Local Luminosity Function Research Articles

The Contribution of Low Surface Brightness Galaxies to Faint Galaxy Counts

view Abstract Citations (80) References (90) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Contribution of Low Surface Brightness Galaxies to Faint Galaxy Counts Ferguson, Henry C. ; McGaugh, Stacy S. Abstract Recent observations have revealed a population of blue galaxies at intermediate redshift with a space density well in excess of expectations from the local luminosity function and standard cosmology. The colors and luminosities of these faint blue galaxies are similar to nearby low surface brightness (LSB) galaxies. Such galaxies are severely underrepresented in surveys used to define the local luminosity function, but could in principle be detected in deep surveys. If LSB galaxy density is high enough, the faint-galaxy counts could be explained without requiring rapid galaxy evolution. To explore the consequences of including LSB galaxies, we construct catalogs of simulated nonevolving galaxies drawn from a multivariate distribution of galaxy luminosities, central surface brightnesses, bulge/disk ratios, and spectral-energy distributions. We compare two models dominated by LSB galaxies to a "standard" nonevolving model. Model galaxies are convolved with seeing and selected in a manner that closely matches real surveys. For each model we compute the local Bj band luminosity function, H I mass function, number counts in the Bj, I, and K bands, redshift distributions and color distributions. We find it possible to include a large population of LSB galaxies and incorporate a steep faint-end slope of the luminosity function in our simulations without violating the constraints on the local field-galaxy luminosity function or the H I mass function. For q0 = 0.5, the most favorable model matches the counts to B = 23, but falls short of the observations at fainter magnitudes. The discrepancy at faint magnitudes is smaller in the I and K bands. The colors and redshift distributions remain roughly consistent with observations to B = 24. The most serious discrepancy with observations is in the distribution of re at faint magnitudes, suggesting that the model contains too many LSB galaxies. Nevertheless, the results suggest that LSB galaxies could be a significant contributor to faint-galaxy counts, reducing the need for such extreme models of galaxy evolution as rapid merging or bursting dwarf galaxies. We propose several tests to assess the contribution of LSB galaxies to faint galaxy counts and to differentiate models involving moderate galaxy evolution from models involving rapid merging or starbursts. Publication: The Astrophysical Journal Pub Date: February 1995 DOI: 10.1086/175289 arXiv: arXiv:astro-ph/9409071 Bibcode: 1995ApJ...440..470F Keywords: COSMOLOGY: OBSERVATIONS; GALAXIES: LUMINOSITY FUNCTION; MASS FUNCTION; GALAXIES: PHOTOMETRY; Astrophysics E-Print: 39p, uuencoded compressed postscript, 18/21 figs included, full paper from http://planxty.stsci.edu:1024/ ferguson/lsb/lsbpp_b.ps,STScI 874 full text sources arXiv | ADS | data products SIMBAD (2)

Resurrection of traditional luminosity evolution models to explain faint fields galaxies

We explore the nature of the evolution of faint field galaxies by assuming that the local luminosity function is not well defined. We use a non-negative least squares technique to derive a near optimal set of local luminosity functions for different spectral types of galaxies by fitting to the observed optical and near-infrared counts, B-R colors, and redshift distributions for galaxies with 15 < B < 27. We report here the results of using only traditional luminosity evolution (ie. the photometric evolution of stars in a galaxy over time given reasonable assumptions of the form of the star formation history for various galaxy types), and simple galaxy reddening and find excellent fits to the observed data to B = 27. We conclude that models more exotic than traditional luminosity evolution are not yet required to explain existing faint field galaxy data and thus the need for contributions by mergers or new populations of galaxies is at least 5x less than previously estimated.

Simulations of deep galaxy fields. 1: Monte Carlo simulations of optical and near-infrared counts

Monte Carlo simulations of three-dimensional galaxy distributions are performed, following the 1988 prescription of Chokshi & Wright, to study the photometric properties of evolving galaxy populations in the optical and near-infrared bands to high redshifts. In this paper, the first of a series, we present our baseline model in which galaxy numbers are conserved, and in which no explicit 'starburst' population is included. We use the model in an attempt to simultaneously fit published blue and near-infrared photometric and spectroscopic observations of deep fields. We find that our baseline models, with a formation redshift, z(sub f), of 1000, and H(sub 0) = 50, are able to reproduce the blue counts to b(sub j) = 22, independent of the value of Omega(sub 0), and also to provide a satisfactory fit to the observed blue-band redshift distributions, but for no value of Omega(sub 0) do we achieve an acceptable fit to the fainter blue counts. In the K band, we fit the number counts to the limit of the present-day surveys only for an Omega(sub 0) = 0 cosmology. We investigate the effect on the model fits of varying the cosmological parameters H(sub 0), the formation red-shift z(sub f), and the local luminosity function. Changing H(sub 0) does not improve the fits to the observations. However, reducing the epoch of a galaxy formation used in our simulations has a substantial effect. In particular, a model with z(sub f) approximately equal to 5 in a low Omega(sub 0) universe improves the fit to the faintest photometric blue data without any need to invoke a new population of galaxies, substantial merging, or a significant starburst galaxy population. For an Omega(sub 0) = 1 universe, however, reducing z(sub f) is less successful at fitting the blue-band counts and has little effect at all at K. Varying the parameters of the local luminosity function can also have a significant effect. In particular the steep low end slope of the local luminosity function of Franceschini et al. allows an acceptable fit to the b(sub j) less than or equal to 25 counts for Omega(sub 0) = 1, but is incompatible with Omega(sub 0) = 0.

An optical study of the faint end of the stellar luminosity function

We implement a new method by which to study the faint end of the field star luminosity function. The method relies on deep, multicolor photometry of fields projected against highly obscured, nearby molecular clouds. The clouds act as nearby opaque screens and delimit a well-defined survey volume which is in principle free of the problem of distinguishing nearby, intrinsically faint dwarf stars from more distant red giants. This study is based upon deep photographic and CCD photometry at optical (V, R, I) bandpasses toward the most highly obscured portions of the Taurus and Ophiuchus molecular clouds. The total volume delimited by the clouds is approximately 200 cu pc. Within this region our survey is complete for all stars brighter than M<SUB>V</SUB> = 16-17 mag; at R and I, the survey is complete down to the lowest mass stars capable of sustaining core hydrogen burning. We estimate the faint end of the field star luminosity function for the composite Taurus and Ophiuchus foreground sample and find that it resembles the local luminosity function down to M<SUB>V</SUB> approx. 16. At still fainter magnitudes we find more stars than do photometric parallex studies of the polar regions. This difference widens dramatically if even the simplest correction for incompleteness is applied to our data. We therefore tentatively conclude that the luminosity function rises beyond M<SUB>V</SUB> approx. 16; even if we discard our attempts to correct for incompleteness in the faintest magnitude bins, the luminosity function at least remains flat for the lowest mass stars. Our provisional finding that the luminosity function rises beyond its well-known peak at M<SUB>V</SUB> approx. 12-13, implies that the initial mass function (IMF) probably rises beyond the turnover point associated with this peak. Even if our most conservative estimate for the faint end of the luminosity function is used-in which no corrections are made for incompleteness-the IMF must at least remain flat down to the edge of the hydrogen-burning main sequence.

Application of the Loh-Spillar Cosmological Test to Quasars

view Abstract Citations (2) References (21) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Application of the Loh-Spillar Cosmological Test to Quasars Schade, David ; Hartwick, F. D. A. Abstract The Loh-Spillar (L-S) cosmological test relies on a knowledge of the local space density of a population of test particles and a luminosity function for that population whose redshift dependence can be described by pure luminosity evolution. Using a newly derived local luminosity function for active galactic nuclei (AGNs) from a complete X-ray-selected sample of 78 objects at z < 0.15 and the previously known property of complete quasar samples to apparently exhibit pure luminosity evolution, we apply the L-S test to a combined sample of 447 quasars and derive a value of {OMEGA}_0_ = 0.2_-0.1_^+0.15^ (1 σ errors) assuming λ_0_ = 0 or {OMEGA}_0_ = 0.4_-0.06_^+0.1^ in a cosmologically flat model ({OMEGA}_0_ +λ_0_= 1). The formal errors are remarkably small but do not account for systematic errors which are present if any of the requirements of the L-S technique are not met. Alternatively, we can state that the adopted pure luminosity evolution model for the evolution of the quasar luminosity function, including a normalization of the local AGN population at the same level as that of high-redshift quasars, is inconsistent with {OMEGA}_0_ = 1 at a high level of significance. Publication: The Astrophysical Journal Pub Date: March 1994 DOI: 10.1086/187242 Bibcode: 1994ApJ...423L..85S Keywords: COSMOLOGY: OBSERVATIONS; GALAXIES: QUASARS: GENERAL; GALAXIES: ACTIVE; GALAXIES: LUMINOSITY FUNCTION; MASS FUNCTION full text sources ADS |

X-ray clusters and gravitiational instability theories

view Abstract Citations (31) References (81) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS X-Ray Clusters and Gravitational Instability Theories Colafrancesco, S. ; Vittorio, N. Abstract We discuss the expected evolution of X-ray clusters of galaxies in different models for structure formation: these are cold dark matter, hybrid, and baryonic isocurvature models. We compare the theoretical predictions with the observed X-ray local luminosity function and with the counts obtained from the Extended Medium Sensitivity Survey (EMSS) of the HEAO 2 satellite. For properly comparing our predictions with the EMSS data we apply several corrections to the theoretical X-ray luminosities and fluxes. We find that the most effective correction comes from considering the finite size of the EMSS detection cell in the HEAO 2 Imaging Proportional Counter cluster images. The available X-ray data are extremely selective. They allow to reject baryonic isocurvature models, as well as hybrid models where hot dark matter provides ~30% of the critical density. The model which performs by far better than the others considered here is a low-density ({OMEGA}_0_ = 0.2, h = 0.75) vacuum-dominated cold dark matter model, with an initial scale-free density fluctuation spectrum. In all models, the brighter X-ray clusters are rare objects originating from the high peaks of the initial density field. This implies that optical galaxies are biased tracers of the mass density field, unless the cluster collapse occurs on timescales longer than those of the ideal pressureless sphere. We discuss our results in the light of the COBE-DMR detection of large scale anisotropy of the cosmic microwave background. Publication: The Astrophysical Journal Pub Date: February 1994 DOI: 10.1086/173740 Bibcode: 1994ApJ...422..443C Keywords: Astronomical Models; Background Radiation; Cosmology; Dark Matter; Galactic Clusters; Galactic Evolution; Gravitation Theory; Mathematical Models; Microwave Emission; Missing Mass (Astrophysics); X Ray Astronomy; Anisotropy; Heao 2; Luminosity; Luminous Intensity; Astronomy; COSMOLOGY: COSMIC MICROWAVE BACKGROUND; COSMOLOGY: DARK MATTER; COSMOLOGY: THEORY; GALAXIES: CLUSTERING; X-RAYS: GALAXIES full text sources ADS |

The Palomar Observatory Dwarf Seyfert Survey

We describe an optical, spectroscopic survey of the nuclei of the 500 brightest galaxies in the northern sky. The primary goal is to search for low-luminosity active galactic nuclei (LLAGNs) in the centers of nearby galaxies. The results of this survey will have many astrophysical applications, including quantifying the faint end of the local AGN luminosity function and estimating the contribution of LLAGNs to the X-ray background. We summarize the statistical properties of the survey, describe our methods of analysis, and present some preliminary results based on ∼ 60% of the sample.

The Hamburg/ESO Survey for Bright QSOs — Slitless Spectroscopy at High Resolution

The digital revolution in the evaluation of photographic plates and the introduction of automated quasar search techniques have drastically increased the number of known QSOs over the past decade. However, most of these QSOs are so faint that their use is limited to statistical studies. The bright end of the quasar population is still dominated by objects selected in other wavebands, such as radio, X-rays, or even infrared. We have started in 1990 a wide-angle objective-prism survey (the Hamburg/ESO Survey, HES) using the 1 m ESO Schmidt telescope (Reimers 1990). The survey is intended to cover 5000 deg2, of which about a third has been acquired up to now. The prime goal is to compile a large sample of bright (B &amp;lt; 17.5) QSOs suited for detailed follow-up studies, in particular for high-resolution spectroscopy. Other objectives are to search for gravitational lens candidates and to directly measure the local luminosity function of quasars. In each Schmidt field, a spectral and a direct plate are scanned with the PDS 1010G microdensitometer at Hamburg, followed by an automated candidate selection and subsequent follow-up spectroscopy with the ESO 1.52 m and 3.6 m telescopes. A novel feature in our survey is the use of an objective-prism with a dispersion of 450 å/mm at Hγ, yielding a seeing-limited spectral resolution of 10–20 å FWHM. A full documentation of the survey techniques is in preparation. First results include the discoveries of the second-brightest QSO in the south (Wisotzki et al. 1991), and of a bright double QSO at high redshift, probably a gravitational lens (Wisotzki et al. 1993). In this contribution I want to show how a wide-angle quasar survey like the HES can benefit from the high resolution of the survey spectra.

Counter-evolution of faint field galaxies

We adopt a new approach to explore the puzzling nature of faint blue field galaxies. Instead of assuming that the local luminosity function is well defined, we first determine whether any non-evolving set of luminosity functions for different spectral types of galaxies is compatible with the observed marginal distributions in optical and near-infrared counts, B - R colors, and redshifts. Exploiting a non-negative least squares method, we derive a new no-evolution model that is found to fit all the observations surprisingly well. We conclude that models more exotic than mild luminosity evolution, such as those requiring rapid evolution in star formation rates, disappearing dwarf galaxy populations, high values of the cosmological constant, rapid mergers, or substantial non-conservation of galaxy numbers with time, are no longer as compelling.

A new survey for low-luminosity emission-line galaxies

view Abstract Citations (25) References (26) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A New Survey for Low-Luminosity Emission-Line Galaxies Boroson, Todd A. ; Salzer, John J. ; Trotter, Adam Abstract A survey for low-luminosity emission-line galaxies is described in which deep CCD images have been obtained through five narrow-band ({DELTA}λ = 80 A) filters. The survey covers 0.7 square degrees to a depth corresponding to a monochromatic magnitude m_6600_ = 21.2 in the emission line plus continuum. The survey is sensitive to objects with strong Hα emission out to a redshift of z = 0.054, as well as higher redshift galaxies with [O III], Hβ, or [O II] emission. Two hundred ninety-three emission-line galaxy candidates were selected based on a (line plus continuum)/continuum ratio of 1.5 or greater. These candidates were observed spectroscopically with a multifiber spectrograph. Eleven low-redshift (z < 0.054) emission-line galaxies were confirmed with moderate to strong Hα emission and M_B_ in the range - 17.8 to - 12.9. Thirty-six additional objects are emission-line galaxies at higher redshift, including 11 in which only one emission line is seen. Nine of the low-redshift emission-line galaxies form an essentially complete sample, and two methods are explored to calculate the luminosity function. While the range of luminosity sampled is small enough that tradeoffs between slope and normalization of the luminosity function are possible, the combination of this survey with the study of Salzer allows fairly restrictive limits on these two quantities. The best-fit Schechter function to the combination of these two data sets has slope α = - 1.35 and normalization, logφ^*^ = -3.15 mag^-1^ Mpc^-3^. In heavy-element abundance, the objects found in this survey span the range defined by known dwarf emission-line galaxies, with the most metal- poor object having an O/H abundance about 0.09 of the solar value. Despite the fact that the survey technique employed is sensitive to the presence of ultra-low metal-abundance galaxies, no such objects were found. One group of higher redshift emission-line galaxies, those with [O III] λ5007 shifted into the Hα region, has relevance to the interpretation of faint blue galaxy counts. These objects are examples of the type of galaxy that has been proposed to account for the excess counts at B = 22 and fainter. We find that the number discovered in the survey is exactly that predicted by the local luminosity function, i.e., there is no evidence for strong evolution in the number density of these objects, in disagreement with that interpretation. Publication: The Astrophysical Journal Pub Date: August 1993 DOI: 10.1086/172940 Bibcode: 1993ApJ...412..524B Keywords: Emission Spectra; Galactic Radiation; Line Spectra; Mass To Light Ratios; Astronomical Photometry; Galactic Mass; Luminosity; Astrophysics; GALAXIES: LUMINOSITY FUNCTION; MASS FUNCTION; GALAXIES: PHOTOMETRY full text sources ADS | data products NED (47) SIMBAD (46)

Binary merging - The other mode of galaxy evolution

view Abstract Citations (18) References (29) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Binary Merging: The Other Mode of Galaxy Evolution Cavaliere, A. ; Menci, N. Abstract We discuss the mode of galaxy evolution based on merging after binary encounters, complementary to the mode based on direct hierarchical collapses. We show that the merging-driven mode produces, mainly by dynamical evolution, a local Schechter-like luminosity function starting at z ~ 2 from a steep mass distribution like Press & Schechter's. Such evolution inside galaxy systems provides a quantitative estimate of the Butcher-Oemler effect and yields an excess of faint blue galaxy counts like that observed. Publication: The Astrophysical Journal Pub Date: April 1993 DOI: 10.1086/186793 Bibcode: 1993ApJ...407L...9C Keywords: Cosmology; Galactic Evolution; Galactic Mass; Mass Distribution; Stellar Luminosity; Galactic Clusters; Galactic Structure; Gravitational Collapse; Star Distribution; Astrophysics; COSMOLOGY: THEORY; GALAXIES: EVOLUTION; GALAXIES: FORMATION full text sources ADS |

Evolution of the blue and far-infrared galaxy luminosity functions

view Abstract Citations (25) References (31) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Evolution of the Blue and Far-Infrared Galaxy Luminosity Functions Lonsdale, Carol J. ; Chokshi, Arati Abstract We construct a blue band luminosity function from published spectroscopic surveys of faint field galaxies (b_j_ > 20) and compare it to three recent determinations of the blue-selected field galaxy luminosity function in the local universe. We find evidence for density evolution for moderate luminosity galaxies (-17.5 > M_b_ > -21.5; h = 0.5) at a rate of (1+z)delta^, with a best fit of δ = 4+/-2, between the current epoch and z >~ 0.1. At M_b_ < -22 we find evidence for about 0.5- 1.5 mag of luminosity evolution in addition to the density evolution, corresponding to an evolutionary rate of L ~ (1+z)gamma^, γ = 0.5-2.5, by a redshift of about 0.4, when the data are compared to the local luminosity function of de Lapparent et al. [ApJ, 343, 1(1989)]. However, in the presence of the above mentioned density evolution, no additional luminosity evolution is required to fit the M_b_ <-22 data if the local luminosity functions of either Efstathiou et al. [MNRAS, 232,431, (1988)] or Loveday et al. [ApJ, 390, 338 (1992)] are used instead. Assuming a steeper faint end slope of α = - 1.3, similar to that observed in the Virgo cluster, could explain the data with a luminosity evolution rate γ = 1-2, without need for any density evolution. We compare the best-fitting composite density and luminosity evolution models to faint IRAS 60 micron source counts. The fits are quite acceptable, implying that the blue and far-infrared evolutionary rates may be similar. Publication: The Astronomical Journal Pub Date: April 1993 DOI: 10.1086/116513 Bibcode: 1993AJ....105.1333L Keywords: Faint Objects; Far Infrared Radiation; Galactic Evolution; Luminosity; Space Density; Blue Stars; Red Shift; Sky Surveys (Astronomy); Stellar Magnitude; Astrophysics; INFRARED: GALAXIES; GALAXIES: EVOLUTION; GALAXIES: LUMINOSITY FUNCTION full text sources ADS |

A near-infrared study of a homogeneous sample of optically selected active galactic nuclei. II - Analysis of the results and interpretation

New imaging and photometric IR data have been used to discuss the properties of nuclei and hosting galaxies of a well-defined and large sample of optically selected Seyfert 1 galaxies. The K-band luminosity distribution of galaxies hosting the active nuclei has been derived, and the comparison with the local luminosity function of the spirals confirms that the probability of a spiral galaxy hosting bright AGNs increases with the luminosity. On average, the colors of the galaxies are slightly redder than those of spirals, suggesting that hosting galaxies usually have moderately enhanced star formation rates

The contribution of galaxy clusters to the soft X-ray background

We examine models for the expected contribution to the X-ray background (XRB) from clusters of galaxies in a flat Universe with a spectrum of fluctuations corresponding to the standard cold dark matter picture and for a power-law spectrum P(k) is proportional to k^n^ with n = - 2. We consider a self-similar scaling model for clusters proposed by Kaiser, along with several variants. The self-similar model produces an appreciable fraction of the soft X-ray background. However, the predicted luminosity function overproduces low-luminosity clusters and expected number counts exceed observations. Incompleteness due to spatial extension of the sources is unlikely to account for these discrepancies. Photon statistics from synthesized maps of deep Einstein fields show a granularity similar to that deduced by Hamilton and Helfand from the Einstein data but overproduces by a large factor the number of discrete sources observed as clusters, and the fluctuation limit derived from the recent correlation analyses of the background. This occurs even though a large fraction of cluster sources may be missed by detection algorithms geared toward detection of point sources. Two alternative models are designed to be consistent with the local luminosity function data. For these, we generate expected deep images for the ROSAT satellite. We predict that a substantial fraction of extragalactic component of the soft (0.1-2.4 keV) XRB might be due to clusters. Clusters of galaxies should be a significant source of background at energies around 2 keV and are likely to contribute up to 30% of the unresolved component. They should produce fluctuations at a level close to present limits. These sources are extended and might easily he missed by use of a point source algorithm for detection. Furthermore, we find that the clusters' number counts as well as their contribution in the soft ROSAT energy ranges are higher in the n = -2 model than in CDM models. ROSAT observations might therefore help in differentiating between these models.

Luminosity functions, relativistic beaming, and unified theories of high-luminosity radio sources

view Abstract Citations (201) References (55) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Luminosity Functions, Relativistic Beaming, and Unified Theories of High-Luminosity Radio Sources Padovani, P. ; Urry, C. M. Abstract If relativistically beamed emission dominates the observed radio flux from flat-spectrum radio quasars, as suggested by their rapid variability, polarization, and superluminal motion, then there must be counterpart sources whose emission is beamed at larger angles to the line of sight. We evaluate such unified schemes quantitatively, with steep- spectrum radio quasars and high-luminosity radio galaxies constituting the misaligned sources. Our procedure compares the number densities and luminosities of the separate populations, taking into account the strong selection effects introduced by relativistic beaming. First, we derive the local luminosity functions of high-luminosity (i.e., Fanaroff-Riley type II) radio galaxies, flat-spectrum quasars, and steep-spectrum quasars. Then we calculate the luminosity functions predicted by a relativistic beaming model and compare them to the observed ones. We find very good agreement both for flat- and steep- spectrum quasars for a distribution of Lorentz factors 5 <~γ <~40 (skewed toward lower values) that was estimated from the observed distribution of superluminal speeds for flat-spectrum quasars. Our model predicts that flat-spectrum quasars have their radio axes within θ~14^deg^ of the line of sight, steep-spectrum quasars are in the range 14^deg^ <~ θ <~ 40^deg^, and high-luminosity radio galaxies occupy the remaining angles. The alternative hypothesis that flat- spectrum quasars are simply the beamed version of steep-spectrum ones, with Fanaroff-Riley type II radio galaxies belonging to a separate class, does not give as good a fit to the data. Publication: The Astrophysical Journal Pub Date: March 1992 DOI: 10.1086/171098 Bibcode: 1992ApJ...387..449P Keywords: Galactic Nuclei; Quasars; Radio Galaxies; Radio Jets (Astronomy); Relativistic Plasmas; Stellar Luminosity; Brightness Distribution; Radio Emission; Unified Field Theory; Very Long Base Interferometry; Astrophysics; GALAXIES: JETS; GALAXIES: NUCLEI; GALAXIES: FUNDAMENTAL PARAMETERS; RADIO CONTINUUM: GALAXIES full text sources ADS | data products SIMBAD (3)

The complete sample of 1 Jansky BL Lacertae objects. I - Summary properties

This paper describes the first homogeneous, flux-limited sample of radio-selected BL Lac objects, taken from the 1 Jy survey of Kuhr et al. These 34 BL Lac objects comprise the only well-defined sample of BL Lac objects outside the X-ray band. The selection criteria include flat radio spectra, optical counterparts visible on Sky Survey Plates, and optical emission lines weaker than 5 A equivalent width in the rest frame. With two exceptions, all of the BL Lac objects also have high optical polarization, P_opt_ &gt; 3%. Redshifts from weak emission lines, usually narrow [O II] λ3727, [O III] λ5007, or broad Mg II λ2798, are available for ~ 3/4 of the sample. The nearby (z &lt; 0.2) BL Lac objects, at least, sit in elliptical galaxies and may occur in groups or small clusters of galaxies. Gravitational lensing appears to affect one of the high-redshift (z &gt;~ 0.5) BL Lac objects and could be important in others as well. The radio number counts derived from the 1 Jy BL Lac sample are roughly Euclidean over the range between 1 and ~ 5 Jy, and there is evidence for evolution at the 2 σ level. The local radio luminosity function of BL Lac objects is derived and the total number density for P_5 GHz_ &gt;~ 6 x 10^31^ ergs s^-1^ Hz^-1^ is ~ 40 Gpc^-3^.

On the redshift-volume measurement of the cosmological density parameter

The systematic bias due to galaxy evolution in the red-shift volume measurement of the cosmological deceleration parameter q(0) is investigated. Galaxies are classified into five types, E/SO, Sab, Sbc, Scd, and Sdm, which evolve with different star formation histories. The red-shift volume test in the light of galaxy evolution is considered by using the type-dependent evolution models by Arimoto and Yoshii. It is found that for z less than 1, the bias Delta q is mostly equal to -0.2 if the parameters for local luminosity function of galaxies are adopted in the analysis. To determine q(0) within this accuracy it is indispensable to obtain a sample of redshifts for galaxies as deep as m(lim) = about 23 mag at 650 nm or m(lim) = about 24 mag at 800 nm. 11 refs.

Contributions of low-luminosity sources to the X-ray background

HEAO 1 A-2 data are used to determine hard X-ray fluxes, or upper limits, for complete optically selected samples of active and normal galaxies, in order to estimate or to constrain their local X-ray luminosity functions. It is found that the luminosity function of Seyfert nuclei must flatten down drastically shortly below the observational limit of Piccinotti et al (1982); little can be added by dwarf active nuclei hidden in otherwise normal galaxies. Also analyzed is the possible contribution to the X-ray background from galaxies with strong star-formation activity, in the light of the possibility of a substantial cosmological evolution suggested by recent radio and IRAS data. 94 refs.

The 1.4 gigahertz luminosity function and its evolution

view Abstract Citations (224) References (35) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The 1.4 GHz Luminosity Function and Its Evolution Condon, J. J. Abstract The local luminosity function was determined at v = 1.4 GHz from radio observations of two low-redshift galaxy samples: (1) spiral and irregular galaxies with apparent blue magnitudes B_T_ <= + 12 and declinations δ >= -45^deg^ and (2) galaxies of all morphologies with blue angular diameters θ_M_ >= 1.0' in the declination range -2.5^deg^ <= δ <= +82^deg^. Separate luminosity functions for the radio source populations powered by "starbursts" and "monsters" were obtained from the latter sample. Locally these two energy sources contribute almost equally to the 1.4 GHz spectral power density (U ~ 2 x 10^19^ W Hz^-1^ Mpc^-3^ and U ~ 3 x 10^19^ W Hz^-1^ Mpc^-3^, respectively, for H_0_ = 50 km s^-1^ Mpc^-1^). The new luminosity functions and the counts of faint (S <= 1 mJy) radio sources found at v = 1.4 GHz together imply strong cosmological evolution of sources fainter than L ~ 10^24^ W Hz^-1^. This evolution is so strong that most features of the observed radio source counts and redshift distributions can be explained by a remarkably simple evolutionary model that places all radio sources in a hollow spherical shell at z ~ 0.8. Publication: The Astrophysical Journal Pub Date: March 1989 DOI: 10.1086/167176 Bibcode: 1989ApJ...338...13C Keywords: Evolution (Development); Irregular Galaxies; Luminosity; Radio Sources (Astronomy); Spiral Galaxies; Brightness Distribution; Red Shift; Starburst Galaxies; Visible Spectrum; Astrophysics; COSMOLOGY; GALAXIES: CLUSTERING; LUMINOSITY FUNCTION; RADIO SOURCES: GALAXIES full text sources ADS | data products NED (25) SIMBAD (24)

Interaction of the Beams of Active Galactic Nuclei with Their Environment at High Redshifts

Aiming at a physical interpretation of the cosmological evolution of radio galaxies, we extend to a high redshift our analytical model for the propagation of relativistic beams first through a hot gaseous halo of the parent elliptical galaxy and then through an even hotter, but less dense, diffuse IGM, after crossing a pressure-matched interface between the two media1–5. This model, verified by quasi-hydrodynamical numerical simulations5 has earlier explained: (1) the current mean size of classical double radio sources (D ∼350 kpc), (2) their steep linear-size evolution with redshift, z: D α (1+z)−3, (3). The correlation between size and radio luminosity (at fixed z): D α P0.3, (4) the number and &lt;P&gt; of giant radio galaxies, and (5) the break in the local radio luminosity function (LRLF), occurring near P ∼1024W.Hz−1 at 1 GHz (Ho = 50 kms−1 Mpc−1). Inputs to the model are observationally based average parameters of the halo1 {kTh∼1 keV, n(r) ∼10−2cm−3[1+(r/2kpc)2]−3/4}, IGM7 {kTIGM ∼18 keV (1+z)2, nIGM ∼7.10−7cm−3(1+z)3} and the beam4 {opening angle θ (radian) = 0.02 + 0.03 [29 - log P(t=0)]}. We assume a reasonable value of ∊ = 0.1 for the initial efficiency of conversion of the beam power, Lb (Watts) into (total) radio output Pt ∼1010. P(W.Hz−1). A gradual weakening of magnetic field within the expanding source raises the significance of inverse Compton losses against the Cosmic Microwave Background (CMB), leading to a reduced radio efficiency (RRE)3,2.