variations in the richness of the environments. Many, but certainly not all, powerful z ∼1 radio galaxies lie in (proto)cluster environments. 相似文献
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S. Andreon 《Monthly notices of the Royal Astronomical Society》2008,386(2):1045-1052
We measure the relative evolution of the number of bright and faint (as faint as 0.05 L *) red galaxies in a sample of 28 clusters, out of which 16 are at 0.50 ≤ z ≤ 1.27 , all observed through a pair of filters bracketing the 4000-Å break rest frame. The abundance of red galaxies, relative to bright ones, is constant over all the studied redshift range, 0 < z < 1.3 , and rules out a differential evolution between bright and faint red galaxies as large as claimed in some past works. Faint red galaxies are largely assembled and in place at z = 1.3 and their abundance does not depend on cluster mass, parametrized by velocity dispersion or X-ray luminosity. Our analysis, with respect to the previous one, samples a wider redshift range, minimizes systematics and put a more attention to statistical issues, keeping at the same time a large number of clusters. 相似文献
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Elaine M. Sadler Russell D. Cannon Tom Mauch Paul J. Hancock David A. Wake Nic Ross Scott M. Croom Michael J. Drinkwater Alastair C. Edge Daniel Eisenstein rew M. Hopkins Helen M. Johnston Robert Nichol Kevin A. Pimbblet Roberto De Propris Isaac G. Roseboom Donald P. Schneider Tom Shanks 《Monthly notices of the Royal Astronomical Society》2007,381(1):211-227
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L. Tresse S. J. Maddox O. Le Fèvre J.-G. Cuby 《Monthly notices of the Royal Astronomical Society》2002,337(1):369-383
We describe ISAAC/ESO-VLT observations of the Hαλ6563 Balmer line of 33 field galaxies from the Canada–France Redshift Survey (CFRS) with redshifts selected between 0.5 and 1.1. We detect Hα in emission in 30 galaxies and compare the properties of this sample with the low-redshift sample of CFRS galaxies at z ∼ 0.2 . We find that the Hα luminosity, L (Hα) , is tightly correlated to M ( B AB ) in the same way for both the low- and high-redshift samples. L (Hα) is also correlated to L ([O ii ]λ3727), and again the relation appears to be similar at low and high redshifts. The ratio L (lsqb;O ii ])/ L (Hα) decreases for brighter galaxies by as much as a factor of 2 on average. Derived from the Hα luminosity function, the comoving Hα luminosity density increases by a factor 12 from 〈 z 〉= 0.2 to 〈 z 〉= 1.3 . Our results confirm a strong rise of the star formation rate (SFR) at z < 1.3 , proportional to (1 + z )4.1±0.3 (with H 0 = 50 km s−1 Mpc−1 , q 0 = 0.5 ). We find an average SFR(2800 Å)/SFR (Hα) ratio of 3.2 using the Kennicutt SFR transformations. This corresponds to the dust correction that is required to make the near-ultraviolet data consistent with the reddening-corrected Hα data within the self-contained, I -selected CFRS sample. 相似文献
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M. Povi&#x; A.M. Prez García M. Snchez‐Portal A. Bongiovanni J. Cepa M. Fernndez Lorenzo M.A. Lara‐Lpez J. Gallego A. Ederoclite I. Mrquez J. Masegosa E. Alfaro H. Castaeda J.I. Gonzlez‐Serrano J.J. Gonzlez 《Astronomische Nachrichten》2013,334(3):288-299
Luminosity functions are one of the most important observational clues when studying galaxy evolution over cosmic time. In this paper we present the X‐ray luminosity functions for X‐ray detected AGN in the SXDS and GWS fields. The limiting fluxes of our samples are 9.0 ×10–15 and 4.8 ×10–16 erg cm–2 s–1 in the 0.5–7.0 keV band in the two fields, respectively. We carried out analysis in three X‐ray bands and in two redshift intervals up to z ≤ 1.4. Moreover, we derive the luminosity functions for different optical morphologies and X‐ray types. We confirm strong luminosity evolution in all three bands, finding the most luminous objects at higher redshift. However, no signs of density evolution are found in any tested X‐ray band. We obtain similar results for compact and early‐type objects. Finally, we observe the “Steffen effect”, where X‐ray type‐1 sources are more numerous at higher luminosities in comparison with type‐2 sources. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Michael McDonald † Stéphane Courteau R. Brent Tully 《Monthly notices of the Royal Astronomical Society》2009,393(2):628-640
We present bulge and disc (B/D) decompositions of existing K ' surface brightness profiles for 65 Ursa Major (UMa) cluster spiral galaxies. This improves upon the disc-only fits of Tully et al. The 1996 disc fits were used by Tully & Verheijen for their discovery of the bimodality of structural parameters in the UMa cluster galaxies. It is shown that our new one-dimensional B/D decompositions yield disc structural parameters that differ only slightly from the basic fits of Tully et al. and evidence for structural bimodality of UMa galaxies is maintained. Our B/D software for the decomposition of one-dimensional surface brightness profiles of galaxies uses a non-linear minimization scheme to recover the best-fitting Sérsic bulge and the exponential disc while accounting for the possible presence of a compact nucleus and spiral arms and for the effects of seeing and disc truncations. In agreement with Tully & Verheijen, we find that the distribution of near-infrared disc central surface brightnesses is bimodal with an F-test confidence of 80 per cent. There is also strong evidence for a local minimum in the luminosity function at . A connection between the brightness bimodality and a dynamical bimodality, based on new H i linewidths, is identified. The B/D parameters are presented in Table 1 .
Table 1. B/D parameters. 相似文献
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Simon P. Driver Warrick J. Couch Steven Phillipps & Rodney Smith 《Monthly notices of the Royal Astronomical Society》1998,301(2):357-368
We present detailed simulations of long-exposure CCD images. The simulations are used to explore the validity of the statistical method for reconstructing the luminosity distribution of galaxies within a rich cluster, i.e., by the subtraction of field number-counts from those of a sight-line through the cluster. In particular, we use the simulations to establish the reliability of our observational data to be presented in Paper III. Based on our intended CCD field-of-view (6.5 × 6.5 arcmin2 ) and a 1σ detection limit of 26 mag arcsec−2 , we conclude that the luminosity distribution can be robustly determined over a wide range of absolute magnitude (−23 < M R < −16) provided: (a) the cluster has an Abell richness 1.5 or greater; (b) the redshift of the cluster lies in the range 0.1 < z < 0.3; (c) the seeing is better than FWHM 1.25 arcsec, and (d) the photometric zero-points are accurate to within Δ m = ± 0.12. If these conditions are not met, then the recovered luminosity distribution is unreliable. Finally, although the method clearly has limitations, within these limitations the technique represents an extremely promising probe of galaxy evolution and environmental dependences. 相似文献
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Metcalfe Ratcliffe Shanks & Fong 《Monthly notices of the Royal Astronomical Society》1998,294(1):147-164
Using the PDS microdensitometer at the Royal Greenwich Observatory, we have acquired U , B , V , R and I surface photometry from UK Schmidt photographic plates for all the galaxies with measured redshifts in the Durham–AAT redshift survey. By comparison with CCD photometry we show that such precision photographic photometry of galaxies off IIIa emulsions is capable of an accuracy as good as a few hundredths of a magnitude. We discuss the colour-related properties of these galaxies, and derive luminosity functions in each waveband. We show that when divided by colour, the faint-end slope of the luminosity function of the bluer galaxies is significantly steeper than that for the redder ones. 相似文献
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J. Liske D. J. Lemon S. P. Driver N. J. G. Cross W. J. Couch 《Monthly notices of the Royal Astronomical Society》2003,344(1):307-324
The Millennium Galaxy Catalogue (MGC) is a 37.5 deg2 , medium-deep, B -band imaging survey along the celestial equator, taken with the Wide Field Camera on the Isaac Newton Telescope. The survey region is contained within the regions of both the Two Degree Field Galaxy Redshift Survey (2dFGRS) and the Sloan Digital Sky Survey Early Data Release (SDSS-EDR). The survey has a uniform isophotal detection limit of 26 mag arcsec−2 and it provides a robust, well-defined catalogue of stars and galaxies in the range 16 ≤ B MGC < 24 mag .
Here we describe the survey strategy, the photometric and astrometric calibration, source detection and analysis, and present the galaxy number counts that connect the bright and faint galaxy populations within a single survey. We argue that these counts represent the state of the art and use them to constrain the normalizations (φ*) of a number of recent estimates of the local galaxy luminosity function. We find that the 2dFGRS, SDSS Commissioning Data (CD), ESO Slice Project, Century Survey, Durham/UKST, Mt Stromlo/APM, SSRS2 and NOG luminosity functions require a revision of their published φ* values by factors of 1.05 ± 0.05, 0.76 ± 0.10, 1.02 ± 0.22, 1.02 ± 0.16, 1.16 ± 0.28, 1.75 ± 0.37, 1.40 ± 0.26 and 1.01 ± 0.39 , respectively. After renormalizing the galaxy luminosity functions we find a mean local bJ luminosity density of . 1 相似文献
Here we describe the survey strategy, the photometric and astrometric calibration, source detection and analysis, and present the galaxy number counts that connect the bright and faint galaxy populations within a single survey. We argue that these counts represent the state of the art and use them to constrain the normalizations (φ*) of a number of recent estimates of the local galaxy luminosity function. We find that the 2dFGRS, SDSS Commissioning Data (CD), ESO Slice Project, Century Survey, Durham/UKST, Mt Stromlo/APM, SSRS2 and NOG luminosity functions require a revision of their published φ* values by factors of 1.05 ± 0.05, 0.76 ± 0.10, 1.02 ± 0.22, 1.02 ± 0.16, 1.16 ± 0.28, 1.75 ± 0.37, 1.40 ± 0.26 and 1.01 ± 0.39 , respectively. After renormalizing the galaxy luminosity functions we find a mean local b
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I. K. Baldry K. Glazebrook S. P. Driver 《Monthly notices of the Royal Astronomical Society》2008,388(3):945-959
A comparison between published field galaxy stellar mass functions (GSMFs) shows that the cosmic stellar mass density is in the range 4–8 per cent of the baryon density (assuming Ωb = 0.045 ). There remain significant sources of uncertainty for the dust correction and underlying stellar mass-to-light ratio even assuming a reasonable universal stellar initial mass function. We determine the z < 0.05 GSMF using the New York University Value-Added Galaxy Catalog sample of 49 968 galaxies derived from the Sloan Digital Sky Survey and various estimates of stellar mass. The GSMF shows clear evidence for a low-mass upturn and is fitted with a double Schechter function that has α2 ≃−1.6 . At masses below ∼108.5 M⊙ , the GSMF may be significantly incomplete because of missing low-surface-brightness galaxies. One interpretation of the stellar mass–metallicity relation is that it is primarily caused by a lower fraction of available baryons converted to stars in low-mass galaxies. Using this principle, we determine a simple relationship between baryonic mass and stellar mass and present an 'implied baryonic mass function'. This function has a faint-end slope, α2 ≃−1.9 . Thus, we find evidence that the slope of the low-mass end of the galaxy mass function could plausibly be as steep as the halo mass function. We illustrate the relationship between halo baryonic mass function → galaxy baryonic mass function → GSMF. This demonstrates the requirement for peak galaxy formation efficiency at baryonic masses ∼1011 M⊙ corresponding to a minimum in feedback effects. The baryonic-infall efficiency may have levelled off at lower masses. 相似文献
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M. Le Delliou C. G. Lacey C. M. Baugh S. L. Morris 《Monthly notices of the Royal Astronomical Society》2006,365(3):712-726
We present detailed predictions for the properties of Lyα-emitting galaxies in the framework of the Λ cold dark matter cosmology, calculated using the semi-analytical galaxy formation model galform . We explore a model that assumes a top-heavy initial mass function in starbursts and that has previously been shown to explain the sub-millimetre number counts and the luminosity function of Lyman-break galaxies at high redshift. We show that this model, with the simple assumption that a fixed fraction of Lyα photons escape from each galaxy, is remarkably successful at explaining the observed luminosity function of Lyα emitters (LAEs) over the redshift range 3 < z < 6.6 . We also examine the distribution of Lyα equivalent widths and the broad-band continuum magnitudes of emitters, which are in good agreement with the available observations. We look more deeply into the nature of LAEs, presenting predictions for fundamental properties such as the stellar mass and radius of the emitting galaxy and the mass of the host dark matter halo. The model predicts that the clustering of LAEs at high redshifts should be strongly biased relative to the dark matter, in agreement with observational estimates. We also present predictions for the luminosity function of LAEs at z > 7 , a redshift range that is starting to be be probed by near-infrared surveys and using new instruments such as the Dark Ages Z Lyman Explorer (DAzLE). 相似文献
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Elizabeth R. Stanway Malcolm N. Bremer Matthew D. Lehnert 《Monthly notices of the Royal Astronomical Society》2008,385(1):493-510
A large population of z > 5 Lyman-break galaxies has been identified in recent years. However, the high-redshift galaxies selected by different surveys are subject to a variety of selection effects – some overt, others more subtle. We present an analysis of sample completeness and contamination issues in high-redshift surveys, focusing on surveys at z ≈ 5 and using a spectroscopically confirmed low-redshift sample from the DEEP2 survey in order to characterize contaminant galaxies. We find that most surveys underestimate their contamination from highly clustered galaxies at z ≈ 1 and stars. We consider the consequences of this for both the rest-frame ultraviolet luminosity function and the clustering signal from z ≈ 5 galaxies. We also find that sources with moderate strength Lyman α emission lines can be omitted from dropout surveys due to their blue colours, again effecting the derived luminosity functions. We discuss the points of comparison between different samples, and the applicability of survey-specific results to the population at z > 5 in general. 相似文献
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P. N. Best J. N. Arts H. J. A. Röttgering R. Rengelink M. H. Brookes J. Wall 《Monthly notices of the Royal Astronomical Society》2003,346(2):627-683
A new sample of radio sources, with the designated name CENSORS (A Combined EIS–NVSS Survey Of Radio Sources), has been defined by combining the National Radio Astronomy Observatory Very Large Array Sky Survey (NVSS) at 1.4 GHz with the ESO Imaging Survey (EIS) Patch D, a 3° by 2° region of sky centred at RA , Dec. −21°00'00' (J2000). New radio observations of 199 NVSS radio sources with NVSS flux densities S 1.4 GHz > 7.8 mJy are presented, and are compared with the EIS I -band imaging observations which reach a depth of I ∼ 23 ; optical identifications are obtained for over two-thirds of the ∼150 confirmed radio sources within the EIS field. The radio sources have a median linear size of 6 arcsec, consistent with the trend for lower flux density radio sources to be less extended. Other radio source properties, such as the lobe flux density ratios, are consistent with those of brighter radio source samples. From the optical information, 30–40 per cent of the sources are expected to lie at redshifts z ≳ 1.5 .
One of the key goals of this survey is to accurately determine the high-redshift evolution of the radio luminosity function. These radio sources are at the ideal flux density level to achieve this goal; at redshifts z ∼ 2 they have luminosities which are around the break of the luminosity function and so provide a much more accurate census of the radio source population at those redshifts than the existing studies of extreme, high radio power sources. Other survey goals include investigating the dual-population unification schemes for radio sources, studying the radio luminosity dependence of the evolution of radio source environments, and understanding the radio power dependence of the K – z relation for radio galaxies. 相似文献
One of the key goals of this survey is to accurately determine the high-redshift evolution of the radio luminosity function. These radio sources are at the ideal flux density level to achieve this goal; at redshifts z ∼ 2 they have luminosities which are around the break of the luminosity function and so provide a much more accurate census of the radio source population at those redshifts than the existing studies of extreme, high radio power sources. Other survey goals include investigating the dual-population unification schemes for radio sources, studying the radio luminosity dependence of the evolution of radio source environments, and understanding the radio power dependence of the K – z relation for radio galaxies. 相似文献