Galaxy populations in the Fornax and Virgo clusters

In these first results from a photographic survey of nearby clusters and groups of galaxies, we compare the luminosity functions of galaxies of various Hubble types in the core of the Formax cluster to luminosity functions in the core of the Virgo cluster from Sandageet al. (1985). The galaxy classifications for the two clusters are based on identical plate material, and are hence directly comparable. The properties (galaxy density, velocity dispersion, X-ray luminosity) of the two clusters are quite different, yet we find few significant differences in the luminosity functions, or in the morphological mix of galaxies between the two clusters. In particular, while there is some indication that the ratios of giants to dwarfs and early to late-type galaxies in the two clusters differ, we cannot exclude the possibility that the ratios are identical. We discuss the selection limits of our survey and the completeness corrections that must be applied to the faint end of the luminosity function. The effective surface brightness of early-type galaxies in our sample decreases with decreasing luminosity. We show that this correlation is not an artifact of our selection criteria for dwarf spheroidal galaxies and use it to determine the relative distances to the Fornax and Virgo clusters. We also present evidence for a radial variation in the luminosity function of dwarf ellipticals within the two clusters in the sense that the faint end of the luminosity distribution is enhanced at the centre of each cluster.     

Faint Gigahertz Peaked Spectrum sources and the evolution of young radio sources

GPS sources are the objects of choice to study the initial evolution of extragalactic radio sources, since it is most likely that they are the young counterparts of large scale radio sources. Correlations found between their peak frequency, peak flux density and angular size provide strong evidence that synchrotron self absorption is the cause of the spectral turnovers, and indicate that young radio sources evolve in a self-similar way. The difference in redshift distribution between young and old radio sources must be due to a difference in slope of their luminosity functions, and we argue that this slope is strongly affected by the luminosity evolution of the individual sources. A luminosity evolution scenario is proposed in which GPS sources increase in luminosity and large scale radio sources decrease in luminosity with time. It is shown that such a scenario agrees with the local luminosity function of GPS galaxies.     

The galaxy luminosity function in clusters and the field

We present the results from a CCD survey of the B -band luminosity function of nine clusters of galaxies, and compare them to published photographic luminosity functions of nearby poor clusters like Virgo and Fornax, and also to the field luminosity function. We derive a composite luminosity function by taking the weighted mean of all the individual cluster luminosity functions; this composite luminosity function is steep at bright and faint magnitudes and is shallow in-between.
All clusters have luminosity functions consistent with this single composite function. This is true both for rich clusters like Coma and for poor clusters like Virgo.
This same composite function is also individually consistent with the deep field luminosity functions found by Cowie et al. and Ellis et al., and also with the faint end of the Las Campanas Redshift Survey R -band luminosity function, shifted by 1.5 mag. A comparison with the Loveday et al. field luminosity function, which is well determined at the bright end, shows that the composite function, which fits the field data well fainter than M _B=−19, drops too steeply between M _B=−19 and −22 to fit the field data there.     

Evolution of the luminosity function and colours of galaxies in a Λ cold dark matter universe

The luminosity function of galaxies is derived from a cosmological hydrodynamic simulation of a Λ cold dark matter universe with the aid of a stellar population synthesis model. At     , the resulting B -band luminosity function has a flat faint-end slope of     with the characteristic luminosity and the normalization in fair agreement with observations, while the dark matter halo mass function is steep with a slope of     . The colour distribution of galaxies also agrees well with local observations. We also discuss the evolution of the luminosity function, and the colour distribution of galaxies from     to 5. A large evolution of the characteristic mass in the stellar mass function as a result of number evolution is compensated by luminosity evolution; the characteristic luminosity increases only by 0.8 mag from     to 2, and then declines towards higher redshift, while the B -band luminosity density continues to increase from     to 5 (but only slowly at     .     

Dependence of the mean luminosity of flare stars on the age of the system

We study the luminosity of the brightest flare star and the mean luminosity of flare stars in a system as functions of the age of the system. We obtain estimates for the mean value and variance of the initial luminosity function of flare stars.Translated fromAstrofizika, Vol. 38, No. 2, 1995.     

An improved method of constructing binned luminosity functions

We show that binned differential luminosity functions constructed using the 1/ V _a method have a significant systematic error for objects close to the flux limit(s) of their parent sample. This is particularly noticeable when luminosity functions are produced for a number of different redshift ranges as is common in the study of AGN or galaxy evolution. We present a simple method of constructing a binned luminosity function which overcomes this problem and has a number of other advantages over the traditional 1/ V _a method. We also describe a practical method for comparing binned and model luminosity functions, by calculating the expectation values of the binned luminosity function from the model.
Binned luminosity functions produced by the two methods are compared for simulated data and for the Large Bright QSO Survey (LBQS). It is shown that the 1/ V _a method produces a very misleading picture of evolution in the LBQS. The binned luminosity function of the LBQS is then compared with a model two-power-law luminosity function undergoing pure luminosity evolution from Boyle et al. The comparison is made using a model luminosity function averaged over each redshift shell, and using the expectation values for the binned luminosity function calculated from the model. The luminosity function averaged in each redshift shell gives a misleading impression that the model over predicts the number of QSOs at low luminosity even for 1.0< z <1.5, when model and data are consistent. The expectation values show that there are significant differences between model and data: the model overpredicts the number of low luminosity sources at both low and high redshift. The luminosity function does not appear to steepen relative to the model as redshift increases.     

A Possible Connection Between the Variation of Light Curve and theChange of the Orbital Period in the Contact Binary CK Bootis

The O–C curve of the contact binary CK Boo have been analyzed with Kalimeris et al. (1994) method. It is shown that the orbital period is changing in a quasi-sinusoidal form with a period of about ∼ 14 yr superposed on a secular period increase. The correlation of the variations of the light level at MinI, MaxI and II in the light curve implies that the luminosity of secondary component is variable. Comparing the change of the quasi-periodic component in the orbital period with that of the secondary's luminosity, we find that the luminosity of the secondary component and the orbital period may vary with the same cycle length ∼14 yr; the variation of the secondary's luminosity is in the same phase with that of the orbital period. This connection is different from those of the RS CVn-type close binaries (e.g. CG Cyg, V471 Tau, RT Lac). The mechanisms that may have produced this relation of the variations of the orbital period and the luminosity of the secondary are also discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

A simple model for the evolution of supermassive black holes and the quasar population

An empirically motivated model is presented for accretion-dominated growth of supermassive black holes (SMBH) in galaxies, and the implications are studied for the evolution of the quasar population in the Universe. We investigate the core aspects of the quasar population, including space density evolution, evolution of the characteristic luminosity, plausible minimum masses of quasars, the mass function of SMBH and their formation epoch distribution. Our model suggests that the characteristic luminosity in the quasar luminosity function arises primarily as a consequence of a characteristic mass scale above which there is a systematic separation between the black hole and the halo merging rates. At lower mass scales, black hole merging closely tracks the merging of dark haloes. When combined with a declining efficiency of black hole formation with redshift, the model can reproduce the quasar luminosity function over a wide range of redshifts. The observed space density evolution of quasars is well described by formation rates of SMBH above  ∼10⁸  M_⊙  . The inferred mass density of SMBH agrees with that found independently from estimates of the SMBH mass function derived empirically from the quasar luminosity function.     

Radio Luminosity, Black Hole Mass and Eddington Ratio for Quasars from the Sloan Digital Sky Survey

We investigate the MBH-O'.relation for radio-loud quasars with redshift z＜0.83 in Data Release 3 of the Sloan Digital Sky Survey (SDSS).The sample consists of 3772 quasars with better models of the H/~ and [O III] lines and available radio luminosity,including 306 radio-loud quasars,3466 radio-quiet quasars with measured radio luminosity or upper-limit of radio luminosity (181 radio-quiet quasars with measured radio luminosity).The virial supermassive black hole mass (MBH) is calculated from the broad H/line,and the host stellar velocity dispersion (σ*) is traced by the core [O III] gaseous velocity dispersion.The radio luminosity and radio loudness are derived from the FIRST catalog.Our results are as follows:(1) For radio-quiet quasars,we confirm that there is no obvious deviation from the MBH-O".relation defined for inactive galaxies when the uncertainties in MBH and the luminosity bias are concerned.(2) We find that the radio-loud quasars deviate more from the MBH-σ.relation than do the radio-quiet quasars.This deviation is only partly due to a possible cosmological evolution of the MBH-σ* relation and the luminosity bias.(3) The radioluminosity is proportional to M128 0.23-0.16 BH(LBol/LEdd)1.29 0.31-0.24 for radio-quiet quasars and to M3.10 0.6.-0.70(LBol.LEdd)4.18 1.40-1.10 for radio-loud quasars.The weaker dependence of the radio luminosity on the mass and the Eddington ratio for radio-loud quasars shows that other physical effects would account for their radio luminosities,such as the spin of the black hole.     

The white dwarf luminosity function – II. The effect of the measurement errors and other biases

The disc white dwarf luminosity function is an important tool for studying the solar neighbourhood, since it allows the determination of several Galactic parameters, the most important one being the age of the Galactic disc. However, only the     method has been employed so far for observationally determining the white dwarf luminosity function, whereas for other kind of luminosity functions several other methods have been frequently used. Moreover, the procedures to determine the white dwarf luminosity function are not free of biases. These biases have two different origins: they can either be of statistical nature or a consequence of the measurement errors. In a previous paper we carried out an in-depth study of the first category of biases for several luminosity function estimators. In this paper we focus on the biases introduced by the measurement errors and on the effects of the degree of contamination of the input sample used to build the disc white dwarf luminosity function by different kinematical populations. To assess the extent of these biases we use a Monte Carlo simulator to generate a controlled synthetic population and analyse the behaviour of the disc white dwarf luminosity function for several assumptions about the magnitude of the measurement errors and for several degrees of contamination, comparing the performances of the most robust luminosity function estimators under such conditions.     

Evolution of the Radio Luminosities of the Tycho and Kepler Supernovae Remnants

Radio emission of the historical supernovae remnants Tycho (SNR1572) and Kepler (SNR1604) and evolution of their luminosity are considered. Measurement data of secular luminosity decrease rate, obtained earlier by the authors, were corrected with account of variation in time of the flux density of the reference sources. As a result, it is found that the SNR1604 luminosity at 1667 MHz is weakening with an annual mean rate equal to (0.2 ± 0.07)%. The corresponding rate for SNR1572 is (0.47 ± 0.05)%. Since the radio luminosity evolution, as well as energy densities of magnetic field and relativistic electrons inside SNR1604 and SNR1572 are essentially different, these remnants should be considered as different types of supernovae. Bandiera classified SN1604 as type SNIb or SNII.     

A note on the puzzling spindown behavior of the Galactic center magnetar SGR J1745-2900

SGR J1745-2900 is a magnetar near the Galactic center. X-ray observations of this source found a decreasing X-ray luminosity accompanied by an enhanced spindown rate. This negative correlation between X-ray luminosity and spindown rate is hard to understand. The wind braking model of magnetars is employed to explain this puzzling spindown behavior. During the release of magnetic energy of magnetars,a system of particles may be generated. Some of these particles remain trapped in the magnetosphere and may contribute to the X-ray luminosity. The rest of the particles can flow out and take away the rotational energy of the central neutron star. A smaller polar cap angle will cause the decrease of X-ray luminosity and enhanced spindown rate of SGR J1745-2900. This magnetar is shortly expected to have a maximum spindown rate.     

Evidence for merger-driven activity in the clustering of high-redshift quasars

Recently, a very large clustering length has been measured for quasars at a redshift of   z ∼ 4  . In combination with the observed quasar luminosity function, we assess the implications of this clustering for the relationship between quasar luminosity and dark matter halo mass. Our analysis allows for non-linearity and finite scatter in the relation between quasar luminosity and halo mass, as well as a luminosity dependent quasar lifetime. The additional novel ingredient in our modelling is the allowance for an excess in the observed bias over the underlying halo bias owing to the merger driven nature of quasar activity. We find that the observations of clustering and luminosity function can be explained only if both of the following conditions hold: (i) the luminosity to halo mass ratio increases with halo mass; (ii) the observed clustering amplitude is in excess of that expected solely from halo bias. The latter result is statistically significant at the 99 per cent level. Taken together, the observations provide compelling evidence for merger driven quasar activity, with a black-hole growth that is limited by feedback. In difference from previous analyses, we show that there could be scatter in the luminosity–halo mass relation of up to 1 dex, and that quasar clustering cannot be used to estimate the quasar lifetime.     

Phase differences between luminosity and velocity measurements of the acoustic modes

With two photometric stations (Tenerife and Baja California) the luminosity p-mode spectrum at different wavelengths has been identified. After a coherence analysis between data from both stations to verify the solar origin of the peaks identified in luminosity, a comparative study with simultaneous velocity measurements (obtained at Tenerife only) has also been made. As a result the frequency dependence of the phase difference between luminosity and velocity p-modes has been obtained that is interpreted in terms of a nonadiabatic behaviour of the solar atmosphere. The amplitude ratios between luminosity and velocity p-modes have also been obtained. All these results are compared with theoretical expectations.     

Particle motion in the vicinity of the protosun with variable luminosity

Variations of luminosity of the protosun during its Hayashi stage produced variations of its repulsive radiative action on small particles in its vicinity — or, in other words, variations of the effective mass of the protosun. Changes of the effective mass produced changes of size of orbits for particles circling around the protosun. When the luminosity increased, the effect of variable luminosity (EVL) diminished or overbalanced the Poynting-Robertson effect (PRE), hindering the small particles in their drift toward the protosun, and reinforced PRE when the luminosity decreased. An analysis of quasicircular motion of small uncharged particles moving in transparent circumsolar space under both effects — EVL and PRE — is given.     

Testing model predictions of the cold dark matter cosmology for the sizes, colours, morphologies and luminosities of galaxies with the SDSS

The huge size and uniformity of the Sloan Digital Sky Survey (SDSS) make possible an exacting test of current models of galaxy formation. We compare the predictions of the galform semi-analytical galaxy formation model for the luminosities, morphologies, colours and scalelengths of local galaxies. galform models the luminosity and size of the disc and bulge components of a galaxy, and so we can compute quantities which can be compared directly with SDSS observations, such as the Petrosian magnitude and the Sérsic index. We test the predictions of two published models set in the cold dark matter cosmology: the Baugh et al. model, which assumes a top-heavy initial mass function (IMF) in starbursts and superwind feedback, and the Bower et al. model, which uses active galactic nucleus feedback and a standard IMF. The Bower et al. model better reproduces the overall shape of the luminosity function, the morphology–luminosity relation and the colour bimodality observed in the SDSS data, but gives a poor match to the size–luminosity relation. The Baugh et al. model successfully predicts the size–luminosity relation for late-type galaxies. Both models fail to reproduce the sizes of bright early-type galaxies. These problems highlight the need to understand better both the role of feedback processes in determining galaxy sizes, in particular the treatment of the angular momentum of gas reheated by supernovae, and the sizes of the stellar spheroids formed by galaxy mergers and disc instabilities.     

Investigation of the correlation between morphology and luminosity for two classes of main galaxies

Using an apparent-magnitude limited Main galaxy sample of the Sloan Digital Sky Survey Data Release 7(SDSS DR7), we investigate the correlation between morphologies and luminosity for the Main galaxy sample. Our Main galaxy sample is divided into two classes: Main galaxies only with TARGET_GALAXY flag (bestPrimtarget = 64), and ones also with other flags. It is found that for the second class Main galaxies, the early-type proportion monotonously increases with increasing luminosity nearly in the whole luminosity region. But for the first class Main galaxies, the early-type proportion increases with increasing luminosity only within a certain luminosity region (−22.2 < M _r  < −19.8). In the high luminosity region (M _r  < −22.2), the early-type proportion of the first class Main galaxies even decreases dramatically with increasing luminosity. We also analyze the correlation between morphologies and luminosity of galaxies around the peak of the redshift distribution ( 0.07 ≤ z ≤ 0.08 ). In such a narrow redshift region, we still observe strong correlation between morphologies and luminosity, which shows that this correlation is fundamental.     

Constraints on the luminosities of gamma-ray bursts

Constraints are found on the gamma-ray burst luminosity function from an analysis of the combined BATSE/PVO intensity distribution. If bursts originate in an extended Galactic halo, then the intrinsic luminosity range is narrow, with bursts spanning only a factor of five or less in luminosity. If bursts originate in a simple Friedmann cosmology with = 1 and = 0, then very few luminosity constraints exist.National Research Council Fellow at NASA/MSFC     

SN 1987A: an investigation of the bolometric luminosity evolution and the interior neutron star

In this paper the contributions of various radioactive substances (⁵⁶Co, ⁵⁷Co, ⁴⁴Ti and ²²Na) in the envelope of the supernova SN 1987A to the evolution of the bolometric luminosity are calculated and the several types of radiation, which may probably exist in the interior neutron star, as well as their contributions to the bolometric luminosity are investigated. After comparison of the results of calculation with the observation of CTIO and ESO, it is believed that after about 900 days the nuclear decay energy is no longer the unique energy source which determines the bolometric luminosity evolution of SN 1987A, that the radiation coming from the interior neutron star begins to play a dominating role in the bolometric luminosity evolution and that the most important mechanism of radiation of the neutron star is accretion.     

Approximating the solar/stellar energy generation rate,luminosity gradient,and the hydrogen content

In this paper we wish to develop an analytical technique for modelling the energy generation rate and the luminosity gradient for a one solar mass star like the Sun. Following the MDV method for approximating the solar/stellar structure (Doorish, 1989) we derive dimensionless variables for the energy generation rate and luminosity which are used in an expansion equation (on the order of a simple general confluent hypergeometric function). Modelling the luminosity of the Sun is complicated due to the nature of the energy generation rate. For this reason, we attempt to first derive approximation of the energy generation rate. The resulting solutions bring about a model of the luminosity gradient and the corresponding energy generation rate for the proton-proton cycle. Also, we are able to derive, analytically, the hydrogen content from the center of the star to the surface using concepts derived from the energy generation rate.Presented at the 2nd UN/ESA Workshop, held in Bogotá, Colombia, 9–13 November, 1992.