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1.
We present a measurement of the K -band luminosity function (LF) of field galaxies obtained from near-infrared imaging of a sample of 345 galaxies selected from the Stromlo-APM Redshift Survey. The LF is reasonably well fitted over the 10-mag range −26 M K −16 by a Schechter function with parameters α =−1.16±0.19, M *=−23.58±0.42 and φ *=0.012±0.008 Mpc−3, assuming a Hubble constant of H 0=100 km s−1 Mpc−1. We have also estimated the LF for two subsets of galaxies subdivided by the equivalent width of the H α emission line at EW(H α )=10 Å. There is no significant difference in LF shape between the two samples, although there is a hint (∼1 σ significance) that emission-line galaxies (ELGs) have M * roughly 1 mag fainter than non-ELGs. Contrary to the optical LF, there is no difference in faint-end slope α between the two samples.  相似文献   

2.
We present a new determination of the local volume-averaged star formation rate from the 1.4-GHz luminosity function of star forming galaxies. Our sample, taken from the   B ≤12  Revised Shapley–Ames catalogue (231 normal spiral galaxies over an effective area of 7.1 sr) has ≃100 per cent complete radio detections and is insensitive to dust obscuration and cirrus contamination. After removal of known active galaxies, the best-fitting Schechter function has a faint-end slope of  −1.27±0.07  in agreement with the local H α luminosity function, characteristic luminosity   L ∗=(2.6±0.7)×1022 W Hz−1  and density   φ ∗=(4.8±1.1)×10−4 Mpc−3.  The inferred local radio luminosity density of  (1.73±0.37±0.03)×1019 W Hz−1 Mpc−3  (Poisson noise, large-scale structure fluctuations) implies a volume-averaged star formation rate ∼2 times larger than the Gallego et al. H α estimate, i.e.   ρ 1.4 GHz=(2.10±0.45±0.04)×10−2 M yr−1 Mpc−3  for a Salpeter initial mass function from  0.1–125 M  and Hubble constant of 50 km s−1 Mpc−1. We demonstrate that the Balmer decrement is a highly unreliable extinction estimator, and argue that optical–ultraviolet (UV) star formation rates (SFRs) are easily underestimated, particularly at high redshift.  相似文献   

3.
A deep   K s   -band photometric catalogue of galaxies at the core of the rich, nearby Norma cluster (ACO3627) is presented. The survey covers about  45 × 45 arcmin2  (slightly less than 1/3 Abell radius), which corresponds to  ∼0.8  h −270 Mpc2  at the adopted distance  ( v CMB/ H 0)  of  70  h −170 Mpc  of this cluster. The survey is estimated to be complete to a magnitude of     . This extends into the dwarf regime, 6 mag below     . The catalogue contains 390 objects, 235 of which are classified as likely or definite galaxies and 155 as candidate galaxies. The   K s   -band luminosity function (LF) is constructed from the photometric sample, using a spectroscopic subsample to correct for fore and background contamination. We fit a Schechter function with a characteristic magnitude of     and faint-end slope of  α=−1.26 ± 0.10  to the data. The shape of the LF is similar to those found in previous determinations of the cluster LF, in both optical and near-infrared. The Schechter parameters agree well with those of recent field LFs, suggesting that the shape of both the bright-end and the faint-end slopes are relatively insensitive to environment.  相似文献   

4.
We produce and analyse u -band (  λ≈ 355  nm) luminosity functions (LFs) for the red and blue populations of galaxies using data from the Sloan Digital Sky Survey (SDSS) u -band Galaxy Survey ( u GS) and Deep Evolutionary Exploratory Probe 2 (DEEP2) survey. From a spectroscopic sample of 41 575 SDSS u GS galaxies and 24 561 DEEP2 galaxies, we produce colour magnitude diagrams and make use of the colour bimodality of galaxies to separate red and blue populations. LFs for eight redshift slices in the range  0.01 < z < 1.2  are determined using the  1/ V max  method and fitted with Schechter functions showing that there is significant evolution in   M *  , with a brightening of 1.4 mag for the combined population. The integration of the Schechter functions yields the evolution in the u -band luminosity density (LD) out to   z ∼ 1  . By parametrizing the evolution as  ρ∝ (1 + z )β  , we find that  β= 1.36 ± 0.2  for the combined populations and  β= 2.09 ± 0.2  for the blue population. By removing the contribution of the old stellar population to the u -band LD and correcting for dust attenuation, we estimate the evolution in the star formation rate (SFR) of the Universe to be  βSFR= 2.5 ± 0.3  . Discrepancies between our result and higher evolution rates measured using the infrared and far-UV can be reconciled by considering possibilities such as an underestimated dust correction at high redshifts or evolution in the stellar initial mass function.  相似文献   

5.
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   

6.
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 b J luminosity density of     . 1  相似文献   

7.
We determine the underlying shapes of spiral and elliptical galaxies in the Sloan Digital Sky Survey Data Release 6 (SDSS DR6) from the observed distribution of projected galaxy shapes, taking into account the effects of dust extinction and reddening. We assume that the underlying shapes of spirals and ellipticals are well approximated by triaxial ellipsoids. The elliptical galaxy data are consistent with oblate spheroids, with a correlation between luminosity and ellipticity: the mean values of minor to middle axis ratios are 0.41 ± 0.03 for   M r ≈−18  ellipticals and 0.76 ± 0.04 for   M r ≈−22.5  ellipticals. Ellipticals show almost no dependence of axial ratio on galaxy colour, implying a negligible dust optical depth.
There is a strong variation of spiral galaxy shapes with colour indicating the presence of dust. The intrinsic shapes of spiral galaxies in the SDSS DR6 are consistent with flat discs with a mean and dispersion of thickness to diameter ratio of (21 ± 2) per cent, and a face-on ellipticity, e , of  ln( e ) =−2.33 ± 0.79  . Not including the effects of dust in the model leads to discs that are systematically rounder by up to 60 per cent. More luminous spiral galaxies tend to have thicker and rounder discs than lower luminosity spirals. Both elliptical and spiral galaxies tend to be rounder for larger galaxies.
The marginalized value of the edge-on r -band dust extinction E 0 in spiral galaxies is   E 0≃ 0.45  mag for galaxies of median colours, increasing to   E 0= 1  mag for   g − r > 0.9  and   E 0= 1.9  for the luminous and most compact galaxies, with half-light radii  <2  h −1 kpc  .  相似文献   

8.
We present K -band observations of the low-luminosity galaxies in the Coma cluster, which are responsible for the steep upturn in the optical luminosity function at M R∼−16, discovered recently. The main results of this study are as follows.
(i) The optical–near-infrared colours of these galaxies imply that they are dwarf spheroidal galaxies. The median B − K colour for galaxies with −19.3< MK <−16.3 is 3.6 mag.
(ii) The K -band luminosity function in the Coma cluster is not well constrained, because of the uncertainties due to the field-to-field variance of the background. However, within the estimated large errors, this is consistent with the R -band luminosity function, shifted by ∼3 mag.
(iii) Many of the cluster dwarfs lie in a region of the B − K versus B − R colour–colour diagram where background galaxies are rare ( B − K <5; 1.2< B − R <1.6). Local dwarf spheroidal galaxies lie in this region too. This suggests that a better measurement of the K -band cluster luminosity can be made if the field-to-field variance of the background can be measured as a function of colour, even if it is large.
(iv) If we assume that none of the galaxies in the region of the B − K versus B − R plane given in (iii) in our cluster fields are background, and that all the cluster galaxies with 15.5< K <18.5 lie in this region of the plane, then we measure α=−1.41+0.34−0.37 for −19.3< MK −16.3, where α is the logarithmic slope of the luminosity function. The uncertainties in this number come from counting statistics.  相似文献   

9.
We have used far-infrared data from IRAS , Infrared Space Observatory ( ISO ), Spitzer Wide-Area Infrared Extragalactic (SWIRE), Submillimetre Common User Bolometer Array (SCUBA) and Max-Planck Millimetre Bolometer (MAMBO) to constrain statistically the mean far-infrared luminosities of quasars. Our quasar compilation at redshifts  0 < z < 6.5  and I -band luminosities  −20 < I AB < −32  is the first to distinguish evolution from quasar luminosity dependence in such a study. We carefully cross-calibrate IRAS against Spitzer and ISO , finding evidence that IRAS 100-μm fluxes at <1 Jy are overestimated by ∼30 per cent. We find evidence for a correlation between star formation in quasar hosts and the quasar optical luminosities, varying as star formation rate (SFR)  ∝ L 0.44±0.07opt  at any fixed redshift below   z = 2  . We also find evidence for evolution of the mean SFR in quasar host galaxies, scaling as  (1 + z )1.6±0.3  at   z < 2  for any fixed quasar I -band absolute magnitude fainter than −28. We find no evidence for any correlation between SFR and black hole mass at  0.5 < z < 4  . Our data are consistent with feedback from black hole accretion regulating stellar mass assembly at all redshifts.  相似文献   

10.
We present time-resolved spectroscopy and photometry of the cataclysmic variable (CV) SDSS J133941.11+484727.5 (SDSS 1339) which has been discovered in the Sloan Digital Sky Survey (SDSS) Data Release 4. The orbital period determined from radial velocity studies is 82.524(24) min, close to the observed period minimum. The optical spectrum of SDSS 1339 is dominated to 90 per cent by emission from the white dwarf (WD). The spectrum can be successfully reproduced by a three-component model (white dwarf, disc, secondary) with   T WD=12 500 K  for a fixed  log   g = 8.0, d = 170 pc  , and a spectral type of the secondary later than M8. The mass-transfer rate corresponding to the optical luminosity of the accretion disc is very low,  ≃ 1.7 × 10−13 M yr−1  . Optical photometry reveals a coherent variability at 641 s with an amplitude of 0.025 mag, which we interpret as non-radial pulsations of the white dwarf. In addition, a long-period photometric variation with a period of either 320 or 344 min and an amplitude of 0.025 mag is detected, which bears no apparent relation with the orbital period of the system. Similar long-period photometric signals have been found in the CVs SDSS J123813.73−033933.0, SDSS J204817.85−061044.8, GW Lib and FS Aur, but so far no working model for this behaviour is available.  相似文献   

11.
The kinematics of satellite galaxies reflect the masses of the extended dark matter haloes in which they orbit, and thus shed light on the mass–luminosity relation (MLR) of their corresponding central galaxies. In this paper, we select a large sample of centrals and satellites from the Sloan Digital Sky Survey and measure the kinematics (velocity dispersions) of the satellite galaxies as a function of the r -band luminosity of the central galaxies. Using the analytical framework presented in More, van den Bosch & Cacciato, we use these data to infer both the mean and the scatter of the MLR of central galaxies, carefully taking account of selection effects and biases introduced by the stacking procedure. As expected, brighter centrals on average reside in more massive haloes. In addition, we find that the scatter in halo masses for centrals of a given luminosity,  σlog  M   , also increases with increasing luminosity. As we demonstrate, this is consistent with  σlog  L   , which reflects the scatter in the conditional probability function   P ( L c| M )  , being independent of halo mass. Our analysis of the satellite kinematics yields  σlog  L = 0.16  ±  0.04  , in excellent agreement with constraints from clustering and group catalogues, and with predictions from a semi-analytical model of galaxy formation. We thus conclude that the amount of stochasticity in galaxy formation, which is characterized by  σlog  L   , is well constrained, independent of halo mass and in a good agreement with current models of galaxy formation.  相似文献   

12.
We present the results of a proper motion survey of the Hyades to search for brown dwarfs, based on UKIRT Deep Sky Survey (UKIDSS) and Two-Micron All Sky Survey (2MASS) data. This survey covers  ∼275 deg2  to a depth of   K ∼ 15  mag, equivalent to a mass of  ∼0.05 M  assuming a cluster age of 625 Myr. The discovery of 12 L dwarf Hyades members is reported. These members are also brown dwarfs, with masses between  0.05 < M < 0.075 M  . A high proportion of these L dwarfs appear to be photometric binaries.  相似文献   

13.
We measure the     B -band optical luminosity function (LF) for galaxies selected in a blind H  i survey. The total LF of the H  i selected sample is flat, with Schechter parameters     and     , in good agreement with LFs of optically selected late-type galaxies. Bivariate distribution functions of several galaxy parameters show that the H  i density in the local Universe is more widely spread over galaxies of different size, central surface brightness and luminosity than the optical luminosity density is. The number density of very low surface brightness (LSB ) (>24.0 mag arcsec−2) gas-rich galaxies is considerably lower than that found in optical surveys designed to detect dim galaxies. This suggests that only a part of the population of LSB galaxies is gas-rich and that the rest must be gas-poor. However, we show that this gas-poor population must be cosmologically insignificant in baryon content. The contribution of gas-rich LSB galaxies (>23.0 mag arcsec−2) to the local cosmological gas and luminosity density is modest     and     per cent respectively); their contribution to Ωmatter is not well-determined, but probably <11 per cent. These values are in excellent agreement with the low redshift results from the Hubble Deep Field.  相似文献   

14.
We present phase resolved optical spectroscopy and photometry of V4580 Sagittarii, the optical counterpart to the accretion powered millisecond pulsar SAX J1808.4−3658, obtained during the 2008 September/October outburst. Doppler tomography of the N  iii λ4640.64 Bowen blend emission line reveals a focused spot of emission at a location consistent with the secondary star. The velocity of this emission occurs at  324 ± 15 km s−1  ; applying a ' K -correction', we find the velocity of the secondary star projected on to the line of sight to be  370 ± 40 km s−1  . Based on existing pulse timing measurements, this constrains the mass ratio of the system to be  0.044+0.005−0.004  , and the mass function for the pulsar to be  0.44+0.16−0.13 M  . Combining this mass function with various inclination estimates from other authors, we find no evidence to suggest that the neutron star in SAX J1808.4−3658 is more massive than the canonical value of  1.4 M  . Our optical light curves exhibit a possible superhump modulation, expected for a system with such a low mass ratio. The equivalent width of the Ca  ii H and K interstellar absorption lines suggest that the distance to the source is ∼2.5 kpc. This is consistent with previous distance estimates based on type-I X-ray bursts which assume cosmic abundances of hydrogen, but lower than more recent estimates which assume helium-rich bursts.  相似文献   

15.
We use accurate absolute proper motions and Two-Micron All-Sky Survey   Ks   -band apparent magnitudes for 364 Galactic RR Lyrae variables to determine the kinematical parameters of the Galactic RR Lyrae population and constrain the zero-point of the   Ks   -band period–luminosity relation for these stars via statistical parallax. We find the mean velocities of the halo- and thick-disc RR Lyrae populations in the solar neighbourhood to be  [ U 0(Halo), V 0(Halo), W 0(Halo)]= (−12 ± 10, −217 ± 9, −6 ± 6) km s−1  and  [ U 0(Disc), V 0(Disc), W 0(Disc)]= (−15 ± 7, −44 ± 7, −25 ± 5) km s−1  , respectively, and the corresponding components of the velocity-dispersion ellipsoids,  [σ VR (Halo), σ V θ(Halo), σ W (Halo)]= (167 ± 9, 86 ± 6, 78 ± 5) km s−1  and  [σ VR (Disc), σ V θ(Disc), σ W (Disc)]= (55 ± 7, 44 ± 6, 30 ± 4) km s−1  , respectively. The fraction of thick-disc stars is estimated at  0.25 ± 0.03  . The corrected infrared period–luminosity relation is     , implying a Large Magellanic Cloud (LMC) distance modulus of  18.27 ± 0.08  and a solar Galactocentric distance of  7.58 ± 0.40 kpc  . Our results suggest no or slightly prograde rotation for the population of halo RR Lyraes in the Milky Way.  相似文献   

16.
We compute two-point correlation functions and measure the shear signal due to galaxy–galaxy lensing for 80 000 optically identified and 5700 radio-loud active galactic nuclei (AGN) from Data Release 4 of the Sloan Digital Sky Survey. Halo occupation models are used to estimate halo masses and satellite fractions for these two types of AGN. The large sample size allows us to separate AGN according to the stellar mass of their host galaxies. We study how the halo masses of optical and radio AGN differ from those of the parent population at fixed   M *  . Halo masses deduced from clustering and from lensing agree satisfactorily. Radio AGN are found in more massive haloes than optical AGN: in our samples, their mean halo masses are  1.6 × 1013  and  8 × 1011  h −1 M  , respectively. Optical AGN follow the same relation between stellar mass and halo mass as galaxies selected without regard to nuclear properties, but radio-loud AGN deviate significantly from this relation. The dark matter haloes of radio-loud AGN are about twice as massive as those of control galaxies of the same stellar mass. This boost is independent of radio luminosity, and persists even when our analysis is restricted to field galaxies. The large-scale gaseous environment of the galaxy clearly plays a crucial role in producing observable radio emission. The dark matter halo masses that we derive for the AGN in our two samples are in good agreement with recent models in which feedback from radio AGN becomes dominant in haloes where gas cools quasi-statically.  相似文献   

17.
We present a study of the X-ray emission from the nuclei of galaxies observed in the core of the Perseus cluster in a deep exposure with Chandra . Point sources are found coincident with the nuclei of 13 early-type galaxies, as well as the central galaxy NGC 1275. This corresponds to all galaxies brighter than M B > −18 in the Chandra field. All of these sources have a steep power-law spectral component and four have an additional thermal component. The unabsorbed power-law luminosities in the 0.5–7.0 keV band range from 8 × 1038 to 5 × 1040 erg s−1. We find no simple correlations between the K -band luminosity, or the FUV and NUV AB magnitudes of these galaxies and their X-ray properties. We have estimated the black hole masses of the nuclei using the K -band   M BH– L K bol  relation and again find no correlation between black hole mass and the X-ray luminosity. Bondi accretion on to the black holes in the galaxies with minihaloes should make them much more luminous than observed.  相似文献   

18.
We present CCD (charge-coupled device) photometry for galaxies around 204 bright ( m Z<15.5) Zwicky galaxies in the equatorial extension of the APM Galaxy Survey, sampling an area over 400 deg2, which extends 6 h in right ascension. We fit a best linear relation between the Zwicky magnitude system, m Z, and the CCD photometry, B CCD, by doing a likelihood analysis that corrects for Malmquist bias. This fit yields a mean scale error in Zwicky of 0.38 mag mag−1: i.e. Δ m Z≃(0.62±0.05)Δ B CCD and a mean zero-point of 〈 B CCD− m Z〉=−0.35±0.15 mag. The scatter around this fit is about 0.4 mag. Correcting the Zwicky magnitude system with the best-fitting model results in a 60 per cent lower normalization and 0.35-mag brighter M * in the luminosity function. This brings the CfA2 luminosity function closer to the other low-redshift estimations (e.g. Stromlo-APM or LCRS). We find a significant positive angular correlation of magnitudes and position in the sky at scales smaller than about 5 arcmin, which corresponds to a mean separation of 120  h −1 kpc. We also present colours, sizes and ellipticities for galaxies in our fields, which provides a good local reference for the studies of galaxy evolution.  相似文献   

19.
It has been known for a long time that the clustering of galaxies changes as a function of galaxy type. This galaxy bias acts as a hindrance to the extraction of cosmological information from the galaxy power spectrum or correlation function. Theoretical arguments show that a change in the amplitude of the clustering between galaxies and mass on large scales is unavoidable, but cosmological information can be easily extracted from the shape of the power spectrum or correlation function if this bias is independent of scale. Scale-dependent bias is generally small on large scales,   k < 0.1  h  Mpc−1  , but on smaller scales can affect the recovery of  Ωm h   from the measured shape of the clustering signal, and have a small effect on the Baryon Acoustic Oscillations. In this paper, we investigate the transition from scale-independent to scale-dependent galaxy bias as a function of galaxy population. We use the Sloan Digital Sky Survey Data Release 5 sample to fit various models, which attempt to parametrize the turn-off from scale-independent behaviour. For blue galaxies, we find that the strength of the turn-off is strongly dependent on galaxy luminosity, with stronger scale-dependent bias on larger scales for more luminous galaxies. For red galaxies, the scale dependence is a weaker function of luminosity. Such trends need to be modelled in order to optimally extract the information available in future surveys, and can help with the design of such surveys.  相似文献   

20.
We present the K -band (2.2 μm) luminosity functions (LFs) of the X-ray-luminous clusters MS1054–0321 ( z  = 0.823), MS0451–0305 ( z  = 0.55), Abell 963 ( z  = 0.206), Abell 665 ( z  = 0.182) and Abell 1795 ( z  = 0.063) down to absolute magnitudes M K  = −20. Our measurements probe fainter absolute magnitudes than do any previous studies of the near-infrared LFs of clusters. All the clusters are found to have similar LFs within the errors, when the galaxy populations are evolved to redshift z  = 0. It is known that the most massive bound systems in the Universe at all redshifts are X-ray-luminous clusters. Therefore, assuming that the clusters in our sample correspond to a single population seen at different redshifts, the results here imply that not only had the stars in present-day ellipticals in rich clusters formed by z  = 0.8, but that they existed in as luminous galaxies then as they do today.   Additionally, the clusters have K -band LFs which appear to be consistent with the K -band field LF in the range −24 <  M K  < −22, although the uncertainties in both the field and cluster samples are large.  相似文献   

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