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Sample records for quasar luminosity function

  1. The luminosity function of quasars

    NASA Technical Reports Server (NTRS)

    Pei, Yichuan C.

    1995-01-01

    We propose a new evolutionary model for the optical luminosity function of quasars. Our analytical model is derived from fits to the empirical luminosity function estimated by Hartwick and Schade and Warren, Hewett, and Osmer on the basis of more than 1200 quasars over the range of redshifts 0 approximately less than z approximately less than 4.5. We find that the evolution of quasars over this entire redshift range can be well fitted by a Gaussian distribution, while the shape of the luminosity function can be well fitted by either a double power law or an exponential L(exp 1/4) law. The predicted number counts of quasars, as a function of either apparent magnitude or redshift, are fully consistent with the observed ones. Our model indicates that the evolution of quasars reaches its maximum at z approximately = 2.8 and declines at higher redshifts. An extrapolation of the evolution to z approximately greater than 4.5 implies that quasars may have started their cosmic fireworks at z(sub f) approximately = 5.2-5.5. Forthcoming surveys of quasars at these redshifts will be critical to constrain the epoch of quasar formation. All the results we derived are based on observed quasars and are therefore subject to the bias of obscuration by dust in damped Ly alpha systems. Future surveys of these absorption systems at z approximately greater than 3 will also be important if the formation epoch of quasars is to be known unambiguously.

  2. THE z = 5 QUASAR LUMINOSITY FUNCTION FROM SDSS STRIPE 82

    SciTech Connect

    McGreer, Ian D.; Fan Xiaohui; Jiang Linhua; Richards, Gordon T.; Strauss, Michael A.; Ross, Nicholas P.; White, Martin; Shen Yue; Schneider, Donald P.; Brandt, W. Niel; Myers, Adam D.; DeGraf, Colin; Glikman, Eilat; Ge Jian; Streblyanska, Alina

    2013-05-10

    We present a measurement of the Type I quasar luminosity function at z = 5 using a large sample of spectroscopically confirmed quasars selected from optical imaging data. We measure the bright end (M{sub 1450} < -26) with Sloan Digital Sky Survey (SDSS) data covering {approx}6000 deg{sup 2}, then extend to lower luminosities (M{sub 1450} < -24) with newly discovered, faint z {approx} 5 quasars selected from 235 deg{sup 2} of deep, coadded imaging in the SDSS Stripe 82 region (the celestial equator in the Southern Galactic Cap). The faint sample includes 14 quasars with spectra obtained as ancillary science targets in the SDSS-III Baryon Oscillation Spectroscopic Survey, and 59 quasars observed at the MMT and Magellan telescopes. We construct a well-defined sample of 4.7 < z < 5.1 quasars that is highly complete, with 73 spectroscopic identifications out of 92 candidates. Our color selection method is also highly efficient: of the 73 spectra obtained, 71 are high-redshift quasars. These observations reach below the break in the luminosity function (M{sub 1450}{sup *}{approx}-27). The bright-end slope is steep ({beta} {approx}< -4), with a constraint of {beta} < -3.1 at 95% confidence. The break luminosity appears to evolve strongly at high redshift, providing an explanation for the flattening of the bright-end slope reported previously. We find a factor of {approx}2 greater decrease in the number density of luminous quasars (M{sub 1450} < -26) from z = 5 to z = 6 than from z = 4 to z = 5, suggesting a more rapid decline in quasar activity at high redshift than found in previous surveys. Our model for the quasar luminosity function predicts that quasars generate {approx}30% of the ionizing photons required to keep hydrogen in the universe ionized at z = 5.

  3. The intrinsic quasar luminosity function: Accounting for accretion disk anisotropy

    SciTech Connect

    DiPompeo, M. A.; Myers, A. D.; Brotherton, M. S.; Runnoe, J. C.; Green, R. F.

    2014-05-20

    Quasar luminosity functions are a fundamental probe of the growth and evolution of supermassive black holes. Measuring the intrinsic luminosity function is difficult in practice, due to a multitude of observational and systematic effects. As sample sizes increase and measurement errors drop, characterizing the systematic effects is becoming more important. It is well known that the continuum emission from the accretion disk of quasars is anisotropic—in part due to its disk-like structure—but current luminosity function calculations effectively assume isotropy over the range of unobscured lines of sight. Here, we provide the first steps in characterizing the effect of random quasar orientations and simple models of anisotropy on observed luminosity functions. We find that the effect of orientation is not insignificant and exceeds other potential corrections such as those from gravitational lensing of foreground structures. We argue that current observational constraints may overestimate the intrinsic luminosity function by as much as a factor of ∼2 on the bright end. This has implications for models of quasars and their role in the universe, such as quasars' contribution to cosmological backgrounds.

  4. The quasar luminosity function from a variability-selected sample

    NASA Astrophysics Data System (ADS)

    Hawkins, M. R. S.; Veron, P.

    1993-01-01

    A sample of quasars is selected from a 10-yr sequence of 30 UK Schmidt plates. Luminosity functions are derived in several redshift intervals, which in each case show a featureless power-law rise towards low luminosities. There is no sign of the 'break' found in the recent UVX sample of Boyle et al. It is suggested that reasons for the disagreement are connected with biases in the selection of the UVX sample. The question of the nature of quasar evolution appears to be still unresolved.

  5. The luminosity function of quasars and its evolution: A comparison of optically selected quasars and quasars found in radio catalogs

    NASA Technical Reports Server (NTRS)

    Petrosian, V.

    1973-01-01

    The luminosity function of quasars and its evolution are discussed, based on comparison of available data on optically selected quasars and quasars found in radio catalogs. It is assumed that the red shift of quasars is cosmological and the results are expressed in the framework of the Lambda = 0, Q sub Q = 1 cosmological model. The predictions of various density evolution laws are compared with observations of an optically selected sample of quasars and quasar samples from radio catalogs. The differences between the optical luminosity functions, the red shift distributions and the radio to optical luminosity ratios of optically selected quasars and radio quasars rule out luminosity functions where there is complete absence of correlation between radio and optical luminosities. These differences also imply that Schmidt's (1970) luminosity function, where there exists a statistical correlation between radio and optical luminosities, although may be correct for high red shift objects, disagrees with observation at low red shifts. These differences can be accounted for by postulating existence of two classes (1 and 2) of objects.

  6. The Mid-infrared Luminosity Evolution and Luminosity Function of Quasars with WISE and SDSS

    NASA Astrophysics Data System (ADS)

    Singal, J.; George, J.; Gerber, A.

    2016-11-01

    We determine the 22 μm luminosity evolution and luminosity function for quasars from a data set of over 20,000 objects obtained by combining flux-limited Sloan Digital Sky Survey optical and Wide field Infrared Survey Explorer mid-infrared data. We apply methods developed in previous works to access the intrinsic population distributions non-parametrically, taking into account the truncations and correlations inherent in the data. We find that the population of quasars exhibits positive luminosity evolution with redshift in the mid-infrared, but with considerably less mid-infrared evolution than in the optical or radio bands. With the luminosity evolutions accounted for, we determine the density evolution and local mid-infrared luminosity function. The latter displays a sharp flattening at local luminosities below ∼ {10}31 erg s‑1 Hz‑1, which has been reported previously at 15 μm for AGN classified as both type 1 and type 2. We calculate the integrated total emission from quasars at 22 μm and find it to be a small fraction of both the cosmic infrared background light and the integrated emission from all sources at this wavelength.

  7. THE SDSS-III BARYON OSCILLATION SPECTROSCOPIC SURVEY: THE QUASAR LUMINOSITY FUNCTION FROM DATA RELEASE NINE

    SciTech Connect

    Ross, Nicholas P.; White, Martin; Bailey, Stephen; McGreer, Ian D.; Richards, Gordon T.; Myers, Adam D.; Palanque-Delabrouille, Nathalie; Yeche, Christophe; Strauss, Michael A.; Anderson, Scott F.; Shen, Yue; Swanson, Molly E. C.; Brandt, W. N.; Aubourg, Eric; Bovy, Jo; DeGraf, Colin; Di Matteo, Tiziana; and others

    2013-08-10

    We present a new measurement of the optical quasar luminosity function (QLF), using data from the Sloan Digital Sky Survey-III: Baryon Oscillation Spectroscopic Survey (SDSS-III: BOSS). From the SDSS-III Data Release Nine, a uniform sample of 22,301 i {approx}< 21.8 quasars are selected over an area of 2236 deg{sup 2}, with confirmed spectroscopic redshifts between 2.2 < z < 3.5, filling in a key part of the luminosity-redshift plane for optical quasar studies. The completeness of the survey is derived through simulated quasar photometry, and this completeness estimate is checked using a sample of quasars selected by their photometric variability within the BOSS footprint. We investigate the level of systematics associated with our quasar sample using the simulations, in the process generating color-redshift relations and a new quasar K-correction. We probe the faint end of the QLF to M{sub i} (z = 2.2) Almost-Equal-To -24.5 and see a clear break in the QLF at all redshifts up to z = 3.5. A log-linear relation (in log {Phi}* - M*) for a luminosity evolution and density evolution model is found to adequately describe our data within the range 2.2 < z < 3.5; across this interval the break luminosity increases by a factor of {approx}2.6 while {Phi}* declines by a factor of {approx}8. At z {approx}< 2.2 our data are reasonably well fit by a pure luminosity evolution model, and only a weak signature of ''AGN downsizing'' is seen, in line with recent studies of the hard X-ray luminosity function. We compare our measured QLF to a number of theoretical models and find that models making a variety of assumptions about quasar triggering and halo occupation can fit our data over a wide range of redshifts and luminosities.

  8. VizieR Online Data Catalog: Quasar luminosity function (Hawkins+, 1993)

    NASA Astrophysics Data System (ADS)

    Hawkins, M. R. S.; Veron, P.

    1994-11-01

    A sample of quasars is selected from a 10-yr sequence of 30 UK Schmidt plates. Luminosity functions are derived in several redshift intervals, which in each case show a featureless power-law rise towards low luminosities. There is no sigh of the 'break' found in the recent UVX sample of Boyle, Shanks & Peterson. It is suggested that reasons for the disagreement are connected with biases in the selection of the UVX sample. The question of the nature of quasar evolution appears to be still unresolved. (1 data file).

  9. CONSTRAINTS ON THE FAINT END OF THE QUASAR LUMINOSITY FUNCTION AT z {approx} 5 IN THE COSMOS FIELD

    SciTech Connect

    Ikeda, H.; Matsuoka, K.; Kajisawa, M.; Nagao, T.; Taniguchi, Y.; Shioya, Y.; Enoki, M.; Capak, P.; Masters, D.; Scoville, N. Z.; Civano, F.; Koekemoer, A. M.; Morokuma, T.; Salvato, M.; Schinnerer, E.

    2012-09-10

    We present the result of our low-luminosity quasar survey in the redshift range of 4.5 {approx}< z {approx}< 5.5 in the COSMOS field. Using the COSMOS photometric catalog, we selected 15 quasar candidates with 22 < i' < 24 at z {approx} 5 that are {approx}3 mag fainter than the Sloan Digital Sky Survey quasars in the same redshift range. We obtained optical spectra for 14 of the 15 candidates using FOCAS on the Subaru Telescope and did not identify any low-luminosity type-1 quasars at z {approx} 5, while a low-luminosity type-2 quasar at z {approx} 5.07 was discovered. In order to constrain the faint end of the quasar luminosity function at z {approx} 5, we calculated the 1{sigma} confidence upper limits of the space density of type-1 quasars. As a result, the 1{sigma} confidence upper limits on the quasar space density are {Phi} < 1.33 Multiplication-Sign 10{sup -7} Mpc{sup -3} mag{sup -1} for -24.52 < M{sub 1450} < -23.52 and {Phi} < 2.88 Multiplication-Sign 10{sup -7} Mpc{sup -3} mag{sup -1} for -23.52 < M{sub 1450} < -22.52. The inferred 1{sigma} confidence upper limits of the space density are then used to provide constraints on the faint-end slope and the break absolute magnitude of the quasar luminosity function at z {approx} 5. We find that the quasar space density decreases gradually as a function of redshift at low luminosity (M{sub 1450} {approx} -23), being similar to the trend found for quasars with high luminosity (M{sub 1450} < -26). This result is consistent with the so-called downsizing evolution of quasars seen at lower redshifts.

  10. The radio luminosity function and redshift evolution of radio-mode and quasar-mode AGN

    NASA Astrophysics Data System (ADS)

    Pracy, Mike

    2016-08-01

    The properties of the AGN population indicate that there are two fundamentally different accretion modes operating. In the quasar-mode, material is accreted onto the supermassive black hole via a small, thin, optically luminous accretion disc. Accretion in this mode is recognisable by emission lines in the optical spectrum. However, there is a population of AGN observable only by their radio emission and without optical emission lines. These radio-mode AGN are likely powered by radiatively inefficient accretion from a hot gas halo. I will describe the cosmic evolution of these two populations via radio luminosity functions. The radio luminosity functions are constructed from a new survey of over 4000 radio galaxies out to z=1, all with confirmed redshifts and their accretion mode classified from their optical spectra. This is 20 times larger than the only other survey used to make such a measurement. The radio-mode AGN population displays no statistically significant evolution in space density out to redshift z=1. In contrast the quasar mode AGN exhibits rapid evolution in space density, increasing by a factor of 8 over the same redshift range. The characteristic break in the radio luminosity function occurs at a significantly higher power for the quasar-mode AGN in comparison to the radio-mode AGN and we demonstrate this is consistent with the two populations representing fundamentally different accretion modes. The radio luminosity function is used to estimate the total amount of mechanical energy available for radio mode feedback as a function of redshift, and is found to be in good agreement with cosmological models and previous measurements. Again, by separating by accretion mode, the previously estimated increase in available mechanical energy per unit volume out to z=1 (approximately a factor of 2) can be attributed to the rapid evolution of the quasar-mode AGN, while for the classical radio-mode AGN the total mechanical energy output remains roughly

  11. Optical Variability of Quasars as a Function of Luminosity and Redshift

    NASA Astrophysics Data System (ADS)

    Gaskell, C. M.; Koratkar, A. P.; Kwon, T.-Y.; Liang, Y.; Scott, J. H.; Wysota, A.

    1987-09-01

    Various models of the "central engine" in quasars make different predictions of how the degree of variability and its timescale vary with luminosity. In the past there have been conflicting claims about the luminosity and redshift dependence of quasar variability. We have examined the photographic light curves obtained at the Rosemary Hill Observatory (U. of Florida) and the Royal Greenwich Observatory (Herstmonceux) for over a hundred quasars (both radio-loud and radio-quiet). We demonstrate how the previously-reported redshift dependence is a consequence of time dilation, and find that, after allowance for this, there is no luminosity dependence in the amplitude of variability. High-luminosity quasars are not less variable than their low-luminosity counterparts. This creates major difficulties for some classes of quasar model with discrete accretion events (e.g., gas cloud or disrupted stars being "swallowed" directly).

  12. THE FAINT END OF THE QUASAR LUMINOSITY FUNCTION AT z {approx} 4

    SciTech Connect

    Glikman, Eilat; Bogosavljevic, Milan; Djorgovski, S. G.; Mahabal, Ashish; Stern, Daniel; Dey, Arjun; Jannuzi, Buell T.

    2010-02-20

    The evolution of the quasar luminosity function (QLF) is one of the basic cosmological measures providing insight into structure formation and mass assembly in the universe. We have conducted a spectroscopic survey to find faint quasars (-26.0 < M{sub 1450} < -22.0) at redshifts z = 3.8-5.2 in order to measure the faint end of the QLF at these early times. Using available optical imaging data from portions of the NOAO Deep Wide-Field Survey and the Deep Lens Survey, we have color-selected quasar candidates in a total area of 3.76 deg{sup 2}. Thirty candidates have R <= 23 mag. We conducted spectroscopic follow-up for 28 of our candidates and found 23 QSOs, 21 of which are reported here for the first time, in the 3.74 < z < 5.06 redshift range. We estimate our survey completeness through detailed Monte Carlo simulations and derive the first measurement of the density of quasars in this magnitude and redshift interval. We find that the binned luminosity function (LF) is somewhat affected by the K-correction used to compute the rest-frame absolute magnitude at 1450 A. Considering only our R <= 23 sample, the best-fit single power law (PHI {proportional_to} L {sup beta}) gives a faint-end slope beta = -1.6 +- 0.2. If we consider our larger, but highly incomplete sample going 1 mag fainter, we measure a steeper faint-end slope -2 < beta < -2.5. In all cases, we consistently find faint-end slopes that are steeper than expected based on measurements at z {approx} 3. We combine our sample with bright quasars from the Sloan Digital Sky Survey to derive parameters for a double-power-law LF. Our best fit finds a bright-end slope, alpha = -2.4 +- 0.2, and faint-end slope, beta = -2.3 +- 0.2, without a well-constrained break luminosity. This is effectively a single power law, with beta = -2.7 +- 0.1. We use these results to place limits on the amount of ultraviolet radiation produced by quasars and find that quasars are able to ionize the intergalactic medium at these redshifts.

  13. The Faint End of the Quasar Luminosity Function at z ~ 4

    NASA Astrophysics Data System (ADS)

    Glikman, Eilat; Bogosavljević, Milan; Djorgovski, S. G.; Stern, Daniel; Dey, Arjun; Jannuzi, Buell T.; Mahabal, Ashish

    2010-02-01

    The evolution of the quasar luminosity function (QLF) is one of the basic cosmological measures providing insight into structure formation and mass assembly in the universe. We have conducted a spectroscopic survey to find faint quasars (-26.0 < M 1450 < -22.0) at redshifts z = 3.8-5.2 in order to measure the faint end of the QLF at these early times. Using available optical imaging data from portions of the NOAO Deep Wide-Field Survey and the Deep Lens Survey, we have color-selected quasar candidates in a total area of 3.76 deg2. Thirty candidates have R <= 23 mag. We conducted spectroscopic follow-up for 28 of our candidates and found 23 QSOs, 21 of which are reported here for the first time, in the 3.74 < z < 5.06 redshift range. We estimate our survey completeness through detailed Monte Carlo simulations and derive the first measurement of the density of quasars in this magnitude and redshift interval. We find that the binned luminosity function (LF) is somewhat affected by the K-correction used to compute the rest-frame absolute magnitude at 1450 Å. Considering only our R <= 23 sample, the best-fit single power law (Φ vprop L β) gives a faint-end slope β = -1.6 ± 0.2. If we consider our larger, but highly incomplete sample going 1 mag fainter, we measure a steeper faint-end slope -2 < β < -2.5. In all cases, we consistently find faint-end slopes that are steeper than expected based on measurements at z ~ 3. We combine our sample with bright quasars from the Sloan Digital Sky Survey to derive parameters for a double-power-law LF. Our best fit finds a bright-end slope, α = -2.4 ± 0.2, and faint-end slope, β = -2.3 ± 0.2, without a well-constrained break luminosity. This is effectively a single power law, with β = -2.7 ± 0.1. We use these results to place limits on the amount of ultraviolet radiation produced by quasars and find that quasars are able to ionize the intergalactic medium at these redshifts. The data presented herein were obtained at the

  14. The extended Baryon Oscillation Spectroscopic Survey: Variability selection and quasar luminosity function

    NASA Astrophysics Data System (ADS)

    Palanque-Delabrouille, N.; Magneville, Ch.; Yèche, Ch.; Pâris, I.; Petitjean, P.; Burtin, E.; Dawson, K.; McGreer, I.; Myers, A. D.; Rossi, G.; Schlegel, D.; Schneider, D.; Streblyanska, A.; Tinker, J.

    2016-03-01

    The extended Baryon Oscillation Spectroscopic Survey of the Sloan Digital Sky Survey (SDSS-IV/eBOSS) has an extensive quasar program that combines several selection methods. Among these, the photometric variability technique provides highly uniform samples, which are unaffected by the redshift bias of traditional optical-color selections, when z = 2.7-3.5 quasars cross the stellar locus or when host galaxy light affects quasar colors at z< 0.9. We present the variability selection of quasars in eBOSS, focusing on a specific program that led to a sample of 13 876 quasars to gdered = 22.5 over a 94.5 deg2 region in Stripe 82, which has an areal density 1.5 times higher than over the rest of the eBOSS footprint. We use these variability-selected data to provide a new measurement of the quasar luminosity function (QLF) in the redshift range of 0.68 luminosity-function evolution (PLE) with bright-end and faint-end slopes allowed to be different on either side of z = 2.2. The other is a simple PLE at z< 2.2, combined with a model that comprises both luminosity and density evolution (LEDE) at z> 2.2. Both models are constrained to be continuous at z = 2.2. They present a flattening of the bright-end slope at high redshift. The LEDE model indicates a reduction of the break density with increasing redshift, but the evolution of the break magnitude depends on the parameterization. The models are in excellent accord, predicting quasar counts that agree within 0.3% (resp., 1.1%) to g< 22.5 (resp., g< 23). The models are also in good agreement over the entire redshift range with models from previous studies.

  15. The 2dF-SDSS LRG and QSO (2SLAQ) Survey: the z < 2.1 quasar luminosity function from 5645 quasars to g= 21.85

    NASA Astrophysics Data System (ADS)

    Richards, Gordon T.; Croom, Scott M.; Anderson, Scott F.; Bland-Hawthorn, Joss; Boyle, Brian J.; De Propris, Roberto; Drinkwater, Michael J.; Fan, Xiaohui; Gunn, James E.; Ivezić, Željko; Jester, Sebastian; Loveday, Jon; Meiksin, Avery; Miller, Lance; Myers, Adam; Nichol, Robert C.; Outram, Phil J.; Pimbblet, Kevin A.; Roseboom, Isaac G.; Ross, Nic; Schneider, Donald P.; Shanks, Tom; Sharp, Robert G.; Stoughton, Chris; Strauss, Michael A.; Szalay, Alexander S.; Vanden Berk, Daniel E.; York, Donald G.

    2005-07-01

    We have used the Two-Degree Field (2dF) instrument on the Anglo-Australian Telescope (AAT) to obtain redshifts of a sample of z < 3 and 18.0 < g < 21.85 quasars selected from Sloan Digital Sky Survey (SDSS) imaging. These data are part of a larger joint programme between the SDSS and 2dF communities to obtain spectra of faint quasars and luminous red galaxies, namely the 2dF-SDSS LRG and QSO (2SLAQ) Survey. We describe the quasar selection algorithm and present the resulting number counts and luminosity function of 5645 quasars in 105.7 deg2. The bright-end number counts and luminosity functions agree well with determinations from the 2dF QSO Redshift Survey (2QZ) data to g~ 20.2. However, at the faint end, the 2SLAQ number counts and luminosity functions are steeper (i.e. require more faint quasars) than the final 2QZ results from Croom et al., but are consistent with the preliminary 2QZ results from Boyle et al. Using the functional form adopted for the 2QZ analysis (a double power law with pure luminosity evolution characterized by a second-order polynomial in redshift), we find a faint-end slope of β=-1.78 +/- 0.03 if we allow all of the parameters to vary, and β=-1.45 +/- 0.03 if we allow only the faint-end slope and normalization to vary (holding all other parameters equal to the final 2QZ values). Over the magnitude range covered by the 2SLAQ survey, our maximum-likelihood fit to the data yields 32 per cent more quasars than the final 2QZ parametrization, but is not inconsistent with other g > 21 deep surveys for quasars. The 2SLAQ data exhibit no well-defined `break' in the number counts or luminosity function, but do clearly flatten with increasing magnitude. Finally, we find that the shape of the quasar luminosity function derived from 2SLAQ is in good agreement with that derived from Type I quasars found in hard X-ray surveys.

  16. The Radio luminosity Function of Radio-Loud Quasars from the 7C Redshift Survey

    NASA Technical Reports Server (NTRS)

    Willott, Chris J.; Rawlings, Steve; Blundell, Katherine M.; Lacy, Mark

    1998-01-01

    We present a complete sample of 24 radio-loud quasars (RLQs) from the new 7C Redshift Survey. Every quasar with a low-frequency (151 MHz) radio flux-density S(sub 151) > 0.5 Jy in two regions of the sky covering 0.013 sr is included; 23 of these have sufficient extended flux to meet the selection criteria, 18 of these have steep radio spectra (hereafter denoted as SSQs). The key advantage of this sample over most samples of RLQs is the lack of an optical magnitude limit. By combining the 7C and 3CRR samples, we have investigated the properties of RLQs as a function of redshift z and radio luminosity L(sub 151). We derive the radio luminosity function (RLF) of RLQs and find that the data are well fitted by a single power-law with slope alpha(sub 1) = 1.9 +/- 0.1 (for H(sub 0) = 50 km/s.Mpc, OMEGA(sub M) = 1, OMEGA(sub DELTA) = 0). We find that there must be a break in the RLQ RLF at log(sub 10)(L(sub 151)/W Hz.sr) approximately < or = 27, in order for the models to be consistent with the 7C and 6C source counts. The z-dependence of the RLF follows a one-tailed gaussian which peaks at z = 1.7 +/- 0.2. We find no evidence for a decline in the co-moving space density of RLQs at higher redshifts. A positive correlation between the radio and optical luminosities of SSQs is observed, confirming a result of Serjeant. We are able to rule out this correlation being due to selection effects or biases in our combined sample. The radio-optical correlation and best-fit model RLF enable us to estimate the distribution of optical magnitudes of quasars in samples selected at low radio frequencies, We con- clude that for samples with S(sub 151) approximately < or = 1 Jy one must use optical data significantly deeper than the POSS-I limit (R approximately equal 20), in order to avoid severe incompleteness.

  17. PROBING THE FAINT END OF THE QUASAR LUMINOSITY FUNCTION AT z{approx} 4 IN THE COSMOS FIELD

    SciTech Connect

    Ikeda, H.; Nagao, T.; Matsuoka, K.; Ideue, Y.; Taniguchi, Y.; Shioya, Y.; Trump, J. R.; Comastri, A.; Enoki, M.; Koekemoer, A. M.; Morokuma, T.; Murayama, T.; Saito, T.; Silverman, J. D.; Salvato, M.; Schinnerer, E.

    2011-02-20

    We searched for quasars that are {approx}3 mag fainter than the SDSS quasars in the redshift range 3.7 {approx}< z {approx}< 4.7 in the COSMOS field to constrain the faint end of the quasar luminosity function (QLF). Using optical photometric data, we selected 31 quasar candidates with 22 < i' < 24 at z {approx} 4. We obtained optical spectra for most of these candidates using FOCAS on the Subaru telescope and identified eight low-luminosity quasars at z {approx} 4. In order to derive the QLF based on our spectroscopic follow-up campaign, we estimated the photometric completeness of our quasar survey through detailed Monte Carlo simulations. Our QLF at z {approx} 4 has a much shallower faint-end slope ({beta} = -1.67{sup +0.11}{sub -0.17}) than that obtained by other recent surveys in the same redshift. Our result is consistent with the scenario of downsizing evolution of active galactic nuclei inferred by recent optical and X-ray quasar surveys at lower redshifts.

  18. A Survey of Luminous High-redshift Quasars with SDSS and WISE. II. the Bright End of the Quasar Luminosity Function at z ≈ 5

    NASA Astrophysics Data System (ADS)

    Yang, Jinyi; Wang, Feige; Wu, Xue-Bing; Fan, Xiaohui; McGreer, Ian D.; Bian, Fuyan; Yi, Weimin; Yang, Qian; Ai, Yanli; Dong, Xiaoyi; Zuo, Wenwen; Green, Richard; Jiang, Linhua; Wang, Shu; Wang, Ran; Yue, Minghao

    2016-09-01

    This is the second paper in a series on a new luminous z ˜ 5 quasar survey using optical and near-infrared colors. Here we present a new determination of the bright end of the quasar luminosity function (QLF) at z ˜ 5. Combining our 45 new quasars with previously known quasars that satisfy our selections, we construct the largest uniform luminous z ˜ 5 quasar sample to date, with 99 quasars in the range of 4.7 ≤ z < 5.4 and -29 < M 1450 ≤ -26.8, within the Sloan Digital Sky Survey (SDSS) footprint. We use a modified 1/V a method including flux limit correction to derive a binned QLF, and we model the parametric QLF using maximum likelihood estimation. With the faint-end slope of the QLF fixed as α = -2.03 from previous deeper samples, the best fit of our QLF gives a flatter bright end slope β = -3.58 ± 0.24 and a fainter break magnitude {M}1450* = -26.98 ± 0.23 than previous studies at similar redshift. Combined with previous work at lower and higher redshifts, our result is consistent with a luminosity evolution and density evolution model. Using the best-fit QLF, the contribution of quasars to the ionizing background at z ˜ 5 is found to be 18%-45% with a clumping factor C of 2-5. Our sample suggests an evolution of radio loud fraction with optical luminosity but no obvious evolution with redshift.

  19. Seeking the epoch of maximum luminosity for dusty quasars

    SciTech Connect

    Vardanyan, Valeri; Weedman, Daniel; Sargsyan, Lusine E-mail: dweedman@isc.astro.cornell.edu

    2014-08-01

    Infrared luminosities νL{sub ν}(7.8 μm) arising from dust reradiation are determined for Sloan Digital Sky Survey (SDSS) quasars with 1.4 luminosity does not show a maximum at any redshift z < 5, reaching a plateau for z ≳ 3 with maximum luminosity νL{sub ν}(7.8 μm) ≳ 10{sup 47} erg s{sup –1}; luminosity functions show one quasar Gpc{sup –3} having νL{sub ν}(7.8 μm) > 10{sup 46.6} erg s{sup –1} for all 2 quasars first reached their maximum luminosity has not yet been identified at any redshift below 5. The most ultraviolet luminous quasars, defined by rest frame νL{sub ν}(0.25 μm), have the largest values of the ratio νL{sub ν}(0.25 μm)/νL{sub ν}(7.8 μm) with a maximum ratio at z = 2.9. From these results, we conclude that the quasars most luminous in the ultraviolet have the smallest dust content and appear luminous primarily because of lessened extinction. Observed ultraviolet/infrared luminosity ratios are used to define 'obscured' quasars as those having >5 mag of ultraviolet extinction. We present a new summary of obscured quasars discovered with the Spitzer Infrared Spectrograph and determine the infrared luminosity function of these obscured quasars at z ∼ 2.1. This is compared with infrared luminosity functions of optically discovered, unobscured quasars in the SDSS and in the AGN and Galaxy Evolution Survey. The comparison indicates comparable numbers of obscured and unobscured quasars at z ∼ 2.1 with a possible excess of obscured quasars at fainter luminosities.

  20. Seeking the Epoch of Maximum Luminosity for Dusty Quasars

    NASA Astrophysics Data System (ADS)

    Vardanyan, Valeri; Weedman, Daniel; Sargsyan, Lusine

    2014-08-01

    Infrared luminosities νL ν(7.8 μm) arising from dust reradiation are determined for Sloan Digital Sky Survey (SDSS) quasars with 1.4 luminosity does not show a maximum at any redshift z < 5, reaching a plateau for z >~ 3 with maximum luminosity νL ν(7.8 μm) >~ 1047 erg s-1 luminosity functions show one quasar Gpc-3 having νL ν(7.8 μm) > 1046.6 erg s-1 for all 2 quasars first reached their maximum luminosity has not yet been identified at any redshift below 5. The most ultraviolet luminous quasars, defined by rest frame νL ν(0.25 μm), have the largest values of the ratio νL ν(0.25 μm)/νL ν(7.8 μm) with a maximum ratio at z = 2.9. From these results, we conclude that the quasars most luminous in the ultraviolet have the smallest dust content and appear luminous primarily because of lessened extinction. Observed ultraviolet/infrared luminosity ratios are used to define "obscured" quasars as those having >5 mag of ultraviolet extinction. We present a new summary of obscured quasars discovered with the Spitzer Infrared Spectrograph and determine the infrared luminosity function of these obscured quasars at z ~ 2.1. This is compared with infrared luminosity functions of optically discovered, unobscured quasars in the SDSS and in the AGN and Galaxy Evolution Survey. The comparison indicates comparable numbers of obscured and unobscured quasars at z ~ 2.1 with a possible excess of obscured quasars at fainter luminosities.

  1. The Luminosity Function of Quasars (active Galactic Nuclei) in a Merging Model with the Eddington Limit Taken Into Account

    NASA Astrophysics Data System (ADS)

    Kontorovich, V. M.; Krivitsky, D. S.

    The influence of Eddington's limit on the active galactic nuclei (AGN) luminosity function within the framework of a phenomenological activity model (Kats and Kontorovich, 1990, 1991) based on angular momentum compensation in the process of galaxy merging is investigated. In particular, it is shown that in spite of the essential dependence of the galaxy merging probability on their masses in the most important and interesting case it behaves effectively as a constant, so that the abovementioned (Kats and Kontorovich, 1991) correspondence between the observed galaxy mass function (Binggeli et al., 1988) and quasar luminosity function power exponents (Boyle et al., 1988; Koo and Kron, 1988; Cristiani et al., 1993) for a constant merger probability takes place in reality. A break in the power-law dependence of the luminosity function due to Eddington's restriction (cf. Dibai, 1981; Padovani and Rafanelli, 1988) is obtained in certain cases. Possible correlation between masses of black holes in AGN and masses of their host galaxies is discussed. A more detailed paper containing the results presented at this conference was published in Pis'ma v Astron. Zh. (Kontorovich and Krivitsky, 1995). Here we have added also some additional notes and references.

  2. The Luminosity Function of Fermi-detected Flat-Spectrum Radio Quasars

    SciTech Connect

    Ajello, M.; Shaw, M.S.; Romani, R.W.; Dermer, C.D.; Costamante, L.; King, O.G.; Max-Moerbeck, W.; Readhead, A.; Reimer, A.; Richards, J.L.; Stevenson, M.

    2012-04-16

    Fermi has provided the largest sample of {gamma}-ray selected blazars to date. In this work we use a complete sample of FSRQs detected during the first year of operation to determine the luminosity function (LF) and its evolution with cosmic time. The number density of FSRQs grows dramatically up to redshift {approx}0.5-2.0 and declines thereafter. The redshift of the peak in the density is luminosity dependent, with more luminous sources peaking at earlier times; thus the LF of {gamma}-ray FSRQs follows a luminosity-dependent density evolution similarly to that of radio-quiet AGN. Also using data from the Swift Burst Alert Telescope we derive the average spectral energy distribution of FSRQs in the 10 keV-100GeV band and show that there is no correlation of the peak {gamma}-ray luminosity with {gamma}-ray peak frequency. The coupling of the SED and LF allows us to predict that the contribution of FSRQs to the Fermi isotropic {gamma}-ray background is 9.3{sub -1.0}{sup +1.6}% ({+-}3% systematic uncertainty) in the 0.1-100GeV band. Finally we determine the LF of unbeamed FSRQs, finding that FSRQs have an average Lorentz factor of {gamma} = 11.7{sub -2.2}{sup +3.3}, that most are seen within 5{sup o} of the jet axis, and that they represent only {approx}0.1% of the parent population.

  3. On the Radio and Optical Luminosity Evolution of Quasars

    SciTech Connect

    Singal, J.; Petrosian, V.; Lawrence, A.; Stawarz, L.; /JAXA, Sagamihara /Jagiellonian U., Astron. Observ.

    2011-05-20

    We calculate simultaneously the radio and optical luminosity evolutions of quasars, and the distribution in radio loudness R defined as the ratio of radio and optical luminosities, using a flux limited data set containing 636 quasars with radio and optical fluxes from White et al. We first note that when dealing with multivariate data it is imperative to first determine the true correlations among the variables, not those introduced by the observational selection effects, before obtaining the individual distributions of the variables. We use the methods developed by Efron and Petrosian which are designed to obtain unbiased correlations, distributions, and evolution with redshift from a data set truncated due to observational biases. It is found that as expected the population of quasars exhibits strong positive correlation between the radio and optical luminosities and that this correlation deviates from a simple linear relation in a way indicating that more luminous quasars are more radio loud. We also find that there is a strong luminosity evolution with redshift in both wavebands, with significantly higher radio than optical evolution. We conclude that the luminosity evolution obtained by arbitrarily separating the sources into radio loud (R > 10) and radio quiet (R < 10) populations introduces significant biases that skew the result considerably. We also construct the local radio and optical luminosity functions and the density evolution. Finally, we consider the distribution of the radio loudness parameter R obtained from careful treatment of the selection effects and luminosity evolutions with that obtained from the raw data without such considerations. We find a significant difference between the two distributions and no clear sign of bi-modality in the true distribution. Our results indicate therefore, somewhat surprisingly, that there is no critical switch in the efficiency of the production of disk outflows/jets between very radio quiet and very radio

  4. THE DEMOGRAPHICS OF BROAD-LINE QUASARS IN THE MASS-LUMINOSITY PLANE. II. BLACK HOLE MASS AND EDDINGTON RATIO FUNCTIONS

    SciTech Connect

    Kelly, Brandon C.; Shen, Yue

    2013-02-10

    We employ a flexible Bayesian technique to estimate the black hole (BH) mass and Eddington ratio functions for Type 1 (i.e., broad line) quasars from a uniformly selected data set of {approx}58, 000 quasars from the Sloan Digital Sky Survey (SDSS) DR7. We find that the SDSS becomes significantly incomplete at M {sub BH} {approx}< 3 Multiplication-Sign 10{sup 8} M {sub Sun} or L/L {sub Edd} {approx}< 0.07, and that the number densities of Type 1 quasars continue to increase down to these limits. Both the mass and Eddington ratio functions show evidence of downsizing, with the most massive and highest Eddington ratio BHs experiencing Type 1 quasar phases first, although the Eddington ratio number densities are flat at z < 2. We estimate the maximum Eddington ratio of Type 1 quasars in the observable universe to be L/L {sub Edd} {approx} 3. Consistent with our results in Shen and Kelly, we do not find statistical evidence for a so-called sub-Eddington boundary in the mass-luminosity plane of broad-line quasars, and demonstrate that such an apparent boundary in the observed distribution can be caused by selection effect and errors in virial BH mass estimates. Based on the typical Eddington ratio in a given mass bin, we estimate growth times for the BHs in Type 1 quasars and find that they are comparable to or longer than the age of the universe, implying an earlier phase of accelerated (i.e., with higher Eddington ratios) and possibly obscured growth. The large masses probed by our sample imply that most of our BHs reside in what are locally early-type galaxies, and we interpret our results within the context of models of self-regulated BH growth.

  5. THE FAINT END OF THE QUASAR LUMINOSITY FUNCTION AT z {approx} 4: IMPLICATIONS FOR IONIZATION OF THE INTERGALACTIC MEDIUM AND COSMIC DOWNSIZING

    SciTech Connect

    Glikman, Eilat; Lee, Kyoung-Soo; Djorgovski, S. G.; Stern, Daniel; Dey, Arjun; Jannuzi, Buell T.

    2011-02-20

    We present an updated determination of the z {approx} 4 QSO luminosity function (QLF), improving the quality of the determination of the faint end of the QLF presented by Glikman et al. (2010). We have observed an additional 43 candidates from our survey sample, yielding one additional QSO at z = 4.23 and increasing the completeness of our spectroscopic follow-up to 48% for candidates brighter than R = 24 over our survey area of 3.76 deg{sup 2}. We study the effect of using K-corrections to compute the rest-frame absolute magnitude at 1450 A compared with measuring M{sub 1450} directly from the object spectra. We find a luminosity-dependent bias: template-based K-corrections overestimate the luminosity of low-luminosity QSOs, likely due to their reliance on templates derived from higher luminosity QSOs. Combining our sample with bright quasars from the Sloan Digital Sky Survey and using spectrum-based M{sub 1450} for all the quasars, we fit a double power law to the binned QLF. Our best fit has a bright-end slope, {alpha} = 3.3 {+-} 0.2, and faint-end slope, {beta} = 1.6{sup +0.8}{sub -0.6}. Our new data revise the faint-end slope of the QLF down to flatter values similar to those measured at z {approx} 3. The break luminosity, though poorly constrained, is at M* = -24.1{sup +0.7}{sub -1.9}, approximately 1-1.5 mag fainter than at z {approx} 3. This QLF implies that QSOs account for about half the radiation needed to ionize the intergalactic medium at these redshifts.

  6. The Faint End of the Quasar Luminosity Function at z ~ 4: Implications for Ionization of the Intergalactic Medium and Cosmic Downsizing

    NASA Astrophysics Data System (ADS)

    Glikman, Eilat; Djorgovski, S. G.; Stern, Daniel; Dey, Arjun; Jannuzi, Buell T.; Lee, Kyoung-Soo

    2011-02-01

    We present an updated determination of the z ~ 4 QSO luminosity function (QLF), improving the quality of the determination of the faint end of the QLF presented by Glikman et al. (2010). We have observed an additional 43 candidates from our survey sample, yielding one additional QSO at z = 4.23 and increasing the completeness of our spectroscopic follow-up to 48% for candidates brighter than R = 24 over our survey area of 3.76 deg2. We study the effect of using K-corrections to compute the rest-frame absolute magnitude at 1450 Å compared with measuring M 1450 directly from the object spectra. We find a luminosity-dependent bias: template-based K-corrections overestimate the luminosity of low-luminosity QSOs, likely due to their reliance on templates derived from higher luminosity QSOs. Combining our sample with bright quasars from the Sloan Digital Sky Survey and using spectrum-based M 1450 for all the quasars, we fit a double power law to the binned QLF. Our best fit has a bright-end slope, α = 3.3 ± 0.2, and faint-end slope, β = 1.6+0.8 -0.6. Our new data revise the faint-end slope of the QLF down to flatter values similar to those measured at z ~ 3. The break luminosity, though poorly constrained, is at M* = -24.1+0.7 -1.9, approximately 1-1.5 mag fainter than at z ~ 3. This QLF implies that QSOs account for about half the radiation needed to ionize the intergalactic medium at these redshifts. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

  7. Luminosity calibration of low redshift quasars

    NASA Technical Reports Server (NTRS)

    Wampler, E. J.

    1983-01-01

    European (SERC) were combined with U.S. shifts on the IUE in order to obtain the long integration times required to record spectra of faint quasars. LWR spectra of the nearby giant radio galaxy Centarus A(NGC 5548) was attempted in an effort to determine the chemical composition and stellar populations in this unusual galaxy. The IUE results from the low redshift quasar study, combined with the data from an extensive ground based survey, are described.

  8. MEASURING LENSING MAGNIFICATION OF QUASARS BY LARGE SCALE STRUCTURE USING THE VARIABILITY-LUMINOSITY RELATION

    SciTech Connect

    Bauer, Anne H.; Jerke, Jonathan; Scalzo, Richard; Rabinowitz, David; Ellman, Nancy; Baltay, Charles

    2011-05-10

    We introduce a technique to measure gravitational lensing magnification using the variability of type I quasars. Quasars' variability amplitudes and luminosities are tightly correlated, on average. Magnification due to gravitational lensing increases the quasars' apparent luminosity, while leaving the variability amplitude unchanged. Therefore, the mean magnification of an ensemble of quasars can be measured through the mean shift in the variability-luminosity relation. As a proof of principle, we use this technique to measure the magnification of quasars spectroscopically identified in the Sloan Digital Sky Survey (SDSS), due to gravitational lensing by galaxy clusters in the SDSS MaxBCG catalog. The Palomar-QUEST Variability Survey, reduced using the DeepSky pipeline, provides variability data for the sources. We measure the average quasar magnification as a function of scaled distance (r/R{sub 200}) from the nearest cluster; our measurements are consistent with expectations assuming Navarro-Frenk-White cluster profiles, particularly after accounting for the known uncertainty in the clusters' centers. Variability-based lensing measurements are a valuable complement to shape-based techniques because their systematic errors are very different, and also because the variability measurements are amenable to photometric errors of a few percent and to depths seen in current wide-field surveys. Given the volume data of the expected from current and upcoming surveys, this new technique has the potential to be competitive with weak lensing shear measurements of large-scale structure.

  9. Measuring Lensing Magnification of Quasars by Large Scale Structure Using the Variability-Luminosity Relation

    NASA Astrophysics Data System (ADS)

    Bauer, Anne H.; Seitz, Stella; Jerke, Jonathan; Scalzo, Richard; Rabinowitz, David; Ellman, Nancy; Baltay, Charles

    2011-05-01

    We introduce a technique to measure gravitational lensing magnification using the variability of type I quasars. Quasars' variability amplitudes and luminosities are tightly correlated, on average. Magnification due to gravitational lensing increases the quasars' apparent luminosity, while leaving the variability amplitude unchanged. Therefore, the mean magnification of an ensemble of quasars can be measured through the mean shift in the variability-luminosity relation. As a proof of principle, we use this technique to measure the magnification of quasars spectroscopically identified in the Sloan Digital Sky Survey (SDSS), due to gravitational lensing by galaxy clusters in the SDSS MaxBCG catalog. The Palomar-QUEST Variability Survey, reduced using the DeepSky pipeline, provides variability data for the sources. We measure the average quasar magnification as a function of scaled distance (r/R 200) from the nearest cluster; our measurements are consistent with expectations assuming Navarro-Frenk-White cluster profiles, particularly after accounting for the known uncertainty in the clusters' centers. Variability-based lensing measurements are a valuable complement to shape-based techniques because their systematic errors are very different, and also because the variability measurements are amenable to photometric errors of a few percent and to depths seen in current wide-field surveys. Given the volume data of the expected from current and upcoming surveys, this new technique has the potential to be competitive with weak lensing shear measurements of large-scale structure.

  10. Evolution of the luminosity function of extragalactic objects

    NASA Technical Reports Server (NTRS)

    Petrosian, V.

    1985-01-01

    A nonparametric procedure for determination of the evolution of the luminosity function of extragalactic objects and use of this for prediction of expected redshift and luminosity distribution of objects is described. The relation between this statistical evolution of the population and their physical evolution, such as the variation with cosmological epoch of their luminosity and formation rate is presented. This procedure when applied to a sample of optically selected quasars with redshifts less than two shows that the luminosity function evolves more strongly for higher luminosities, indicating a larger quasar activity at earlier epochs and a more rapid evolution of the objects during their higher luminosity phases. It is also shown that absence of many quasars at redshifts greater than three implies slowing down of this evolution in the conventional cosmological models, perhaps indicating that this is near the epoch of the birth of the quasar (and galaxies).

  11. The x-ray luminosity-redshift relationship of quasars.

    PubMed

    Segal, I E; Segal, W

    1980-06-01

    Chronometric cosmology provides an excellent fit for the phenomenological x-ray luminosity-redshift relationship for 49 quasars observed by the Einstein satellite. Analysis of the data on the basis of the Friedmann cosmology leads to a correlation of absolute x-ray luminosity with redshift of >0.8, which is increased to approximately 1 in the bright envelope. Although the trend might be ascribed a priori to an observational magnitude bias, it persists after nonparametric, maximum-likelihood removal of this bias.

  12. The x-ray luminosity-redshift relationship of quasars

    PubMed Central

    Segal, I. E.; Segal, W.

    1980-01-01

    Chronometric cosmology provides an excellent fit for the phenomenological x-ray luminosity-redshift relationship for 49 quasars observed by the Einstein satellite. Analysis of the data on the basis of the Friedmann cosmology leads to a correlation of absolute x-ray luminosity with redshift of >0.8, which is increased to ∼1 in the bright envelope. Although the trend might be ascribed a priori to an observational magnitude bias, it persists after nonparametric, maximum-likelihood removal of this bias. PMID:16592826

  13. Characterizing Quasar Outflows III: SEDs, and Bolometric Luminosity Estimates

    NASA Astrophysics Data System (ADS)

    Richmond, Joseph; Robbins, J. M.; Ganguly, R.; Stark, M. A.; Christenson, D. H.; Derseweh, J. A.; Townsend, S. L.

    2012-05-01

    Galaxy evolution models have shown that quasars are a crucial ingredient in the evolution of massive galaxies. Outflows play a key role in the story of quasars and their host galaxies, by helping regulate the accretion process, the star-formation rate and mass of the host galaxy (i.e., feedback). The prescription for modeling outflows as a contributor to feedback requires knowledge of the outflow velocity, geometry, and column density. In particular, we need to understand how these depend on physical parameters and how much is determined stochastically (and with what distribution). For this purpose, we are examining a sample of 11000 z=1.7-2.0 quasars from the Sloan Digital Sky Survey. This redshift range permits the following from the SDSS spectra: (1) separation of objects that do and do not exhibit outflows; (2) classification/measurement of outflow properties (ionization, velocity, velocity width); and (3) measurements of UV emission line and continuum parameters. In this poster, we add photometry from both the Two Micron All-Sky Survey (2MASS) and from the Wide-Field Infrared Survey Explorer (WISE). 2MASS photometry covers the rest-frame optical regime of these qusars, while the WISE W1, W2, and W3 bands cover the rest-frame wavelength ranges 0.9-1.27 micron, 1.35-1.75 micron, and 2.52-5.51 micron, respectively. The preliminary release of WISE data cover 3800 of our quasars. In an accompnying poster, we have subjectively divided these quasars into four categories: broad absorption-line quasars (2700 objects), associated absorption-line quasars (1700 objects), reddened quasars (160 objects), and unabsorbed/unreddened quasars (6300 objects). Here, we present average SEDs for these subsamples, estimates of bolometric luminosity, and explore changes in SED based on both outflow properties and quasar physical properties. This material is based upon work supported by the National Aeronautics and Space Administration under Grant No. 09-ADP09-0016 issued through the

  14. Cross-correlation of SDSS DR7 quasars and DR10 BOSS galaxies: The weak luminosity dependence of quasar clustering at z ∼ 0.5

    SciTech Connect

    Shen, Yue; McBride, Cameron K.; Swanson, Molly E. C.; White, Martin; Kirkpatrick, Jessica A.; Ross, Nicholas P.; Schlegel, David J.; Zheng, Zheng; Myers, Adam D.; Guo, Hong; Zehavi, Idit; Padmanabhan, Nikhil; Parejko, John K.; Schneider, Donald P.; Streblyanska, Alina; Pan, Kaike; Bizyaev, Dmitry; Brewington, Howard; Ebelke, Garrett; Malanushenko, Viktor; and others

    2013-12-01

    We present the measurement of the two-point cross-correlation function (CCF) of 8198 Sloan Digital Sky Survey Data Release 7 quasars and 349,608 Data Release 10 CMASS galaxies from the Baryonic Oscillation Spectroscopic Survey at 0.3 < z < 0.9. The CCF can be reasonably well fit by a power-law model ξ{sub QG}(r) = (r/r {sub 0}){sup –γ} on projected scales of r{sub p} = 2-25 h {sup –1} Mpc with r {sub 0} = 6.61 ± 0.25 h {sup –1} Mpc and γ = 1.69 ± 0.07. We estimate a quasar linear bias of b{sub Q} = 1.38 ± 0.10 at (z) = 0.53 from the CCF measurements, which corresponds to a characteristic host halo mass of ∼4 × 10{sup 12} h {sup –1} M {sub ☉}, compared with a ∼10{sup 13} h {sup –1} M {sub ☉} characteristic host halo mass for CMASS galaxies. Based on the clustering measurements, most quasars at z-bar ∼0.5 are not the descendants of their higher luminosity counterparts at higher redshift, which would have evolved into more massive and more biased systems at low redshift. We divide the quasar sample in luminosity and constrain the luminosity dependence of quasar bias to be db{sub Q} /dlog L = 0.20 ± 0.34 or 0.11 ± 0.32 (depending on different luminosity divisions) for quasar luminosities –23.5 > M{sub i} (z = 2) > –25.5, implying a weak luminosity dependence of clustering for luminous quasars at z-bar ∼0.5. We compare our measurements with theoretical predictions, halo occupation distribution (HOD) models, and mock catalogs. These comparisons suggest that quasars reside in a broad range of host halos. The host halo mass distributions significantly overlap with each other for quasars at different luminosities, implying a poor correlation between halo mass and instantaneous quasar luminosity. We also find that the quasar HOD parameterization is largely degenerate such that different HODs can reproduce the CCF equally well, but with different satellite fractions and host halo mass distributions. These results highlight the limitations

  15. Heavily reddened type 1 quasars at z > 2 - I. Evidence for significant obscured black hole growth at the highest quasar luminosities

    NASA Astrophysics Data System (ADS)

    Banerji, Manda; Alaghband-Zadeh, S.; Hewett, Paul C.; McMahon, Richard G.

    2015-03-01

    We present a new population of z > 2 dust-reddened, type 1 quasars with 0.5 ≲ E(B - V) ≲ 1.5, selected using near-infrared (NIR) imaging data from the UKIDSS-LAS (Large Area Survey), ESO-VHS (European Southern Obseratory-VISTA Hemisphere Survey) and WISE surveys. NIR spectra obtained using the Very Large Telescope for 24 new objects bring our total sample of spectroscopically confirmed hyperluminous (>1013 L⊙), high-redshift dusty quasars to 38. There is no evidence for reddened quasars having significantly different Hα equivalent widths relative to unobscured quasars. The average black hole masses (˜109-1010 M⊙) and bolometric luminosities (˜1047 erg s-1) are comparable to the most luminous unobscured quasars at the same redshift, but with a tail extending to very high luminosities of ˜1048 erg s-1. 66 per cent of the reddened quasars are detected at >3σ at 22 μm by WISE. The average 6-μm rest-frame luminosity is log10(L6 μm/ erg s-1) = 47.1 ± 0.4, making the objects among the mid-infrared brightest active galactic nuclei (AGN) currently known. The extinction-corrected space density estimate now extends over three magnitudes (-30 < Mi < -27) and demonstrates that the reddened quasar luminosity function is significantly flatter than that of the unobscured quasar population at z = 2-3. At the brightest magnitudes, Mi ≲ -29, the space density of our dust-reddened population exceeds that of unobscured quasars. A model where the probability that a quasar becomes dust reddened increases at high luminosity is consistent with the observations and such a dependence could be explained by an increase in luminosity and extinction during AGN-fuelling phases. The properties of our obscured type 1 quasars are distinct from the heavily obscured, Compton-thick AGN that have been identified at much fainter luminosities and we conclude that they likely correspond to a brief evolutionary phase in massive galaxy formation.

  16. Subaru High-z Exploration of Low-luminosity Quasars (SHELLQs). I. Discovery of 15 Quasars and Bright Galaxies at 5.7 z > 6.9

    NASA Astrophysics Data System (ADS)

    Matsuoka, Yoshiki; Onoue, Masafusa; Kashikawa, Nobunari; Iwasawa, Kazushi; Strauss, Michael A.; Nagao, Tohru; Imanishi, Masatoshi; Niida, Mana; Toba, Yoshiki; Akiyama, Masayuki; Asami, Naoko; Bosch, James; Foucaud, Sébastien; Furusawa, Hisanori; Goto, Tomotsugu; Gunn, James E.; Harikane, Yuichi; Ikeda, Hiroyuki; Kawaguchi, Toshihiro; Kikuta, Satoshi; Komiyama, Yutaka; Lupton, Robert H.; Minezaki, Takeo; Miyazaki, Satoshi; Morokuma, Tomoki; Murayama, Hitoshi; Nishizawa, Atsushi J.; Ono, Yoshiaki; Ouchi, Masami; Price, Paul A.; Sameshima, Hiroaki; Silverman, John D.; Sugiyama, Naoshi; Tait, Philip J.; Takada, Masahiro; Takata, Tadafumi; Tanaka, Masayuki; Tang, Ji-Jia; Utsumi, Yousuke

    2016-09-01

    We report the discovery of 15 quasars and bright galaxies at 5.7 < z < 6.9. This is the initial result from the Subaru High-z Exploration of Low-Luminosity Quasars project, which exploits the exquisite multiband imaging data produced by the Subaru Hyper Suprime-Cam (HSC) Strategic Program survey. The candidate selection is performed by combining several photometric approaches including a Bayesian probabilistic algorithm to reject stars and dwarfs. The spectroscopic identification was carried out with the Gran Telescopio Canarias and the Subaru Telescope for the first 80 deg2 of the survey footprint. The success rate of our photometric selection is quite high, approaching 100% at the brighter magnitudes (z AB < 23.5 mag). Our selection also recovered all the known high-z quasars on the HSC images. Among the 15 discovered objects, six are likely quasars, while the other six with interstellar absorption lines and in some cases narrow emission lines are likely bright Lyman-break galaxies. The remaining three objects have weak continua and very strong and narrow Lyα lines, which may be excited by ultraviolet light from both young stars and quasars. These results indicate that we are starting to see the steep rise of the luminosity function of z ≥ 6 galaxies, compared with that of quasars, at magnitudes fainter than M 1450 ˜ ‑22 mag or z AB ˜ 24 mag. Follow-up studies of the discovered objects as well as further survey observations are ongoing.

  17. Subaru High-z Exploration of Low-luminosity Quasars (SHELLQs). I. Discovery of 15 Quasars and Bright Galaxies at 5.7 < z < 6.9

    NASA Astrophysics Data System (ADS)

    Matsuoka, Yoshiki; Onoue, Masafusa; Kashikawa, Nobunari; Iwasawa, Kazushi; Strauss, Michael A.; Nagao, Tohru; Imanishi, Masatoshi; Niida, Mana; Toba, Yoshiki; Akiyama, Masayuki; Asami, Naoko; Bosch, James; Foucaud, Sébastien; Furusawa, Hisanori; Goto, Tomotsugu; Gunn, James E.; Harikane, Yuichi; Ikeda, Hiroyuki; Kawaguchi, Toshihiro; Kikuta, Satoshi; Komiyama, Yutaka; Lupton, Robert H.; Minezaki, Takeo; Miyazaki, Satoshi; Morokuma, Tomoki; Murayama, Hitoshi; Nishizawa, Atsushi J.; Ono, Yoshiaki; Ouchi, Masami; Price, Paul A.; Sameshima, Hiroaki; Silverman, John D.; Sugiyama, Naoshi; Tait, Philip J.; Takada, Masahiro; Takata, Tadafumi; Tanaka, Masayuki; Tang, Ji-Jia; Utsumi, Yousuke

    2016-09-01

    We report the discovery of 15 quasars and bright galaxies at 5.7 < z < 6.9. This is the initial result from the Subaru High-z Exploration of Low-Luminosity Quasars project, which exploits the exquisite multiband imaging data produced by the Subaru Hyper Suprime-Cam (HSC) Strategic Program survey. The candidate selection is performed by combining several photometric approaches including a Bayesian probabilistic algorithm to reject stars and dwarfs. The spectroscopic identification was carried out with the Gran Telescopio Canarias and the Subaru Telescope for the first 80 deg2 of the survey footprint. The success rate of our photometric selection is quite high, approaching 100% at the brighter magnitudes (z AB < 23.5 mag). Our selection also recovered all the known high-z quasars on the HSC images. Among the 15 discovered objects, six are likely quasars, while the other six with interstellar absorption lines and in some cases narrow emission lines are likely bright Lyman-break galaxies. The remaining three objects have weak continua and very strong and narrow Lyα lines, which may be excited by ultraviolet light from both young stars and quasars. These results indicate that we are starting to see the steep rise of the luminosity function of z ≥ 6 galaxies, compared with that of quasars, at magnitudes fainter than M 1450 ˜ -22 mag or z AB ˜ 24 mag. Follow-up studies of the discovered objects as well as further survey observations are ongoing.

  18. THE REDSHIFT DISTRIBUTION OF INTERVENING WEAK Mg II QUASAR ABSORBERS AND A CURIOUS DEPENDENCE ON QUASAR LUMINOSITY

    SciTech Connect

    Evans, Jessica L.; Churchill, Christopher W.; Nielsen, Nikole M.; Klimek, Elizabeth S.; Murphy, Michael T.

    2013-05-01

    We have identified 469 Mg II {lambda}{lambda}2796, 2803 doublet systems having W{sub r} {>=} 0.02 A in 252 Keck/High Resolution Echelle Spectrometer and UVES/Very Large Telescope quasar spectra over the redshift range 0.1 < z < 2.6. Using the largest sample yet of 188 weak Mg II systems (0.02 A {<=}W{sub r} < 0.3 A), we calculate their absorber redshift path density, dN/dz. We find clear evidence of evolution, with dN/dz peaking at z {approx} 1.2, and that the product of the absorber number density and cross section decreases linearly with increasing redshift; weak Mg II absorbers seem to vanish above z {approx_equal} 2.7. If the absorbers are ionized by the UV background, we estimate number densities of 10{sup 6}-10{sup 9} Mpc{sup -3} for spherical geometries and 10{sup 2}-10{sup 5} Mpc{sup -3} for more sheetlike geometries. We also find that dN/dz toward intrinsically faint versus bright quasars differs significantly for weak and strong (W{sub r} {>=} 1.0 A) absorbers. For weak absorption, dN/dz toward bright quasars is {approx}25% higher than toward faint quasars (10{sigma} at low redshift, 0.4 {<=} z {<=} 1.4, and 4{sigma} at high redshift, 1.4 < z {<=} 2.34). For strong absorption the trend reverses, with dN/dz toward faint quasars being {approx}20% higher than toward bright quasars (also 10{sigma} at low redshift and 4{sigma} at high redshift). We explore scenarios in which beam size is proportional to quasar luminosity and varies with absorber and quasar redshifts. These do not explain dN/dz's dependence on quasar luminosity.

  19. The Redshift Distribution of Intervening Weak Mg II Quasar Absorbers and a Curious Dependence on Quasar Luminosity

    NASA Astrophysics Data System (ADS)

    Evans, Jessica L.; Churchill, Christopher W.; Murphy, Michael T.; Nielsen, Nikole M.; Klimek, Elizabeth S.

    2013-05-01

    We have identified 469 Mg II λλ2796, 2803 doublet systems having Wr >= 0.02 Å in 252 Keck/High Resolution Echelle Spectrometer and UVES/Very Large Telescope quasar spectra over the redshift range 0.1 < z < 2.6. Using the largest sample yet of 188 weak Mg II systems (0.02 Å <=Wr < 0.3 Å), we calculate their absorber redshift path density, dN/dz. We find clear evidence of evolution, with dN/dz peaking at z ~ 1.2, and that the product of the absorber number density and cross section decreases linearly with increasing redshift; weak Mg II absorbers seem to vanish above z ~= 2.7. If the absorbers are ionized by the UV background, we estimate number densities of 106-109 Mpc-3 for spherical geometries and 102-105 Mpc-3 for more sheetlike geometries. We also find that dN/dz toward intrinsically faint versus bright quasars differs significantly for weak and strong (Wr >= 1.0 Å) absorbers. For weak absorption, dN/dz toward bright quasars is ~25% higher than toward faint quasars (10σ at low redshift, 0.4 <= z <= 1.4, and 4σ at high redshift, 1.4 < z <= 2.34). For strong absorption the trend reverses, with dN/dz toward faint quasars being ~20% higher than toward bright quasars (also 10σ at low redshift and 4σ at high redshift). We explore scenarios in which beam size is proportional to quasar luminosity and varies with absorber and quasar redshifts. These do not explain dN/dz's dependence on quasar luminosity.

  20. A TENTATIVE SIZE-LUMINOSITY RELATION FOR THE IRON EMISSION-LINE REGION IN QUASARS

    SciTech Connect

    Chelouche, Doron; Rafter, Stephen E.; Cotlier, Gabriel I.; Kaspi, Shai; Barth, Aaron J. E-mail: rafter@physics.technion.ac.il E-mail: barth@uci.edu

    2014-03-10

    New reverberation mapping measurements of the size of the optical iron emission-line region in quasars are provided, and a tentative size-luminosity relation for this component is reported. Combined with lag measurements in low-luminosity sources, the results imply an emission-region size that is comparable to and at most twice that of the Hβ line, and is characterized by a similar luminosity dependence. This suggests that the physics underlying the formation of the optical iron blends in quasars may be similar to that of other broad emission lines.

  1. THE RADIO AND OPTICAL LUMINOSITY EVOLUTION OF QUASARS. II. THE SDSS SAMPLE

    SciTech Connect

    Singal, J.; Petrosian, V.; Stawarz, L.; Lawrence, A.

    2013-02-10

    We determine the radio and optical luminosity evolutions and the true distribution of the radio-loudness parameter R, defined as the ratio of the radio to optical luminosity, for a set of more than 5000 quasars combining Sloan Digital Sky Survey optical and Faint Images of the Radio Sky at Twenty cm (FIRST) radio data. We apply the method of Efron and Petrosian to access the intrinsic distribution parameters, taking into account the truncations and correlations inherent in the data. We find that the population exhibits strong positive evolution with redshift in both wavebands, with somewhat greater radio evolution than optical. With the luminosity evolutions accounted for, we determine the density evolutions and local radio and optical luminosity functions. The intrinsic distribution of the radio-loudness parameter R is found to be quite different from the observed one and is smooth with no evidence of a bimodality in radio loudness for log R {>=} -1. The results we find are in general agreement with the previous analysis of Singal et al., which used POSS-I optical and FIRST radio data.

  2. The Radio and Optical Luminosity Evolution of Quasars II - The SDSS Sample

    SciTech Connect

    Singal, J.; Petrosian, V.; Stawarz, L.; Lawrence, A.

    2012-12-28

    We determine the radio and optical luminosity evolutions and the true distribution of the radio loudness parameter R, defined as the ratio of the radio to optical luminosity, for a set of more than 5000 quasars combining SDSS optical and FIRST radio data. We apply the method of Efron and Petrosian to access the intrinsic distribution parameters, taking into account the truncations and correlations inherent in the data. We find that the population exhibits strong positive evolution with redshift in both wavebands, with somewhat greater radio evolution than optical. With the luminosity evolutions accounted for, we determine the density evolutions and local radio and optical luminosity functions. The intrinsic distribution of the radio loudness parameter R is found to be quite different than the observed one, and is smooth with no evidence of a bi-modality in radio loudness. The results we find are in general agreement with the previous analysis of Singal et al., 2011 which used POSS-I optical and FIRST radio data.

  3. The 2QDES Pilot: the luminosity and redshift dependence of quasar clustering

    NASA Astrophysics Data System (ADS)

    Chehade, Ben; Shanks, T.; Findlay, J.; Metcalfe, N.; Sawangwit, U.; Irwin, M.; González-Solares, E.; Fine, S.; Drinkwater, M. J.; Croom, S.; Jurek, R. J.; Parkinson, D.; Bielby, R.

    2016-06-01

    We present a new redshift survey, the 2dF Quasar Dark Energy Survey pilot (2QDESp), which consists of ≈10 000 quasars from ≈150 deg2 of the southern sky, based on VST-ATLAS imaging and 2dF/AAOmega spectroscopy. Combining our optical photometry with the WISE (W1,W2) bands we can select essentially contamination free quasar samples with 0.8 < z < 2.5 and g < 20.5. At fainter magnitudes, optical UVX selection is still required to reach our g ≈ 22.5 limit. Using both these techniques we observed quasar redshifts at sky densities up to 90 deg-2. By comparing 2QDESp with other surveys (SDSS, 2QZ and 2SLAQ) we find that quasar clustering is approximately luminosity independent, with results for all four surveys consistent with a correlation scale of r0 = 6.1 ± 0.1 h-1 Mpc, despite their decade range in luminosity. We find a significant redshift dependence of clustering, particularly when BOSS data with r0 = 7.3 ± 0.1 h-1 Mpc are included at z ≈ 2.4. All quasars remain consistent with having a single host halo mass of ≈2 ± 1 × 1012 h-1 M⊙. This result implies that either quasars do not radiate at a fixed fraction of the Eddington luminosity or AGN black hole and dark matter halo masses are weakly correlated. No significant evidence is found to support fainter, X-ray selected quasars at low redshift having larger halo masses as predicted by the `hot halo' mode AGN model of Fanidakis et al. (2013). Finally, although the combined quasar sample reaches an effective volume as large as that of the original SDSS LRG sample, we do not detect the BAO feature in these data.

  4. INFRARED CLASSIFICATION AND LUMINOSITIES FOR DUSTY ACTIVE GALACTIC NUCLEI AND THE MOST LUMINOUS QUASARS

    SciTech Connect

    Weedman, Daniel; Sargsyan, Lusine; Houck, James; Barry, Donald; Lebouteiller, Vianney

    2012-12-20

    Mid-infrared spectroscopic measurements from the Infrared Spectrometer (IRS) on Spitzer are given for 125 hard X-ray active galactic nuclei (AGNs; 14-195 keV) from the Swift Burst Alert Telescope (BAT) sample and for 32 AGNs with black hole masses (BHMs) from reverberation mapping. The 9.7 {mu}m silicate feature in emission or absorption defines an infrared AGN classification describing whether AGNs are observed through dust clouds, indicating that 55% of the BAT AGNs are observed through dust. The mid-infrared dust continuum luminosity is shown to be an excellent indicator of intrinsic AGN luminosity, scaling closely with the hard X-ray luminosity, log {nu}L{sub {nu}}(7.8 {mu}m)/L(X) = -0.31 {+-} 0.35, and independent of classification determined from silicate emission or absorption. Dust luminosity scales closely with BHM, log {nu}L{sub {nu}}(7.8 {mu}m) = (37.2 {+-} 0.5) + 0.87 log BHM for luminosity in erg s{sup -1} and BHM in M{sub Sun }. The 100 most luminous type 1 quasars as measured in {nu}L{sub {nu}}(7.8 {mu}m) are found by comparing Sloan Digital Sky Survey (SDSS) optically discovered quasars with photometry at 22 {mu}m from the Wide-Field Infrared Survey Explorer (WISE), scaled to rest frame 7.8 {mu}m using an empirical template determined from IRS spectra. The most luminous SDSS/WISE quasars have the same maximum infrared luminosities for all 1.5 < z < 5, reaching total infrared luminosity L{sub IR} = 10{sup 14.4} L{sub Sun }. Comparing with dust-obscured galaxies from Spitzer and WISE surveys, we find no evidence of hyperluminous obscured quasars whose maximum infrared luminosities exceed the maximum infrared luminosities of optically discovered quasars. Bolometric luminosities L{sub bol} estimated from rest-frame optical or ultraviolet luminosities are compared to L{sub IR}. For the local AGN, the median log L{sub IR}/L{sub bol} = -0.35, consistent with a covering factor of 45% for the absorbing dust clouds. For the SDSS/WISE quasars, the median log L

  5. Metallicity and far-infrared luminosity of high-redshift quasars

    NASA Astrophysics Data System (ADS)

    Simon, Leah E.; Hamann, Fred

    2010-09-01

    We present the results of an exploratory study of broad-line region (BLR) metallicity in 34 2.2 <= z <= 4.6 quasars with far-infrared (FIR) luminosities (LFIR) from 1013.4 to <=1012.1 Lsolar. Quasar samples sorted by LFIR might represent an evolutionary sequence if the star formation rates (SFRs) in quasar hosts generally diminish across quasar lifetimes. We use rest-frame ultraviolet spectra from the Sloan Digital Sky Survey to construct three composite spectra sorted by LFIR, corresponding to average SFRs of 4980, 2130 and <=340 Msolar yr-1 after correcting for a nominal quasar FIR contribution. The measured NV λ1240/CIV λ1550 and SiIV λ1397+OIV] λ1402/CIV λ1550 emission line ratios indicate supersolar BLR metallicities in all three composites, with no evidence for a trend with the star formation rate. The formal derived metallicities, Z ~ 5-9Zsolar, are similar to those derived for the BLRs of other quasars at similar redshifts and luminosities. These results suggest that the ongoing star formation in the host is not responsible for the metal enrichment of the BLR gas. Instead, the BLR gas must have been enriched before the visible quasar phase. These results for high quasar metallicities, regardless of LFIR, are consistent with evolution scenarios wherein visibly bright quasars appear after the main episode(s) of star formation and metal enrichment in the host galaxies. Finally, young quasars, those more closely associated with a recent merger or a blowout of gas and dust, may exhibit tracers of these events, such as redder continuum slopes and higher incidence of narrow absorption lines. With the caveat of small sample sizes, we find no relation between LFIR and the reddening or the incidence of absorption lines.

  6. Luminosity function for galaxy clusters

    NASA Astrophysics Data System (ADS)

    Bajan, K.; Biernacka, M.; Flin, P.; Godłowski, W.; Panko, E.; Popiela, J.

    2016-10-01

    We constructed and studied the luminosity function of 6188 galaxyclusters. This was performed by counting brightness of galaxiesbelonging to clusters in the PF catalogue, taking galaxy data fromMRSS. Our result shows that the investigated structures arecharacterized by a luminosity function different from that ofoptical galaxies and radiogalaxies (Machalski & Godłowski2000). The implications of this result for theoriesof galaxy formation are briefly discussed.

  7. The Luminosity Dependence of Quasar UV Continuum Slope: Dust Extinction Scenario

    NASA Astrophysics Data System (ADS)

    Xie, Xiaoyi; Shao, Zhengyi; Shen, Shiyin; Liu, Hui; Li, Linlin

    2016-06-01

    We investigate the UV continuum slope α of a large quasar sample from SDSS DR7. By using specific continuum windows, we build two samples at lower (0.71\\lt z\\lt 1.19) and higher (1.90\\lt z\\lt 3.15) redshifts, which correspond to the continuum slopes at longer (near-UV) and shorter (far-UV) rest wavelength ranges, respectively. Overall, the average continuum slopes are -0.36 and -0.51 for {α }{{NUV}} and {α }{{FUV}} with similar dispersions {σ }α ˜ 0.5. For both samples, we confirm the luminosity dependence of the continuum slope, i.e., fainter quasars have redder spectra. We further find that both {α }{{NUV}} and {α }{{FUV}} have a common upper limit (˜ 1/3), which is almost independent of the quasar luminosity {L}{{bol}}. This finding implies that the intrinsic quasar continuum (or the bluest quasar), at any luminosity, obeys the standard thin-disk model. We propose that the other quasars with redder α are caused by the reddening from the dust locally. With this assumption, we employ the dust extinction scenario to model the observed {L}{{bol}}{--}α relation. We find that a typical value of E(B-V)˜ 0.1{--}0.3 {mag} (depending on the types of extinction curve) of the quasar local dust is enough to explain the discrepancy of α between the observation (˜ -0.5) and the standard accretion disk model prediction (˜ 1/3).

  8. The Luminosity Function of QSO Host Galaxies

    NASA Technical Reports Server (NTRS)

    Hamilton, Timothy S.; Casertano, Stefano; Turnshek, David A.; White, Nicholas E. (Technical Monitor)

    2002-01-01

    We present some results from our HST archival image study of 71 QSO host galaxies. The objects are selected to have z less than or equal to 0.46 and total absolute magnitude M(sub v) less than or equal to -23 in our adopted cosmology (H(sub 0) = 50 kilometers per second Mpc(sup-1), q(sub 0) = 0.5, lambda = 0)). The aim of this initial study is to investigate the composition of the sample with respect to host morphology and radio loudness, as well as derive the QSO host galaxy luminosity function. We have analyzed available WFPC2 images in R or I band (U in one case), using a uniform set of procedures. The host galaxies span a narrow range of luminosities and are exceptionally bright, much more so than normal galaxies, usually L greater than L*(sub v). The QSOs are almost equally divided among three subclasses: radio-loud QSOs with elliptical hosts, radio-quiet QSOs with elliptical hosts, and radio-quiet QSOs with spiral hosts. Radio-loud QSOs with spiral hosts are extremely rare. Using a weighting procedure, we derive the combined luminosity function of QSO host galaxies. We find that the luminosity function of QSO hosts differs in shape from that of normal galaxies but that they coincide at the highest luminosities. The ratio of the number of quasar hosts to the number of normal galaxies at a luminosity L*(sub v) is R = (Lv/11.48L*(sub v))(sup 2.46), where L*(sub v) corresponds to M*(sub v)= -22.35, and a QSO is defined to be an object with total nuclear plus host light M(sub v) less than or equal to -23. This ratio can be interpreted as the probability that a galaxy with luminosity L(sub V) will host a QSO at redshift z approximately equal to 0.26.

  9. Quasars.

    PubMed

    Smith, H J

    1966-11-01

    A short historical outline of the discovery and a description of observed properties of quasars introduces questions as to their nature. Some of the principal arguments concerning their reality, distance, intrinsic properties and age lead to the conclusion that, while there is room for other points of view; a strong case can be made for the interpretation, on which quasars are the most distant observable objects in the known universe. To produce such luminosities over times of thousands to millions of years requires the presence of millions of solar masses. For each quasar this enormous mass may be concentrated into a single object, in which case novel physics comes into play. Whatever the final interpretation, quasars seem certain to illuminate such questions as the origin and evolution of galaxies, perhaps also the structure and origin of the universe.

  10. The white dwarf luminosity function

    NASA Astrophysics Data System (ADS)

    García-Berro, Enrique; Oswalt, Terry D.

    2016-06-01

    White dwarfs are the final remnants of low- and intermediate-mass stars. Their evolution is essentially a cooling process that lasts for ∼ 10 Gyr. Their observed properties provide information about the history of the Galaxy, its dark matter content and a host of other interesting astrophysical problems. Examples of these include an independent determination of the past history of the local star formation rate, identification of the objects responsible for the reported microlensing events, constraints on the rate of change of the gravitational constant, and upper limits to the mass of weakly interacting massive particles. To carry on these tasks the essential observational tools are the luminosity and mass functions of white dwarfs, whereas the theoretical tools are the evolutionary sequences of white dwarf progenitors, and the corresponding white dwarf cooling sequences. In particular, the observed white dwarf luminosity function is the key manifestation of the white dwarf cooling theory, although other relevant ingredients are needed to compare theory and observations. In this review we summarize the recent attempts to empirically determine the white dwarf luminosity function for the different Galactic populations. We also discuss the biases that may affect its interpretation. Finally, we elaborate on the theoretical ingredients needed to model the white dwarf luminosity function, paying special attention to the remaining uncertainties, and we comment on some applications of the white dwarf cooling theory. Astrophysical problems for which white dwarf stars may provide useful leverage in the near future are also discussed.

  11. Dependence of the Broad Absorption Line Quasar Fraction on Radio Luminosity

    NASA Astrophysics Data System (ADS)

    Shankar, Francesco; Dai, Xinyu; Sivakoff, Gregory R.

    2008-11-01

    We find that the fraction of classical broad absorption line quasars (BALQSOs) among the FIRST radio sources in the Sloan Data Release 3, is 20.5+ 7.3-5.9% at the faintest radio powers detected (L1.4 GHz ~ 1032 erg s-1), and rapidly drops to lesssim8% at L1.4 GHz ~ 3 × 1033 erg s-1. Similarly, adopting the broader absorption index (AI) definition of Trump et al., we find the fraction of radio BALQSOs to be 44+ 8.1-7.8%, reducing to 23.1+ 7.3-6.1% at high luminosities. While the high fraction at low radio power is consistent with the recent near-IR estimates by Dai et al., the lower fraction at high radio powers is intriguing and confirms previous claims based on smaller samples. The trend is independent of the redshift range, the optical and radio flux selection limits, or the exact definition of a radio match. We also find that at fixed optical magnitude, the highest bins of radio luminosity are preferentially populated by non-BALQSOs, consistent with the overall trend. We do find, however, that those quasars identified as AI-BALQSOs but not under the classical definition do not show a significant drop in their fraction as a function of radio power, further supporting independent claims that these sources, characterized by lower equivalent width, may represent an independent class from the classical BALQSOs. We find the balnicity index, a measure of the absorption trough in BALQSOs, and the mean maximum wind velocity to be roughly constant at all radio powers. We discuss several plausible physical models which may explain the observed fast drop in the fraction of the classical BALQSOs with increasing radio power, although none is entirely satisfactory. A strictly evolutionary model for the BALQSO and radio emission phases requires a strong fine-tuning to work, while a simple geometric model, although still not capable of explaining polar BALQSOs and the paucity of FRII BALQSOs, is statistically successful in matching the data if part of the apparent radio

  12. Optical Variability of Two High-Luminosity Radio-Quiet Quasars, PDS 456 and PHL 1811

    NASA Astrophysics Data System (ADS)

    Gaskell, C. M.; Benker, A. J.; Campbell, J. S.; Crowley, K. A.; George, T. A.; Hedrick, C. H.; Hiller, M. E.; Klimek, E. S.; Leonard, J. P.; Peterson, B. W.; Sanders, K. M.

    2003-12-01

    PDS 456 and PHL 1811 are two of the highest luminosity low-redshift quasars. Both have optical luminosities comparable to 3C 273, but they have low radio luminosities. PDS 456 is a broad line object but PHL 1811 could be classified as a high-luminosity Narrow-Line Seyfert 1 (NLS1) object. We present the results of optical (V-band) continuum monitoring of PDS 456 and PHL 1811. We compare the variability properties of these two very different AGNs compared with the radio-loud AGN 3C 273, and we discuss the implications for the origin of the optical continuum variability in AGNs. This research has been supported in part by the Howard Hughes Foundation, Nebraska EPSCoR, the University of Nebraska Layman Fund, the University of Nebraska Undergraduate Creative Activities and Research Experiences, Pepsi-Cola, and the National Science Foundation through grant AST 03-07912.

  13. Ultraviolet Fe II emission in fainter quasars: luminosity dependences, and the influence of environments

    NASA Astrophysics Data System (ADS)

    Clowes, Roger G.; Haberzettl, Lutz; Raghunathan, Srinivasan; Williger, Gerard M.; Mitchell, Sophia M.; Söchting, Ilona K.; Graham, Matthew J.; Campusano, Luis E.

    2016-08-01

    We investigate the strength of ultraviolet Fe II emission in fainter quasars compared with brighter quasars for 1.0 ≤ z ≤ 1.8, using the Sloan Digital Sky Survey (SDSS) DR7QSO catalogue and spectra of Schneider et al., and the SDSS Faint Quasar Survey (SFQS) catalogue and spectra of Jiang et al. We quantify the strength of the UV Fe II emission using the W2400 equivalent width of Weymann et al., which is defined between two rest-frame continuum windows at 2240-2255 and 2665-2695 Å. The main results are the following. (1) We find that for W2400 ≳ 25 Å there is a universal (i.e. for quasars in general) strengthening of W2400 with decreasing intrinsic luminosity, L3000. (2) In conjunction with previous work by Clowes et al., we find that there is a further, differential, strengthening of W2400 with decreasing L3000 for those quasars that are members of Large Quasar Groups (LQGs). (3) We find that increasingly strong W2400 tends to be associated with decreasing full width at half maximum (FWHM) of the neighbouring Mg II λ2798 broad emission line. (4) We suggest that the dependence of W2400 on L3000 arises from Lyα fluorescence. (5) We find that stronger W2400 tends to be associated with smaller virial estimates from Shen et al. of the mass of the central black hole, by a factor of ˜2 between the ultrastrong emitters and the weak. Stronger W2400 emission would correspond to smaller black holes that are still growing. The differential effect for LQG members might then arise from preferentially younger quasars in the LQG environments.

  14. THE DEMOGRAPHICS OF BROAD-LINE QUASARS IN THE MASS-LUMINOSITY PLANE. I. TESTING FWHM-BASED VIRIAL BLACK HOLE MASSES

    SciTech Connect

    Shen Yue; Kelly, Brandon C.

    2012-02-20

    We jointly constrain the luminosity function (LF) and black hole mass function (BHMF) of broad-line quasars with forward Bayesian modeling in the quasar mass-luminosity plane, based on a homogeneous sample of {approx}58, 000 Sloan Digital Sky Survey (SDSS) Data Release 7 quasars at z {approx} 0.3-5. We take into account the selection effect of the sample flux limit; more importantly, we deal with the statistical scatter between true BH masses and FWHM-based single-epoch virial mass estimates, as well as potential luminosity-dependent biases of these mass estimates. The LF is tightly constrained in the regime sampled by SDSS and makes reasonable predictions when extrapolated to {approx}3 mag fainter. Downsizing is seen in the model LF. On the other hand, we find it difficult to constrain the BHMF to within a factor of a few at z {approx}> 0.7 (with Mg II and C IV-based virial BH masses). This is mainly driven by the unknown luminosity-dependent bias of these mass estimators and its degeneracy with other model parameters, and secondly driven by the fact that SDSS quasars only sample the tip of the active BH population at high redshift. Nevertheless, the most likely models favor a positive luminosity-dependent bias for Mg II and possibly for C IV, such that at fixed true BH mass, objects with higher-than-average luminosities have overestimated FWHM-based virial masses. There is tentative evidence that downsizing also manifests itself in the active BHMF, and the BH mass density in broad-line quasars contributes an insignificant amount to the total BH mass density at all times. Within our model uncertainties, we do not find a strong BH mass dependence of the mean Eddington ratio, but there is evidence that the mean Eddington ratio (at fixed BH mass) increases with redshift.

  15. THE BLACK HOLE MASS-GALAXY LUMINOSITY RELATIONSHIP FOR SLOAN DIGITAL SKY SURVEY QUASARS

    SciTech Connect

    Salviander, S.; Shields, G. A.; Bonning, E. W. E-mail: shields@astro.as.utexas.edu

    2015-02-01

    We investigate the relationship between the mass of the central supermassive black hole, M {sub BH}, and the host galaxy luminosity, L {sub gal}, in a sample of quasars from the Sloan Digital Sky Survey Data Release 7. We use composite quasar spectra binned by black hole mass and redshift to assess galaxy features that would otherwise be overwhelmed by noise in individual spectra. The black hole mass is calculated using the photoionization method, and the host galaxy luminosity is inferred from the depth of the Ca II H+K features in the composite spectra. We evaluate the evolution in the M {sub BH}-L {sub gal} relationship by examining the redshift dependence of Δ log M {sub BH}, the offset in M {sub BH} from the local M {sub BH}-L {sub gal} relationship. There is little systematic trend in Δ log M {sub BH} out to z = 0.8. Using the width of the [O III] emission line as a proxy for the stellar velocity dispersion, σ{sub *}, we find agreement of our derived host luminosities with the locally observed Faber-Jackson relation. This supports the utility of the width of the [O III] line as a proxy for σ{sub *} in statistical studies.

  16. Quasar Spectral Energy Distributions As A Function Of Physical Property

    NASA Astrophysics Data System (ADS)

    Townsend, Shonda; Ganguly, R.; Stark, M. A.; Derseweh, J. A.; Richmond, J. M.

    2012-05-01

    Galaxy evolution models have shown that quasars are a crucial ingredient in the evolution of massive galaxies. Outflows play a key role in the story of quasars and their host galaxies, by helping regulate the accretion process, the star-formation rate and mass of the host galaxy (i.e., feedback). The prescription for modeling outflows as a contributor to feedback requires knowledge of the outflow velocity, geometry, and column density. In particular, we need to understand how these depend on physical parameters and how much is determined stochastically (and with what distribution). In turn, models of outflows have shown particular sensitivity to the shape of the spectral energy distribution (SED), depending on the UV luminosity to transfer momentum to the gas, the X-ray luminosity to regulate how efficiently that transfer can be, etc. To investigate how SED changes with physical properties, we follow up on Richards et al. (2006), who constructed SEDs with varying luminosity. Here, we construct SEDs as a function of redshift, and physical property (black hole mass, bolometric luminosity, Eddington ratio) for volume limited samples drawn from the Sloan Digital Sky Survey, with photometry supplemented from 2MASS, WISE, GALEX, ROSAT, and Chandra. To estimate black hole masses, we adopt the scaling relations from Greene & Ho (2005) based on the H-alpha emission line FWHM. This requires redshifts less than 0.4. To construct volume-limited subsamples, we begin by adopting g=19.8 as a nominal limiting magnitude over which we are guaranteed to detect z<0.4 quasars. At redshift 0.4, we are complete down to Mg=-21.8, which yields 3300 objects from Data Release 7. At z=0.1, we are complete down to Mg=-18.5. This material is based upon work supported by the National Aeronautics and Space Administration under Grant No. 09-ADP09-0016 issued through the Astrophysics Data Analysis Program.

  17. MAD Adaptive Optics Imaging of High-luminosity Quasars: A Pilot Project

    NASA Astrophysics Data System (ADS)

    Liuzzo, E.; Falomo, R.; Paiano, S.; Treves, A.; Uslenghi, M.; Arcidiacono, C.; Baruffolo, A.; Diolaiti, E.; Farinato, J.; Lombini, M.; Moretti, A.; Ragazzoni, R.; Brast, R.; Donaldson, R.; Kolb, J.; Marchetti, E.; Tordo, S.

    2016-08-01

    We present near-IR images of five luminous quasars at z ˜ 2 and one at z ˜ 4 obtained with an experimental adaptive optics (AO) instrument at the European Southern Observatory Very Large Telescope. The observations are part of a program aimed at demonstrating the capabilities of multi-conjugated adaptive optics imaging combined with the use of natural guide stars for high spatial resolution studies on large telescopes. The observations were mostly obtained under poor seeing conditions but in two cases. In spite of these nonoptimal conditions, the resulting images of point sources have cores of FWHM ˜ 0.2 arcsec. We are able to characterize the host galaxy properties for two sources and set stringent upper limits to the galaxy luminosity for the others. We also report on the expected capabilities for investigating the host galaxies of distant quasars with AO systems coupled with future Extremely Large Telescopes. Detailed simulations show that it will be possible to characterize compact (2-3 kpc) quasar host galaxies for quasi-stellar objects at z = 2 with nucleus K-magnitude spanning from 15 to 20 (corresponding to absolute magnitude -31 to -26) and host galaxies that are 4 mag fainter than their nuclei.

  18. A high-redshift IRAS galaxy with huge luminosity - Hidden quasar or protogalaxy?

    NASA Technical Reports Server (NTRS)

    Rowan-Robinson, M.; Broadhurst, T.; Oliver, S. J.; Taylor, A. N.; Lawrence, A.; Mcmahon, R. G.; Lonsdale, C. J.; Hacking, P. B.; Conrow, T.

    1991-01-01

    An emission line galaxy with the enormous far-IR luminosity of 3 x 10 to the 14th solar has been found at z = 2.286. The spectrum is very unusual, showing lines of high excitation but with very weak Lyman-alpha emission. A self-absorbed synchrotron model for the IR energy distribution cannot be ruled out, but a thermal origin seems more plausible. A radio-quiet quasar embedded in a very dusty galaxy could account for the IR emission, as might a starburst embedded in 1-10 billion solar masses of dust. The latter case demands so much dust that the object would probably be a massive galaxy in the process of formation. The presence of a large amount of dust in an object of such high redshift implies the generation of heavy elements at an early cosmological epoch.

  19. Cosmological tests with the FSRQ gamma-ray luminosity function

    NASA Astrophysics Data System (ADS)

    Zeng, Houdun; Melia, Fulvio; Zhang, Li

    2016-11-01

    The extensive catalogue of gamma-ray selected flat-spectrum radio quasars (FSRQs) produced by Fermi during a four-year survey has generated considerable interest in determining their gamma-ray luminosity function (GLF) and its evolution with cosmic time. In this paper, we introduce the novel idea of using this extensive database to test the differential volume expansion rate predicted by two specific models, the concordance Λ cold dark matter (ΛCDM) and Rh = ct cosmologies. For this purpose, we use two well-studied formulations of the GLF, one based on pure luminosity evolution (PLE) and the other on a luminosity-dependent density evolution (LDDE). Using a Kolmogorov-Smirnov test on one-parameter cumulative distributions (in luminosity, redshift, photon index and source count), we confirm the results of earlier works showing that these data somewhat favour LDDE over PLE; we show that this is the case for both ΛCDM and Rh = ct. Regardless of which GLF one chooses, however, we also show that model selection tools very strongly favour Rh = ct over ΛCDM. We suggest that such population studies, though featuring a strong evolution in redshift, may none the less be used as a valuable independent check of other model comparisons based solely on geometric considerations.

  20. Soft X-ray spectral observations of quasars and high X-ray luminosity Seyfert galaxies

    NASA Technical Reports Server (NTRS)

    Petre, R.; Mushotzky, R. F.; Krolik, J. H.; Holt, S. S.

    1983-01-01

    Results of the analysis of 28 Einstein SSS observations of 15 high X-ray luminosity (L(x) 10 to the 435 power erg/s) quasars and Seyfert type 1 nuclei are presented. The 0.75-4.5 keV spectra are in general well fit by a simple model consisting of a power law plus absorption by cold gas. The averager spectral index alpha is 0.66 + or - .36, consistent with alpha for the spectrum of these objects above 2 keV. In all but one case, no evidence was found for intrinsic absorption, with an upper limit of 2 x 10 to the 21st power/sq cm. Neither was evidence found for partial covering of the active nucleus by dense, cold matter (N(H) 10 to the 22nd power/sq cm; the average upper limit on the partial covering fraction is 0.5. There is no obvious correlation between spectral index and 0175-4.5 keV X-ray luminosity (which ranges from 3 x 10 to the 43rd to 47th powers erg/s or with other source properties. The lack of intrinsic X-ray absorption allows us to place constraints on the density and temperature of the broad-line emission region, and narrow line emission region, and the intergalactic medium.

  1. A Compton-thick Wind in the High Luminosity Quasar, PDS 456

    NASA Technical Reports Server (NTRS)

    Reeves, J. N.; O'Brien, P. T.; Behar, E.; Miller, L.; Turner, T. J.; Braito, V.; Fabian, A. C.; Kaspi, S.; Mushotzky, R.; Ward, M.

    2009-01-01

    PDS 456 is a nearby (z=0.184), luminous (L(sub bol) approximately equal to 10(exp 47) ergs(exp -1) type I quasar. A deep 190 ks Suzaku observation in February 2007 revealed the complex, broad band X-ray spectrum of PDS 456. The Suzaku spectrum exhibits highly statistically significant absorption features near 9 keV in the quasar rest-frame. We show that the most plausible origin of the absorption is from blue-shifted resonance (1s-2p) transitions of hydrogen-like iron (at 6.97 keV in the rest frame). This indicates that a highly ionized outflow may be present moving at near relativistic velocities (0.26-0.31c). A possible hard X-ray excess is detected above 15 keV with HXD (at 99.8% confidence), which may arise from high column density gas (N(sub H) greater than 10(exp 24)cm(exp -2) partially covering the X-ray emission, or through strong Compton reflection. Here we propose that the iron K-shell absorption in PDS 456 is associated with a thick, possibly clumpy outflow, covering about 20% of 4(pi) steradian solid angle. The outflow is likely launched from the inner accretion disk, within 15-100 gravitational radii of the black hole. The kinetic power of the outflow may be similar to the bolometric luminosity of PDS 456. Such a powerful wind could have a significant effect on the co-evolution of the host galaxy and its supermassive black hole, through feedback.

  2. A direct measurement of the mean occupation function of quasars: Breaking degeneracies between halo occupation distribution models

    SciTech Connect

    Chatterjee, Suchetana; Nguyen, My L.; Myers, Adam D.; Zheng, Zheng

    2013-12-20

    Recent work on quasar clustering suggests a degeneracy in the halo occupation distribution constrained from two-point correlation functions. To break this degeneracy, we make the first empirical measurement of the mean occupation function (MOF) of quasars at z ∼ 0.2 by matching quasar positions with groups and clusters identified in the MaxBCG sample. We fit two models to the MOF, a power law and a four-parameter model. The number distribution of quasars in host halos is close to Poisson, and the slopes of the MOF obtained from our best-fit models (for the power-law case) favor an MOF that monotonically increases with halo mass. The best-fit slopes are 0.53 ± 0.04 and 1.03 ± 1.12 for the power-law model and the four-parameter model, respectively. We measure the radial distribution of quasars within dark matter halos and find it to be adequately described by a power law with a slope –2.3 ± 0.4. We measure the conditional luminosity function (CLF) of quasars and show that there is no evidence that quasar luminosity depends on host halo mass, similar to the inferences drawn from clustering measurements. We also measure the conditional black hole mass function (CMF) of our quasars. Although the results are consistent with no dependence on halo mass, we observe a slight indication of downsizing of the black hole mass function. The lack of halo mass dependence in the CLF and CMF shows that quasars residing in galaxy clusters have characteristic luminosity and black hole mass scales.

  3. Radio luminosity function of brightest cluster galaxies

    NASA Astrophysics Data System (ADS)

    Yuan, Z. S.; Han, J. L.; Wen, Z. L.

    2016-08-01

    By cross-matching the currently largest optical catalogue of galaxy clusters and the NVSS radio survey data base, we obtain a large complete sample of brightest cluster galaxies (BCGs) in the redshift range of 0.05 < z ≤ 0.45, which have radio emission and redshift information. We confirm that more powerful radio BCGs tend to be these optically very bright galaxies located in more relaxed clusters. We derived the radio luminosity functions of the largest sample of radio BCGs, and find that the functions depend on the optical luminosity of BCGs and the dynamic state of galaxy clusters. However, the radio luminosity function does not show significant evolution with redshift.

  4. STELLAR VELOCITY DISPERSION MEASUREMENTS IN HIGH-LUMINOSITY QUASAR HOSTS AND IMPLICATIONS FOR THE AGN BLACK HOLE MASS SCALE

    SciTech Connect

    Grier, C. J.; Martini, P.; Peterson, B. M.; Pogge, R. W.; Zu, Y.; Watson, L. C.; Bentz, M. C.; Dasyra, K. M.; Dietrich, M.; Ferrarese, L.

    2013-08-20

    We present new stellar velocity dispersion measurements for four luminous quasars with the Near-Infrared Integral Field Spectrometer instrument and the ALTAIR laser guide star adaptive optics system on the Gemini North 8 m telescope. Stellar velocity dispersion measurements and measurements of the supermassive black hole (BH) masses in luminous quasars are necessary to investigate the coevolution of BHs and galaxies, trace the details of accretion, and probe the nature of feedback. We find that higher-luminosity quasars with higher-mass BHs are not offset with respect to the M{sub BH}-{sigma}{sub *} relation exhibited by lower-luminosity active galactic nuclei (AGNs) with lower-mass BHs, nor do we see correlations with galaxy morphology. As part of this analysis, we have recalculated the virial products for the entire sample of reverberation-mapped AGNs and used these data to redetermine the mean virial factor (f) that places the reverberation data on the quiescent M{sub BH}-{sigma}{sub *} relation. With our updated measurements and new additions to the AGN sample, we obtain (f) = 4.31 {+-} 1.05, which is slightly lower than, but consistent with, most previous determinations.

  5. EVOLUTION OF THE Halpha LUMINOSITY FUNCTION

    SciTech Connect

    Westra, Eduard; Geller, Margaret J.; Kurtz, Michael J.; Fabricant, Daniel G.; Dell'Antonio, Ian

    2010-01-01

    The Smithsonian Hectospec Lensing Survey (SHELS) is a window on the star formation history over the last 4 Gyr. SHELS is a spectroscopically complete survey for R{sub tot} < 20.3 over 4 square{sup 0}. We use the 10k spectra to select a sample of pure star-forming galaxies based on their Halpha emission line. We use the spectroscopy to determine extinction corrections for individual galaxies and to remove active galaxies in order to reduce systematic uncertainties. We use the large volume of SHELS with the depth of a narrowband survey for Halpha galaxies at z approx 0.24 to make a combined determination of the Halpha luminosity function at z approx 0.24. The large area covered by SHELS yields a survey volume big enough to determine the bright end of the Halpha luminosity function from redshift 0.100 to 0.377 for an assumed fixed faint-end slope alpha = -1.20. The bright end evolves: the characteristic luminosity L* increases by 0.84 dex over this redshift range. Similarly, the star formation density increases by 0.11 dex. The fraction of galaxies with a close neighbor increases by a factor of 2-5 for L{sub Ha}lpha approx> L* in each of the redshift bins. We conclude that triggered star formation is an important influence for star-forming galaxies with Halpha emission.

  6. Near-infrared Spectra and Intrinsic Luminosities of Candidate Type II Quasars at 2 < z < 3.4

    NASA Astrophysics Data System (ADS)

    Greene, Jenny E.; Alexandroff, Rachael; Strauss, Michael A.; Zakamska, Nadia L.; Lang, Dustin; Liu, Guilin; Pattarakijwanich, Petchara; Hamann, Frederick; Ross, Nicholas P.; Myers, Adam D.; Brandt, W. Niel; York, Donald; Schneider, Donald P.

    2014-06-01

    We present JHK near-infrared (NIR) spectroscopy of 25 candidate Type II quasars selected from the Sloan Digital Sky Survey (SDSS), using Triplespec on the Apache Point Observatory 3.5 m telescope, the Folded-port InfraRed Echellette at the Magellan/Baade 6.5 m telescope, and the Gemini Near-Infrared Spectrograph on Gemini. At redshifts of 2 < z < 3.4, our NIR spectra probe the rest-frame optical region of these targets, which were initially selected to have strong lines of C IV and Ly α, with FWHM < 2000 km s-1 from the SDSS pipeline. We use the [O III] λ5007 line shape as a model for the narrow-line region emission and find that Hα consistently requires a broad component with FWHMs ranging from 1000 to 7500 km s-1. Interestingly, the C IV lines also require broad bases, but with considerably narrower widths of 1000-4500 km s-1. Estimating the extinction using the Balmer decrement and also the relationship in lower-z quasars between rest equivalent width and luminosity in the [O III] line, we find typical AV values of 0-2 mag, which naturally explains the attenuated C IV lines relative to Hα. We propose that our targets are moderately obscured quasars. We also describe one unusual object with three distinct velocity peaks in its [O III] spectrum.

  7. Near-infrared spectra and intrinsic luminosities of candidate type II quasars at 2 < z < 3.4

    SciTech Connect

    Greene, Jenny E.; Strauss, Michael A.; Pattarakijwanich, Petchara; Alexandroff, Rachael; Zakamska, Nadia L.; Liu, Guilin; Lang, Dustin; Hamann, Frederick; Ross, Nicholas P.; Myers, Adam D.; Brandt, W. Niel; Schneider, Donald P.; York, Donald

    2014-06-10

    We present JHK near-infrared (NIR) spectroscopy of 25 candidate Type II quasars selected from the Sloan Digital Sky Survey (SDSS), using Triplespec on the Apache Point Observatory 3.5 m telescope, the Folded-port InfraRed Echellette at the Magellan/Baade 6.5 m telescope, and the Gemini Near-Infrared Spectrograph on Gemini. At redshifts of 2 < z < 3.4, our NIR spectra probe the rest-frame optical region of these targets, which were initially selected to have strong lines of C IV and Ly α, with FWHM < 2000 km s{sup –1} from the SDSS pipeline. We use the [O III] λ5007 line shape as a model for the narrow-line region emission and find that Hα consistently requires a broad component with FWHMs ranging from 1000 to 7500 km s{sup –1}. Interestingly, the C IV lines also require broad bases, but with considerably narrower widths of 1000-4500 km s{sup –1}. Estimating the extinction using the Balmer decrement and also the relationship in lower-z quasars between rest equivalent width and luminosity in the [O III] line, we find typical A{sub V} values of 0-2 mag, which naturally explains the attenuated C IV lines relative to Hα. We propose that our targets are moderately obscured quasars. We also describe one unusual object with three distinct velocity peaks in its [O III] spectrum.

  8. Deriving Kinetic Luminosity Functions from the Low-Frequency Radio Luminosity Functions of FRII Sources

    NASA Astrophysics Data System (ADS)

    Kapinska, Anna D.; Uttley, P.; Kaiser, C. R.

    2010-03-01

    FRII radio galaxies are relatively simple systems which can be used to determine the influence of jets on their environments. Even simple analytical models of FRII evolution can link the observed lobe luminosities and sizes to fundamental properties such as jet power and density of the ambient medium; these are crucial for understanding AGN feedback. However, due to strong flux selection effects interpreting FRII samples is not straightforward. To overcome this problem we construct Monte Carlo simulations to create artificial samples of radio galaxies. We explore jet power and external density distributions by using them as the simulation input parameters. Further, we compute radio luminosity functions (RLF) and fit them to the observed low-frequency radio data that cover redshifts up to z 2, which gives us the most plausible distributions of FRIIs' fundamental properties. Moreover, based on these RLFs, we obtain the kinetic luminosity functions of these powerful sources.

  9. NLC Luminosity as a Function of Beam Parameters

    SciTech Connect

    Nosochkov, Yuri

    2002-06-06

    Realistic calculation of NLC luminosity has been performed using particle tracking in DIMAD and beam-beam simulations in GUINEA-PIG code for various values of beam emittance, energy and beta functions at the Interaction Point (IP). Results of the simulations are compared with analytic luminosity calculations. The optimum range of IP beta functions for high luminosity was identified.

  10. An improved method of constructing binned luminosity functions

    NASA Astrophysics Data System (ADS)

    Page, M. J.; Carrera, F. J.

    2000-01-01

    We show that binned differential luminosity functions constructed using the 1/Va 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/Va 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/Va 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.

  11. Galaxy luminosity functions in WINGS clusters

    NASA Astrophysics Data System (ADS)

    Moretti, A.; Bettoni, D.; Poggianti, B. M.; Fasano, G.; Varela, J.; D'Onofrio, M.; Vulcani, B.; Cava, A.; Fritz, J.; Couch, W. J.; Moles, M.; Kjærgaard, P.

    2015-09-01

    Aims: Using V band photometry of the WINGS survey, we derive galaxy luminosity functions (LF) in nearby clusters. This sample is complete down to MV = -15.15, and it is homogeneous, thus facilitating the study of an unbiased sample of clusters with different characteristics. Methods: We constructed the photometric LF for 72 out of the original 76 WINGS clusters, excluding only those without a velocity dispersion estimate. For each cluster we obtained the LF for galaxies in a region of radius = 0.5 × r200, and fitted them with single and double Schechter's functions. We also derive the composite LF for the entire sample, and those pertaining to different morphological classes. Finally, we derive the spectroscopic cumulative LF for 2009 galaxies that are cluster members. Results: The double Schechter fit parameters are correlated neither with the cluster velocity dispersion nor with the X-ray luminosity. Our median values of the Schechter's fit slope are, on average, in agreement with measurements of nearby clusters, but are less steep that those derived from large surveys, such as the SDSS. Early-type galaxies out number late-types at all magnitudes, but both early and late types contribute equally to the faint end of the LF. Finally, the spectroscopic LF is in excellent agreement with the one derived for A2199, A85 and Virgo, and with the photometric LF at the bright magnitudes (where both are available). Conclusions: There is a large spread in the LF of different clusters, however, this spread is not caused by correlation of the LF shape with cluster characteristics such as X-ray luminosity or velocity dispersions. The faint end is flatter than previously derived (αf = -1.7), which is at odds with that predicted from numerical simulations. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile. Progs. ID 67.A-0030, 68.A-0139, and 69.A-0119.Table 1 and full Fig. 1 (Fig. A.1) are available in

  12. Dusty Quasars at High Redshifts

    NASA Astrophysics Data System (ADS)

    Weedman, Daniel; Sargsyan, Lusine

    2016-09-01

    A population of quasars at z ˜ 2 is determined based on dust luminosities νL ν (7.8 μm) that includes unobscured, partially obscured, and obscured quasars. Quasars are classified by the ratio νL ν (0.25 μm)/νL ν (7.8 μm) = UV/IR, assumed to measure obscuration of UV luminosity by the dust that produces IR luminosity. Quasar counts at rest-frame 7.8 μm are determined for quasars in the Boötes field of the NOAO Deep Wide Field Survey using 24 μm sources with optical redshifts from the AGN and Galaxy Evolution Survey (AGES) or infrared redshifts from the Spitzer Infrared Spectrograph. Spectral energy distributions are extended to far-infrared wavelengths using observations from the Herschel Space Observatory Spectral and Photometric Imaging Receiver (SPIRE), and new SPIRE photometry is presented for 77 high-redshift quasars from the Sloan Digital Sky Survey. It is found that unobscured and obscured quasars have similar space densities at rest-frame 7.8 μm, but the ratio L ν (100 μm)/L ν (7.8 μm) is about three times higher for obscured quasars than for unobscured, so that far-infrared or submillimeter quasar detections are dominated by obscured quasars. We find that only ˜5% of high-redshift submillimeter sources are quasars and that existing 850 μm surveys or 2 mm surveys should already have detected sources at z ˜ 10 if quasar and starburst luminosity functions remain the same from z = 2 until z = 10.

  13. SIX MORE QUASARS AT REDSHIFT 6 DISCOVERED BY THE CANADA-FRANCE HIGH-z QUASAR SURVEY

    SciTech Connect

    Willott, Chris J.; Crampton, David; Hutchings, John B.; Schade, David; Delorme, Philippe; Delfosse, Xavier; Forveille, Thierry; Reyle, Celine; Albert, Loic; Bergeron, Jacqueline; Omont, Alain; McLure, Ross J.

    2009-03-15

    We present imaging and spectroscopic observations for six quasars at z {>=} 5.9 discovered by the Canada-France High-z Quasar Survey (CFHQS). The CFHQS contains subsurveys with a range of flux and area combinations to sample a wide range of quasar luminosities at z {approx} 6. The new quasars have luminosities 10-75 times lower than the most luminous Sloan Digital Sky Survey quasars at this redshift. The least luminous quasar, CFHQS J0216-0455 at z = 6.01, has absolute magnitude M {sub 1450} = -22.21, well below the likely break in the luminosity function. This quasar is not detected in a deep XMM-Newton survey showing that optical selection is still a very efficient tool for finding high-redshift quasars.

  14. A new sample of quasars to B = 22.0

    NASA Technical Reports Server (NTRS)

    Marano, B.; Zamorani, G.; Zitelli, V.

    1988-01-01

    A new sample of quasars with complete spectroscopic information down to about 22 mag is presented. The candidate selection and preliminary spectroscopic results are reported. Results are reported from the application of color-color diagrams, grism plates, and variability analysis in the quasar selection. The results on quasar counts, redshift distribution, and luminosity function at high redshift are discussed.

  15. a New Luminosity Function for Galaxies as Given by the Mass-Luminosity Relationship

    NASA Astrophysics Data System (ADS)

    Zaninetti, Lorenzo

    2008-04-01

    The search for a luminosity function for galaxies both alternative or companion to a Schechter function is a key problem in the reduction of data from catalogs of galaxies. Two luminosity functions for galaxies can be built starting from two distributions of mass as given by the fragmentation. A first overall distribution function is the Kiang function, which represents a useful description of the area and volume distribution of the Poisson Voronoi diagrams. The second distribution, which covers the case of low-mass galaxies, is the truncated Pareto distribution: in this model we have a natural bound due to the minimum mass/luminosity observed and an upper bound (function of the considered environment) represented by the boundary with the observed mass/luminosity overall behavior. The mass distribution is then converted into a luminosity distribution through a standard mass-luminosity relationship. The mathematical rules to convert the probability density function are used and the two new functions are normalized to the total number of galaxies per unit volume. The test of the two new luminosity functions for galaxies that cover different ranges in magnitude was made on the Sloan Digital Sky Survey (SDSS) in five different bands; the results are comparable to those of the Schechter function. A new parameter, which indicates the stellar content, is derived. The joint distribution in redshift and flux, the mean redshift and the number density connected with the first luminosity function for galaxies are obtained by analogy with the Schechter function. A new formula, which allows us to express the mass as a function of the absolute magnitude, is derived.

  16. Observations of the Ca ii IR Triplet in High Luminosity Quasars: Exploring the Sample

    NASA Astrophysics Data System (ADS)

    Martínez-Aldama, Mary Loli; Marziani, Paola; Dultzin, Deborah; Sulentic, Jack W.; Bressan, Alessandro; Chen, Yang; Stirpe, Giovanna M.

    2015-12-01

    We present a new spectroscopic sample of 11 quasars at intermediate redshift observed with the Infrared Spectrometer and Array Camera (ISAAC) on the ESO Very Large Telescope (VLT), covering O i λ8446 and the Ca ii triplet 8498, 8542, 8662. The new observations - that supplement the sample presented by Martínez-Aldama et al. (2015) - allow us to confirm the constraints on physical conditions and location of the region emitting the low ionization lines, as well as the relation between Ca ii and Fe ii.

  17. Quasar clustering in a galaxy and quasar formation model based on ultra high-resolution N-body simulations

    NASA Astrophysics Data System (ADS)

    Oogi, Taira; Enoki, Motohiro; Ishiyama, Tomoaki; Kobayashi, Masakazu A. R.; Makiya, Ryu; Nagashima, Masahiro

    2016-02-01

    We investigate clustering properties of quasars using a new version of our semi-analytic model of galaxy and quasar formation with state-of-the-art cosmological N-body simulations. In this study, we assume that a major merger of galaxies triggers cold gas accretion on to a supermassive black hole and quasar activity. Our model can reproduce the downsizing trend of the evolution of quasars. We find that the median mass of quasar host dark matter haloes increases with cosmic time by an order of magnitude from z = 4 (a few 1011 M⊙) to z = 1 (a few 1012 M⊙), and depends only weakly on the quasar luminosity. Deriving the quasar bias through the quasar-galaxy cross-correlation function in the model, we find that the quasar bias does not depend on the quasar luminosity, similar to observed trends. This result reflects the fact that quasars with a fixed luminosity have various Eddington ratios and thus have various host halo masses that primarily determine the quasar bias. We also show that the quasar bias increases with redshift, which is in qualitative agreement with observations. Our bias value is lower than the observed values at high redshifts, implying that we need some mechanisms that make quasars inactive in low-mass haloes and/or that make them more active in high-mass haloes.

  18. Study of quasar variability

    NASA Astrophysics Data System (ADS)

    Jerke, Jonathan Lee

    The Palomar-QUEST Variability Survey has been completed. This thesis has analyzed the data set with the goal of determining the variability of a large sample of quasars. We construct light curves for each individual quasar. We interpret the light curves in terms of a structure function analysis. A slope is extracted from the scaling of the structure function to measure the power law of the quasar optical variability, taking the power spectral density to behave as a power law of the frequency of variation, f-alpha. Monte carlo simulations are used to estimate the errors on the model and the final data quality. With these estimates, individual quasars are assigned a chi2 value and nearly every event has a reduced chi 2 less than 10. The first 100 light curves and structure functions with errors are shown in the Appendix. We have shown that the final distribution of power law coefficients alpha of 1944 quasars is inconsistent with a model with a simple value of alpha. Several models with different alpha are required to explain the behavior of the sample. We find that quasars are less variable on all time scales for increasing luminosity. We also find that the quasars with black hole masses below 10 8 show a lower power law then the average. This means less massive quasars are less variable at long time scales.

  19. A SIMPLE MODEL FOR QUASAR DEMOGRAPHICS

    SciTech Connect

    Conroy, Charlie; White, Martin

    2013-01-10

    We present a simple model for the relationship between quasars, galaxies, and dark matter halos from 0.5 < z < 6. In the model, black hole (BH) mass is linearly related to galaxy mass, and galaxies are connected to dark matter halos via empirically constrained relations. A simple 'scattered' light bulb model for quasars is adopted, wherein BHs shine at a fixed fraction of the Eddington luminosity during accretion episodes, and Eddington ratios are drawn from a lognormal distribution that is redshift independent. This model has two free, physically meaningful parameters at each redshift: the normalization of the M {sub BH}-M {sub gal} relation and the quasar duty cycle; these parameters are fit to the observed quasar luminosity function (LF) over the interval 0.5 < z < 6. This simple model provides an excellent fit to the LF at all epochs and also successfully predicts the observed projected two-point correlation of quasars from 0.5 < z < 2.5. It is significant that a single quasar duty cycle at each redshift is capable of reproducing the extant observations. The data are therefore consistent with a scenario wherein quasars are equally likely to exist in galaxies, and therefore dark matter halos, over a wide range in masses. The knee in the quasar LF is a reflection of the knee in the stellar-mass-halo-mass relation. Future constraints on the quasar LF and quasar clustering at high redshift will provide strong constraints on the model. In the model, the autocorrelation function of quasars becomes a strong function of luminosity only at the very highest luminosities and will be difficult to observe because such quasars are so rare. Cross-correlation techniques may provide useful constraints on the bias of such rare objects. The simplicity of the model allows for rapid generation of quasar mock catalogs from N-body simulations that match the observed LF and clustering to high redshift.

  20. SDSS J013127.34–032100.1: A NEWLY DISCOVERED RADIO-LOUD QUASAR AT z = 5.18 WITH EXTREMELY HIGH LUMINOSITY

    SciTech Connect

    Yi, Wei-Min; Bai, Jin-Ming; Zhang, Ju-jia; Wang, Fang; Wang, Jian-Guo; Fan, Yu-Feng; Chang, Liang; Wang, Chuan-Jun; Lun, Bao-Li; Wang, Feige; Wu, Xue-Bing; Yang, Jinyi; Ho, Luis C.; Zuo, Wenwen; Yang, Qian; Ai, Yanli; Fan, Xiaohui; Brandt, William N.; Kim, Minjin; Wang, Ran; and others

    2014-11-10

    Very few of the z > 5 quasars discovered to date have been radio-loud, with radio-to-optical flux ratios (radio-loudness parameters) higher than 10. Here we report the discovery of an optically luminous radio-loud quasar, SDSS J013127.34–032100.1 (J0131–0321 in short), at z = 5.18 ± 0.01 using the Lijiang 2.4 m and Magellan telescopes. J0131–0321 has a spectral energy distribution consistent with that of radio-loud quasars. With an i-band magnitude of 18.47 and a radio flux density of 33 mJy, its radio-loudness parameter is ∼100. The optical and near-infrared spectra taken by Magellan enable us to estimate its bolometric luminosity to be L {sub bol} ∼ 1.1 × 10{sup 48} erg s{sup –1}, approximately 4.5 times greater than that of the most distant quasar known to date. The black hole mass of J0131–0321 is estimated to be 2.7 × 10{sup 9} M {sub ☉}, with an uncertainty up to 0.4 dex. Detailed physical properties of this high-redshift, radio-loud, potentially super-Eddington quasar can be probed in the future with more dedicated and intensive follow-up observations using multi-wavelength facilities.

  1. SDSS J013127.34-032100.1: A Newly Discovered Radio-loud Quasar at z = 5.18 with Extremely High Luminosity

    NASA Astrophysics Data System (ADS)

    Yi, Wei-Min; Wang, Feige; Wu, Xue-Bing; Yang, Jinyi; Bai, Jin-Ming; Fan, Xiaohui; Brandt, William N.; Ho, Luis C.; Zuo, Wenwen; Kim, Minjin; Wang, Ran; Yang, Qian; Zhang, Ju-jia; Wang, Fang; Wang, Jian-Guo; Ai, Yanli; Fan, Yu-Feng; Chang, Liang; Wang, Chuan-Jun; Lun, Bao-Li; Xin, Yu-Xin

    2014-11-01

    Very few of the z > 5 quasars discovered to date have been radio-loud, with radio-to-optical flux ratios (radio-loudness parameters) higher than 10. Here we report the discovery of an optically luminous radio-loud quasar, SDSS J013127.34-032100.1 (J0131-0321 in short), at z = 5.18 ± 0.01 using the Lijiang 2.4 m and Magellan telescopes. J0131-0321 has a spectral energy distribution consistent with that of radio-loud quasars. With an i-band magnitude of 18.47 and a radio flux density of 33 mJy, its radio-loudness parameter is ~100. The optical and near-infrared spectra taken by Magellan enable us to estimate its bolometric luminosity to be L bol ~ 1.1 × 1048 erg s-1, approximately 4.5 times greater than that of the most distant quasar known to date. The black hole mass of J0131-0321 is estimated to be 2.7 × 109 M ⊙, with an uncertainty up to 0.4 dex. Detailed physical properties of this high-redshift, radio-loud, potentially super-Eddington quasar can be probed in the future with more dedicated and intensive follow-up observations using multi-wavelength facilities.

  2. The width of the gamma-ray burst luminosity function

    NASA Technical Reports Server (NTRS)

    Ulmer, Andrew; Wijers, Ralph A. M. J.

    1995-01-01

    We examine the width of the gamma-ray burst (GRB) luminosity function through the distribution of GRB peak count rates, C(sub peak), as detected by Burst and Transient Source Experiment (BATSE) (1993). In the context of Galactic corona spatial distribution models, we attempt to place constaints on the characteristic width of the luminosity function by comparing the observed intensity distribution with those produced by a range of density and luminosity functions. We find that the intrinsic width of the luminosity function cannot be very well restricted. However, the distribution of intrinsic luminosities of detected bursts can be limited: we find that most observed bursts have luminosities that are in a range of one to two decades, but a significant population of undetected less luminous bursts cannot be excluded. These findings demonstrate that the assumption that GRB are standard candles is sufficient but not necessary to explain the observed intensity distribution. We show that the main reason for the relatively poor constraints is the fact that the bright-end part of the GRB flux distribution is not yet sampled by BATSE, and better sampling in the future may lead to significantly stronger constraints on the width of the luminosity function.

  3. COMPARING SYMBIOTIC NEBULAE AND PLANETARY NEBULAE LUMINOSITY FUNCTIONS

    SciTech Connect

    Frankowski, Adam; Soker, Noam E-mail: soker@physics.technion.ac.i

    2009-10-01

    We compare the observed symbiotic nebulae (SyN) luminosity function (SyNLF) in the [O III] lambda5007 A line to the planetary nebulae (PN) luminosity function (PNLF) and find that the intrinsic SyNLF (ISyNLF) of galactic SyNs has-within its uncertainty of 0.5-0.8 mag-very similar cutoff luminosity and general shape to those of the PNLF. The [O III]/(Halpha+[N II]) line ratios of SyNs and PNs are shown to be also related. Possible implications of these results for the universality of the PNLF are briefly outlined.

  4. Luminosity function and jet structure of Gamma-Ray Burst

    NASA Astrophysics Data System (ADS)

    Pescalli, A.; Ghirlanda, G.; Salafia, O. S.; Ghisellini, G.; Nappo, F.; Salvaterra, R.

    2015-02-01

    The structure of gamma-ray burst (GRB) jets impacts on their prompt and afterglow emission properties. The jet of GRBs could be uniform, with constant energy per unit solid angle within the jet aperture, or it could be structured, namely with energy and velocity that depend on the angular distance from the axis of the jet. We try to get some insight about the still unknown structure of GRBs by studying their luminosity function. We show that low (1046-48 erg s-1) and high (i.e. with L ≥ 1050 erg s-1) luminosity GRBs can be described by a unique luminosity function, which is also consistent with current lower limits in the intermediate luminosity range (1048-50 erg s-1). We derive analytical expressions for the luminosity function of GRBs in uniform and structured jet models and compare them with the data. Uniform jets can reproduce the entire luminosity function with reasonable values of the free parameters. A structured jet can also fit adequately the current data, provided that the energy within the jet is relatively strongly structured, i.e. E ∝ θ-k with k ≥ 4. The classical E ∝ θ-2 structured jet model is excluded by the current data.

  5. A Mixture Evolution Scenario of the AGN Radio Luminosity Function

    NASA Astrophysics Data System (ADS)

    Yuan, Zunli; Wang, Jiancheng; Zhou, Ming; Mao, Jirong

    2016-03-01

    We propose a mixture evolution scenario to model the evolution of the radio luminosity function (RLF) of steep-spectrum AGNs (active galactic nuclei), based on a Bayesian method. In this scenario, the shape of the RLF is determined by both the density and luminosity evolution. Our models indicate that the density evolution is positive until a redshift of ∼ 0.9, at which point it becomes negative, while the luminosity evolution is positive to a higher redshift (z∼ 5 for model B and z∼ 3.5 for model C), where it becomes negative. Our mixture evolution model works well, and the modeled RLFs are in good agreement with previous determinations. The mixture evolution scenario can naturally explain the luminosity-dependent evolution of the RLFs.

  6. Luminosity functions for very low mass stars and brown dwarfs

    NASA Technical Reports Server (NTRS)

    Laughlin, Gregory; Bodenheimer, Peter

    1993-01-01

    A theoretical investigation of the luminosity function for low-mass objects to constrain the stellar initial mass function at the low-mass end is reported. The ways in which luminosity functions for low-mass stars are affected by star formation histories, brown dwarf and premain-sequence cooling rates and main-sequence mass luminosity relations, and the IMF are examined. Cooling rates and the mass-luminosity relation are determined through a new series of evolutionary calculations for very low mass stars and brown dwarfs in the range 0.05-0.50 solar mass. Model luminosity functions are constructed for specific comparison with the results of four recent observational surveys. The likelihood that the stellar mass function in the solar neighborhood is increasing at masses near the bottom of the main sequence and perhaps at lower masses is confirmed. In the most optimistic case, brown dwarfs contribute half of the local missing disk mass. The actual contribution is likely to be considerably less.

  7. The galaxy luminosity function and the Local Hole

    NASA Astrophysics Data System (ADS)

    Whitbourn, J. R.; Shanks, T.

    2016-06-01

    In a previous study Whitbourn & Shanks have reported evidence for a local void underdense by ≈15 per cent extending to 150-300 h-1 Mpc around our position in the Southern Galactic Cap (SGC). Assuming a local luminosity function they modelled K- and r-limited number counts and redshift distributions in the 6dFGS/2MASS and SDSS redshift surveys and derived normalized n(z) ratios relative to the standard homogeneous cosmological model. Here we test further these results using maximum likelihood techniques that solve for the galaxy density distributions and the galaxy luminosity function simultaneously. We confirm the results from the previous analysis in terms of the number density distributions, indicating that our detection of the `Local Hole' in the SGC is robust to the assumption of either our previous, or newly estimated, luminosity functions. However, there are discrepancies with previously published K- and r-band luminosity functions. In particular the r-band luminosity function has a steeper faint end slope than the r0.1 results of Blanton et al. but is consistent with the r0.1 results of Montero-Dorta & Prada and Loveday et al.

  8. MAGNITUDE GAP STATISTICS AND THE CONDITIONAL LUMINOSITY FUNCTION

    SciTech Connect

    More, Surhud

    2012-12-20

    In a recent preprint, Hearin et al. (H12) suggest that the halo mass-richness calibration of clusters can be improved by using the difference in the magnitude of the brightest and the second brightest galaxy (magnitude gap) as an additional observable. They claim that their results are at odds with the results from Paranjape and Sheth (PS12) who show that the magnitude distribution of the brightest and second brightest galaxies can be explained based on order statistics of luminosities randomly sampled from the total galaxy luminosity function. We find that a conditional luminosity function (CLF) for galaxies which varies with halo mass, in a manner which is consistent with existing observations, naturally leads to a magnitude gap distribution which changes as a function of halo mass at fixed richness, in qualitative agreement with H12. We show that, in general, the luminosity distribution of the brightest and the second brightest galaxy depends upon whether the luminosities of galaxies are drawn from the CLF or the global luminosity function. However, we also show that the difference between the two cases is small enough to evade detection in the small sample investigated by PS12. This shows that the luminosity distribution is not the appropriate statistic to distinguish between the two cases, given the small sample size. We argue in favor of the CLF (and therefore H12) based upon its consistency with other independent observations, such as the kinematics of satellite galaxies, the abundance and clustering of galaxies, and the galaxy-galaxy lensing signal from the Sloan Digital Sky Survey.

  9. 1. 4 gigahertz luminosity function and its evolution

    SciTech Connect

    Condon, J. J.

    1989-03-01

    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 and declinations and (2) galaxies of all morphologies with blue angular diameters of 1.0 arcmin or greater in the declination range between -2.5 deg and +82 deg. Separate luminosity functions for the radio source populations powered by 'starbursts' and 'monsters' were obtained from the latter sample. The amount of evolution required for the local luminosity function to account for the faint sources is discussed. The cosmological evolution of extragalactic radio sources appears to be so strong at all observed luminosities that the local luminosity function and counts of all sources between S of roughly 10 micro-Jy and S of roughly 10 Jy at v = 1.4 GHz can be matched with a model in which most sources are confined to a hollow shell with z of roughly 0.8. 36 refs.

  10. Luminosity Function of Faint Globular Clusters in M87

    SciTech Connect

    Waters, Christopher Z.; Zepf, Stephen E.; Lauer, Tod R.; Baltz, Edward A.; Silk, Joseph; /Oxford U.

    2006-07-14

    We present the luminosity function to very faint magnitudes for the globular clusters in M87, based on a 30 orbit Hubble Space Telescope (HST) WFPC2 imaging program. The very deep images and corresponding improved false source rejection allow us to probe the mass function further beyond the turnover than has been done before. We compare our luminosity function to those that have been observed in the past, and confirm the similarity of the turnover luminosity between M87 and the Milky Way. We also find with high statistical significance that the M87 luminosity function is broader than that of the Milky Way. We discuss how determining the mass function of the cluster system to low masses can constrain theoretical models of the dynamical evolution of globular cluster systems. Our mass function is consistent with the dependence of mass loss on the initial cluster mass given by classical evaporation, and somewhat inconsistent with newer proposals that have a shallower mass dependence. In addition, the rate of mass loss is consistent with standard evaporation models, and not with the much higher rates proposed by some recent studies of very young cluster systems. We also find that the mass-size relation has very little slope, indicating that there is almost no increase in the size of a cluster with increasing mass.

  11. The Gamma-Ray Luminosity Function of Radio Pulsars

    NASA Technical Reports Server (NTRS)

    Helfand, David J.

    1998-01-01

    This final report is a study of gamma-ray luminosity function of radio pulsars. The goal is to constrain certain parameters in order to address such diverse issues as the high energy emission mechanism in pulsars and the fraction of the Galaxy's gamma ray emission attributable to these objects.

  12. The Radio Luminosity Function and Galaxy Evolution of Abell 2256

    NASA Astrophysics Data System (ADS)

    Forootaninia, Zahra

    2015-05-01

    This thesis presents a study of the radio luminosity function and the evolution of galaxies in the Abell 2256 cluster (z=0.058, richness class 2). Using the NED database and VLA deep data with an rms sensitivity of 18 mu Jy.beam--1, we identified 257 optical galaxies as members of A2256, of which 83 are radio galaxies. Since A2256 is undergoing a cluster-cluster merger, it is a good candidate to study the radio activity of galaxies in the cluster. We calculated the Univariate and Bivariate radio luminosity functions for A2256, and compared the results to studies on other clusters. We also used the SDSS parameter fracDev to roughly classify galaxies as spirals and ellipticals, and investigated the distribution and structure of galaxies in the cluster. We found that most of the radio galaxies in A2256 are faint, and are distributed towards the outskirts of the cluster. On the other hand, almost all very bright radio galaxies are ellipticals which are located at the center of the cluster. We also found there is an excess in the number of radio spiral galaxies in A2256 compared to the number of radio ellipticals, counting down to a radio luminosity of log(luminosity)=20.135 W/Hz..

  13. QUASAR-GALAXY CLUSTERING THROUGH PROJECTED GALAXY COUNTS AT z = 0.6-1.2

    SciTech Connect

    Zhang Shaohua; Zhou Hongyan; Wang Tinggui; Wang Huiyuan E-mail: twang@ustc.edu.cn

    2013-08-20

    We investigate the spatial clustering of galaxies around quasars at z = 0.6-1.2 using photometric data from Sloan Digital Sky Survey Stripe 82. The quasar and galaxy cross-correlation functions are measured through the projected galaxy number density n(r{sub p} ) on scales of 0.05 < r{sub p} < 20 h {sup -1} Mpc around quasars for a sample of 2300 quasars from Schneider et al. We detect strong clustering signals at all redshifts and find that the clustering amplitude increases significantly with redshift. We examine the dependence of quasar-galaxy clustering on quasar and galaxy properties and find that the clustering amplitude is significantly larger for quasars with more massive black holes or with bluer colors, while there is no dependence on quasar luminosity. We also show that quasars have a stronger correlation amplitude with blue galaxies than with red galaxies. We finally discuss the implications of our findings.

  14. Physical Evolution of Quasars

    NASA Astrophysics Data System (ADS)

    Kuhn, Olga Patricia

    1996-01-01

    The evolution of the quasar luminosity function is well described by pure luminosity evolution (PLE), in which the statistical luminosity, L^*(z), declines by a factor of ~100 from z = 3 to z sim 0.1 (Boyle et al. 1988a). If PLE is produced by the gradual dimming of a single generation of long-lived quasars, then the emitted continua of high redshift, younger, quasars are expected to differ from those of their low redshift, older, counterparts. This thesis aims to test this interpretation of PLE via a statistical comparison between the continua of sets of high and low redshift quasars which match in evolved luminosity, having similar L/L^ *(z).. Rest-frame ~ 1200A-5500A spectral energy distributions were constructed for 15 high redshift quasars and compared to those of 27 z sim 0.1 quasars (Elvis et al. 1994a). Optical/UV spectral indices, alpha (F_ nu ~nu^alpha), were determined by fitting single power laws through narrow (Deltalambda/lambda < 2%) continuum bands at 1285A, 1460A, 4200A, 4650A and 5100A. The mean spectral indices are -0.38 +/- 0.07 for the low and -0.32 +/- 0.07 for the high redshift samples. No significant evolution is found in the optical/UV continuum shapes. K-S tests give probabilities < 4% that the distributions of alpha for the high and low redshift samples differ. There is a significant range in continuum shapes within the low (alpha = -1.2 to +0.5) and high (alpha = { -}0.75 to +0.2) redshift samples. The spread is real, being about 20 times greater than the typical errors, sim 0.01 - 0.08. The distributions of spectral indices that result from fits using a power law plus SMC reddening model are not consistent with the hypothesis that the range is produced by intrinsic extinction. The predicted spectra from non-steady accretion disks, as would result from temperature redistribution due to irradiation or unstable mass accretion, can explain values of alpha from 1/3 down to at least - 1, and may account for the full range. The strengths of

  15. Clustering, Cosmology and a New Era of Black Hole Demographics - I. The Conditional Luminosity Function of Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Ballantyne, D. R.

    2016-09-01

    Deep X-ray surveys have provided a comprehensive and largely unbiased view of active galactic nuclei (AGN) evolution stretching back to z ˜ 5. However, it has been challenging to use the survey results to connect this evolution to the cosmological environment that AGNs inhabit. Exploring this connection will be crucial to understanding the triggering mechanisms of AGNs and how these processes manifest in observations at all wavelengths. In anticipation of upcoming wide-field X-ray surveys that will allow quantitative analysis of AGN environments, this paper presents a method to observationally constrain the Conditional Luminosity Function (CLF) of AGNs at a specific z. Once measured, the CLF allows the calculation of the AGN bias, mean dark matter halo mass, AGN lifetime, halo occupation number, and AGN correlation function - all as a function of luminosity. The CLF can be constrained using a measurement of the X-ray luminosity function and the correlation length at different luminosities. The method is illustrated at z ≈ 0 and 0.9 using the limited data that is currently available, and a clear luminosity dependence in the AGN bias and mean halo mass is predicted at both z, supporting the idea that there are at least two different modes of AGN triggering. In addition, the CLF predicts that z ≈ 0.9 quasars may be commonly hosted by haloes with Mh ˜ 1014 M⊙. These `young cluster' environments may provide the necessary interactions between gas-rich galaxies to fuel luminous accretion. The results derived from this method will be useful to populate AGNs of different luminosities in cosmological simulations.

  16. LUMINOUS SATELLITES. II. SPATIAL DISTRIBUTION, LUMINOSITY FUNCTION, AND COSMIC EVOLUTION

    SciTech Connect

    Nierenberg, A. M.; Treu, T.; Auger, M. W.; Marshall, P. J.; Fassnacht, C. D.; Busha, Michael T.

    2012-06-20

    We infer the normalization and the radial and angular distributions of the number density of satellites of massive galaxies (log{sub 10}[M*{sub h}/M{sub Sun }] > 10.5) between redshifts 0.1 and 0.8 as a function of host stellar mass, redshift, morphology, and satellite luminosity. Exploiting the depth and resolution of the COSMOS Hubble Space Telescope images, we detect satellites up to 8 mag fainter than the host galaxies and as close as 0.3 (1.4) arcsec (kpc). Describing the number density profile of satellite galaxies to be a projected power law such that P(R){proportional_to}R{sup {gamma}{sub p}}, we find {gamma}{sub p} = -1.1 {+-} 0.3. We find no dependency of {gamma}{sub p} on host stellar mass, redshift, morphology, or satellite luminosity. Satellites of early-type hosts have angular distributions that are more flattened than the host light profile and are aligned with its major axis. No significant average alignment is detected for satellites of late-type hosts. The number of satellites within a fixed magnitude contrast from a host galaxy is dependent on its stellar mass, with more massive galaxies hosting significantly more satellites. Furthermore, high-mass late-type hosts have significantly fewer satellites than early-type galaxies of the same stellar mass, possibly indicating that they reside in more massive halos. No significant evolution in the number of satellites per host is detected. The cumulative luminosity function of satellites is qualitatively in good agreement with that predicted using SubHalo Abundance Matching techniques. However, there are significant residual discrepancies in the absolute normalization, suggesting that properties other than the host galaxy luminosity or stellar mass determine the number of satellites.

  17. Low-luminosity stellar mass functions in globular clusters

    SciTech Connect

    Richer, H.B.; Fahlman, G.G.; Buonanno, R.; Fusi Pecci, F. Roma Osservatorio Astronomico, Rome Bologna Universita )

    1990-08-01

    New data are presented on cluster luminosity functions and mass functions for selected fields in the globular clusters M13 and M71, extending down the main sequence to at least 0.2 solar mass. In this experiment, CCD photometry data were obtained at the prime focus of the CFHT on the cluster fields that were far from the cluster center. Luminosity functions were constructed, using the ADDSTAR routine to correct for the background, and mass functions were derived using the available models. The mass functions obtained for M13 and M71 were compared to existing data for NGC 6397. Results show that (1) all three globular clusters display a marked change in slope at about 0.4 solar mass, with the slopes becoming considerably steeper toward lower masses; (2) there is no correlation between the slope of the mass function and metallicity; and (3) the low-mass slope of the mass function for M13 is much steeper than for NGC 6397 and M71. 22 refs.

  18. The deep luminosity function of the globular cluster M30

    NASA Technical Reports Server (NTRS)

    Piotto, Giampaolo; King, Ivan R.; Capaccioli, Massimo; Ortolani, Sergio; Djorgovski, S.

    1990-01-01

    An effort is made to determine the mass function in low-metallicity, postcore-collapse globular cluster M30, as well as to analyze its radial trend, using new deep CCD photometry. It is confirmed that oxygen-enhanced isochrones yield a good representation of the color-magnitude diagrams. Luminosity functions are constructed and corrected for for field-object contamination and incompleteness. The data presented agree with the power-law trend ascertained by Pryor et al. (1986) for a multimass King-Michie model, yielding a global slope of 0.7.

  19. The deep luminosity function of the globular cluster M30

    SciTech Connect

    Piotto, G.; King, I.R.; Capaccioli, M.; Ortolani, S.; Djorgovski, S. California Univ., Berkeley Osservatorio Astronomico, Padua California Institute of Technology, Pasadena )

    1990-02-01

    An effort is made to determine the mass function in low-metallicity, postcore-collapse globular cluster M30, as well as to analyze its radial trend, using new deep CCD photometry. It is confirmed that oxygen-enhanced isochrones yield a good representation of the color-magnitude diagrams. Luminosity functions are constructed and corrected for for field-object contamination and incompleteness. The data presented agree with the power-law trend ascertained by Pryor et al. (1986) for a multimass King-Michie model, yielding a global slope of 0.7. 29 refs.

  20. The deep luminosity function of the globular cluster M30

    NASA Astrophysics Data System (ADS)

    Piotto, Giampaolo; King, Ivan R.; Capaccioli, Massimo; Ortolani, Sergio; Djorgovski, S.

    1990-02-01

    An effort is made to determine the mass function in low-metallicity, postcore-collapse globular cluster M30, as well as to analyze its radial trend, using new deep CCD photometry. It is confirmed that oxygen-enhanced isochrones yield a good representation of the color-magnitude diagrams. Luminosity functions are constructed and corrected for for field-object contamination and incompleteness. The data presented agree with the power-law trend ascertained by Pryor et al. (1986) for a multimass King-Michie model, yielding a global slope of 0.7.

  1. Applying the luminosity function statistics in the fireshell model

    NASA Astrophysics Data System (ADS)

    Rangel Lemos, L. J.; Bianco, C. L.; Ruffini, R.

    2015-12-01

    The luminosity function (LF) statistics applied to the data of BATSE, GBM/Fermi and BAT/Swift is the theme approached in this work. The LF is a strong statistical tool to extract useful information from astrophysical samples, and the key point of this statistical analysis is in the detector sensitivity, where we have performed careful analysis. We applied the tool of the LF statistics to three GRB classes predicted by the Fireshell model. We produced, by LF statistics, predicted distributions of: peak ux N(Fph pk), redshift N(z) and peak luminosity N(Lpk) for the three GRB classes predicted by Fireshell model; we also used three GRB rates. We looked for differences among the distributions, and in fact we found. We performed a comparison between the distributions predicted and observed (with and without redshifts), where we had to build a list with 217 GRBs with known redshifts. Our goal is transform the GRBs in a standard candle, where a alternative is find a correlation between the isotropic luminosity and the Band peak spectral energy (Liso - Epk).

  2. Quasar populations in a cosmological constant-dominated flat universe

    NASA Technical Reports Server (NTRS)

    Malhotra, Sangeeta; Turner, Edwin L.

    1995-01-01

    Most physical properties derived for quasars, as single entities or as a population, depend upon the cosmology assumed. In this paper, we calculate the quasar luminosity function and some related quantities for a flat universe dominated by a cosmological constant Lambda (Lambda = 0.9, Omega = 0.1) and compare them with those deduced for a flat universe with zero cosmological constant (Lambda = 0, Omega = 1). We use the ATT quasar survey data (Boyle et al. 1990) as input in both cases. The data are fitted well by a pure luminosity evolution model for both the cosmologies but with different evolutionary parameters. From the luminosity function, we predict (extrapolate) a greater number of quasars at faint apparent magnitudes (twice the number at B = 24, z is less than 2.2) for the Lambda-dominated universe. This population of faint quasars at high redshift would result in a higher incidence of gravitational lensing. The total luminosity of the quasar population and the total mass tied up in black hole remnants of quasars is not sensitive to the cosmology. However, for a Lambda cosmology, this mass is tied up in fewer but more massive black holes.

  3. Feedback from AGN: The Kinetic/Radio Luminosity Function

    NASA Astrophysics Data System (ADS)

    Melini, Gabriele; La Franca, Fabio; Fiore, Fabrizio

    2010-05-01

    We have measured the probability distribution function of the ratio RX = log L1.4/LX, where L1.4/LX = ν Lν(1.4 GHz)/LX(2-10 keV), between the 1.4 GHz and the unabsorbed 2-10 keV luminosities and its dependence on LX and z. We have used a complete sample of ~1800 hard X-ray selected AGN, observed in the 1.4 GHz band, cross-correlated in order to exclude FR II-type objects, and thus obtain a contemporaneous measure of the radio and X-ray emission. The distribution P(RX|LX,z) is shown in Figure 1. Convolution of the distribution P(RX|LX,z) with the 2-10 keV X-ray AGN luminosity function from La Franca et al. (2005) and the relations between radio power and kinetic energy from Best et al. (2006) and Willott et al. (1999) allows us to derive the AGN kinetic power and its evolution. As shown in Figure 1, our results are in good agreement with the predictions of the most recent models of galaxy formation and evolution (e.g., Croton et al. 2006), where AGN radio feedback is required to quench the star formation.

  4. Maximum likelihood random galaxy catalogues and luminosity function estimation

    NASA Astrophysics Data System (ADS)

    Cole, Shaun

    2011-09-01

    We present a new algorithm to generate a random (unclustered) version of an magnitude limited observational galaxy redshift catalogue. It takes into account both galaxy evolution and the perturbing effects of large-scale structure. The key to the algorithm is a maximum likelihood (ML) method for jointly estimating both the luminosity function (LF) and the overdensity as a function of redshift. The random catalogue algorithm then works by cloning each galaxy in the original catalogue, with the number of clones determined by the ML solution. Each of these cloned galaxies is then assigned a random redshift uniformly distributed over the accessible survey volume, taking account of the survey magnitude limit(s) and, optionally, both luminosity and number density evolution. The resulting random catalogues, which can be employed in traditional estimates of galaxy clustering, make fuller use of the information available in the original catalogue and hence are superior to simply fitting a functional form to the observed redshift distribution. They are particularly well suited to studies of the dependence of galaxy clustering on galaxy properties as each galaxy in the random catalogue has the same list of attributes as measured for the galaxies in the genuine catalogue. The derivation of the joint overdensity and LF estimator reveals the limit in which the ML estimate reduces to the standard 1/Vmax LF estimate, namely when one makes the prior assumption that the are no fluctuations in the radial overdensity. The new ML estimator can be viewed as a generalization of the 1/Vmax estimate in which Vmax is replaced by a density corrected Vdc, max.

  5. MEASURING THE LUMINOSITY AND VIRIAL BLACK HOLE MASS DEPENDENCE OF QUASAR–GALAXY CLUSTERING AT z ∼ 0.8

    SciTech Connect

    Krolewski, Alex G.; Eisenstein, Daniel J.

    2015-04-10

    We study the dependence of quasar clustering on quasar luminosity and black hole mass by measuring the angular overdensity of photometrically selected galaxies imaged by the Wide-field Infrared Survey Explorer (WISE) about z ∼ 0.8 quasars from SDSS. By measuring the quasar–galaxy cross-correlation function and using photometrically selected galaxies, we achieve a higher density of tracer objects and a more sensitive detection of clustering than measurements of the quasar autocorrelation function. We test models of quasar formation and evolution by measuring the luminosity dependence of clustering amplitude. We find a significant overdensity of WISE galaxies about z ∼ 0.8 quasars at 0.2–6.4 h{sup −1} Mpc in projected comoving separation. We find no appreciable increase in clustering amplitude with quasar luminosity across a decade in luminosity, and a power-law fit between luminosity and clustering amplitude gives an exponent of −0.01 ± 0.06 (1 σ error). We also fail to find a significant relationship between clustering amplitude and black hole mass, although our dynamic range in true mass is suppressed due to the large uncertainties in virial black hole mass estimates. Our results indicate that a small range in host dark matter halo mass maps to a large range in quasar luminosity.

  6. Tracing galaxy evolution by their present-day luminosity function

    NASA Astrophysics Data System (ADS)

    Tempel, Elmo

    2011-04-01

    Galaxies, which are complex objects containing up to several tens of billions stars, as well as gas and dust, are remarkable objects. The Universe contains a very diverse "zoo" of galaxies: there are galaxies with a discy shape and spiral structure, elliptical galaxies, and even galaxies, which show no sign of structure. This variety of galaxies leads to the basic question: how the galaxies form and evolve and which processes shape the structure of galaxies? Due to the complexity of galaxy formation and evolution, this question is still an unresolved puzzle and it is one of the biggest challenges in modern cosmology. The present thesis is based on large galaxy surveys and concentrates on the large-scale structure: how galaxy evolution is related to the surrounding large-scale environment of superclusters and voids. To study the evolution of galaxies, we use the luminosity function, which is in this respect one of the most fundamental of all cosmological observables. One of the principal results of the present study was the conclusion that the evolution of spiral galaxies is almost independent of the global environment, especially for blue and red spirals separately, showing that the formation of spiral galaxies has to be similar in all environments. Meanwhile, the luminosity function of elliptical galaxies depends strongly on the environment. This shows that the global environmental density is an important factor (via merging history) in the formation of elliptical galaxies. The results of the present study show clearly, that besides the local/group environment, the global (supercluster-void) environment plays also an important role in the formation and evolution of galaxies. Accounting for the role of global environment can help to solve several problems in the present picture of galaxy formation and evolution.

  7. The Galaxy UV Luminosity Function before the Epoch of Reionization

    NASA Astrophysics Data System (ADS)

    Mason, Charlotte A.; Trenti, Michele; Treu, Tommaso

    2015-11-01

    We present a model for the evolution of the galaxy ultraviolet (UV) luminosity function (LF) across cosmic time where star formation is linked to the assembly of dark matter halos under the assumption of a mass-dependent, but redshift-independent, efficiency. We introduce a new self-consistent treatment of the halo star formation history, which allows us to make predictions at z > 10 (lookback time ≲500 Myr), when growth is rapid. With a calibration at a single redshift to set the stellar-to-halo mass ratio, and no further degrees of freedom, our model captures the evolution of the UV LF over all available observations (0 ≲ z ≲ 10). The significant drop in luminosity density of currently detectable galaxies beyond z ˜ 8 is explained by a shift of star formation toward less massive, fainter galaxies. Assuming that star formation proceeds down to atomic cooling halos, we derive a reionization optical depth τ ={0.056}-0.010+0.007, fully consistent with the latest Planck measurement, implying that the universe is fully reionized at z={7.84}-0.98+0.65. In addition, our model naturally produces smoothly rising star formation histories for galaxies with L ≲ L* in agreement with observations and hydrodynamical simulations. Before the epoch of reionization at z > 10 we predict the LF to remain well-described by a Schechter function, but with an increasingly steep faint-end slope (α ˜ -3.5 at z ˜ 16). Finally, we construct forecasts for surveys with James Webb Space Telescope (JWST) and Wide-field Infrared Survey Telescope (WFIRST) and predict that galaxies out to z ˜ 14 will be observed. Galaxies at z > 15 will likely be accessible to JWST and WFIRST only through the assistance of strong lensing magnification.

  8. Deep luminosity function of the globular cluster M13

    SciTech Connect

    Drukier, G.A.; Fahlman, G.G.; Richter, H.B.; Vandenberg, D.A.

    1988-05-01

    The luminosity function in a field of M13 at 14 core radii has been observed to M(V) = +12.0, and new theoretical, low-mass, stellar models appropriate to M13 are used to convert the function to a mass function which extends to M = 0.18 solar, within a factor of two of brown dwarf masses at this metal abundance. As the number of stars observed in each magnitude bin is still increasing at the limit of the data, the presence of stars with masses lower than 0.18 solar is probable. This result sets an upper limit of 0.18 solar mass for low-mass cutoffs in dynamical models of M13. No single power law mass function fits all the observations. The trend of the data supports the idea of a steep increase in the slope of the mass function for M less than 0.4 solar. The results imply that the total mass in low-mass stars in M13, and by implication elsewhere, is higher than was previously thought. 26 references.

  9. Helium Reionization Simulations. I. Modeling Quasars as Radiation Sources

    NASA Astrophysics Data System (ADS)

    La Plante, Paul; Trac, Hy

    2016-09-01

    We introduce a new project to understand helium reionization using fully coupled N-body, hydrodynamics, and radiative transfer simulations. This project aims to capture correctly the thermal history of the intergalactic medium as a result of reionization and make predictions about the Lyα forest and baryon temperature-density relation. The dominant sources of radiation for this transition are quasars, so modeling the source population accurately is very important for making reliable predictions. In this first paper, we present a new method for populating dark matter halos with quasars. Our set of quasar models includes two different light curves, a lightbulb (simple on/off) and symmetric exponential model, and luminosity-dependent quasar lifetimes. Our method self-consistently reproduces an input quasar luminosity function given a halo catalog from an N-body simulation, and propagates quasars through the merger history of halo hosts. After calibrating quasar clustering using measurements from the Baryon Oscillation Spectroscopic Survey, we find that the characteristic mass of quasar hosts is {M}h˜ 2.5× {10}12 {h}-1 {M}⊙ for the lightbulb model, and {M}h˜ 2.3× {10}12 {h}-1 {M}⊙ for the exponential model. In the latter model, the peak quasar luminosity for a given halo mass is larger than that in the former, typically by a factor of 1.5-2. The effective lifetime for quasars in the lightbulb model is 59 Myr, and in the exponential case, the effective time constant is about 15 Myr. We include semi-analytic calculations of helium reionization, and discuss how to include these quasars as sources of ionizing radiation for full hydrodynamics with radiative transfer simulations in order to study helium reionization.

  10. Helium Reionization Simulations. I. Modeling Quasars as Radiation Sources

    NASA Astrophysics Data System (ADS)

    La Plante, Paul; Trac, Hy

    2016-09-01

    We introduce a new project to understand helium reionization using fully coupled N-body, hydrodynamics, and radiative transfer simulations. This project aims to capture correctly the thermal history of the intergalactic medium as a result of reionization and make predictions about the Lyα forest and baryon temperature–density relation. The dominant sources of radiation for this transition are quasars, so modeling the source population accurately is very important for making reliable predictions. In this first paper, we present a new method for populating dark matter halos with quasars. Our set of quasar models includes two different light curves, a lightbulb (simple on/off) and symmetric exponential model, and luminosity-dependent quasar lifetimes. Our method self-consistently reproduces an input quasar luminosity function given a halo catalog from an N-body simulation, and propagates quasars through the merger history of halo hosts. After calibrating quasar clustering using measurements from the Baryon Oscillation Spectroscopic Survey, we find that the characteristic mass of quasar hosts is {M}h∼ 2.5× {10}12 {h}-1 {M}ȯ for the lightbulb model, and {M}h∼ 2.3× {10}12 {h}-1 {M}ȯ for the exponential model. In the latter model, the peak quasar luminosity for a given halo mass is larger than that in the former, typically by a factor of 1.5–2. The effective lifetime for quasars in the lightbulb model is 59 Myr, and in the exponential case, the effective time constant is about 15 Myr. We include semi-analytic calculations of helium reionization, and discuss how to include these quasars as sources of ionizing radiation for full hydrodynamics with radiative transfer simulations in order to study helium reionization.

  11. THE SUBARU HIGH-z QUASAR SURVEY: DISCOVERY OF FAINT z ∼ 6 QUASARS

    SciTech Connect

    Kashikawa, Nobunari; Furusawa, Hisanori; Niino, Yuu; Ishizaki, Yoshifumi; Onoue, Masafusa; Toshikawa, Jun; Ishikawa, Shogo; Willott, Chris J.; Im, Myungshin; Shimasaku, Kazuhiro; Ouchi, Masami; Hibon, Pascale

    2015-01-01

    We present the discovery of one or two extremely faint z ∼ 6 quasars in 6.5 deg{sup 2} utilizing a unique capability of the wide-field imaging of the Subaru/Suprime-Cam. The quasar selection was made in (i'-z{sub B} ) and (z{sub B} -z{sub R} ) colors, where z{sub B} and z{sub R} are bandpasses with central wavelengths of 8842 Å and 9841 Å, respectively. The color selection can effectively isolate quasars at z ∼ 6 from M/L/T dwarfs without the J-band photometry down to z{sub R} < 24.0, which is 3.5 mag deeper than the Sloan Digital Sky Survey (SDSS). We have selected 17 promising quasar candidates. The follow-up spectroscopy for seven targets identified one apparent quasar at z = 6.156 with M {sub 1450} = –23.10. We also identified one possible quasar at z = 6.041 with a faint continuum of M {sub 1450} = –22.58 and a narrow Lyα emission with HWHM =427 km s{sup –1}, which cannot be distinguished from Lyman α emitters. We derive the quasar luminosity function at z ∼ 6 by combining our faint quasar sample with the bright quasar samples by SDSS and CFHQS. Including our data points invokes a higher number density in the faintest bin of the quasar luminosity function than the previous estimate employed. This suggests a steeper faint-end slope than lower z, though it is yet uncertain based on a small number of spectroscopically identified faint quasars, and several quasar candidates still remain to be diagnosed. The steepening of the quasar luminosity function at the faint end does increase the expected emission rate of the ionizing photon; however, it only changes by a factor of approximately two to six. This was found to still be insufficient for the required photon budget of reionization at z ∼ 6.

  12. The Main Sequence Luminosity Function of Palomar 5

    NASA Astrophysics Data System (ADS)

    Smith, Graeme

    1996-07-01

    Palomar 5 appears to represent an extreme in the dynamical evolution of globular clusters. A low mass, large core radius, and a low central concentration suggest that Pal 5 has lost a large fraction of it's initial mass and has expanded as a consequence. If the dynamical evolution of Pal 5 has been dominated by the effects of star loss, then theoretical arguments suggest that the stellar mass function should be deficient in low-mass stars. From a dynamical study of NGC 5466 Pryor et al. concluded that the best fitting King-Michie models for that cluster are those which have a cutoff in the stellar mass function at about 0.4 solar masses. A similar or even more extreme truncation in the Pal 5 mass function is possible. We propose to directly test this conclusion by determining the stellar luminosity function of Pal 5 down to V = 27.0 from WFPC2 F555W and F814W frames. Two fields within Pal 5 will be observed, one located near the cluster center and the other just within the half-light radius. A magnitude of V = 27.0 in Pal 5 corresponds to a stellar mass of about 0.3 solar masses, which is fainter than the predicted truncation mass.

  13. Volume-limited SDSS/First quasars and the radio dichotomy

    SciTech Connect

    Sebastian Jester; R.G. Kron

    2004-03-12

    Much evidence has been presented in favor of and against the existence of two distinct populations of quasars, radio-loud and radio-quiet. The SDSS differs from earlier optically selected quasar surveys in the large number of quasars and the targeting of FIRST radio source counterparts as quasar candidates. This allows a qualitatively different approach of constructing a series of samples at different redshifts which are volume-limited with respect to both radio and optical luminosity. This technique avoids any biases from the strong evolution of quasar counts with redshift and potential redshift-dependent selection effects. We find that optical and radio luminosities of quasars detected in both SDSS and FIRST are not well correlated within each redshift shell, although the fraction of radio detections among optically selected quasars remains roughly constant at 10% for z {le} 3.2. The distribution in the luminosity-luminosity plane does not appear to be strongly bimodal. The optical luminosity function is marginally flatter at higher radio luminosities.

  14. The GRB luminosity function: prediction of the internal shock model and comparison to observations

    SciTech Connect

    Zitouni, H.; Daigne, F.; Mochkovitch, R.

    2008-05-22

    We compute the expected GRB luminosity function in the internal shock model. We find that if the population of GRB central engines produces all kind of relativistic outflows, from very smooth to highly variable, the luminosity function has to branchs: at low luminosity, the distribution is dominated by low efficiency GRBs and is close to a power law of slope -0.5, whereas at high luminosity, the luminosity function follows the distribution of injected kinetic power. Using Monte Carlo simulations and several observational constrains (BATSE logN-logP diagram, peak energy distribution of bright BATSE bursts, fraction of XRFs in the HETE2 sample), we show that it is currently impossible to distinguish between a single power law or a broken power law luminosity function. However, when the second case is considered, the low-luminosity slope is found to be -0.6{+-}0.2, which is compatible with the prediction of the internal shock model.

  15. The galaxy luminosity function in groups and clusters: the faint-end upturn and the connection to the field luminosity function

    NASA Astrophysics Data System (ADS)

    Lan, Ting-Wen; Ménard, Brice; Mo, Houjun

    2016-07-01

    We characterize the luminosity functions of galaxies residing in z ˜ 0 groups and clusters over the broadest ranges of luminosity and mass reachable by the Sloan Digital Sky Survey. Our measurements cover four orders of magnitude in luminosity, down to about Mr = -12 mag or L = 107 L⊙, and three orders of magnitude in halo mass, from 1012 to 1015 M⊙. We find a characteristic scale, Mr ˜ -18 mag or L ˜ 109 L⊙, below which the slope of the luminosity function becomes systematically steeper. This trend is present for all halo masses and originates mostly from red satellites. This ubiquitous faint-end upturn suggests that it is formation, rather than halo-specific environmental effect, that plays a major role in regulating the stellar masses of faint satellites. We show that the satellite luminosity functions can be described in a simple manner by a double Schechter function with amplitudes scaling with halo mass over the entire range of observables. Combining these conditional luminosity functions with the dark matter halo mass function, we accurately recover the entire field luminosity function over 10 visual magnitudes and reveal that satellite galaxies dominate the field luminosity function at magnitudes fainter than -17. We find that the luminosity functions of blue and red satellite galaxies show distinct shapes and we present estimates of the stellar mass fraction as a function of halo mass and galaxy type. Finally, using a simple model, we demonstrate that the abundances and the faint-end slopes of blue and red satellite galaxies can be interpreted in terms of their formation history, with two distinct modes separated by some characteristic time.

  16. Isochrones and Luminosity Functions for Old White Dwarfs

    NASA Astrophysics Data System (ADS)

    Richer, Harvey B.; Hansen, Brad; Limongi, Marco; Chieffi, Alessandro; Straniero, Oscar; Fahlman, Gregory G.

    2000-01-01

    Using a new grid of models of cooling white dwarfs, we calculate isochrones and luminosity functions in the Johnson-Kron/Cousins and Hubble Space Telescope (HST) filter sets for systems containing old white dwarfs. These new models incorporate a nongray atmosphere that is necessary to properly describe the effects of molecular opacity at the cool temperatures of old white dwarfs. The various functions calculated and extensively tabulated and plotted are meant to be as utilitarian as possible for observers, so all results are listed in quantities that observers will obtain. The tables and plots developed should eventually prove critical in interpreting the results of HST's Advanced Camera observations of the oldest white dwarfs in nearby globular clusters, in understanding the results of searches for old white dwarfs in the Galactic halo, and in determining ages for star clusters using white dwarfs. As a practical application we demonstrate the use of these results by deriving the white dwarf cooling age of the old Galactic cluster M67.

  17. A physical model for the evolving ultraviolet luminosity function of high redshift galaxies and their contribution to the cosmic reionization

    SciTech Connect

    Cai, Zhen-Yi; Lapi, Andrea; Bressan, Alessandro; De Zotti, Gianfranco; Danese, Luigi; Negrello, Mattia

    2014-04-10

    pointing to a rapid drop of the ionization degree above z ≅ 6, such as indications of a decrease of the comoving emission rate of ionizing photons at z ≅ 6, a decrease of sizes of quasar near zones, and a possible decline of the Lyα transmission through the intergalactic medium at z > 6. On the other hand, the electron scattering optical depth, τ{sub es}, inferred from cosmic microwave background (CMB) experiments favor an ionization degree close to unity up to z ≅ 9-10. Consistency with CMB data can be achieved if M {sub crit} ≅ 10{sup 8.5} M {sub ☉}, implying that the UV luminosity functions extend to M {sub UV} ≅ –13, although the corresponding τ{sub es} is still on the low side of CMB-based estimates.

  18. The Connection Between Galaxy Environment and the Luminosity Function Slopes of Star-Forming Regions

    NASA Astrophysics Data System (ADS)

    Cook, David O.; Dale, Daniel A.; Lee, Janice C.; Thilker, David A.; Calzetti, Daniela; Kennicutt, Robert

    2016-06-01

    We present the first study of GALEX far ultra-violet (FUV) luminosity functions of individual star-forming regions within a sample of 258 nearby galaxies spanning a large range in total stellar mass and star formation properties. We identify ~65,000 star-forming regions (i.e., FUV sources), measure each galaxy's luminosity function, and characterize the relationships between the luminosity function slope (α) and several global galaxy properties. A final sample of \

  19. The Quasar Fraction in Low-Frequency Selected Complete Samples and Implications for Unified Schemes

    NASA Technical Reports Server (NTRS)

    Willott, Chris J.; Rawlings, Steve; Blundell, Katherine M.; Lacy, Mark

    2000-01-01

    Low-frequency radio surveys are ideal for selecting orientation-independent samples of extragalactic sources because the sample members are selected by virtue of their isotropic steep-spectrum extended emission. We use the new 7C Redshift Survey along with the brighter 3CRR and 6C samples to investigate the fraction of objects with observed broad emission lines - the 'quasar fraction' - as a function of redshift and of radio and narrow emission line luminosity. We find that the quasar fraction is more strongly dependent upon luminosity (both narrow line and radio) than it is on redshift. Above a narrow [OII] emission line luminosity of log(base 10) (L(sub [OII])/W) approximately > 35 [or radio luminosity log(base 10) (L(sub 151)/ W/Hz.sr) approximately > 26.5], the quasar fraction is virtually independent of redshift and luminosity; this is consistent with a simple unified scheme with an obscuring torus with a half-opening angle theta(sub trans) approximately equal 53 deg. For objects with less luminous narrow lines, the quasar fraction is lower. We show that this is not due to the difficulty of detecting lower-luminosity broad emission lines in a less luminous, but otherwise similar, quasar population. We discuss evidence which supports at least two probable physical causes for the drop in quasar fraction at low luminosity: (i) a gradual decrease in theta(sub trans) and/or a gradual increase in the fraction of lightly-reddened (0 approximately < A(sub V) approximately < 5) lines-of-sight with decreasing quasar luminosity; and (ii) the emergence of a distinct second population of low luminosity radio sources which, like M8T, lack a well-fed quasar nucleus and may well lack a thick obscuring torus.

  20. THE MID-INFRARED LUMINOSITY FUNCTION AT z < 0.3 FROM 5MUSES: UNDERSTANDING THE STAR FORMATION/ACTIVE GALACTIC NUCLEUS BALANCE FROM A SPECTROSCOPIC VIEW

    SciTech Connect

    Wu Yanling; Shi Yong; Helou, George; Armus, Lee; Stierwalt, Sabrina; Dale, Daniel A.; Papovich, Casey; Rahman, Nurur; Dasyra, Kalliopi E-mail: yong@ipac.caltech.edu E-mail: lee@ipac.caltech.edu E-mail: ddale@uwyo.edu E-mail: nurur@astro.umd.edu

    2011-06-10

    We present rest-frame 15 and 24 {mu}m luminosity functions (LFs) and the corresponding star-forming LFs at z < 0.3 derived from the 5MUSES sample. Spectroscopic redshifts have been obtained for {approx}98% of the objects and the median redshift is {approx}0.12. The 5-35 {mu}m Infrared Spectrograph spectra allow us to estimate accurately the luminosities and build the LFs. Using a combination of starburst and quasar templates, we quantify the star formation (SF) and active galactic nucleus (AGN) contributions in the mid-IR spectral energy distribution. We then compute the SF LFs at 15 and 24 {mu}m, and compare with the total 15 and 24 {mu}m LFs. When we remove the contribution of AGNs, the bright end of the LF exhibits a strong decline, consistent with the exponential cutoff of a Schechter function. Integrating the differential LF, we find that the fractional contribution by SF to the energy density is 58% at 15 {mu}m and 78% at 24 {mu}m, while it goes up to {approx}86% when we extrapolate our mid-IR results to the total IR luminosity density. We confirm that the AGNs play more important roles energetically at high luminosities. Finally, we compare our results with work at z {approx} 0.7 and confirm that evolution on both luminosity and density is required to explain the difference in the LFs at different redshifts.

  1. Optical and Radio Properties of QSOS as a Function of Absolute Luminosity.

    NASA Astrophysics Data System (ADS)

    Pica, Andrew Joseph

    1982-03-01

    Photometric data for nearly 250 quasars, BL Lacertids, and active galaxies have been obtained at the Rosemary Hill Observatory during a continuous 13-year monitoring program. Long-term optical records for 130 of these sources are employed in an effort to assess the physical and cosmological properties of quasi-stellar objects. Photographic P and B magnitudes were obtained with the 76- and 46-cm telescopes at Rosemary Hill. Corrections for galactic absorption, emission lines, and the K-term are applied to the raw data yielding monochromatic flux densities at a standard emitted wavelength of 2500 (ANGSTROM). Long -term light curves are compiled for all objects and 3 levels of activity are determined for each individual source. The MEAN, BASE, and MAX brightness levels are then used to study QSOs in their average, quiescent, and active phases, respectively. Absolute intrinsic luminosities of all sources in the sample are computed from the monochromatic flux densities based on relativistic cosmological models. Radio -emitting quasars, radio-quiet QSOs, and active galaxies fall into 3 distinct groups and are examined separately. The cosmological properties of QSOs are studied by plotting apparent magnitude vs. redshift, the so-called Hubble diagram. Scatter in the diagram due to variability is substantially reduced by plotting log z vs. the MEAN, BASE, and MAX flux densities. The brightest QSOs at each redshift are then chosen as "standard candles" in an effort to determine if quasars obey Hubble's law for expanding universe. It is found that they fit the Hubble relation quite well if certain selection effects are accounted for. Other evidence for the cosmological origin of QSOs is briefly discussed. Variability provides a test as to whether individual quasars are essentially multiple in nature (the "Christmas Tree" model), or are single coherent sources (such as a massive black hole). The amplitude of variability vs. absolute luminosity relation is used to discriminate

  2. Modeling the Near-Infrared Luminosity Function of Young Stellar Clusters

    NASA Astrophysics Data System (ADS)

    Muench, A. A.; Lada, E. A.; Lada, C. J.

    1999-12-01

    We present the results of numerical experiments designed to evaluate the usefulness of near-infrared luminosity functions for constraining the Initial Mass Function (IMF) of young (0-10 Myr) stellar populations. Using Monte Carlo techniques, we create a suite of model luminosity functions systematically varying each of these basic underlying relations: the underlying IMF, cluster star forming history, and theoretical pre-main sequence mass-to-luminosity relations. Our modeling techniques also allow us to explore the effects of unresolved binaries, infrared excess emission from circumstellar disks, and interstellar extinction on the cluster luminosity function. From this numerical modeling, we find that the luminosity function of a young stellar population is considerably more sensitive to variations in the underlying initial mass function than to either variations in the star forming history or assumed pre-main-sequence (PMS) mass-to-luminosity relation. To illustrate the potential effectiveness of using the KLF of a young cluster to constrain its IMF, we model the observed K band luminosity function of the nearby Trapezium cluster. Our derived mass function for the Trapezium spans two orders of magnitude in stellar mass (5>Msun>0.02) and has a peak near the hydrogen burning limit. Below the hydrogen burning limit, the mass function steadily decreases with decreasing mass throughout the brown dwarf regime. We also test the hypothesis of a space varying IMF by performing model fits to the K band luminosity functions of several other young clusters.

  3. A revisit of gamma-ray luminosity function and contribution to the extragalactic diffuse gamma-ray background for Fermi FSRQs

    NASA Astrophysics Data System (ADS)

    Zeng, Houdun; Yan, Dahai; Zhang, Li

    2013-05-01

    A clean sample of flat-spectrum radio quasars (FSRQs) has been provided by Fermi Large Area Telescope (LAT) in two years of operation. Based on this sample, we reconstruct the gamma-ray luminosity function (GLF) in the framework of the luminosity-dependent density evolution (LDDE) model, and obtain the best-fitting GLF by comparing the distributions of observed redshifts, luminosities, indexes and source counts with the predicted distribution of the GLF through the Markov Chain Monte Carlo (MCMC) method which constrains the model parameters in an efficient way. Using the best-fitting GLF, we estimate the contribution of Fermi-undetected FSRQs to the extragalactic diffuse gamma-ray background (EGRB), and find that the contribution of unresolved FSRQs to the EGRB is 10.1 ± 4.7 per cent in the 0.1-100 GeV band. We also study the influence of different bins of redshifts, luminosities and spectral indices on the contribution to EGRB from the unresolved FSRQs, and find that the contributions of unresolved FSRQs in the redshift range of z = 0.0-2.0 and in the gamma-ray luminosity range of 1044-1048 erg s-1 are ˜90 per cent, respectively.

  4. The Herschel ATLAS: Evolution of the 250 Micrometer Luminosity Function Out to z = 0.5

    NASA Technical Reports Server (NTRS)

    Dye, S.; Dunne, L.; Eales, S.; Smith, D. J. B.; Amblard, A.; Auld, R.; Baes, M.; Baldry, I. K.; Bamford, S.; Blain, A. W.; Bonfield, D. G.; Bremer, M.; Burgarella, D.; Buttiglione, S.; Cameron, E.; Cava, A.; Clements, D. L.; Cooray, A.; Croom, S.; Dariush, A.; de Zotti, G.; Driver, S.; Dunlop, J. S.; Frayer, D.; Leeuw, L.

    2010-01-01

    We have determined the luminosity function of 250 micrometer-selected galaxies detected in the approximately equal to 14 deg(sup 2) science demonstration region of the Herschel-ATLAS project out to a redshift of z = 0.5. Our findings very clearly show that the luminosity function evolves steadily out to this redshift. By selecting a sub-group of sources within a fixed luminosity interval where incompleteness effects are minimal, we have measured a smooth increase in the comoving 250 micrometer luminosity density out to z = 0.2 where it is 3.6(sup +1.4) (sub -0.9) times higher than the local value.

  5. LUMINOSITY FUNCTIONS OF SPITZER-IDENTIFIED PROTOSTARS IN NINE NEARBY MOLECULAR CLOUDS

    SciTech Connect

    Kryukova, E.; Megeath, S. T.; Allen, T. S.; Gutermuth, R. A.; Pipher, J.; Allen, L. E.; Myers, P. C.; Muzerolle, J.

    2012-08-15

    We identify protostars in Spitzer surveys of nine star-forming (SF) molecular clouds within 1 kpc: Serpens, Perseus, Ophiuchus, Chamaeleon, Lupus, Taurus, Orion, Cep OB3, and Mon R2, which combined host over 700 protostar candidates. These clouds encompass a variety of SF environments, including both low-mass and high-mass SF regions, as well as dense clusters and regions of sparsely distributed star formation. Our diverse cloud sample allows us to compare protostar luminosity functions in these varied environments. We combine near- and mid-infrared photometry from the Two Micron All Sky Survey and Spitzer to create 1-24 {mu}m spectral energy distributions (SEDs). Using protostars from the c2d survey with well-determined bolometric luminosities, we derive a relationship between bolometric luminosity, mid-IR luminosity (integrated from 1-24 {mu}m), and SED slope. Estimations of the bolometric luminosities for protostar candidates are combined to create luminosity functions for each cloud. Contamination due to edge-on disks, reddened Class II sources, and galaxies is estimated and removed from the luminosity functions. We find that luminosity functions for high-mass SF clouds (Orion, Mon R2, and Cep OB3) peak near 1 L{sub Sun} and show a tail extending toward luminosities above 100 L{sub Sun }. The luminosity functions of the low-mass SF clouds (Serpens, Perseus, Ophiuchus, Taurus, Lupus, and Chamaeleon) do not exhibit a common peak, however the combined luminosity function of these regions peaks below 1 L{sub Sun }. Finally, we examine the luminosity functions as a function of the local surface density of young stellar objects. In the Orion molecular clouds, we find a significant difference between the luminosity functions of protostars in regions of high and low stellar density, the former of which is biased toward more luminous sources. This may be the result of primordial mass segregation, although this interpretation is not unique. We compare our luminosity

  6. The Luminosity Function of OB Associations in the Galaxy

    NASA Astrophysics Data System (ADS)

    McKee, Christopher F.; Williams, Jonathan P.

    1997-02-01

    OB associations ionize the interstellar medium, producing both localized H II regions and diffuse ionized gas. The supernovae resulting from these associations pressurize and stir the interstellar medium. Using Smith, Biermann, & Mezger's compilation of radio H II regions in the Galaxy, and Kennicutt, Edgar, & Hodge's optical study of H II regions in nearby galaxies, we show that the luminosity distribution of giant OB associations in the Galaxy can be fit by a truncated power law of the form \\Nscra(>S)=\\Nscrau[(Su/S)-1], where S is the ionizing photon luminosity, \\Nscra(>S) is the number of associations with a luminosity of at least S, and Su is the upper limit to the distribution. The coefficient \\Nscrau is the number of the most luminous associations, with a luminosity between 0.5Su and Su. For the Galaxy, \\Nscrau=6.1 the fact that the number of the most luminous associations is significantly larger than unity indicates that there is a physical limit to the maximum size of H II regions in the Galaxy. To extend the luminosity distribution to small H II regions, we assume that the birthrate of associations, \\Nscr\\dota(>\\Nscr*), is also a truncated power law, \\Nscr\\dota(>\\Nscr*)~[(\\Nscr*u/\\Nscr*)-1], where \\Nscr* is the number of stars in the association. For large associations, the ionizing luminosity is proportional to the number of stars, S~\\Nscr* for smaller associations, we use both an analytic and a Monte Carlo approach to find the resulting luminosity distribution \\Nscra(>S). H II regions are generally centrally concentrated, with only the dense central regions being bright enough to appear in radio catalogs. Anantharamaiah postulated that radio H II regions have extended envelopes in order to account for diffuse radio recombination line emission in the Galaxy. Some of these envelopes are visible as the ionized ``worms'' discussed by Heiles and coworkers. We estimate that on the average the envelopes of radio H II regions absorb about twice

  7. The Environments of Obscured Quasars

    NASA Astrophysics Data System (ADS)

    Jones, Kristen M.; Lacy, Mark; Nielsen, Danielle

    2016-01-01

    Supermassive Black Hole (SMBH) feedback is prescribed for driving the high-end shape of the galaxy luminosity function, clearing the circumnuclear environment during the end stages of mergers, and eventually turning off its own accretion. Yet the dominant processes and characteristics of active galactic nuclei are indistinct. Chief among this confusion is how significant the role of dust is in each galaxy. Orientation of the dusty torus is attributed to causing the differences between Sy1 and Sy2, but whether obscured quasars are found in particularly dusty host galaxies, if they exist at a different stage in the merger process (early on, before the dust is blown out), or if they are merely oriented differently than optical quasars is not yet so well distinguished. With obscured quasars now observed to make up 50% or greater of the population of quasars, the question of what causes obscuration becomes vital to address. With this in mind, I study matched samples of obscured and unobscured quasars to characterize their environments, with the intent of addressing what contribution environment has to obscuration levels. I investigate the megaparsec-scale environments of SIRTF Wide-field Infra-Red Extragalactic Survey (SWIRE) quasars at z ˜ 1-3 by cross-correlating the sample with 3.8 million galaxies from the Spitzer Extragalactic Representative Volume Survey (SERVS). Optically obscured quasars are compared to a control sample of optically-bright quasars via selection in the mid-infrared. Environments were observed at 3.6 and 4.5 μm to a depth of ≈ 2 μJy (AB = 23.1). Recent work has found diverse results in such studies, with dependence of environmental richness on both redshift and level of obscuration. I find that, within reasonable error, on average there is no distinct difference between the level of clustering for obscured and normal quasars, and that there is no dependence on redshift of this result within the range of 1.3 < z < 2.5. I compare our results

  8. THE COLOR VARIABILITY OF QUASARS

    SciTech Connect

    Schmidt, Kasper B.; Rix, Hans-Walter; Knecht, Matthias; Hogg, David W.; Shields, Joseph C.; Maoz, Dan; Bovy, Jo

    2012-01-10

    We quantify quasar color variability using an unprecedented variability database-ugriz photometry of 9093 quasars from Sloan Digital Sky Survey (SDSS) Stripe 82, observed over 8 years at {approx}60 epochs each. We confirm previous reports that quasars become bluer when brightening. We find a redshift dependence of this blueing in a given set of bands (e.g., g and r), but show that it is the result of the flux contribution from less-variable or delayed emission lines in the different SDSS bands at different redshifts. After correcting for this effect, quasar color variability is remarkably uniform, and independent not only of redshift, but also of quasar luminosity and black hole mass. The color variations of individual quasars, as they vary in brightness on year timescales, are much more pronounced than the ranges in color seen in samples of quasars across many orders of magnitude in luminosity. This indicates distinct physical mechanisms behind quasar variability and the observed range of quasar luminosities at a given black hole mass-quasar variations cannot be explained by changes in the mean accretion rate. We do find some dependence of the color variability on the characteristics of the flux variations themselves, with fast, low-amplitude, brightness variations producing more color variability. The observed behavior could arise if quasar variability results from flares or ephemeral hot spots in an accretion disk.

  9. The connection between galaxy environment and the luminosity function slopes of star-forming regions

    NASA Astrophysics Data System (ADS)

    Cook, David O.; Dale, Daniel A.; Lee, Janice C.; Thilker, David; Calzetti, Daniela; Kennicutt, Robert C.

    2016-11-01

    We present the first study of GALEX far-ultraviolet (FUV) luminosity functions of individual star-forming regions within a sample of 258 nearby galaxies spanning a large range in total stellar mass and star formation properties. We identify ˜65 000 star-forming regions (i.e. FUV sources), measure each galaxy's luminosity function, and characterize the relationships between the luminosity function slope (α) and several global galaxy properties. A final sample of 82 galaxies with reliable luminosity functions are used to define these relationships and represent the largest sample of galaxies with the largest range of galaxy properties used to study the connection between luminosity function properties and galaxy environment. We find that α correlates with global star formation properties, where galaxies with higher star formation rates and star formation rate densities (ΣSFR) tend to have flatter luminosity function slopes. In addition, we find that neither stochastic sampling of the luminosity function in galaxies with low-number statistics nor the effects of blending due to distance can fully account for these trends. We hypothesize that the flatter slopes in high ΣSFR galaxies is due to higher gas densities and higher star formation efficiencies which result in proportionally greater numbers of bright star-forming regions. Finally, we create a composite luminosity function composed of star-forming regions from many galaxies and find a break in the luminosity function at brighter luminosities. However, we find that this break is an artefact of varying detection limits for galaxies at different distances.

  10. Galaxy luminosity function and Tully-Fisher relation: reconciled through rotation-curve studies

    SciTech Connect

    Cattaneo, Andrea; Salucci, Paolo; Papastergis, Emmanouil E-mail: salucci@sissa.it

    2014-03-10

    The relation between galaxy luminosity L and halo virial velocity v {sub vir} required to fit the galaxy luminosity function differs from the observed Tully-Fisher relation between L and disk speed v {sub rot}. Because of this, the problem of reproducing the galaxy luminosity function and the Tully-Fisher relation simultaneously has plagued semianalytic models since their inception. Here we study the relation between v {sub rot} and v {sub vir} by fitting observational average rotation curves of disk galaxies binned in luminosity. We show that the v {sub rot}-v {sub vir} relation that we obtain in this way can fully account for this seeming inconsistency. Therefore, the reconciliation of the luminosity function with the Tully-Fisher relation rests on the complex dependence of v {sub rot} on v {sub vir}, which arises because the ratio of stellar mass to dark matter mass is a strong function of halo mass.

  11. The X-ray luminosity functions of Abell clusters from the Einstein Cluster Survey

    NASA Technical Reports Server (NTRS)

    Burg, R.; Giacconi, R.; Forman, W.; Jones, C.

    1994-01-01

    We have derived the present epoch X-ray luminosity function of northern Abell clusters using luminosities from the Einstein Cluster Survey. The sample is sufficiently large that we can determine the luminosity function for each richness class separately with sufficient precision to study and compare the different luminosity functions. We find that, within each richness class, the range of X-ray luminosity is quite large and spans nearly a factor of 25. Characterizing the luminosity function for each richness class with a Schechter function, we find that the characteristic X-ray luminosity, L(sub *), scales with richness class as (L(sub *) varies as N(sub*)(exp gamma), where N(sub *) is the corrected, mean number of galaxies in a richness class, and the best-fitting exponent is gamma = 1.3 +/- 0.4. Finally, our analysis suggests that there is a lower limit to the X-ray luminosity of clusters which is determined by the integrated emission of the cluster member galaxies, and this also scales with richness class. The present sample forms a baseline for testing cosmological evolution of Abell-like clusters when an appropriate high-redshift cluster sample becomes available.

  12. Implications of the Observed Ultraluminous X-Ray Source Luminosity Function

    NASA Technical Reports Server (NTRS)

    Swartz, Douglas A.; Tennant, Allyn; Soria, Roberto; Yukita, Mihoko

    2012-01-01

    We present the X-ray luminosity function (XLF) of ultraluminous X-ray (ULX) sources with 0.3-10.0 keV luminosities in excess of 10(sup 39) erg/s in a complete sample of nearby galaxies. The XLF shows a break or cut-off at high luminosities that deviates from its pure power law distribution at lower luminosities. The cut-off is at roughly the Eddington luminosity for a 90-140 solar mass accretor. We examine the effects on the observed XLF of sample biases, of small-number statistics (at the high luminosity end) and of measurement uncertainties. We consider the physical implications of the shape and normalization of the XLF. The XLF is also compared and contrasted to results of other recent surveys.

  13. The galaxy luminosity function and the redshift-distance controversy (A Review)

    PubMed Central

    Salpeter, E. E.; Hoffman, G. L.

    1986-01-01

    The mean relation between distance and redshift for galaxies is reviewed as an observational question. The luminosity function for galaxies is an important ingredient and is given explicitly. We discuss various observational selection effects that are important for comparison of the linear and quadratic distance-redshift laws. Several lines of evidence are reviewed, including the distribution of galaxy luminosities in various redshift ranges, the luminosities of brightest galaxies in groups and clusters at various redshifts, and the Tully-Fisher correlation between neutral hydrogen velocity widths and luminosity. All of these strongly favor the linear law over the quadratic. PMID:16593693

  14. The optical variability of the quasar 3C 446

    SciTech Connect

    Barbieri, C.; Vio, R.; Cappellaro, E; Turatto, M Padova Osservatorio Astronomico, Padua )

    1990-08-01

    The optical variability of the quasar 3C 446 is investigated using power spectrum and structure function analysis along with a new set of observations that extend the available data till 1989. No contradiction is found between the PS and SF analyses. The presence of the 1540-day periodicity is strengthened by the occurrence of the 1988 luminosity peak, suggesting that the next burst will occur in the northern spring of 1992. The time series of the quasar is nonstationary. The light variations are determined by a sequence of luminosity bursts, mostly regularly spaced in time and lasting up to 2 yr. 25 refs.

  15. Constraints on the luminosity function of gamma-ray bursts detected by BATSE

    NASA Technical Reports Server (NTRS)

    Horack, J. M.; Emslie, A. G.; Meegan, C. A.

    1994-01-01

    We have utilized the integral moment analysis technique of Horack & Emslie to extract information on the allowable form of the luminosity function for gamma-ray bursts observed by Burst and Transient Source Experiment (BATSE). Using the general properties of moments, we are able to derive constraints on the range of luminosity from which the gamma-ray bursts must be sampled. These constraints are independent of the form of the radial distribution of the gamma-ray bursts, and depend only on the assumptions that space is Euclidean and that the luminosity function phi(L) is distance independent. For power-law luminosity functions of the form phi(L) = A(sub 0)L(exp -alpha), we find that the range of luminosity from which 80% of the gamma-ray bursts must be sampled cannot exceed approximately 6.5, with a 3 sigma upper limit of 12-15, regardless of the value of alpha.

  16. The Geometry of Quasar Outflows

    NASA Astrophysics Data System (ADS)

    Ganguly, Rajib

    2012-10-01

    Quasar outflows are important for understanding the accretion and growth processes of the central black hole, but also potentially play a role in feedback to the galaxy, halting star formation and infall of gas. A big uncertainty lies in the geometry and density of these outflows, especially as a function of ionization and velocity. We aim to tackle this using the archival COS M grating spectra of 266 quasars. We separate the geometry of outflows into two parts: the solid angle subtended around the black hole, and the distance of the outflow from the central engine. Large numbers of quasars with high resolution spectra are required for each aspect of this statistical investigation. First, we will determine which/how many absorption-line systems are intrinsic through both partial covering methods and statistical assessments. Second, we will consider the incidence of intrinsic absorbers as a function of quasar property {e.g., radio-loudness, SED shape, black hole mass, bolometric luminosity}. This will reveal what determines the solid angle. This can only be done at moderate redshifts where quasars with a larger range of properties are observable, and hence requires HST/COS. Third, we will use the wide range of diagnostic lines to constrain the physical conditions of the absorbers. We will target the CIII*1175 complex and apply photoionization models to constrain the densities and ionization parameters. This will provide the largest set yet of intrinsic absorbers with systematic distance constraints. In tandem with the solid angles, this work will inform models regarding the geometry of quasar outflows.

  17. The Environmental Dependence of the Galaxy Luminosity Function in the ECO Survey

    NASA Astrophysics Data System (ADS)

    Andrews, Hayley; Andreas A. Berlind, Victor Calderon, Kathleen D. Eckert, Sheila J. Kannappan, Amanda J. Moffett, David V. Stark

    2016-01-01

    We study the environmental dependence of the galaxy luminosity function in the ECO survey and compare it with models that associate galaxies with dark matter halos. Specifically, we quantify the environment of each galaxy in the ECO survey using an Nth nearest neighbor distance metric, and we measure how the galaxy luminosity distribution varies from low density to high density environments. As expected, we find that luminous galaxies preferentially populate high density regions, while low luminosity galaxies preferentially populate lower density environments. We investigate whether this trend can be explained simply by the correlation of galaxy luminosity and dark matter halo mass combined with the environmental dependence of the halo mass function. In other words, we test the hypothesis that the luminosity of a galaxy depends solely on the mass of its dark matter halo and does not exhibit a residual dependence on the halo's larger environment. To test this hypothesis, we first construct mock ECO catalogs by populating dark matter halos in an N-body simulation with galaxies using a model that preserves the overall clustering strength of the galaxy population. We then assign luminosities to the mock galaxies using physically motivated models that connect luminosity to halo mass and are constrained to match the global ECO luminosity function. Finally, we impose the radial and angular selection functions of the ECO survey and repeat our environmental analysis on the mock catalogs. Though our mock catalog luminosity functions display similar qualitative trends as those from the ECO data, the trends are not in agreement quantitatively. Our results thus suggest that the simple models used to build the mocks are incomplete and that galaxy luminosity is possibly correlated with the larger scale density field.

  18. [Automated recognition of quasars based on adaptive radial basis function neural networks].

    PubMed

    Zhao, Mei-Fang; Luo, A-Li; Wu, Fu-Chao; Hu, Zhan-Yi

    2006-02-01

    Recognizing and certifying quasars through the research on spectra is an important method in the field of astronomy. This paper presents a novel adaptive method for the automated recognition of quasars based on the radial basis function neural networks (RBFN). The proposed method is composed of the following three parts: (1) The feature space is reduced by the PCA (the principal component analysis) on the normalized input spectra; (2) An adaptive RBFN is constructed and trained in this reduced space. At first, the K-means clustering is used for the initialization, then based on the sum of squares errors and a gradient descent optimization technique, the number of neurons in the hidden layer is adaptively increased to improve the recognition performance; (3) The quasar spectra recognition is effectively carried out by the above trained RBFN. The author's proposed adaptive RBFN is shown to be able to not only overcome the difficulty of selecting the number of neurons in hidden layer of the traditional RBFN algorithm, but also increase the stability and accuracy of recognition of quasars. Besides, the proposed method is particularly useful for automatic voluminous spectra processing produced from a large-scale sky survey project, such as our LAMOST, due to its efficiency.

  19. DISCOVERY OF A FAINT QUASAR AT z ∼ 6 AND IMPLICATIONS FOR COSMIC REIONIZATION

    SciTech Connect

    Kim, Yongjung; Im, Myungshin; Jeon, Yiseul; Choi, Changsu; Hong, Jueun; Hyun, Minhee; Jun, Hyunsung David; Kim, Dohyeong; Kim, Duho; Kim, Jae-Woo; Lee, Seong-Kook; Taak, Yoon Chan; Yoon, Yongmin; Kim, Minjin; Park, Won-Kee; Karouzos, Marios; Kim, Ji Hoon; Pak, Soojong E-mail: mim@astro.snu.ac.kr

    2015-11-10

    Recent studies suggest that faint active galactic nuclei may be responsible for the reionization of the universe. Confirmation of this scenario requires spectroscopic identification of faint quasars (M{sub 1450} > −24 mag) at z ≳ 6, but only a very small number of such quasars have been spectroscopically identified so far. Here, we report the discovery of a faint quasar IMS J220417.92+011144.8 at z ∼ 6 in a 12.5 deg{sup 2} region of the SA22 field of the Infrared Medium-deep Survey (IMS). The spectrum of the quasar shows a sharp break at ∼8443 Å, with emission lines redshifted to z = 5.944 ± 0.002 and rest-frame ultraviolet continuum magnitude M{sub 1450} = −23.59 ± 0.10 AB mag. The discovery of IMS J220417.92+011144.8 is consistent with the expected number of quasars at z ∼ 6 estimated from quasar luminosity functions based on previous observations of spectroscopically identified low-luminosity quasars. This suggests that the number of M{sub 1450} ∼ −23 mag quasars at z ∼ 6 may not be high enough to fully account for the reionization of the universe. In addition, our study demonstrates that faint quasars in the early universe can be identified effectively with a moderately wide and deep near-infrared survey such as the IMS.

  20. Constraints on the gamma-ray burst luminosity function from Pioneer Venus Orbiter and BATSE observations

    NASA Technical Reports Server (NTRS)

    Ulmer, Andrew; Wijers, Ralph A. M. J.; Fenimore, Edward E.

    1995-01-01

    We examine the width of the gamma ray burst luminosity function through the distribution of Gamma Ray Burst (GRB) peak fluxes as detected by the Pioneer Venus Orbiter (PVO) and the Burst and Transient Source Experiment (BATSE). The strength of the analysis is greatly enhanced by using a merged catalog of peak fluxes from both instruments with good cross-calibration of their sensitivities. The range of peak fluxes is increased by approximately a factor of 20 relative to the BATSE catalog. Thus, more sensitive investigations of the log N - log P distribution are possible. We place constraints on the width of the luminosity function of gamma-ray bursts brighter than the BATSE completeness limit by comparing the intensity distribution in the merged catalog with those produced by a variety of spatial density and luminosity functions. For the models examined, 90% of the detectable bursts have peak luminosities within a range of 10, indicating that the peak luminosities of gamma-ray bursts span a markedly less wide range of values than many other of their measurable properties. We also discuss for which slopes of a power-law luminosity function the observed width is at the upper end of the constrained range. This is essential in determining the power-law slopes for which luminosity-duration correlations could be important.

  1. The luminosity functions of the 1969 Perseid and Orionid meteor showers

    NASA Technical Reports Server (NTRS)

    Krisciunas, K.

    1980-01-01

    Observations of the 1969 Perseid and Orionid meteor showers are presented and used to derive luminosity functions for the 288 Perseids and 56 Orionids detected. Visual counts were performed under very good to excellent seeing conditions at the times of peak activities, and the brightnesses of the meteors were estimated to the nearest magnitude by comparison with the magnitudes of known objects. Maximum likelihood estimates of the power law index of the luminosity function of 1.56 + or - 0.06 for the Perseids and of 1.85 + or - 0.1 for the Orionids are obtained which are lower than the values found by other investigators. Under the assumption that the luminosity of visual meteors is proportional to their mass, the luminosity function power law may also be used to characterize the mass function.

  2. Clustering, Cosmology and a New Era of Black Hole Demographics - II. The Conditional Luminosity Functions of Type 2 and Type 1 Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Ballantyne, D. R.

    2016-09-01

    The orientation-based unification model of active galactic nuclei (AGNs) posits that the principle difference between obscured (Type 2) and unobscured (Type 1) AGNs is the line-of-sight into the central engine. If this model is correct than there should be no difference in many of the properties of AGN host galaxies (e.g., the mass of the surrounding dark matter haloes). However, recent clustering analyses of Type 1 and Type 2 AGNs have provided some evidence for a difference in the halo mass, in conflict with the orientation-based unified model. In this work, a method to compute the Conditional Luminosity Function (CLF) of Type 2 and Type 1 AGNs is presented. The CLF allows many fundamental halo properties to be computed as a function of AGN luminosity, which we apply to the question of the host halo masses of Type 1 and 2 AGNs. By making use of the total AGN CLF, the Type 1 X-ray luminosity function, and the luminosity-dependent Type 2 AGN fraction, the CLFs of Type 1 and 2 AGNs are calculated at z ≈ 0 and 0.9. At both z, there is no statistically significant difference in the mean halo mass of Type 2 and 1 AGNs at any luminosity. There is marginal evidence that Type 1 AGNs may have larger halo masses than Type 2s, which would be consistent with an evolutionary picture where quasars are initially obscured and then subsequently reveal themselves as Type 1s. As the Type 1 lifetime is longer, the host halo will increase somewhat in mass during the Type 1 phase. The CLF technique will be a powerful way to study the properties of many AGNs subsets (e.g., radio-loud, Compton-thick) as future wide-area X-ray and optical surveys substantially increase our ability to place AGNs in their cosmological context.

  3. Probing the Ultraviolet Luminosity Function of the Earliest Galaxies with the Renaissance Simulations

    NASA Astrophysics Data System (ADS)

    O'Shea, Brian W.; Wise, John H.; Xu, Hao; Norman, Michael L.

    2015-07-01

    In this paper, we present the first results from the Renaissance Simulations, a suite of extremely high-resolution and physics-rich AMR calculations of high-redshift galaxy formation performed on the Blue Waters supercomputer. These simulations contain hundreds of well-resolved galaxies at z˜ 25-8, and make several novel, testable predictions. Most critically, we show that the ultraviolet luminosity function of our simulated galaxies is consistent with observations of high-z galaxy populations at the bright end of the luminosity function ({M}1600≤slant -17), but at lower luminosities is essentially flat rather than rising steeply, as has been inferred by Schechter function fits to high-z observations, and has a clearly defined lower limit in UV luminosity. This behavior of the luminosity function is due to two factors: (i) the strong dependence of the star formation rate (SFR) on halo virial mass in our simulated galaxy population, with lower-mass halos having systematically lower SFRs and thus lower UV luminosities; and (ii) the fact that halos with virial masses below ≃ 2× {10}8 {M}⊙ do not universally contain stars, with the fraction of halos containing stars dropping to zero at ≃ 7× {10}6 {M}⊙ . Finally, we show that the brightest of our simulated galaxies may be visible to current and future ultra-deep space-based surveys, particularly if lensed regions are chosen for observation.

  4. Effects of Formation Epoch Distribution on X-Ray Luminosity and Temperature Functions of Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Enoki, Motohiro; Takahara, Fumio; Fujita, Yutaka

    2001-07-01

    We investigate statistical properties of galaxy clusters in the context of a hierarchical clustering scenario, taking into account their formation epoch distribution; this study is motivated by the recent finding by Fujita and Takahara that X-ray clusters form a fundamental plane in which the mass and the formation epoch are regarded as two independent parameters. Using the formalism that discriminates between major mergers and accretion, the epoch of a cluster formation is identified with that of the last major merger. Since tiny mass accretion following formation does not much affect the core structure of clusters, the properties of X-ray emission from clusters are determined by the total mass and density at their formation time. Under these assumptions, we calculate X-ray luminosity and temperature functions of galaxy clusters. We find that the behavior of the luminosity function differs from the model that does not take into account formation epoch distribution; the behavior of the temperature function, however, is not much different. In our model, the luminosity function is shifted to a higher luminosity and shows no significant evolution up to z~1, independent of cosmological models. The clusters are populated on the temperature-luminosity plane, with a finite dispersion. Since the simple scaling model in which the gas temperature is equal to the virial temperature fails to reproduce the observed luminosity-temperature relation, we also consider a model that takes into account the effects of preheating. The preheating model reproduces the observations much more accurately.

  5. The Cluster and Large Scale Environments of Quasars at z<0.9

    NASA Astrophysics Data System (ADS)

    Harris, Kathryn A.

    2012-01-01

    In this thesis, I present an investigation into the environments of quasars with respect to galaxy clusters, and environment evolution with redshift and luminosity. The orientation of the quasar with respect to the major axis of the closest cluster was calculated, introducing new information to previous work. The aim of this work was i.) to study the large scale environment over a large redshift range, ii.) to study the evolution as well as any change in environment with quasar luminosity and redshift, and iii.) to study the orientation of a quasar with respect to a galaxy cluster. There is a deficit of quasars lying close to cluster centres for 0.4quasars as a function of absolute quasar magnitude, nor preferred orientation between the quasar and the cluster major axis for bright or faint quasars. Spectra of a selection of 680 star forming galaxies, red galaxies, and AGN were taken, and used to study the environments of quasars with respect to star-forming galaxies and galaxy clusters. The objects were classified (33 classed as AGN), and star formation rates calculated. Three AGN and 10 star forming galaxies lie at the same redshift (z=0.29) as three galaxy clusters. The three galaxy clusters have the same orientation angle and may be part of a filament along with the star forming galaxies and AGN. A number of high redshift quasars showed evidence of ultra-strong UV FeII emission in their spectra in the direction of three LQGs in the redshift range 1.1Quasar Group (CCLQG). Though there has been no previous indication that the LQG environment is unique, the high level of iron emission may indicate a difference in environment.

  6. Cosmological Evolution of the FSRQ Gamma-ray Luminosity Function and Spectra and the Contribution to the Background Based on Fermi-LAT Observations

    NASA Astrophysics Data System (ADS)

    Singal, Jack; Petrosian, V.; Ko, A.

    2013-04-01

    The Fermi-LAT has accumulated a large sample of blazars with known flux and spectral index. However, since blazars with harder spectra can be detected to lower fluxes than ones with softer ones with the LAT, the observed bi-variate flux-index distribution is severely truncated at low fluxes and softer spectra. Previously we have used the non-parametric method developed by Efron and Petrosian (EP) to correct the Fermi data for this truncation and obtained the true mono-variate distributions of spectral index and flux (commonly called the logN-logS relation) from which we obtained the blazar contribution to EGB as a function of flux directly from the data (Singal et al. 2012). Extrapolating this to lowest possible fluxes we estimated the total contribution of blazars to the EGB. By now many of the FSRQ blazars are identified with active galactic nuclei and their redshifts measured or obtained from archives (M. Shaw et al., 2012). With the addition of the redshifts we can now calculate the FSRQ blazar luminosities and from the tri-variate luminosity-index-redshift distribution determine the luminosity function and index distribution and their evolutions with redshifts. The EP method can be generalized to this three dimensional case (as we done for SDSS quasars; Singal et al. 2013). In this talk we will present the results from this analysis, which will allow us to compare the density and luminosity evolution of FSRQ blazars with other AGNs. In addition, we can determine the redshift and luminosity (instead of flux) variation of the contribution to the EGB which may allow a more reliable estimate of the total contribution of FSRQ blazars to the EGB.

  7. The X-ray Luminosity Function of Point Sources in Elliptical Galaxies

    NASA Astrophysics Data System (ADS)

    Diehl, Steven; Statler, Thomas

    2004-04-01

    The sub-arcsecond spatial resolution of Chandra recently revealed that early-type galaxies comprise a significant number of low-mass X-ray binaries (LMXBs). Early studies suggest the existence of a 'knee' in their X-ray luminosity function near the Eddington luminosity of a 1.4 Mo neutron star, indicating a transition from neutron star to black hole binaries. Recent analyses show however that a thorough correction for incompleteness is crucial, and able to remove the need for this break luminosity, leaving single power law fits more suitable for the data. We present luminosity functions of 65 elliptical galaxies in the Chandra archive which represents the largest uniformly reduced sample so far. An iterative Bayesian algorithm takes incompleteness and local background variation into account and generates the unbiased luminosity functions. This new non-parametric approach uncovers the significance of the contribution of unresolved LMXBs to the diffuse emission and the degree to which a break luminosity is required.

  8. Modeling the Near-Infrared Luminosity Functions of Young Stellar Clusters

    NASA Astrophysics Data System (ADS)

    Muench, August A.; Lada, Elizabeth A.; Lada, Charles J.

    2000-04-01

    We present the results of numerical experiments designed to evaluate the usefulness of near-infrared (NIR) luminosity functions for constraining the initial mass function (IMF) of young stellar populations. We test the sensitivity of the NIR K-band luminosity function (KLF) of a young stellar cluster to variations in the underlying IMF, star-forming history, and pre-main-sequence mass-to-luminosity relations. Using Monte Carlo techniques, we create a suite of model luminosity functions systematically varying each of these basic underlying relations. From this numerical modeling, we find that the luminosity function of a young stellar population is considerably more sensitive to variations in the underlying initial mass function than to either variations in the star-forming history or assumed pre-main-sequence (PMS) mass-to-luminosity relation. Variations in a cluster's star-forming history are also found to produce significant changes in the KLF. In particular, we find that the KLFs of young clusters evolve in a systematic manner with increasing mean age. Our experiments indicate that variations in the PMS mass-to-luminosity relation, resulting from differences in adopted PMS tracks, produce only small effects on the form of the model luminosity functions and that these effects are mostly likely not detectable observationally. To illustrate the potential effectiveness of using the KLF of a young cluster to constrain its IMF, we model the observed KLF of the nearby Trapezium cluster. With knowledge of the star-forming history of this cluster obtained from optical spectroscopic studies, we derive the simplest underlying IMF whose model luminosity function matches the observations. Our derived mass function for the Trapezium spans 2 orders of magnitude in stellar mass (5>Msolar>0.02) and has a peak near the hydrogen-burning limit. Below the hydrogen-burning limit, the mass function steadily decreases with decreasing mass throughout the brown dwarf regime. Comparison

  9. A New Model for Dark Matter Halos Hosting Quasars

    NASA Astrophysics Data System (ADS)

    Cen, Renyue; Safarzadeh, Mohammadtaher

    2015-01-01

    A new model for quasar-hosting dark matter halos, meeting two physical conditions, is put forth. First, significant interactions are taken into consideration to trigger quasar activities. Second, satellites in very massive halos at low redshift are removed from consideration due to their deficiency in cold gas. We analyze the Millennium Simulation to find halos that meet these two conditions and simultaneously match two-point auto-correlation functions of quasars and cross-correlation functions between quasars and galaxies at z = 0.5-3.2. The masses of the quasar hosts found decrease with decreasing redshift, with the mass thresholds being [(2-5) × 1012, (2-5) × 1011, (1-3) × 1011] M ⊙ for median luminosities of ~[1046, 1046, 1045] erg s-1 at z = (3.2, 1.4, 0.53), respectively, an order of magnitude lower than those inferred based on halo occupation distribution modeling. In this model, quasar hosts are primarily massive central halos at z >= 2-3 but increasingly dominated by lower mass satellite halos experiencing major interactions toward lower redshift. However, below z = 1, satellite halos in groups more massive than ~2 × 1013 M ⊙ do not host quasars. Whether for central or satellite halos, imposing the condition of significant interactions substantially boosts the clustering strength compared to the total population with the same mass cut. The inferred lifetimes of quasars at z = 0.5-3.2 of 3-30 Myr are in agreement with observations. Quasars at z ~ 2 would be hosted by halos of mass ~5 × 1011 M ⊙ in this model, compared to ~3 × 1012 M ⊙ previously thought, which would help reconcile with the observed, otherwise puzzling high covering fractions for Lyman limit systems around quasars.

  10. Luminosity functions and color-magnitude diagrams for three OB associations in the Large Magellanic Cloud

    NASA Technical Reports Server (NTRS)

    Degioia-Eastwood, K.; Meyers, R. P.; Jones, D. P.

    1993-01-01

    Using the point spread function photometry program DAOPHOT, we have used UBV CCD photometry to construct color-magnitude diagrams and luminosity functions for three OB associations in the Large Magellanic Cloud. The region LH 76 appears to be completely coeval; the region LH 13 shows some evidence for noncoevality which will need to be checked with spectra of the stars in question. The region LH 105, which lies on the southern edge of 30 Doradus, shows significant contamination by an underlying older population, possibly from previous star forming events. The luminosity functions, which serve as the first step toward determining the initial mass function in these regions, are calculated.

  11. Cosmic Reionization on Computers: The Faint End of the Galaxy Luminosity Function

    NASA Astrophysics Data System (ADS)

    Gnedin, Nickolay Y.

    2016-07-01

    Using numerical cosmological simulations completed under the “Cosmic Reionization On Computers” project, I explore theoretical predictions for the faint end of the galaxy UV luminosity functions at z≳ 6. A commonly used Schechter function approximation with the magnitude cut at {M}{{cut}}˜ -13 provides a reasonable fit to the actual luminosity function of simulated galaxies. When the Schechter functional form is forced on the luminosity functions from the simulations, the magnitude cut {M}{{cut}} is found to vary between -12 and -14 with a mild redshift dependence. An analytical model of reionization from Madau et al., as used by Robertson et al., provides a good description of the simulated results, which can be improved even further by adding two physically motivated modifications to the original Madau et al. equation.

  12. Cosmic reionization on computers: The faint end of the galaxy luminosity function

    DOE PAGES

    Gnedin, Nickolay Y.

    2016-07-01

    Using numerical cosmological simulations completed under the “Cosmic Reionization On Computers” project, I explore theoretical predictions for the faint end of the galaxy UV luminosity functions atmore » $$z\\gtrsim 6$$. A commonly used Schechter function approximation with the magnitude cut at $${M}_{{\\rm{cut}}}\\sim -13$$ provides a reasonable fit to the actual luminosity function of simulated galaxies. When the Schechter functional form is forced on the luminosity functions from the simulations, the magnitude cut $${M}_{{\\rm{cut}}}$$ is found to vary between -12 and -14 with a mild redshift dependence. Here, an analytical model of reionization from Madau et al., as used by Robertson et al., provides a good description of the simulated results, which can be improved even further by adding two physically motivated modifications to the original Madau et al. equation.« less

  13. Extra-galactic high-energy transients: event rate density and luminosity function

    NASA Astrophysics Data System (ADS)

    Sun, Hui; Zhang, Bing; Li, Zhuo

    2015-08-01

    Several types of extra-galactic high-energy transients have been discovered, which include high-luminosity and low-luminosity long-duration gamma-ray bursts (GRBs), short-duration GRBs, supernova shock breakouts (SBOs), and tidal disruption events (TDEs) without or with a relativistic jet. In this paper, we apply a unified method to systematically study the reshift-dependent event rate densities and luminosity functions of these extra-galactic high-energy transients. We consider star formation history as the tracer of the redshift distribution for long GRBs and SBOs. For short GRBs, we consider the compact star merger model to introduce several possible merger delay time distribution models. For TDEs, we consider the mass distribution of supermassive black holes as a function of redshift. We derive some empirical formulae for the redshift-dependent event rate density for different types of transients. Based on the observed events, we derive the local specific event rate density, ρ0,L ∝ dρ0/dL for each type of transient, which represents its luminosity function. All the transients are consistent with having a single power law luminosity function, except the high luminosity long GRBs (HL-lGRBs), whose luminosity function can be well described by a broken power law. The total event rate density for a particular transient depends on the luminosity threshold, and we obtain the following values in units of Gpc-3 yr-1: 2.82^{+0.41}_{-0.36} for HL-lGRBs above 4×1049 erg s-1 218^{+130}_{-86} for low luminosity long GRBs above 6×1046 erg s-1 3.18^{+0.88}_{-0.70}, 2.87^{+0.80}_{-0.64}, and 6.25^{+1.73}_{-1.38} above 5×1049 erg s-1 for short GRBs with three different merger delay models (Gaussian, log-normal, and power law); 2.0^{+2.6}_{-1.3}×104 above 9×1043 erg s-1 for SBOs, 3.0^{+1.0}_{-0.8}×105 for normal TDEs above 1042 erg s-1 and 6.2^{+8.2}_{-4.0} above 3×1047 erg s-1for TDE jets as discovered by Swift. Intriguingly, the global specific event rate densities

  14. The faint end of the 250 μm luminosity function at z < 0.5

    NASA Astrophysics Data System (ADS)

    Wang, L.; Norberg, P.; Bethermin, M.; Bourne, N.; Cooray, A.; Cowley, W.; Dunne, L.; Dye, S.; Eales, S.; Farrah, D.; Lacey, C.; Loveday, J.; Maddox, S.; Oliver, S.; Viero, M.

    2016-08-01

    Aims: We aim to study the 250 μm luminosity function (LF) down to much fainter luminosities than achieved by previous efforts. Methods: We developed a modified stacking method to reconstruct the 250 μm LF using optically selected galaxies from the SDSS survey and Herschel maps of the GAMA equatorial fields and Stripe 82. Our stacking method not only recovers the mean 250 μm luminosities of galaxies that are too faint to be individually detected, but also their underlying distribution functions. Results: We find very good agreement with previous measurements in the overlapping luminosity range. More importantly, we are able to derive the LF down to much fainter luminosities (~ 25 times fainter) than achieved by previous studies. We find strong positive luminosity evolution L*250(z)∝(1+z)4.89±1.07 and moderate negative density evolution Φ*250(z)∝(1+z)-1.02±0.54 over the redshift range 0.02

  15. The most powerful quasar outflows as revealed by the Civ λ1549 resonance line

    NASA Astrophysics Data System (ADS)

    Marziani, P.; Martínez Carballo, M. A.; Sulentic, J. W.; Del Olmo, A.; Stirpe, G. M.; Dultzin, D.

    2016-01-01

    Outflows from quasars may be almost ubiquitous, but there are significant differences on a source- by-source basis. These differences can be organized along the 4D Eigenvector 1 sequence: at low z, only the Population A sources radiating at relatively high Eddington ratio show evidences of prominent high- velocity outflows from the Civλ1549 line profiles. Here we discuss, starting from recent observations of high-luminosity sample of Hamburg-ESO quasars, the Civλ1549 emission line profiles and how they are affected by outflow motion as a function of the quasar luminosity. Our high-luminosity sample has the notable advantage that the rest frame has been set by previous Hβ observations in the J, H, and K band, therefore making measurements of inter-line shift accurate and free of systemic biases. As the redshift increases and the luminosity of the brightest quasars grows, powerful, high-velocity outflows may become more frequent. We then discuss the outflow contextualisation following the 4DE1 approach as a tool for unveiling the nature of the so-called Weak Lined Quasars (WLQs) that have emerged in recent years as a new, poorly understood class of quasars. We estimate the kinetic power associated with the Civλ1549 emitting gas in outflow, and we suggest that the host galaxies of the most luminous sources may experience a significant feedback effect.

  16. On the luminosity function, lifetimes, and origin of blue stragglers in globular clusters

    NASA Technical Reports Server (NTRS)

    Bailyn, Charles D.; Pinsonneault, Marc H.

    1995-01-01

    We compute theoretical evolutionary tracks of blue stragglers created by mergers. Two formation scenarios are considered: mergers of primordial binaries, and stellar collisions. These two scenarios predict strikingly different luminosity functions, which are potentially distinguishable observationally. Tabulated theoretical luminosity functions and lifetimes are presented for blue stragglers formed under a variety of input conditions. We compare our results with observations of the blue straggler sequences in 47 Tucanae and M3. In the case of 47 Tuc, the luminosity function and the formation rate are compatible with the hypothesis that the blue stragglers formed through the collision of single stars. Mergers of primordial binaries are only marginally cosistent with the data, and a significant enhancement of the collision cross section by binary-single-star encounters appears to be ruled out. In the case of M3, we find that the innermost blue stragglers have a luminosity function significantly different from that of the outer stragglers, thus confirming earlier suggestions that there are two distinct populations of blue stragglers in this cluster. The inner stragglers are preferentially brighter and bluer, as would be expected if they were made by collisions, but there are so many of them that the collision rate would need to be enhanced by interactions involving wide binaries. The luminosity function of the outer stragglers is almost identical to the predictions of mergers from primordial binaries and is inconsistent with the collision hypothesis.

  17. The nearby Abell clusters. III. Luminosity functions for eight rich clusters

    SciTech Connect

    Oegerle, W.R.; Hoessel, J.G. Washburn Observatory, Madison, WI )

    1989-11-01

    Red photographic data on eight rich Abell clusters are combined with previous results on four other Abell clusters to study the luminosity functions of the clusters. The results produce a mean value of the characteristic galaxy magnitude (M asterisk) that is consistent with previous results. No relation is found between the magnitude of the first-ranked cluster galaxy and M asterisk, suggesting that the value of M asterisk is not changed by dynamical evolution. The faint ends of the luminosity functions for many of the clusters are quite flat, validating the nonuniversality in the parametrization of Schechter (1976) functions for rich clusters of galaxies. 40 refs.

  18. Heavily obscured quasar host galaxies at z ∼ 2 are discs, not major mergers

    NASA Astrophysics Data System (ADS)

    Schawinski, Kevin; Simmons, Brooke D.; Urry, C. Megan; Treister, Ezequiel; Glikman, Eilat

    2012-09-01

    We explore the nature of heavily obscured quasar host galaxies at z˜ 2 using deep Hubble Space Telescope Wide Field Camera 3/infrared imaging of 28 dust-obscured galaxies (DOGs) to investigate the role of major mergers in driving black hole growth. The high levels of obscuration of the quasars selected for this study act as a natural coronagraph, blocking the quasar light and allowing a clear view of the underlying host galaxy. The sample of heavily obscured quasars represents a significant fraction of the cosmic mass accretion on supermassive black holes as the quasars have inferred bolometric luminosities around the break of the quasar luminosity function. We find that only a small fraction (4 per cent, at most 11-25 per cent) of the quasar host galaxies are major mergers. Fits to their surface brightness profiles indicate that 90 per cent of the host galaxies are either disc dominated, or have a significant disc. This disc-like host morphology, and the corresponding weakness of bulges, is evidence against major mergers and suggests that secular processes are the predominant driver of massive black hole growth. Finally, we suggest that the coincidence of mergers and active galactic nucleus activity is luminosity dependent, with only the most luminous quasars being triggered mostly by major mergers. a MUSYC catalogue ID, see Cardamone et al. (2010). Objects with X-ray detections are marked with *. b See images shown in Fig. 1. c The ratio of the host luminosity to the point source luminosity, reported only when GALFIT requires an unresolved object to yield a physical fit. This may be due to an AGN point source (in the case of the X-ray-detected DOGs) or an unresolved bulge or central concentration, i.e. a central bulge. d See Fig. 2.

  19. Re-analysis of the Radio Luminosity Function of Galactic H II Regions

    NASA Astrophysics Data System (ADS)

    Paladini, R.; De Zotti, G.; Noriega-Crespo, A.; Carey, S. J.

    2009-09-01

    We have re-analyzed continuum and recombination lines radio data available in the literature in order to derive the luminosity function (LF) of Galactic H II regions. The study is performed by considering the first and fourth Galactic quadrants independently. We estimate the completeness level of the sample in the fourth quadrant at 5 Jy, and the one in the first quadrant at 2 Jy. We show that the two samples (fourth or first quadrant) include, as well as giant and supergiant H II regions, a significant number of subgiant sources. The LF is obtained, in each Galactic quadrant, with a generalized Schmidt's estimator using an effective volume derived from the observed spatial distribution of the considered H II regions. The re-analysis also takes advantage of recently published ancillary absorption data allowing to solve the distance ambiguity for several objects. A single power-law fit to the LFs retrieves a slope equal to -2.23 ± 0.07 (fourth quadrant) and to -1.85 ± 0.11 (first quadrant). We also find marginal evidence of a luminosity break at L knee = 1023.45 erg s-1 Hz-1 for the LF in the fourth quadrant. We convert radio luminosities into equivalent Hα and Lyman continuum luminosities to facilitate comparisons with extragalactic studies. We obtain an average total H II regions Lyman continuum luminosity of 0.89 ± 0.23 × 1053 s-1, corresponding to 30% of the total ionizing luminosity of the Galaxy.

  20. In the neighbourhood of Tame Monsters. A study of galaxies near low-redshift quasars

    NASA Astrophysics Data System (ADS)

    Villarroel, B.

    2012-06-01

    Context. The impact of quasars on their galaxy neighbours is an important factor in the understanding of galaxy evolution models. Aims: The aim of this work is to characterize the intermediate-scale environments of quasars at low redshift (z < 0.2) with the most statistically complete sample to date using the seventh data release of the Sloan Digital Sky Survey. Methods: We have used 305 quasar-galaxy associations with spectroscopically measured redshifts within the projected distance range of 350 kpc, to calculate how surface densities of galaxies, colors, degree of ionization, dust extinction and star-formation rates change as a function of the distance to our quasar sample. We also identify the companion active galactic nuclei from our main galaxy sample and calculate surface density for different galaxy types. We have done this in three different quasar-galaxy redshift difference ranges |Δz| < 0.001, 0.006, and 0.012. Results: Our results suggest that there is a significant increase of the surface density of blue neighbours around our low-redshift quasar sample that is steeper than around non-active field galaxies of the same luminosity and redshift range. This may indicate that quasar formation is accomplished via a merging scenario. No significant changes in star formation rate, dust extinction, degree of ionization or color as a function of distance from the quasars was observed. We could not observe any direct effects from quasars on the their companion galaxies.

  1. Estimating the rate and luminosity function of all classes of GRBs

    NASA Astrophysics Data System (ADS)

    Balastegui, A.; Canal, R.; Ruiz-Lapuente, P.

    2011-10-01

    The aim of the present work is to estimate the rate and luminosity functions of short, intermediate and long gamma-ray bursts (GRBs) by fitting their intensity distributions with parameterized explosion rates and luminosity functions. The results show that the parameters of the rate and luminosity function for long GRBs can be calculated with an accuracy of 10-30%. However, some parameters of intermediate and short GRBs have large uncertainties. An important conclusion is that there was initially a large outburst in the frequency of long GRBs, and consequently a large outburst in the star-formation rate, if they come from collapsars. Finally, a simulated intensity distribution has been constructed to test the ability of the method to recover the simulated parameters.

  2. A study of the luminosity and mass functions of very young stellar clusters

    NASA Astrophysics Data System (ADS)

    Muench, August Albert

    We now know that the star formation process results in freely-floating objects with masses spanning nearly four orders of magnitude. However, both the distribution of these objects' masses at birth and the precise physics responsible for the shape of this initial mass function are poorly known and can be improved upon by focusing on very young star clusters just emerging from their parental molecular clouds. In this dissertation I have investigated the usefulness of the observed luminosity function of a very young cluster as a tool for deriving that cluster's underlying mass function. I find that a cluster's luminosity function is an excellent probe of the initial mass function over the entire range of stellar and substellar mass and can be utilized to acquire the statistics necessary for testing the hypothesis of a universal mass function. To study the luminosity and mass functions of such clusters I developed a Monte Carlo based population synthesis algorithm applicable to pre-main sequence stars. Using this algorithm I performed numerical experiments testing the sensitivity of model luminosity functions to changes in fundamental cluster parameters. After showing that the luminosity function is intrinsically most sensitive to the form of the underlying mass function, I studied three young clusters, NGC 2362, IC 348 and the Trapezium, and performed deep near-infrared surveys to construct their K-band luminosity functions. Using the model luminosity function algorithm, I derived each cluster's underlying mass function and found them to be remarkably similar, with all forming broad peaks at subsolar masses. Where these census are sufficiently deep I find that the mass function turns over and declines in number throughout the substellar regime but appears to contain structure near the deuterium-burning limit. Regardless, I find that brown dwarfs do not dominate stars either by number or total mass. Lastly, I use a statistically significant sample of candidate brown

  3. Causes and effects of the first quasars.

    PubMed

    Rees, M J

    1993-06-01

    The light we observe from the most distant known quasars set out when the Universe was about 200 times denser than it is now and less than one-tenth of its present age. The existence of these objects implies that galaxy formation had already, at that early epoch, proceeded to the stage when massive (>10(8)M[symbol, see text]) objects had accumulated in the centers of at least some young galaxies. A specific model is presented to show that the evolution and luminosity function of quasars are compatible with the cold dark matter cosmogony. Most big galaxies probably passed through a quasar phase; the remnant black holes in nearby galaxies may reveal themselves via the flares that occur whenever a star passes too close to them and gets tidally disrupted. The rich absorption spectra of quasars serve as a probe of the intervening medium. The gas responsible for the Lyman alpha absorption lines may be due to primordial gas gravitationally confined in minihalos of dark matter--shallow potential wells whose evolution and relation to dwarf galaxies are briefly discussed. The patchy heat input into the intergalactic medium from early quasars could modulate the environment in which galaxies form, leading to large-scale spatial correlations in the galaxy distribution. This review concludes with general comments on the prospects for a fully quantitative understanding of galaxy formation.

  4. Causes and effects of the first quasars.

    PubMed Central

    Rees, M J

    1993-01-01

    The light we observe from the most distant known quasars set out when the Universe was about 200 times denser than it is now and less than one-tenth of its present age. The existence of these objects implies that galaxy formation had already, at that early epoch, proceeded to the stage when massive (>10(8)M[symbol, see text]) objects had accumulated in the centers of at least some young galaxies. A specific model is presented to show that the evolution and luminosity function of quasars are compatible with the cold dark matter cosmogony. Most big galaxies probably passed through a quasar phase; the remnant black holes in nearby galaxies may reveal themselves via the flares that occur whenever a star passes too close to them and gets tidally disrupted. The rich absorption spectra of quasars serve as a probe of the intervening medium. The gas responsible for the Lyman alpha absorption lines may be due to primordial gas gravitationally confined in minihalos of dark matter--shallow potential wells whose evolution and relation to dwarf galaxies are briefly discussed. The patchy heat input into the intergalactic medium from early quasars could modulate the environment in which galaxies form, leading to large-scale spatial correlations in the galaxy distribution. This review concludes with general comments on the prospects for a fully quantitative understanding of galaxy formation. PMID:11607397

  5. Causes and effects of the first quasars.

    PubMed

    Rees, M J

    1993-06-01

    The light we observe from the most distant known quasars set out when the Universe was about 200 times denser than it is now and less than one-tenth of its present age. The existence of these objects implies that galaxy formation had already, at that early epoch, proceeded to the stage when massive (>10(8)M[symbol, see text]) objects had accumulated in the centers of at least some young galaxies. A specific model is presented to show that the evolution and luminosity function of quasars are compatible with the cold dark matter cosmogony. Most big galaxies probably passed through a quasar phase; the remnant black holes in nearby galaxies may reveal themselves via the flares that occur whenever a star passes too close to them and gets tidally disrupted. The rich absorption spectra of quasars serve as a probe of the intervening medium. The gas responsible for the Lyman alpha absorption lines may be due to primordial gas gravitationally confined in minihalos of dark matter--shallow potential wells whose evolution and relation to dwarf galaxies are briefly discussed. The patchy heat input into the intergalactic medium from early quasars could modulate the environment in which galaxies form, leading to large-scale spatial correlations in the galaxy distribution. This review concludes with general comments on the prospects for a fully quantitative understanding of galaxy formation. PMID:11607397

  6. The Hubble relation for nonstandard candles and the origin of the redshift of quasars

    NASA Technical Reports Server (NTRS)

    Petrosian, V.

    1974-01-01

    It is shown that the magnitude-log (redshift) relation for brightest quasars can have a slope different from the value expected for standard candles. The value of this slope depends on the luminosity function and its evolution. Therefore the difference of this slope from the expected value cannot be used as evidence against the cosmological origin of the redshift of the quasars. It is shown that the observed variation of the luminosity of the brightest objects with redshift is consistent with the cosmological hypothesis and that it agrees with (and perhaps could be used to complement) the luminosity function obtained from V/Vm analysis. It is also shown that the nonzero slope of the magnitude-log (redshift) relation rules out the local quasar hypothesis, where it is assumed that the sources are nearby (less than 500 Mpc), that the bulk of their redshift is intrinsic, and that there is no dependence on distance of the intrinsic properties of the sources.

  7. THE GALAXY OPTICAL LUMINOSITY FUNCTION FROM THE AGN AND GALAXY EVOLUTION SURVEY

    SciTech Connect

    Cool, Richard J.; Eisenstein, Daniel J.; Kochanek, Christopher S.; Brown, Michael J. I.; Caldwell, Nelson; Forman, William R.; Hickox, Ryan C.; Jones, Christine; Murray, Stephen S.; Dey, Arjun; Jannuzi, Buell T.; Moustakas, John

    2012-03-20

    We present the galaxy optical luminosity function for the redshift range 0.05 < z < 0.75 from the AGN and Galaxy Evolution Survey, a spectroscopic survey of 7.6 deg{sup 2} in the Booetes field of the NOAO Deep Wide-Field Survey. Our statistical sample is composed of 12,473 galaxies with known redshifts down to I = 20.4 (AB). Our results at low redshift are consistent with those from Sloan Digital Sky Survey; at higher redshift, we find strong evidence for evolution in the luminosity function, including differential evolution between blue and red galaxies. We find that the luminosity density evolves as (1 + z){sup (0.54{+-}0.64)} for red galaxies and (1 + z){sup (1.64{+-}0.39)} for blue galaxies.

  8. Spatial distribution and luminosity function of OH/IR maser sources

    NASA Astrophysics Data System (ADS)

    Tong, Y.; Sun, J.; Xie, S.-D.; Yang, X.-X.

    1984-12-01

    Published observational data on 127 OH-maser sources for which visible or IR identifications and distance estimates are available (mainly from the list of Engels, 1979) are analyzed statistically to determine their Galactic distribution and luminosity function. The results are presented graphically and discussed. A density distribution with a steep peak at about 7.5 kpc from the Galactic center and FWHM 2.1 kpc, similar to that found for Mira variables by Glass et al. (1982) and markedly different from that of Baud et al. (1979 and 1981) for unidentified objects, is observed. The luminosity function rho(L) is found to be equal to 189.67 L exp -1.79, like that for unidentified objects, despite the fact that the observed luminosity range (0.16-1000 Jy kpc sq) of the identified sources is wider than that determined by Bowers (1978) for unidentified sources.

  9. Dependence of the bright end of composite galaxy luminosity functions on cluster dynamical states

    NASA Astrophysics Data System (ADS)

    Wen, Z. L.; Han, J. L.

    2015-03-01

    The luminosity function of cluster galaxies provides a fundamental constraint on galaxy evolution in cluster environments. By using the bright member galaxies of a large sample of rich clusters identified from the Sloan Digital Sky Survey, we obtain the bright end of composite luminosity functions of cluster galaxies, and study their dependence on a cluster dynamical states. After a redshift-evolution correction of absolute magnitude, the luminosity function of member galaxies can be well fitted by a Schechter function when the brightest cluster galaxies (BCGs) are excluded. The absolute magnitudes of BCGs follow a Gaussian function with a characteristic width of about 0.36 mag. We find that the luminosity function of galaxies in more relaxed clusters has a fainter characteristic absolute magnitude (M*), and these clusters have fewer bright non-BCG member galaxies but a brighter BCG. Our results suggest the co-evolution of galaxy population with a cluster dynamical state and support the hierarchical formation scenario of the BCGs.

  10. Near-Infrared Properties of Moderate-Redshift Galaxy Clusters: Luminosity Functions and Density Profiles

    SciTech Connect

    Muzzin, Adam; Yee, H.K.C.; Hall, Patrick B.; Ellingson, E.; Lin, Huan; /Fermilab

    2006-12-01

    We present K-band imaging for 15 of the Canadian Network for Observational Cosmology (CNOC1) clusters. The extensive spectroscopic dataset available for these clusters allows us to determine the cluster K-band luminosity function and density profile without the need for statistical background subtraction. The luminosity density and number density profiles can be described by NFW models with concentration parameters of c{sub l} = 4.28 {+-} 0.70 and c{sub g} = 4.13 {+-} 0.57 respectively. Comparing these to the dynamical mass analysis of the same clusters shows that the galaxy luminosity and number density profiles are similar to the dark matter profile, and are not less concentrated like in local clusters. The luminosity functions show that the evolution of K. over the redshift range 0.2 < z < 0.5 is consistent with a scenario where the majority of stars in cluster galaxies form at high-redshift (z{sub f} > 1.5) and evolve passively thereafter. The best-fit for the faint-end slope of the luminosity function is {alpha} = -0.84 {+-} 0.08, which indicates that it does not evolve between z = 0 and z = 0.3. Using Principal Component Analysis of the spectra we classify cluster galaxies as either star-forming/recently-star-forming (EM+BAL) or non-star forming (ELL) and compute their respective luminosity functions. The faint-end slope of the ELL luminosity function is much shallower than for the EM+BAL galaxies at z = 0.3, and suggests the number of faint ELL galaxies in clusters decreases by a factor of {approx} 3 from z = 0 to z = 0.3. The redshift evolution of K* for both EM+BAL and ELL types is consistent with a passively evolving stellar population formed at high-redshift. Passive evolution in both classes, as well as the total cluster luminosity function, demonstrates that the bulk of the stellar population in all bright cluster galaxies is formed at high-redshift and subsequent transformations in morphology/color/spectral-type have little effect on the total stellar

  11. THE HALO OCCUPATION DISTRIBUTION OF SDSS QUASARS

    SciTech Connect

    Richardson, Jonathan; Chatterjee, Suchetana; Nagai, Daisuke; Zheng Zheng; Shen Yue

    2012-08-10

    We present an estimate of the projected two-point correlation function (2PCF) of quasars in the Sloan Digital Sky Survey (SDSS) over the full range of one- and two-halo scales, 0.02 h{sup -1} Mpc < r{sub p} < 120 h{sup -1} Mpc. This was achieved by combining data from SDSS DR7 on large scales and Hennawi et al. (with appropriate statistical corrections) on small scales. Our combined clustering sample is the largest spectroscopic quasar clustering sample to date, containing {approx}48, 000 quasars in the redshift range 0.4 {approx}< z {approx}< 2.5 with median redshift 1.4. We interpret these precise 2PCF measurements within the halo occupation distribution (HOD) framework and constrain the occupation functions of central and satellite quasars in dark matter halos. In order to explain the small-scale clustering, the HOD modeling requires that a small fraction of z {approx} 1.4 quasars, f{sub sat} = (7.4 {+-} 1.4) Multiplication-Sign 10{sup -4}, be satellites in dark matter halos. At z {approx} 1.4, the median masses of the host halos of central and satellite quasars are constrained to be M{sub cen} = 4.1{sup +0.3}{sub -0.4} Multiplication-Sign 10{sup 12} h{sup -1} M{sub Sun} and M{sub sat} = 3.6{sup +0.8}{sub -1.0} Multiplication-Sign 10{sup 14} h{sup -1} M{sub Sun }, respectively. To investigate the redshift evolution of the quasar-halo relationship, we also perform HOD modeling of the projected 2PCF measured by Shen et al. for SDSS quasars with median redshift 3.2. We find tentative evidence for an increase in the mass scale of quasar host halos-the inferred median mass of halos hosting central quasars at z {approx} 3.2 is M{sub cen} = 14.1{sup +5.8}{sub -6.9} Multiplication-Sign 10{sup 12} h{sup -1} M{sub Sun }. The cutoff profiles of the mean occupation functions of central quasars reveal that quasar luminosity is more tightly correlated with halo mass at higher redshifts. The average quasar duty cycle around the median host halo mass is inferred to be f{sub q

  12. A Monte Carlo approach to evolution of the far-infrared luminosity function with BLAST

    NASA Astrophysics Data System (ADS)

    Marsden, Gaelen; Chapin, Edward L.; Halpern, Mark; Patanchon, Guillaume; Scott, Douglas; Truch, Matthew D. P.; Valiante, Elisabetta; Viero, Marco P.; Wiebe, Donald V.

    2011-10-01

    We constrain the evolution of the rest-frame far-infrared (FIR) luminosity function out to high redshift, by combining several pieces of complementary information provided by the deep Balloon-borne Large-Aperture Submillimeter Telescope surveys at 250, 350 and 500 μm, as well as other FIR and millimetre data. Unlike most other phenomenological models, we characterize the uncertainties in our fitted parameters using Monte Carlo Markov Chains. We use a bivariate local luminosity function that depends only on FIR luminosity and 60-to-100 μm colour, along with a single library of galaxy spectral energy distributions indexed by colour, and apply simple luminosity and density evolution. We use the surface density of sources, Cosmic Infrared Background (CIB) measurements and redshift distributions of bright sources, for which identifications have been made, to constrain this model. The precise evolution of the FIR luminosity function across this crucial range has eluded studies at longer wavelengths (e.g. using SCUBA and MAMBO) and at shorter wavelengths (e.g. with Spitzer), and should provide a key piece of information required for the study of galaxy evolution. Our adoption of Monte Carlo methods enables us not only to find the best-fitting evolution model, but also to explore correlations between the fitted parameters. Our model-fitting approach allows us to focus on sources of tension coming from the combination of data sets. We specifically find that our choice of parametrization has difficulty fitting the combination of CIB measurements and redshift distribution of sources near 1 mm. Existing and future data sets will be able to dramatically improve the fits, as well as break strong degeneracies among the models. Two particular examples that we find to be crucial are: obtaining robust information on redshift distributions and placing tighter constraints on the range of spectral shapes for low-luminosity (LFIR < 1010 L⊙) sources.

  13. The blazar gamma-ray luminosity function and the diffuse extragalactic gamma-ray background

    NASA Technical Reports Server (NTRS)

    Salamon, M. H.; Stecker, F. W.

    1994-01-01

    We have used the data from the new EGRET catalog on 'grazars' (blazers which are observed to be high-energy gamma-ray sources), together with radio data, to construct a new relation between radio and gamma-ray luminosity for these sources. Using this relation to construct a grazar gamma-ray luminosity function, we then calculate the contribution of unresolved grazars to the cosmic gamma-ray background radiation. We derive the energy spectrum of this background component above 100 MeV and the angular fluctuations in this background implied by our model.

  14. The white dwarf luminosity function - A possible probe of the galactic halo

    SciTech Connect

    Tamanaha, C.M.; Silk, J.; Wood, M.A.; Winget, D.E. McDonald Observatory, Austin, TX )

    1990-07-01

    The dynamically inferred dark halo mass density, amounting to above 0.01 solar masses/cu pc at the sun's Galactocentric radius, can be composed of faint white dwarfs provided that the halo formed in a sufficiently early burst of star formation. The model is constrained by the observed disk white dwarf luminosity function which falls off below log (L/solar L) = -4.4, due to the onset of star formation in the disk. By using a narrow range for the initial mass function and an exponentially decaying halo star formation rate with an e-folding time equal to the free-fall time, all the halo dark matter is allowed to be in cool white dwarfs which lie beyond the falloff in the disk luminosity function. Although it is unlikely that all the dark matter is in these dim white dwarfs, a definite signature in the low-luminosity end of the white dwarf luminosity function is predicted even if they comprise only 1 percent of the dark matter. Current CCD surveys should answer the question of the existence of this population within the next few years. 39 refs.

  15. The white dwarf luminosity function - A possible probe of the galactic halo

    NASA Technical Reports Server (NTRS)

    Tamanaha, Christopher M.; Silk, Joseph; Wood, M. A.; Winget, D. E.

    1990-01-01

    The dynamically inferred dark halo mass density, amounting to above 0.01 solar masses/cu pc at the sun's Galactocentric radius, can be composed of faint white dwarfs provided that the halo formed in a sufficiently early burst of star formation. The model is constrained by the observed disk white dwarf luminosity function which falls off below log (L/solar L) = -4.4, due to the onset of star formation in the disk. By using a narrow range for the initial mass function and an exponentially decaying halo star formation rate with an e-folding time equal to the free-fall time, all the halo dark matter is allowed to be in cool white dwarfs which lie beyond the falloff in the disk luminosity function. Although it is unlikely that all the dark matter is in these dim white dwarfs, a definite signature in the low-luminosity end of the white dwarf luminosity function is predicted even if they comprise only 1 percent of the dark matter. Current CCD surveys should answer the question of the existence of this population within the next few years.

  16. Intensity Distribution and Luminosity Function of the Swift Gamma-Ray Bursts

    NASA Astrophysics Data System (ADS)

    Dai, Xinyu

    2009-05-01

    Using the sample of long gamma-ray bursts (GRBs) detected by Swift-BAT before 2007 June, we measure the cumulative distribution of the peak photon fluxes (log N-log P) of the Swift bursts. Compared with the BATSE sample, we find that the two distributions are consistent after correcting the bandpass difference, suggesting that the two instruments sample the same population of bursts. We also compare the log N-log P distributions for subsamples of the Swift bursts and find evidence for a deficit (99.75% confident) of dark bursts without optical counterparts at high peak flux levels, suggesting different redshift or γ-ray luminosity distributions for these bursts. The consistency between the log N-log P distributions for the optically detected bursts with and without redshift measurements indicates that the current sample of the Swift bursts with redshift measurements, although selected heterogeneously, represents a fair sample of the nondark bursts. We calculate the luminosity functions of this sample in two redshift bins (z < 1 and z >= 1), and find that a broken power law is needed to fit the low-redshift bin, where dN/dL vprop L -1.27±0.06 for high luminosities (L peak > 5 × 1048 ergs-1) and dN/dL vprop L -2.3±0.3 for low luminosities, confirming the results of several studies for a population of low-luminosity GRBs.

  17. Detailed Shape and Evolutionary Behavior of the X-Ray Luminosity Function of Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Miyaji, T.; Hasinger, G.; Salvato, M.; Brusa, M.; Cappelluti, N.; Civano, F.; Puccetti, S.; Elvis, M.; Brunner, H.; Fotopoulou, S.; Ueda, Y.; Griffiths, R. E.; Koekemoer, A. M.; Akiyama, M.; Comastri, A.; Gilli, R.; Lanzuisi, G.; Merloni, A.; Vignali, C.

    2015-05-01

    We construct the rest-frame 2-10 keV intrinsic X-ray luminosity function (XLF) of active galactic nuclei (AGNs) from a combination of X-ray surveys from the all-sky Swift BAT survey to the Chandra Deep Field South. We use ˜3200 AGNs in our analysis, which covers six orders of magnitude in flux. The inclusion of XMM and Chandra COSMOS data has allowed us to investigate the detailed behavior of the XLF and evolution. In deriving our XLF, we take into account realistic AGN spectrum templates, absorption corrections, and probability density distributions in photometric redshift. We present an analytical expression for the overall behavior of the XLF in terms of the luminosity-dependent density evolution, smoothed two-power-law expressions in 11 redshift shells, three-segment power-law expression of the number density evolution in four luminosity classes, and binned XLF. We observe a sudden flattening of the low luminosity end slope of the XLF slope at z ≳0.6. Detailed structures of the AGN downsizing have also been revealed, where the number density curves have two clear breaks at all luminosity classes above log {{L}X}\\gt 43. The two-break structure is suggestive of two-phase AGN evolution, consisting of major merger triggering and secular processes.

  18. Evolution of the Blue and Far-Infrared Galaxy Luminosity Functions

    NASA Technical Reports Server (NTRS)

    Lonsdale, Carol J.; Chokshi, Arati

    1993-01-01

    The space density of blue-selected galaxies at moderate redshifts is determined here directly by deriving the luminosity function. Evidence is found for density evolution for moderate luminosity galaxies at a rate of (1+z) exp delta, with a best fit of delta + 4 +/- 2, between the current epoch and Z greater than about 0.1. At M(b) less than -22 evidence is found for about 0.5-1.5 mag of luminosity evolution in addition to the density evolution, corresponding to an evolutionary rate of about (1+z) exp gamma, with gamma = 0.5-2.5, but a redshift of about 0.4. Assuming a steeper faint end slope of alpha = -1.3 similar to that observed in the Virgo cluster, could explain the data with a luminosity evolution rate of gamma = 1-2, without need for any density evolution. Acceptable fits are found by comparing composite density and luminosity evolution models to faint IRAS 60 micron source counts, implying that the blue and far-IR evolutionary rates may be similar.

  19. The galaxy cluster mid-infrared luminosity function at 1.3 < z < 3.2

    SciTech Connect

    Wylezalek, Dominika; Vernet, Joël; De Breuck, Carlos; Stern, Daniel; Brodwin, Mark; Galametz, Audrey; Gonzalez, Anthony H.; Jarvis, Matt; Hatch, Nina; Seymour, Nick; Stanford, Spencer A.

    2014-05-01

    We present 4.5 μm luminosity functions for galaxies identified in 178 candidate galaxy clusters at 1.3 < z < 3.2. The clusters were identified as Spitzer/Infrared Array Camera (IRAC) color-selected overdensities in the Clusters Around Radio-Loud AGN project, which imaged 420 powerful radio-loud active galactic nuclei (RLAGNs) at z > 1.3. The luminosity functions are derived for different redshift and richness bins, and the IRAC imaging reaches depths of m* + 2, allowing us to measure the faint end slopes of the luminosity functions. We find that α = –1 describes the luminosity function very well in all redshift bins and does not evolve significantly. This provides evidence that the rate at which the low mass galaxy population grows through star formation gets quenched and is replenished by in-falling field galaxies does not have a major net effect on the shape of the luminosity function. Our measurements for m* are consistent with passive evolution models and high formation redshifts (z{sub f} ∼ 3). We find a slight trend toward fainter m* for the richest clusters, implying that the most massive clusters in our sample could contain older stellar populations, yet another example of cosmic downsizing. Modeling shows that a contribution of a star-forming population of up to 40% cannot be ruled out. This value, found from our targeted survey, is significantly lower than the values found for slightly lower redshift, z ∼ 1, clusters found in wide-field surveys. The results are consistent with cosmic downsizing, as the clusters studied here were all found in the vicinity of RLAGNs—which have proven to be preferentially located in massive dark matter halos in the richest environments at high redshift—and they may therefore be older and more evolved systems than the general protocluster population.

  20. Constraining the rate and luminosity function of Swift gamma-ray bursts

    NASA Astrophysics Data System (ADS)

    Howell, E. J.; Coward, D. M.; Stratta, G.; Gendre, B.; Zhou, H.

    2014-10-01

    We compute the intrinsic isotropic peak luminosity function (LF) and formation rate of long gamma-ray bursts (LGRBs) using a novel approach. We complement a standard log N-log P brightness distribution and Vmax estimations with two observation-time relations: a redshift-observation-time relation (log z-log T) and a new luminosity-observation-time relation (log L-log T). We show that this approach reduces degeneracies that exist between the rate and LF of a brightness distribution. To account for the complex triggering algorithm employed by Swift, we use recent results of Lien et al. (2014) to produce a suite of efficiency functions. Using these functions with the above methods, we show that a log L-log T method can provide good constraints on the form of the LF, particularly the high end. Using a sample of 175 peak luminosities determined from redshifts with well-defined selection criteria, our results suggest that LGRBs occur at a local rate (without beaming corrections) of [0.7 < ρ0 < 0.8] Gpc-3 yr-1. Within this range, assuming a broken power-law LF, we find best estimates for the low- and high-energy indices of -0.95 ± 0.09 and -2.59 ± 0.93, respectively, separated by a break luminosity 0.80 ± 0.43 × 1052 erg s-1.

  1. Quasar X-Ray Spectra At z=1.5

    NASA Technical Reports Server (NTRS)

    Siemiginowska, Aneta

    2001-01-01

    The predicted counts for ASCA observation was much higher than actually observed counts in the quasar. However, there are three weak hard x-ray sources in the GIS field. We are adding them to the source counts in modeling of hard x-ray background. The work is in progress. We have published a paper in Ap.J. on the luminosity function and the quasar evolution. Based on the theory described in this paper we are predicting a number of sources and their contribution to the x-ray background at different redshifts. These model predictions will be compared to the observed data in the final paper.

  2. Extragalactic High-energy Transients: Event Rate Densities and Luminosity Functions

    NASA Astrophysics Data System (ADS)

    Sun, Hui; Zhang, Bing; Li, Zhuo

    2015-10-01

    Several types of extragalactic high-energy transients have been discovered, which include high-luminosity and low-luminosity long-duration gamma-ray bursts (GRBs), short-duration GRBs, supernova shock breakouts (SBOs), and tidal disruption events (TDEs) without or with an associated relativistic jet. In this paper, we apply a unified method to systematically study the redshift-dependent event rate densities and the global luminosity functions (GLFs; ignoring redshift evolution) of these transients. We introduce some empirical formulae for the redshift-dependent event rate densities for different types of transients and derive the local specific event rate density, which also represents its GLF. Long GRBs (LGRBs) have a large enough sample to reveal features in the GLF, which is best charaterized as a triple power law (PL). All the other transients are consistent with having a single-power-law (SPL) LF. The total event rate density depends on the minimum luminosity, and we obtain the following values in units of Gpc‑3 yr‑1: {0.8}-0.1+0.1 for high-luminosity LGRBs above 1050 erg s‑1 {164}-65+98 for low-luminosity LGRBs above 5 × 1046 erg s‑1 {1.3}-0.3+0.4, {1.2}-0.3+0.4, and {3.3}-0.8+1.0 above 1050 erg s‑1 for short GRBs with three different merger delay models (Gaussian, lognormal, and PL); {1.9}-1.2+2.4× {10}4 above 1044 erg s‑1 for SBOs, {4.8}-2.1+3.2× {10}2 for normal TDEs above 1044 erg s‑1 and {0.03}-0.02+0.04 above 1048 erg s‑1 for TDE jets as discovered by Swift. Intriguingly, the GLFs of different kinds of transients, which cover over 12 orders of magnitude, are consistent with an SPL with an index of ‑1.6.

  3. Extragalactic High-energy Transients: Event Rate Densities and Luminosity Functions

    NASA Astrophysics Data System (ADS)

    Sun, Hui; Zhang, Bing; Li, Zhuo

    2015-10-01

    Several types of extragalactic high-energy transients have been discovered, which include high-luminosity and low-luminosity long-duration gamma-ray bursts (GRBs), short-duration GRBs, supernova shock breakouts (SBOs), and tidal disruption events (TDEs) without or with an associated relativistic jet. In this paper, we apply a unified method to systematically study the redshift-dependent event rate densities and the global luminosity functions (GLFs; ignoring redshift evolution) of these transients. We introduce some empirical formulae for the redshift-dependent event rate densities for different types of transients and derive the local specific event rate density, which also represents its GLF. Long GRBs (LGRBs) have a large enough sample to reveal features in the GLF, which is best charaterized as a triple power law (PL). All the other transients are consistent with having a single-power-law (SPL) LF. The total event rate density depends on the minimum luminosity, and we obtain the following values in units of Gpc-3 yr-1: {0.8}-0.1+0.1 for high-luminosity LGRBs above 1050 erg s-1 {164}-65+98 for low-luminosity LGRBs above 5 × 1046 erg s-1 {1.3}-0.3+0.4, {1.2}-0.3+0.4, and {3.3}-0.8+1.0 above 1050 erg s-1 for short GRBs with three different merger delay models (Gaussian, lognormal, and PL); {1.9}-1.2+2.4× {10}4 above 1044 erg s-1 for SBOs, {4.8}-2.1+3.2× {10}2 for normal TDEs above 1044 erg s-1 and {0.03}-0.02+0.04 above 1048 erg s-1 for TDE jets as discovered by Swift. Intriguingly, the GLFs of different kinds of transients, which cover over 12 orders of magnitude, are consistent with an SPL with an index of -1.6.

  4. RE-ANALYSIS OF THE RADIO LUMINOSITY FUNCTION OF GALACTIC H II REGIONS

    SciTech Connect

    Paladini, R.; Noriega-Crespo, A.; Carey, S. J.; DeZotti, G.

    2009-09-10

    We have re-analyzed continuum and recombination lines radio data available in the literature in order to derive the luminosity function (LF) of Galactic H II regions. The study is performed by considering the first and fourth Galactic quadrants independently. We estimate the completeness level of the sample in the fourth quadrant at 5 Jy, and the one in the first quadrant at 2 Jy. We show that the two samples (fourth or first quadrant) include, as well as giant and supergiant H II regions, a significant number of subgiant sources. The LF is obtained, in each Galactic quadrant, with a generalized Schmidt's estimator using an effective volume derived from the observed spatial distribution of the considered H II regions. The re-analysis also takes advantage of recently published ancillary absorption data allowing to solve the distance ambiguity for several objects. A single power-law fit to the LFs retrieves a slope equal to -2.23 {+-} 0.07 (fourth quadrant) and to -1.85 {+-} 0.11 (first quadrant). We also find marginal evidence of a luminosity break at L{sub knee} = 10{sup 23.45} erg s{sup -1} Hz{sup -1} for the LF in the fourth quadrant. We convert radio luminosities into equivalent H{alpha} and Lyman continuum luminosities to facilitate comparisons with extragalactic studies. We obtain an average total H II regions Lyman continuum luminosity of 0.89 {+-} 0.23 x 10{sup 53} s{sup -1}, corresponding to 30% of the total ionizing luminosity of the Galaxy.

  5. DISCLOSING THE RADIO LOUDNESS DISTRIBUTION DICHOTOMY IN QUASARS: AN UNBIASED MONTE CARLO APPROACH APPLIED TO THE SDSS-FIRST QUASAR SAMPLE

    SciTech Connect

    Balokovic, M.; Smolcic, V.; Ivezic, Z.; Zamorani, G.; Schinnerer, E.; Kelly, B. C.

    2012-11-01

    We investigate the dichotomy in the radio loudness distribution of quasars by modeling their radio emission and various selection effects using a Monte Carlo approach. The existence of two physically distinct quasar populations, the radio-loud and radio-quiet quasars, is controversial and over the last decade a bimodal distribution of radio loudness of quasars has been both affirmed and disputed. We model the quasar radio luminosity distribution with simple unimodal and bimodal distribution functions. The resulting simulated samples are compared to a fiducial sample of 8300 quasars drawn from the SDSS DR7 Quasar Catalog and combined with radio observations from the FIRST survey. Our results indicate that the SDSS-FIRST sample is best described by a radio loudness distribution which consists of two components, with (12 {+-} 1)% of sources in the radio-loud component. On the other hand, the evidence for a local minimum in the loudness distribution (bimodality) is not strong and we find that previous claims for its existence were probably affected by the incompleteness of the FIRST survey close to its faint limit. We also investigate the redshift and luminosity dependence of the radio loudness distribution and find tentative evidence that at high redshift radio-loud quasars were rarer, on average louder, and exhibited a smaller range in radio loudness. In agreement with other recent work, we conclude that the SDSS-FIRST sample strongly suggests that the radio loudness distribution of quasars is not a universal function, and that more complex models than presented here are needed to fully explain available observations.

  6. Disclosing the Radio Loudness Distribution Dichotomy in Quasars: An Unbiased Monte Carlo Approach Applied to the SDSS-FIRST Quasar Sample

    NASA Astrophysics Data System (ADS)

    Baloković, M.; Smolčić, V.; Ivezić, Ž.; Zamorani, G.; Schinnerer, E.; Kelly, B. C.

    2012-11-01

    We investigate the dichotomy in the radio loudness distribution of quasars by modeling their radio emission and various selection effects using a Monte Carlo approach. The existence of two physically distinct quasar populations, the radio-loud and radio-quiet quasars, is controversial and over the last decade a bimodal distribution of radio loudness of quasars has been both affirmed and disputed. We model the quasar radio luminosity distribution with simple unimodal and bimodal distribution functions. The resulting simulated samples are compared to a fiducial sample of 8300 quasars drawn from the SDSS DR7 Quasar Catalog and combined with radio observations from the FIRST survey. Our results indicate that the SDSS-FIRST sample is best described by a radio loudness distribution which consists of two components, with (12 ± 1)% of sources in the radio-loud component. On the other hand, the evidence for a local minimum in the loudness distribution (bimodality) is not strong and we find that previous claims for its existence were probably affected by the incompleteness of the FIRST survey close to its faint limit. We also investigate the redshift and luminosity dependence of the radio loudness distribution and find tentative evidence that at high redshift radio-loud quasars were rarer, on average louder, and exhibited a smaller range in radio loudness. In agreement with other recent work, we conclude that the SDSS-FIRST sample strongly suggests that the radio loudness distribution of quasars is not a universal function, and that more complex models than presented here are needed to fully explain available observations.

  7. Canada-France Redshift Survey - X. The quasar sample

    NASA Astrophysics Data System (ADS)

    Schade, David; Crampton, David; Hammer, F.; Le Fevre, O.; Lilly, S. J.

    1996-01-01

    Six objects with broad emission lines and redshifts from 0.48 to 2.07 were discovered among 736 extragalactic objects in the Canada-France Redshift Survey (CFRS). Although the luminosities of half of the objects are such that they are in the Seyfert regime (M_B<~-23), all would be designated as quasars in traditional surveys. Since the only selection criterion was that 17.5<=I_AB<=22.5, or approximately B<23 (assuming a continuum power-law slope alpha=-0.5), these quasars represent an unbiased, flux-limited sample. Although uncertain, the implied surface density, 200^-120-80 deg^-2, is the highest yet measured, and is in good agreement with extrapolations from other faint surveys and the evolving luminosity function models of Boyle. The distributions of the continuum properties, emission-line strengths, etc. of the quasars do not differ significantly from those of quasars selected by other means, and therefore they would have been detected in most traditional surveys. Three of the quasars may be associated with clusters or large structures of galaxies at z<~1.

  8. GLOBULAR CLUSTER SYSTEMS IN BRIGHTEST CLUSTER GALAXIES: A NEAR-UNIVERSAL LUMINOSITY FUNCTION?

    SciTech Connect

    Harris, William E.; O'Halloran, Heather; Cockcroft, Robert E-mail: ohallohm@mcmaster.ca; and others

    2014-12-20

    We present the first results from our Hubble Space Telescope brightest cluster galaxy (BCG) survey of seven central supergiant cluster galaxies and their globular cluster (GC) systems. We measure a total of 48,000 GCs in all seven galaxies, representing the largest single GC database. We find that a log-normal shape accurately matches the observed the luminosity function (LF) of the GCs down to the globular cluster luminosity function turnover point, which is near our photometric limit. In addition, the LF has a virtually identical shape in all seven galaxies. Our data underscore the similarity in the formation mechanism of massive star clusters in diverse galactic environments. At the highest luminosities (L ≳ 10{sup 7} L {sub ☉}), we find small numbers of ''superluminous'' objects in five of the galaxies; their luminosity and color ranges are at least partly consistent with those of ultra-compact dwarfs. Last, we find preliminary evidence that in the outer halo (R ≳ 20 kpc), the LF turnover point shows a weak dependence on projected distance, scaling as L {sub 0} ∼ R {sup –0.2}, while the LF dispersion remains nearly constant.

  9. Constructing a bivariate distribution function with given marginals and correlation: application to the galaxy luminosity function

    NASA Astrophysics Data System (ADS)

    Takeuchi, Tsutomu T.

    2010-08-01

    We provide an analytic method to construct a bivariate distribution function (DF) with given marginal distributions and correlation coefficient. We introduce a convenient mathematical tool, called a copula, to connect two DFs with any prescribed dependence structure. If the correlation of two variables is weak (Pearson's correlation coefficient |ρ| < 1/3), the Farlie-Gumbel-Morgenstern (FGM) copula provides an intuitive and natural way to construct such a bivariate DF. When the linear correlation is stronger, the FGM copula cannot work anymore. In this case, we propose using a Gaussian copula, which connects two given marginals and is directly related to the linear correlation coefficient between two variables. Using the copulas, we construct the bivariate luminosity function (BLF) and discuss its statistical properties. We focus especially on the far-infrared-far-ulatraviolet (FUV-FIR) BLF, since these two wavelength regions are related to star-formation (SF) activity. Though both the FUV and FIR are related to SF activity, the univariate LFs have a very different functional form: the former is well described by the Schechter function whilst the latter has a much more extended power-law-like luminous end. We construct the FUV-FIR BLFs using the FGM and Gaussian copulas with different strengths of correlation, and examine their statistical properties. We then discuss some further possible applications of the BLF: the problem of a multiband flux-limited sample selection, the construction of the star-formation rate (SFR) function, and the construction of the stellar mass of galaxies (M*)-specific SFR (SFR/M*) relation. The copulas turn out to be a very useful tool to investigate all these issues, especially for including complicated selection effects.

  10. Bayesian High-redshift Quasar Classification from Optical and Mid-IR Photometry

    NASA Astrophysics Data System (ADS)

    Richards, Gordon T.; Myers, Adam D.; Peters, Christina M.; Krawczyk, Coleman M.; Chase, Greg; Ross, Nicholas P.; Fan, Xiaohui; Jiang, Linhua; Lacy, Mark; McGreer, Ian D.; Trump, Jonathan R.; Riegel, Ryan N.

    2015-08-01

    We identify 885,503 type 1 quasar candidates to i≲ 22 using the combination of optical and mid-IR photometry. Optical photometry is taken from the Sloan Digital Sky Survey-III: Baryon Oscillation Spectroscopic Survey (SDSS-III/BOSS), while mid-IR photometry comes from a combination of data from the Wide-field Infrared Survey Explorer (WISE) “AllWISE” data release and several large-area Spitzer Space Telescope fields. Selection is based on a Bayesian kernel density algorithm with a training sample of 157,701 spectroscopically confirmed type 1 quasars with both optical and mid-IR data. Of the quasar candidates, 733,713 lack spectroscopic confirmation (and 305,623 are objects that we have not previously classified as photometric quasar candidates). These candidates include 7874 objects targeted as high-probability potential quasars with 3.5\\lt z\\lt 5 (of which 6779 are new photometric candidates). Our algorithm is more complete to z\\gt 3.5 than the traditional mid-IR selection “wedges” and to 2.2\\lt z\\lt 3.5 quasars than the SDSS-III/BOSS project. Number counts and luminosity function analysis suggest that the resulting catalog is relatively complete to known quasars and is identifying new high-z quasars at z\\gt 3. This catalog paves the way for luminosity-dependent clustering investigations of large numbers of faint, high-redshift quasars and for further machine-learning quasar selection using Spitzer and WISE data combined with other large-area optical imaging surveys.

  11. The Fall of the Quasar Population

    NASA Astrophysics Data System (ADS)

    Cavaliere, A.; Vittorini, V.

    2000-11-01

    We derive quantitative predictions of the optical and X-ray luminosity functions for quasars in the redshift range z<~3. Based on accreting black holes as primary sources for the quasar outputs, we investigate how the accretion is controlled by the surrounding structures, as these grow hierarchically from the formation of the host galaxies to their assemblage into poor and eventually into rich groups. We argue that for z<3 efficient black hole fueling is triggered by the encounters of a gas-rich host with its companions in a group; these destabilize the gas and induce accretion, giving rise to the following features. The dispersion of the dynamical parameters in the encounters produces luminosity functions with the shape of a double power law. Strong luminosity evolution is produced as these encounters deplete the gas supply in the host; an additional, milder density evolution obtains, since the interactions become progressively rarer as the groups grow richer but less dense. We carry out these arguments to derive a specific model for the evolving luminosity functions. From the agreement with the optical and the X-ray data, we conclude that the evolution of the bright quasars is driven by the development of cosmic structures in two ways. Earlier than z~3 the gas-rich protogalaxies grow by merging, which also induces parallel growth of central holes accreting at their full Eddington rates. In the later era of group assemblage the host encounters with companions drive onto already existing holes further but meager accretion; these events consume the gas reservoirs in the hosts, while they cause supply-limited emissions that are intermittent, go progressively sub-Eddington, and peter out. Then other fueling processes occurring in the field come to the foreground; we specifically discuss the faint emissions, especially noticeable in X-rays, which are expected when hosts in the field cannibalize satellite galaxies with their scant gaseous contents.

  12. MEAN SPECTRAL ENERGY DISTRIBUTIONS AND BOLOMETRIC CORRECTIONS FOR LUMINOUS QUASARS

    SciTech Connect

    Krawczyk, Coleman M.; Richards, Gordon T.; Mehta, Sajjan S.; Vogeley, Michael S.; Gallagher, S. C.; Leighly, Karen M.; Ross, Nicholas P.; Schneider, Donald P.

    2013-05-01

    We explore the mid-infrared (mid-IR) through ultraviolet (UV) spectral energy distributions (SEDs) of 119,652 luminous broad-lined quasars with 0.064 < z < 5.46 using mid-IR data from Spitzer and WISE, near-infrared data from the Two Micron All Sky Survey and UKIDSS, optical data from the Sloan Digital Sky Survey, and UV data from the Galaxy Evolution Explorer. The mean SED requires a bolometric correction (relative to 2500 A) of BC{sub 2500A} =2.75 {+-} 0.40 using the integrated light from 1 {mu}m-2 keV, and we further explore the range of bolometric corrections exhibited by individual objects. In addition, we investigate the dependence of the mean SED on various parameters, particularly the UV luminosity for quasars with 0.5 {approx}< z {approx}< 3 and the properties of the UV emission lines for quasars with z {approx}> 1.6; the latter is a possible indicator of the strength of the accretion disk wind, which is expected to be SED-dependent. Luminosity-dependent mean SEDs show that, relative to the high-luminosity SED, low-luminosity SEDs exhibit a harder (bluer) far-UV spectral slope ({alpha}{sub UV}), a redder optical continuum, and less hot dust. Mean SEDs constructed instead as a function of UV emission line properties reveal changes that are consistent with known Principal Component Analysis trends. A potentially important contribution to the bolometric correction is the unseen extreme UV (EUV) continuum. Our work suggests that lower-luminosity quasars and/or quasars with disk-dominated broad emission lines may require an extra continuum component in the EUV that is not present (or much weaker) in high-luminosity quasars with strong accretion disk winds. As such, we consider four possible models and explore the resulting bolometric corrections. Understanding these various SED-dependent effects will be important for accurate determination of quasar accretion rates.

  13. Predicting the Redshift 2 H-Alpha Luminosity Function Using [OIII] Emission Line Galaxies

    NASA Technical Reports Server (NTRS)

    Mehta, Vihang; Scarlata, Claudia; Colbert, James W.; Dai, Y. S.; Dressler, Alan; Henry, Alaina; Malkan, Matt; Rafelski, Marc; Siana, Brian; Teplitz, Harry I.; Bagley, Micaela; Beck, Melanie; Ross, Nathaniel R.; Rutkowski, Michael; Wang, Yun

    2015-01-01

    Upcoming space-based surveys such as Euclid and WFIRST-AFTA plan to measure Baryonic Acoustic Oscillations (BAOs) in order to study dark energy. These surveys will use IR slitless grism spectroscopy to measure redshifts of a large number of galaxies over a significant redshift range. In this paper, we use the WFC3 Infrared Spectroscopic Parallel Survey (WISP) to estimate the expected number of H-alpha emitters observable by these future surveys. WISP is an ongoing Hubble Space Telescope slitless spectroscopic survey, covering the 0.8 - 1.65 micrometers wavelength range and allowing the detection of H-alpha emitters up to z approximately equal to 1.5 and [OIII] emitters to z approximately equal to 2.3. We derive the H-alpha-[OIII] bivariate line luminosity function for WISP galaxies at z approximately equal to 1 using a maximum likelihood estimator that properly accounts for uncertainties in line luminosity measurement, and demonstrate how it can be used to derive the H-alpha luminosity function from exclusively fitting [OIII] data. Using the z approximately equal to 2 [OIII] line luminosity function, and assuming that the relation between H-alpha and [OIII] luminosity does not change significantly over the redshift range, we predict the H-alpha number counts at z approximately equal to 2 - the upper end of the redshift range of interest for the future surveys. For the redshift range 0.7 less than z less than 2, we expect approximately 3000 galaxies per sq deg for a flux limit of 3 x 10(exp -16) ergs per sec per sq cm (the proposed depth of Euclid galaxy redshift survey) and approximately 20,000 galaxies per sq deg for a flux limit of approximately 10(exp -16) ergs per sec per sq cm (the baseline depth of WFIRST galaxy redshift survey).

  14. The Radio Luminosity Function and Galaxy Evolution in the Coma Cluster

    NASA Technical Reports Server (NTRS)

    Miller, Neal A.; Hornschemeier, Ann E.; Mabasher, Bahram; Brudgesm Terrry J.; Hudson, Michael J.; Marzke, Ronald O.; Smith, Russell J.

    2008-01-01

    We investigate the radio luminosity function and radio source population for two fields within the Coma cluster of galaxies, with the fields centered on the cluster core and southwest infall region and each covering about half a square degree. Using VLA data with a typical rms sensitivity of 28 (mu)Jy per 4.4" beam, we identify 249 radio sources with optical counterparts brighter than r = 22 (equivalent to M(sub r) = -13 for cluster member galaxies). Comprehensive optical spectroscopy identifies 38 of these as members of the Coma cluster, evenly split between sources powered by an active nucleus and sources powered by active star formation. The radio-detected star-forming galaxies are restricted to radio luminosities between about 10(exp 21) and 10(exp 22) W/Hz, an interesting result given that star formation dominates field radio luminosity functions below about 10(exp 23) W/Hz. The majority of the radio-detected star-forming galaxies have characteristics of starbursts, including high specific star formation rates and optical spectra with strong emission lines. In conjunction with prior studies on post-starburst galaxies within the Coma cluster, this is consistent with a picture in which late-type galaxies entering Coma undergo a starburst prior to a rapid cessation of star formation. Optically bright elliptical galaxies (Mr less than or equals -20.5) make the largest contribution to the radio luminosity function at both the high (> approx. 3x10(exp 22) W/Hz) and low (< approx. 10(exp 21) W/Hz) ends. Through a stacking analysis of these optically-bright ellipticals we find that they continue to harbor radio sources down to luminosities as faint as 3x10(exp 19) W/Hz. However, contrary to published results for the Virgo cluster we find no evidence for the existence of a population of optically faint (M(sub r) approx. equals -14) dwarf ellipticals hosting strong radio AGN.

  15. z ∼ 1 Lyα emitters. I. The luminosity function , , ,

    SciTech Connect

    Wold, Isak G. B.; Barger, Amy J.; Cowie, Lennox L. E-mail: barger@astro.wisc.edu

    2014-03-10

    We construct a flux-limited sample of 135 candidate z ∼ 1 Lyα emitters (LAEs) from Galaxy Evolution Explorer (GALEX) grism data using a new data cube search method. These LAEs have luminosities comparable to those at high redshifts and lie within a 7 Gyr gap present in existing LAE samples. We use archival and newly obtained optical spectra to verify the UV redshifts of these LAEs. We use the combination of the GALEX UV spectra, optical spectra, and X-ray imaging data to estimate the active galactic nucleus (AGN) fraction and its dependence on Lyα luminosity. We remove the AGNs and compute the luminosity function (LF) from 60 z ∼ 1 LAE galaxies. We find that the best-fit LF implies a luminosity density increase by a factor of ∼1.5 from z ∼ 0.3 to z ∼ 1 and ∼20 from z ∼ 1 to z ∼ 2. We find a z ∼ 1 volumetric Lyα escape fraction of 0.7% ± 0.4%.

  16. DETERMINING THE LUMINOSITY FUNCTION OF SWIFT LONG GAMMA-RAY BURSTS WITH PSEUDO-REDSHIFTS

    SciTech Connect

    Tan Weiwei; Yu Yunwei; Cao Xiaofeng

    2013-07-20

    The determination of the luminosity function (LF) of gamma-ray bursts (GRBs) is an important role for the cosmological applications of the GRBs, which, however, is seriously hindered by some selection effects due to redshift measurements. In order to avoid these selection effects, we suggest calculating pseudo-redshifts for Swift GRBs according to the empirical L-E{sub p} relationship. Here, such a L-E{sub p} relationship is determined by reconciling the distributions of pseudo- and real redshifts of redshift-known GRBs. The values of E{sub p} taken from Butler's GRB catalog are estimated with Bayesian statistics rather than observed. Using the GRB sample with pseudo-redshifts of a relatively large number, we fit the redshift-resolved luminosity distributions of the GRBs with a broken-power-law LF. The fitting results suggest that the LF could evolve with redshift by a redshift-dependent break luminosity, e.g., L{sub b} = 1.2 Multiplication-Sign 10{sup 51}(1 + z){sup 2} erg s{sup -1}. The low- and high-luminosity indices are constrained to 0.8 and 2.0, respectively. It is found that the proportional coefficient between the GRB event rate and the star formation rate should correspondingly decrease with increasing redshifts.

  17. The bright end of the luminosity function of red sequence galaxies

    NASA Astrophysics Data System (ADS)

    Loh, Yeong-Shang; Strauss, Michael A.

    2006-02-01

    We study the bright end of the luminosity distribution of galaxies in fields with luminous red galaxies (LRG) from the Sloan Digital Sky Survey (SDSS). Using 2099deg2 of SDSS imaging data, we search for luminous (>~L*) early-type galaxies within 1.0h-1Mpc of a volume-limited sample of 12608 spectroscopic LRG in the redshift range 0.12 < z < 0.38. Most of these objects lie in rich environments, with the LRG being the brightest object within 1.0h-1Mpc. The luminosity gap, M12, between the first- and second-ranked galaxies within 1.0h-1Mpc is large (~0.8 mag), substantially larger than can be explained with an exponentially decaying luminosity function of galaxies. The brightest member is less luminous (by 0.1-0.2 mag) and shows a larger gap in LRG selected groups than in cluster-like environments. The large luminosity gap shows little evolution with redshift to z= 0.4, ruling out the scenario that these LRG selected brightest cluster or group galaxies grow by recent cannibalism of cluster members.

  18. The X-ray Luminosity Function for Poor Clusters of Galaxies

    NASA Astrophysics Data System (ADS)

    Burns, J. O.; Ledlow, M.; Loken, C.; Klypin, A.; Voges, W.; White, R. A.; Bryan, G.; Norman, M.

    1995-12-01

    We will present the first X-ray Luminosity Function for poor clusters of galaxies. Using a percolation algorithm, White et al. (1996) has compiled a catalog of 600 optically selected groups composed of Zwicky galaxies. This catalog includes MKW and AWM groups (with cD galaxies), many Hickson compact groups, as well as many more loose condensations. We selected a complete,volume-limited subsample of these poor clusters which have at least 4 Zwicky galaxies, b>30deg , a surface density enhancement of ~50, and z <= 0.03. We then cross-correlated this sample with the ROSAT all-sky X-ray survey. About 50% of this sample of 50 clusters was detected with 0.5-2.0 keV X-ray luminosities >4 x 10(41) h75(-2) ergs/sec. These are the X-ray brightest groups in the northern sky. From this sample, we constructed an X-ray Luminosity Function. We find that this poor cluster luminosity function matches well with that derived for Abell clusters by Briel & Henry (1993). It appears that these groups are low mass extensions of rich clusters. We have also derived a mass function for these groups assuming that the X-ray emission is in hydrostatic equilibrium within the clusters. We will compare this mass function with those expected from different cosmological models with different values of Omega . This research was funded by NSF grant AST93-17596 and NASA grant NAGW-3152.

  19. AGN Feedback: Radio-Loudness Distribution and the Kinetic Luminosity function

    NASA Astrophysics Data System (ADS)

    La Franca, Fabio; Melini, Gabriele; Fiore, Fabrizio

    We have studied the AGN radio emission from the largest existing compilation of hard X-ray selected samples, all observed in the 1.4 GHz band. A total of more than 1600 AGN have been used. For the first time, it was possible to almost completely measure the probability distribution function of the ratio between the radio and the X-ray luminosity RX , which has been function-ally fitted as dependent from the X-ray luminosity and redshift. These measures have allowed us to estimate the AGN kinetic luminosity function and its evo-lution. It results that, in agreement with previous estimates, the efficiency kin in converting the accreted mass energy into kinetic power (LK = kin mc2 ) is on average kin ˜5 × 10-3 . ˙ The derived value and evolution of the kinetic energy density is in qualitative agreement with some of the last generation galaxy evolution models, where radio mode AGN feedback is invoked to quench the star formation in galaxies and slow down the cooling flows in galaxy clusters.

  20. The Sloan Digital Sky Survey Reverberation Mapping Project: Velocity Shifts of Quasar Emission Lines

    NASA Astrophysics Data System (ADS)

    Shen, Yue; Brandt, W. N.; Richards, Gordon T.; Denney, Kelly D.; Greene, Jenny E.; Grier, C. J.; Ho, Luis C.; Peterson, Bradley M.; Petitjean, Patrick; Schneider, Donald P.; Tao, Charling; Trump, Jonathan R.

    2016-11-01

    Quasar emission lines are often shifted from the systemic velocity due to various dynamical and radiative processes in the line-emitting region. The level of these velocity shifts depends both on the line species and on quasar properties. We study velocity shifts for the line peaks (not the centroids) of various narrow and broad quasar emission lines relative to systemic using a sample of 849 quasars from the Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) project. The coadded (from 32 epochs) spectra of individual quasars have sufficient signal-to-noise ratio (S/N) to measure stellar absorption lines to provide reliable systemic velocity estimates, as well as weak narrow emission lines. The large dynamic range in quasar luminosity (∼2 dex) of the sample allowed us to explore potential luminosity dependence of the velocity shifts. We derive average line peak velocity shifts as a function of quasar luminosity for different lines, and quantify their intrinsic scatter. We further quantify how well the peak velocity can be measured as a function of continuum S/N, and demonstrate that there is no systematic bias in the velocity measurements when S/N is degraded to as low as ∼3 per SDSS pixel (∼ 69 {km} {{{s}}}-1). Based on the observed line shifts, we provide empirical guidelines on redshift estimation from [O ii] λ 3727, [O iii] λ 5007, [Ne v] λ 3426, Mg ii, C iii], He ii λ 1640, broad Hβ, C iv, and Si iv, which are calibrated to provide unbiased systemic redshifts in the mean, but with increasing intrinsic uncertainties of 46, 56, 119, 205, 233, 242, 400, 415, and 477 {km} {{{s}}}-1, in addition to the measurement uncertainties. These results demonstrate the infeasibility of measuring quasar redshifts to better than ∼ 200 {km} {{{s}}}-1 with only broad lines.

  1. Flamingos 2 Spectroscopy of Obscured and Unobscured Quasars

    NASA Astrophysics Data System (ADS)

    Ridgway, Susan; Lacy, Mark; Urrutia, Tanya; Petric, Andreea

    2013-08-01

    We will use Flamingos-2 to obtain spectra of luminous AGN and quasars selected in the mid-infrared. Mid-infrared selection is much less biased with respect to obscuration than optical and X-ray techniques, and hence allows for finding obscured (Type-2) quasars as well as Type-1 quasars. Our survey so far has been very successful and has provided an unique opportunity to construct luminosity functions for both Type-1 and Type-2 quasars selected in the same way and covering similar redshifts and luminosities. We have quantifed the change in the obscured fraction with luminosity and redshift for the first time, and find interesting indications that at high redshift the obscured fraction rises, consistent with models for the joint formation of the galaxy and black hole populations. Our samples are, however, still quite incomplete at low fluxes (and therefore lower luminosities at a given redshift), particularly in the southern hemisphere. Near-infrared spectroscopy, such as that we have previously obtained with NIRI at Gemini N, offers us the best possibility of bringing these southern samples to a reasonable completeness level, and will greatly increase the number of high z quasars in our sample. This will allow us to better judge our tantalizing initial results on the redshift evolution of the obscured fraction. In addition, these southern targets can be followed up with ALMA and GEMS/GSAOI to study the morphologies and star-formation properties of the hosts, allowing further exploration of the relationship between the formation of massive bulges and supermassive blackholes in the early universe.

  2. COMBO-17 measurements of the effect of environment on the type-dependent galaxy luminosity function

    NASA Astrophysics Data System (ADS)

    Phleps, S.; Wolf, C.; Peacock, J. A.; Meisenheimer, K.; van Kampen, E.

    2007-06-01

    We have developed a method to calculate overdensities in multicolour surveys, facilitating a direct comparison of the local density contrast measured using galaxy samples that have different redshift error distributions, i.e. for red and blue, or bright and faint galaxies, respectively. We calculate overdensities in small redshift slices (Δ z =0.02, which at z=0.3 corresponds roughly to Δ r_comoving=53~h-1 Mpc) for 9176 galaxies with R≤23.65, MB(Vega)-5log h≤-18, and z≤ 0.7, in three COMBO-17 fields (measuring 31'×31' each). The mean redshift errors of this sample are approximately σ_z/(1+z)≃ 0.015. In the Chandra Deep Field South we identify a region that is underdense by almost a factor 2 compared to the other two fields in the same redshift range (0.25⪉ z ⪉ 0.4). This can be used for an investigation of the variation of the colour-dependent luminosity function with environment: We calculate the luminosity function in this redshift range for red sequence and blue cloud galaxies (as defined by Bell et al. 2004) in each of the fields separately. While the luminosity function of the blue galaxies remains unaffected by different density contrasts, the luminosity function of the red galaxies clearly has a more positive faint-end slope in the Chandra Deep Field South as compared to the other two COMBO-17 fields. The underdensity there is thus mainly due to a deficiency of faint red galaxies. This result is in qualitative agreement with the trends seen at z=0.1, e.g. in the 2dFGRS (Croton et al. 2005), or in the SDSS (Zandivarez et al. 2006).

  3. Discovery of a narrow line quasar

    NASA Technical Reports Server (NTRS)

    Stocke, J.; Liebert, J.; Maccacaro, T.; Griffiths, R. E.; Steiner, J. E.

    1982-01-01

    A stellar object is reported which, while having X-ray and optical luminosities typical of quasars, has narrow permitted and forbidden emission lines over the observed spectral range. The narrow-line spectrum is high-excitation, the Balmer lines seem to be recombinational, and a redder optical spectrum than that of most quasars is exhibited, despite detection as a weak radio source. The object does not conform to the relationships between H-beta parameters and X-ray flux previously claimed for a large sample of the active galactic nuclei. Because reddish quasars with narrow lines, such as the object identified, may not be found by the standard techniques for the discovery of quasars, the object may be a prototype of a new class of quasars analogous to high-luminosity Seyfert type 2 galaxies. It is suggested that these objects cannot comprise more than 10% of all quasars.

  4. The Seven Sisters DANCe. I. Empirical isochrones, luminosity, and mass functions of the Pleiades cluster

    NASA Astrophysics Data System (ADS)

    Bouy, H.; Bertin, E.; Sarro, L. M.; Barrado, D.; Moraux, E.; Bouvier, J.; Cuillandre, J.-C.; Berihuete, A.; Olivares, J.; Beletsky, Y.

    2015-05-01

    Context. The DANCe survey provides photometric and astrometric (position and proper motion) measurements for approximately 2 million unique sources in a region encompassing ~80 deg2 centered on the Pleiades cluster. Aims: We aim at deriving a complete census of the Pleiades and measure the mass and luminosity functions of the cluster. Methods: Using the probabilistic selection method previously described, we identified high probability members in the DANCe (i ≥ 14 mag) and Tycho-2 (V ≲ 12 mag) catalogues and studied the properties of the cluster over the corresponding luminosity range. Results: We find a total of 2109 high-probability members, of which 812 are new, making it the most extensive and complete census of the cluster to date. The luminosity and mass functions of the cluster are computed from the most massive members down to ~0.025 M⊙. The size, sensitivity, and quality of the sample result in the most precise luminosity and mass functions observed to date for a cluster. Conclusions: Our census supersedes previous studies of the Pleiades cluster populations, in terms of both sensitivity and accuracy. Based on service observations made with the William Herschel Telescope operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.Table 1 and Appendices are available in electronic form at http://www.aanda.orgDANCe catalogs (Tables 6 and 7) and full Tables 2-5 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/577/A148

  5. GALACTIC-SCALE ABSORPTION OUTFLOW IN THE LOW-LUMINOSITY QUASAR IRAS F04250-5718: HUBBLE SPACE TELESCOPE/COSMIC ORIGINS SPECTROGRAPH OBSERVATIONS

    SciTech Connect

    Edmonds, Doug; Borguet, Benoit; Arav, Nahum; Dunn, Jay P.; Penton, Steve; Kriss, Gerard A.; Korista, Kirk; Bautista, Manuel; Costantini, Elisa; Kaastra, Jelle; Steenbrugge, Katrien; Ignacio Gonzalez-Serrano, J.; Benn, Chris; Aoki, Kentaro; Behar, Ehud; Micheal Crenshaw, D.; Everett, John; Gabel, Jack; Moe, Maxwell; Scott, Jennifer

    2011-09-20

    We present absorption line analysis of the outflow in the quasar IRAS F04250-5718. Far-ultraviolet data from the Cosmic Origins Spectrograph on board the Hubble Space Telescope reveal intrinsic narrow absorption lines from high ionization ions (e.g., C IV, N V, and O VI) as well as low ionization ions (e.g., C II and Si III). We identify three kinematic components with central velocities ranging from {approx}-50 to {approx}-230 km s{sup -1}. Velocity-dependent, non-black saturation is evident from the line profiles of the high ionization ions. From the non-detection of absorption from a metastable level of C II, we are able to determine that the electron number density in the main component of the outflow is {approx}<30 cm{sup -3}. Photoionization analysis yields an ionization parameter log U{sub H} {approx} -1.6 {+-} 0.2, which accounts for changes in the metallicity of the outflow and the shape of the incident spectrum. We also consider solutions with two ionization parameters. If the ionization structure of the outflow is due to photoionization by the active galactic nucleus, we determine that the distance to this component from the central source is {approx}>3 kpc. Due to the large distance determined for the main kinematic component, we discuss the possibility that this outflow is part of a galactic wind.

  6. Tools for Computing the AGN Feedback: Radio-loudness Distribution and the Kinetic Luminosity Function

    NASA Astrophysics Data System (ADS)

    La Franca, F.; Melini, G.; Fiore, F.

    2010-07-01

    We studied the active galactic nucleus (AGN) radio emission from a compilation of hard X-ray-selected samples, all observed in the 1.4 GHz band. A total of more than 1600 AGNs with 2-10 keV de-absorbed luminosities higher than 1042 erg s-1 cm-2 were used. For a sub-sample of about fifty z <~ 0.1 AGNs, it was possible to reach ~80% of radio detections and therefore, for the first time, it was possible to almost completely measure the probability distribution function of the ratio between the radio and the X-ray luminosity RX = log(L 1.4/LX ), where L 1.4/LX = νL ν(1.4 GHz)/LX (2-10 keV). The probability distribution function of RX was functionally fitted as dependent on the X-ray luminosity and redshift, P(RX |LX , z). It roughly spans over six decades (-7< RX <-1) and does not show any sign of bi-modality. The result is that the probability of finding large values of the RX ratio increases with decreasing X-ray luminosities and (possibly) with increasing redshift. No statistically significant difference was found between the radio properties of the X-ray absorbed (N H>1022 cm-2) and un-absorbed AGNs. Measurement of the probability distribution function of RX allowed us to compute the kinetic luminosity function and the kinetic energy density which, at variance with that assumed in many galaxy evolution models, is observed to decrease by about a factor of 5 at redshift below 0.5. About half of the kinetic energy density results in being produced by the more radio quiet (RX <-4) AGNs. In agreement with previous estimates, the AGN efficiency epsilonkin in converting the accreted mass energy into kinetic power (L_K=ɛ_kin\\dot{m} c^2) is, on average, epsilonkin ~= 5 × 10-3. The data suggest a possible increase of epsilonkin at low redshifts.

  7. THE NEAR-ULTRAVIOLET LUMINOSITY FUNCTION OF YOUNG, EARLY M-TYPE DWARF STARS

    SciTech Connect

    Ansdell, Megan; Baranec, Christoph; Gaidos, Eric; Mann, Andrew W.; Lépine, Sebastien; James, David; Buccino, Andrea; Mauas, Pablo; Petrucci, Romina; Law, Nicholas M.; Riddle, Reed

    2015-01-01

    Planets orbiting within the close-in habitable zones of M dwarf stars will be exposed to elevated high-energy radiation driven by strong magnetohydrodynamic dynamos during stellar youth. Near-ultraviolet (NUV) irradiation can erode and alter the chemistry of planetary atmospheres, and a quantitative description of the evolution of NUV emission from M dwarfs is needed when modeling these effects. We investigated the NUV luminosity evolution of early M-type dwarfs by cross-correlating the Lépine and Gaidos catalog of bright M dwarfs with the Galaxy Evolution Explorer (GALEX) catalog of NUV (1771-2831 Å) sources. Of the 4805 sources with GALEX counterparts, 797 have NUV emission significantly (>2.5σ) in excess of an empirical basal level. We inspected these candidate active stars using visible-wavelength spectra, high-resolution adaptive optics imaging, time-series photometry, and literature searches to identify cases where the elevated NUV emission is due to unresolved background sources or stellar companions; we estimated the overall occurrence of these ''false positives'' (FPs) as ∼16%. We constructed an NUV luminosity function that accounted for FPs, detection biases of the source catalogs, and GALEX upper limits. We found the NUV luminosity function to be inconsistent with predictions from a constant star-formation rate and simplified age-activity relation defined by a two-parameter power law.

  8. The Bivariate Luminosity--HI Mass Distribution Function of Galaxies based on the NIBLES Survey

    NASA Astrophysics Data System (ADS)

    Butcher, Zhon; Schneider, Stephen E.; van Driel, Wim; Lehnert, Matt

    2016-01-01

    We use 21cm HI line observations for 2610 galaxies from the Nançay Interstellar Baryons Legacy Extragalactic Survey (NIBLES) to derive a bivariate luminosity--HI mass distribution function. Our HI survey was selected to randomly probe the local (900 < cz < 12,000 km/s) galaxy population in each 0.5 mag wide bin for the absolute z-band magnitude range of -13.5 < Mz < -24 without regard to morphology or color. This targeted survey allowed more on-source integration time for weak and non-detected sources, enabling us to probe lower HI mass fractions and apply lower upper limits for non-detections than would be possible with the larger blind HI surveys. Additionally, we obtained a factor of four higher sensitivity follow-up observations at Arecibo of 90 galaxies from our non-detected and marginally detected categories to quantify the underlying HI distribution of sources not detected at Nançay. Using the optical luminosity function and our higher sensitivity follow up observations as priors, we use a 2D stepwise maximum likelihood technique to derive the two dimensional volume density distribution of luminosity and HI mass in each SDSS band.

  9. Galaxy luminosity functions, M/L ratios, and closure of the Universe - Numbers and problems

    NASA Technical Reports Server (NTRS)

    Felten, J. E.

    1985-01-01

    Data on the luminosity function (LF) of galaxies are reviewed and compared, and the result of Kirshner et al. (1983) giving a 'standard LF' is chosen as a best guess. Departures from the 'standard LF' for specific galaxy types and environments (clusters, groups, field) are discussed briefly. A luminosity density of about 1.4 x 10 to the -2nd h 'galaxies' per cubic megaparsec is obtained. The mean M/L ratio needed to give critical cosmological density (Omega sub 0 = 1) is then 920 h in solar units on the face-on magnitude system. Comparison with measured M/L ratios for galaxies and clusters, and with constraints imposed by inflation and nucleosynthesis, poses two problems of 'invisible mass'.

  10. CO luminosity function from Herschel-selected galaxies and the contribution of AGN

    NASA Astrophysics Data System (ADS)

    Vallini, L.; Gruppioni, C.; Pozzi, F.; Vignali, C.; Zamorani, G.

    2016-02-01

    We derive the carbon monoxide (CO) luminosity function (LF) for different rotational transitions [i.e. (1-0), (3-2), (5-4)] starting from the Herschel LF by Gruppioni et al. and using appropriate LCO-LIR conversions for different galaxy classes. Our predicted LFs fit the data so far available at z ≈ 0 and 2. We compare our results with those obtained by semi-analytical models (SAMs): while we find a good agreement over the whole range of luminosities at z ≈ 0, at z ≈ 1 and z ≈ 2, the tension between our LFs and SAMs in the faint and bright ends increases. We finally discuss the contribution of luminous active galactic nucleus (LX > 1044 erg s- 1) to the bright end of the CO LF concluding that they are too rare to reproduce the actual CO LF at z ≈ 2.

  11. Predicting the Redshift 2 Hα Luminosity Function Using [OIII] Emission Line Galaxies

    NASA Astrophysics Data System (ADS)

    Mehta, Vihang; Scarlata, Claudia; Colbert, James W.; Dai, Y. S.; Dressler, Alan; Henry, Alaina; Malkan, Matt; Rafelski, Marc; Siana, Brian; Teplitz, Harry I.; Bagley, Micaela; Beck, Melanie; Ross, Nathaniel R.; Rutkowski, Michael; Wang, Yun

    2015-10-01

    Upcoming space-based surveys such as Euclid and WFIRST-AFTA plan to measure baryonic acoustic oscillations in order to study dark energy. These surveys will use IR slitless grism spectroscopy to measure redshifts of a large number of galaxies over a significant redshift range. In this paper, we use the Wide Field Camera 3 Infrared Spectroscopic Parallel Survey (WISP) to estimate the expected number of Hα emitters observable by these future surveys. WISP is an ongoing Hubble Space Telescope slitless spectroscopic survey, covering the 0.8-1.65 μm wavelength range and allowing the detection of Hα emitters up to z ˜ 1.5 and [O iii] emitters to z ˜ 2.3. We derive the Hα-[O iii] bivariate line luminosity function (LLF) for WISP galaxies at z ˜ 1 using a maximum likelihood estimator that properly accounts for uncertainties in line luminosity measurements and we demonstrate how it can be used to derive the Hα luminosity function by exclusively fitting [O iii] data. Using the z˜ 2 [O iii] LLF and assuming that the relation between Hα and [O iii] luminosity does not change significantly over the redshift range, we predict the Hα number counts at z˜ 2—the upper end of the redshift range of interest for future surveys. For the redshift range 0.7\\lt z\\lt 2, we expect ˜3000 galaxies deg-2 for a flux limit of 3 × 10-16 erg s-1 cm-2 (the proposed depth of the Euclid galaxy redshift survey) and ˜20,000 galaxies deg-2 for a flux limit of ˜10-16 erg s-1 cm-2 (the baseline depth of the WFIRST galaxy redshift survey).

  12. Modeling the Redshift Evolution of the Normal Galaxy X-Ray Luminosity Function

    NASA Technical Reports Server (NTRS)

    Tremmel, M.; Fragos, T.; Lehmer, B. D.; Tzanavaris, P.; Belczynski, K.; Kalogera, V.; Basu-Zych, A. R.; Farr, W. M.; Hornschemeier, A.; Jenkins, L.; Ptak, A.; Zezas, A.

    2013-01-01

    Emission from X-ray binaries (XRBs) is a major component of the total X-ray luminosity of normal galaxies, so X-ray studies of high-redshift galaxies allow us to probe the formation and evolution of XRBs on very long timescales (approximately 10 Gyr). In this paper, we present results from large-scale population synthesis models of binary populations in galaxies from z = 0 to approximately 20. We use as input into our modeling the Millennium II Cosmological Simulation and the updated semi-analytic galaxy catalog by Guo et al. to self-consistently account for the star formation history (SFH) and metallicity evolution of each galaxy. We run a grid of 192 models, varying all the parameters known from previous studies to affect the evolution of XRBs. We use our models and observationally derived prescriptions for hot gas emission to create theoretical galaxy X-ray luminosity functions (XLFs) for several redshift bins. Models with low common envelope efficiencies, a 50% twins mass ratio distribution, a steeper initial mass function exponent, and high stellar wind mass-loss rates best match observational results from Tzanavaris & Georgantopoulos, though they significantly underproduce bright early-type and very bright (L(sub x) greater than 10(exp 41)) late-type galaxies. These discrepancies are likely caused by uncertainties in hot gas emission and SFHs, active galactic nucleus contamination, and a lack of dynamically formed low-mass XRBs. In our highest likelihood models, we find that hot gas emission dominates the emission for most bright galaxies. We also find that the evolution of the normal galaxy X-ray luminosity density out to z = 4 is driven largely by XRBs in galaxies with X-ray luminosities between 10(exp 40) and 10(exp 41) erg s(exp -1).

  13. A study of the luminosity function for field galaxies. [non-rich-cluster galaxies

    NASA Technical Reports Server (NTRS)

    Felten, J. E.

    1977-01-01

    Nine determinations of the luminosity function (LF) for field galaxies are analyzed and compared. Corrections for differences in Hubble constants, magnitude systems, galactic absorption functions, and definitions of the LF are necessary prior to comparison. Errors in previous comparisons are pointed out. After these corrections, eight of the nine determinations are in fairly good agreement. The discrepancy in the ninth appears to be mainly an incompleteness effect. The LF data suggest that there is little if any distinction between field galaxies and those in small groups.

  14. Quasar variability in the Palomar Transient Factory Survey

    NASA Astrophysics Data System (ADS)

    Caplar, Neven; Lilly, Simon J.; Trakhtenbrot, Benny; PTF Collaboration

    2016-08-01

    We quantify the quasar variability in the Palomar Transient Factory survey. This is the data survey of unprecedented size with over 2 million observations of 30000 quasars brighter than r=19 over 6 years. Using custom recalibration we greatly improve on the photometric quality of the survey reducing the unaccounted errors to less than 1% at r=19. We split our sample in the redshift, mass and luminosity bins and using the ensemble structure function analysis we find anti-correlation of variability with luminosity, no correlation with redshift and only very weak correlation with mass. We also notice the dependence of the slope of the structure function with mass and luminosity indicating that random walk is not equally good description of QSO variability at all masses and luminosities. We extend the analysis using the power spectral density (PSD) analysis with CARMA models. We observe breaks in the PSD but after extensive simulation effort we conclude that these are artifact arising from the insufficient length of the light curves and non-uniform cadence. We observe the dependence of PSD slope with mass/luminosity further corroborating our finding in the structure function analysis that type of the process that drives variability is dependent on the physical parameters.

  15. Four Quasars above Redshift 6 Discovered by the Canada-France High-z Quasar Survey

    NASA Astrophysics Data System (ADS)

    Willott, Chris J.; Delorme, Philippe; Omont, Alain; Bergeron, Jacqueline; Delfosse, Xavier; Forveille, Thierry; Albert, Loic; Reylé, Céline; Hill, Gary J.; Gully-Santiago, Michael; Vinten, Phillip; Crampton, David; Hutchings, John B.; Schade, David; Simard, Luc; Sawicki, Marcin; Beelen, Alexandre; Cox, Pierre

    2007-12-01

    The Canada-France High-z Quasar Survey (CFHQS) is an optical survey designed to locate quasars during the epoch of reionization. In this paper we present the discovery of the first four CFHQS quasars at redshifts greater than 6, including the most distant known quasar, CFHQS J2329-0301 at z = 6.43. We describe the observational method used to identify the quasars and present optical, infrared, and millimeter photometry and optical and near-infrared spectroscopy. We investigate the dust properties of these quasars, finding an unusual dust extinction curve for one quasar and a high far-infrared luminosity due to dust emission for another. The mean millimeter continuum flux for CFHQS quasars is substantially lower than that for SDSS quasars at the same redshift, likely due to a correlation with quasar UV luminosity. For two quasars with sufficiently high signal-to-noise ratio optical spectra, we use the spectra to investigate the ionization state of hydrogen at z > 5. For CFHQS J1509-1749 at z = 6.12 we find significant evolution (beyond a simple extrapolation of lower redshift data) in the Gunn-Peterson optical depth at z > 5.4. The line of sight to this quasar has one of the highest known optical depths at z approx 5.8. An analysis of the sizes of the highly ionized near-zones in the spectra of two quasars at z = 6.12 and 6.43 suggest that the intergalactic medium surrounding these quasars was substantially ionized before these quasars turned on. Together, these observations point toward an extended reionization process, but we caution that cosmic variance is still a major limitation in z > 6 quasar observations.

  16. THE PROPERTIES OF QUASAR HOSTS AT THE PEAK OF THE QUASAR ACTIVITY

    SciTech Connect

    Kotilainen, Jari K.; Falomo, Renato; Decarli, Roberto; Treves, Aldo; Uslenghi, Michela; Scarpa, Riccardo E-mail: renato.falomo@oapd.inaf.i E-mail: aldo.treves@uninsubria.i E-mail: riccardo.scarpa@gtc.iac.e

    2009-10-01

    We present near-infrared imaging obtained with ESO VLT/ISAAC of a sample of 16 low luminosity radio-quiet quasars (RQQs) at the epoch around the peak of the quasar activity (2 < z < 3), aimed at investigating their host galaxies. For 11 quasars, we are able to detect the host galaxies and derive their properties, while for the other 5 quasars, upper limits to the host luminosity are estimated. The luminosities of the host galaxies of RQQs at high redshift are in the range of those of massive inactive elliptical galaxies. This work complements our previous systematic study of quasar hosts aimed to trace the cosmological luminosity evolution of the host galaxies up to z approx 2 and extends our pilot study of a few luminous quasars at z > 2. The luminosity trend with a cosmic epoch resembles that observed for massive inactive galaxies, suggesting a similar star formation history. In particular, both quasar host galaxies and massive inactive galaxies appear mostly assembled already at the peak age of the quasar activity. This result is of key importance for testing the models of joint formation and evolution of galaxies and their active nuclei.

  17. Quasar microlensing

    NASA Astrophysics Data System (ADS)

    Schmidt, R. W.; Wambsganss, J.

    2010-09-01

    Quasar microlensing deals with the effect of compact objects along the line of sight on the apparent brightness of the background quasars. Due to the relative motion between quasar, lenses and observer, the microlensing magnification changes with time which results in uncorrelated brightness variations in the various images of multiple quasar systems. The amplitudes of the signal can be more than a magnitude with time scales of weeks to months to years. The effect is due to the “granular” nature of the gravitational microlenses—stars or other compact objects in the stellar mass range. Quasar microlensing allows to study the quasar accretion disk with a resolution of tens of microarcseconds, hence quasar microlensing can be used to explore an astrophysical field that is hardly accessible by any other means. Quasar microlensing can also be used to study the lensing objects in a statistical sense, their nature (compact or smoothly distributed, normal stars or dark matter) as well as transverse velocities. Quasar microlensing light curves are now being obtained from monitoring programs across the electromagnetic spectrum from the radio through the infrared and optical range to the X-ray regime. Recently, spectroscopic microlensing was successfully applied, it provides quantitative comparisons with quasar/accretion disk models. There are now more than a handful of systems with several-year long light curves and significant microlensing signal, lending to detailed analysis. This review summarizes the current state of the art of quasar microlensing and shows that at this point in time, observational monitoring programs and complementary intense simulations provide a scenario where some of the early promises of quasar microlensing can be quantitatively applied. It has been shown, e.g., that smaller sources display more violent microlensing variability, first quantitative comparison with accretion disk models has been achieved, and quasar microlensing has been used to

  18. A Survey of Luminous High-redshift Quasars with SDSS and WISE. I. Target Selection and Optical Spectroscopy

    NASA Astrophysics Data System (ADS)

    Wang, Feige; Wu, Xue-Bing; Fan, Xiaohui; Yang, Jinyi; Yi, Weimin; Bian, Fuyan; McGreer, Ian D.; Yang, Qian; Ai, Yanli; Dong, Xiaoyi; Zuo, Wenwen; Jiang, Linhua; Green, Richard; Wang, Shu; Cai, Zheng; Wang, Ran; Yue, Minghao

    2016-03-01

    High-redshift quasars are important tracers of structure and evolution in the early universe. However, they are very rare and difficult to find when using color selection because of contamination from late-type dwarfs. High-redshift quasar surveys based on only optical colors suffer from incompleteness and low identification efficiency, especially at z≳ 4.5. We have developed a new method to select 4.7≲ z≲ 5.4 quasars with both high efficiency and completeness by combining optical and mid-IR Wide-field Infrared Survey Explorer (WISE) photometric data, and are conducting a luminous z˜ 5 quasar survey in the whole Sloan Digital Sky Survey (SDSS) footprint. We have spectroscopically observed 99 out of 110 candidates with z-band magnitudes brighter than 19.5, and 64 (64.6%) of them are quasars with redshifts of 4.4≲ z≲ 5.5 and absolute magnitudes of -29≲ {M}1450≲ -26.4. In addition, we also observed 14 fainter candidates selected with the same criteria and identified 8 (57.1%) of them as quasars with 4.7\\lt z\\lt 5.4. Among 72 newly identified quasars, 12 of them are at 5.2\\lt z\\lt 5.7, which leads to an increase of ˜36% of the number of known quasars at this redshift range. More importantly, our identifications doubled the number of quasars with {M}1450\\lt -27.5 at z\\gt 4.5, which will set strong constraints on the bright end of the quasar luminosity function. We also expand our method to select quasars at z ≳ 5.7. In this paper we report the discovery of four new luminous z ≳ 5.7 quasars based on SDSS-WISE selection.

  19. Deep spectroscopy of nearby galaxy clusters - I. Spectroscopic luminosity function of Abell 85

    NASA Astrophysics Data System (ADS)

    Agulli, I.; Aguerri, J. A. L.; Sánchez-Janssen, R.; Dalla Vecchia, C.; Diaferio, A.; Barrena, R.; Dominguez Palmero, L.; Yu, H.

    2016-05-01

    We present a new deep spectroscopic catalogue for Abell 85, within 3.0 × 2.6 Mpc2 and down to Mr ˜ Mr^{ast } +6. Using the Visible Multi-Object Spectrograph at the Very Large Telescope and the AutoFiber 2 at the William Herschel Telescope, we obtained almost 1430 new redshifts for galaxies with mr ≤ 21 mag and <μe,r> ≤ 24 mag arcsec-2. These redshifts, together with Sloan Digital Sky Survey Data Release 6 and NASA/IPAC Extragaalctic Database spectroscopic information, result in 460 confirmed cluster members. This data set allows the study of the luminosity function (LF) of the cluster galaxies covering three orders of magnitudes in luminosities. The total and radial LFs are best modelled by a double Schechter function. The normalized LFs show that their bright (Mr ≤ -21.5) and faint (Mr ≥ -18.0) ends are independent of clustercentric distance and similar to the field LFs unlike the intermediate luminosity range (-21.5 ≤ Mr ≤ -18.0). Similar results are found for the LFs of the dominant types of galaxies: red, passive, virialized and early-infall members. On the contrary, the LFs of blue, star forming, non-virialized and recent-infall galaxies are well described by a single Schechter function. These populations contribute to a small fraction of the galaxy density in the innermost cluster region. However, in the outskirts of the cluster, they have similar densities to red, passive, virialized and early-infall members at the LF faint end. These results confirm a clear dependence of the colour and star formation of Abell 85 members in the cluster centric distance.

  20. Probabilistic Selection of High-redshift Quasars with Subaru/Hyper Suprime-Cam Survey

    NASA Astrophysics Data System (ADS)

    Onoue, Masafusa

    High-redshift quasars are an important probe of the distant Universe. They enable observational studies of the early growth of supermassive blackholes, cosmic reionization, chemical enrichment of host galaxies, and so on. Through pioneering optical and near-infrared wide-area surveys such as the SDSS and the VIKING Survey, about one hundred quasars have been found at z > 6 (e.g., Fan et al. (2006b), Venemans et al. (2013)). However, its current small sample size and the fact that most of them are the most luminous (M 1450 <~ -24) population in this epoch prevents one from constraining statistics on high-redshift quasars, namely quasar luminosity function (QLF), and redshift evolution of IGM neutral fraction. Thus, discovery of large number of z > 6 quasars, especially low-luminous or z > 7 quasars, is highly desired for further understanding of the early universe. We are now starting a new ground-breaking survey of high-redshift (z > 6) quasars using the exquisite imaging data provided by the Hyper Suprime-Cam (HSC) Subaru Strategic Program (SSP) Survey. Thanks to its extremely wide coverage and its high sensitivity thorough five optical bands (1,400 deg2 to the depth of r ~ 26 in HSC-Wide layer), it is one of the most powerful contemporary surveys that makes it possible for us to increase the number of z > 6 quasars by almost an order of magnitude, i.e., 300 at z ~ 6 and 50 at z ~ 7, based on the current estimate of the QLF at z > 6 by Willott et al. (2010b). One of the biggest challenges in z > 6 quasar candidate selection is contamination of Galactic brown dwarfs, which have the same point-like appearance as and similarly red colors to the quasars. To overcome this issue and maximize the selection efficiency, we apply a double-layered approach to the HSC survey products, namely combination of two probabilistic selections: SED-fitting and Bayesian selection. In particular, we have developed a template SED fitting method optimized to high-redshift quasars

  1. A MUSE View of the HDFS: The Lyα Luminosity Function out to z~6

    NASA Astrophysics Data System (ADS)

    Drake, Alyssa B.; Guiderdoni, Bruno; Blaizot, Jérémy; Richard, Johan; Bacon, Roland; Garel, Thibault; Hashimoto, Takuya

    We present preliminary results from MUSE on the Lyα luminosity function in the Hubble Deep Field South (HDFS). Using a large homogeneous sample of LAEs selected through blind spectroscopy, we utilise the unprecedented detection power of MUSE to study the progenitors of L* galaxies back to when the Universe was just ~2 Gyr old. We present these results in the context of the current literature, and highlight the importance of the forthcoming Hubble Ultra Deep Field (HUDF) study with MUSE, which will increase the size of our sample by a factor of ~ 10.

  2. The discovery of quasars

    NASA Astrophysics Data System (ADS)

    Kellermann, K. I.

    2013-03-01

    Although the extragalactic nature of quasars was discussed as early as 1960, it was rejected largely because of preconceived ideas about what appeared to be an unrealistically high radio and optical luminosity. Following the 1962 occultations of the strong radio source 3C 273 at Parkes, and the subsequent identification with an apparent stellar object, Maarten Schmidt recognized that the relatively simple hydrogen line Balmer series spectrum implied a redshift of 0.16. Successive radio and optical measurements quickly led to the identification of other quasars with increasingly large redshifts and the general, although for some decades not universal, acceptance of quasars as being by far the most distant and the most luminous objects in the Universe. Arguments for a more local population continued for at least several decades, fueled in part by a greater willingness to accept the unclear new physics needed to interpret the large observed redshifts rather than the extreme luminosities and energies implied by the cosmological interpretation of the redshifts. Curiously, 3C 273, which is one of the strongest extragalactic sources in the sky, was first catalogued in 1959 and the magnitude 13 optical counterpart was observed at least as early as 1887. Since 1960, much fainter optical counterparts were being routinely identified using accurate radio interferometer positions, measured primarily at the Caltech Owens Valley Radio Observatory. However, 3C 273 eluded identification until the series of lunar occultation observations led by Cyril Hazard. Subsequent attempts to classify quasars into numerous sub-categories based on their observed optical, radio, IR and high energy properties have perhaps led to more confusion than clarity. However, quasars and the broader class of AGN are now a fundamental part of astrophysics and cosmology. They were the basis for the recognition of supermassive black holes in galactic nuclei, which are intimately tied to the formation and

  3. PRIMUS: Galaxy clustering as a function of luminosity and color at 0.2 < z < 1

    SciTech Connect

    Skibba, Ramin A.; Smith, M. Stephen M.; Coil, Alison L.; Mendez, Alexander J.; Moustakas, John; Aird, James; Blanton, Michael R.; Bray, Aaron D.; Eisenstein, Daniel J.; Cool, Richard J.; Wong, Kenneth C.; Zhu, Guangtun

    2014-04-01

    We present measurements of the luminosity and color-dependence of galaxy clustering at 0.2 < z < 1.0 in the Prism Multi-object Survey. We quantify the clustering with the redshift-space and projected two-point correlation functions, ξ(r{sub p} , π) and w{sub p} (r{sub p} ), using volume-limited samples constructed from a parent sample of over ∼130, 000 galaxies with robust redshifts in seven independent fields covering 9 deg{sup 2} of sky. We quantify how the scale-dependent clustering amplitude increases with increasing luminosity and redder color, with relatively small errors over large volumes. We find that red galaxies have stronger small-scale (0.1 Mpc h {sup –1} < r{sub p} < 1 Mpc h {sup –1}) clustering and steeper correlation functions compared to blue galaxies, as well as a strong color dependent clustering within the red sequence alone. We interpret our measured clustering trends in terms of galaxy bias and obtain values of b {sub gal} ≈ 0.9-2.5, quantifying how galaxies are biased tracers of dark matter depending on their luminosity and color. We also interpret the color dependence with mock catalogs, and find that the clustering of blue galaxies is nearly constant with color, while redder galaxies have stronger clustering in the one-halo term due to a higher satellite galaxy fraction. In addition, we measure the evolution of the clustering strength and bias, and we do not detect statistically significant departures from passive evolution. We argue that the luminosity- and color-environment (or halo mass) relations of galaxies have not significantly evolved since z ∼ 1. Finally, using jackknife subsampling methods, we find that sampling fluctuations are important and that the COSMOS field is generally an outlier, due to having more overdense structures than other fields; we find that 'cosmic variance' can be a significant source of uncertainty for high-redshift clustering measurements.

  4. The Hard X-ray 20-40 keV AGN Luminosity Function

    NASA Technical Reports Server (NTRS)

    Beckmann, V.; Soldi, S.; Shrader, C. R.; Gehrels, N.; Produit, N.

    2006-01-01

    We have compiled a complete, significance limited extragalactic sample based on approximately 25,000 deg(sup 2) to a limiting flux of 3 x 10(exp -11) ergs per square centimeter per second. (approximately 7,000 deg(sup 2)) to a flux limit of 10(exp -11) ergs per square centimeter per second)) in the 20 - 40 keV band with INTEGRAL. We have constructed a detailed exposure map to compensate for effects of non-uniform exposure. The flux-number relation is best described by a power-law with a slope of alpha = 1.66 plus or minus 0.11. The integration of the cumulative flux per unit area leads to f(sub 20-40 keV) = 2.6 x 10(exp -10) ergs per square centimeter per second per sr(sup -1) which is about 1% of the known 20-40 keV X-ray background. We present the first luminosity function of AGN in the 20-40 keV energy range, based on 68 extragalactic objects detected by the imager IBIS/ISGRI on-board INTEGRAL. The luminosity function shows a smoothly connected two power-law form, with an index of gamma (sub 1) = 0.9 below, and gamma (sub 2) = 2.2 above the turn-over luminosity of L(sub *), = 4.6 x 10(sup 43) ergs per second. The emissivity of all INTEGRAL AGNs per unit volume is W(sub 20-40keV)(greater than 10(sup 41) ergs per second) = 2.8 x 10(sup 38) ergs per second h(sup 3)(sub 70) Mpc(sup -3). These results are consistent with those derived in the 2-20keV energy band and do not show a significant contribution by Compton-thick objects. Because the sample used in this study is truly local (z(raised bar) = 0.022)), only limited conclusions can be drawn for the evolution of AGNs in this energy band. But the objects explaining the peak in the cosmic X-ray background are likely to be either low luminosity AGN (L(sub x) less than 10(sup 41) ergs per second) or of other type, such as intermediate mass black holes, clusters, and star forming regions.

  5. COSMOLOGICAL DEPENDENCE OF THE MEASUREMENTS OF LUMINOSITY FUNCTION, PROJECTED CLUSTERING AND GALAXY-GALAXY LENSING SIGNAL

    SciTech Connect

    More, Surhud

    2013-11-10

    Observables such as the galaxy luminosity function, Φ(M), projected galaxy clustering, w {sub p}(r {sub p}), and the galaxy-galaxy lensing signal, ΔΣ(r {sub p}), are often measured from galaxy redshift surveys assuming a fiducial cosmological model for calculating distances to, and between galaxies. There are a growing number of studies that perform joint analyses of these measurements and constrain cosmological parameters. We quantify the amount by which such measurements systematically vary as the fiducial cosmology used for the measurements is changed, and show that these effects can be significant at high redshifts (z ∼ 0.5). Cosmological analyses (or halo occupation distribution analyses) that use the luminosity function, clustering and the galaxy-galaxy lensing signal but ignore such systematic effects may bias the inference of the parameters. We present a simple way to account for the differences in the cosmological model used for the measurements and those used for the prediction of observables, thus allowing a fair comparison between models and data.

  6. Sub-mm emission line deep fields: CO and [C II] luminosity functions out to z = 6

    NASA Astrophysics Data System (ADS)

    Popping, Gergö; van Kampen, Eelco; Decarli, Roberto; Spaans, Marco; Somerville, Rachel S.; Trager, Scott C.

    2016-09-01

    Now that Atacama Large (Sub)Millimeter Array is reaching its full capabilities, observations of sub-mm emission line deep fields become feasible. We couple a semi-analytic model of galaxy formation with a radiative transfer code to make predictions for the luminosity function of CO J =1-0 out to CO J = 6-5 and [C II] at redshifts z= 0-6. We find that (1) our model correctly reproduces the CO and [C II] emission of low- and high-redshift galaxies and reproduces the available constraints on the CO luminosity function at z ≤ 2.75; (2) we find that the CO and [C II] luminosity functions of galaxies increase from z = 6 to z = 4, remain relatively constant till z = 1 and rapidly decrease towards z = 0. The galaxies that are brightest in CO and [C II] are found at z ˜ 2; (3) the CO J = 3-2 emission line is most favourable to study the CO luminosity and global H2 mass content of galaxies, because of its brightness and observability with currently available sub-mm and radio instruments; (4) the luminosity functions of high-J CO lines show stronger evolution than the luminosity functions of low-J CO lines; (5) our model barely reproduces the available constraints on the CO and [C II] luminosity function of galaxies at z ≥ 1.5 and the CO luminosity of individual galaxies at intermediate redshifts. We argue that this is driven by a lack of cold gas in galaxies at intermediate redshifts as predicted by cosmological simulations of galaxy formation.

  7. HST Imaging of Quasar Host Galaxies

    NASA Astrophysics Data System (ADS)

    Hooper, E. J.; Impey, C. D.; Foltz, C. B.

    1996-12-01

    A sample of 16 quasars from the Large Bright Quasar Survey (LBQS) has been imaged with WFPC2 on the Hubble Space Telescope. The sample was selected to cover a range of radio luminosity typical of optically selected quasars in narrow intervals of redshift (0.4 <= z >= 0.5) and absolute magnitude (-25 < MB < -23). Two-dimensional cross-correlation techniques were used to determine the magnitudes of the host galaxies and quasar nuclear components, as well as the axial ratios of the hosts. The derived host galaxy magnitudes are near or below L(*) and are correlated with the quasar nuclear magnitude, similar to the trend in near-infrared host galaxy luminosity found by McLeod & Rieke (1995, ApJ, 454, L77). There is no discernable difference in host galaxy luminosity between radio-loud and radio-quiet quasars in the sample. Preliminary analysis of the host galaxy morphologies indicates that many, including several of the radio-quiet quasars, are probably in early type galaxies, consistent with other high-resolution imaging studies of quasar hosts. However, the distribution of axial ratios is not consistent with a population of early type galaxies. The hosts in the LBQS sample are rather flattened, with half having axial ratios <= 0.5. It is possible that these are inclined disk systems or galaxies with substantial bar components.

  8. AN EXPONENTIAL DECLINE AT THE BRIGHT END OF THE z = 6 GALAXY LUMINOSITY FUNCTION

    SciTech Connect

    Willott, Chris J.; McLure, Ross J.; Bruce, Victoria A.; Hibon, Pascale; McCracken, Henry J.; Kneib, Jean-Paul; Ilbert, Olivier; Bonfield, David G.; Jarvis, Matt J.

    2013-01-01

    We present the results of a search for the most luminous star-forming galaxies at redshifts z Almost-Equal-To 6 based on Canada-France-Hawaii Telescope Legacy Survey data. We identify a sample of 40 Lyman break galaxies (LBGs) brighter than magnitude z' = 25.3 across an area of almost 4 deg{sup 2}. Sensitive spectroscopic observations of seven galaxies provide redshifts for four, of which only two have moderate to strong Ly{alpha} emission lines. All four have clear continuum breaks in their spectra. Approximately half of the LBGs are spatially resolved in 0.7 arcsec seeing images, indicating larger sizes than lower luminosity galaxies discovered with the Hubble Space Telescope, possibly due to ongoing mergers. The stacked optical and infrared photometry is consistent with a galaxy model with stellar mass {approx}10{sup 10} M{sub Sun }. There is strong evidence for substantial dust reddening with a best-fit A{sub V} = 0.75 and A{sub V} > 0.48 at 2{sigma} confidence, in contrast to the typical dust-free galaxies of lower luminosity at this epoch. The spatial extent and spectral energy distribution suggest that the most luminous z Almost-Equal-To 6 galaxies are undergoing merger-induced starbursts. The luminosity function of z = 5.9 star-forming galaxies is derived. This agrees well with previous work and shows strong evidence for an exponential decline at the bright end, indicating that the feedback processes that govern the shape of the bright end are occurring effectively at this epoch.

  9. THE LUMINOSITY FUNCTION OF X-RAY SOURCES IN SPIRAL GALAXIES

    SciTech Connect

    Prestwich, A. H.; Primini, F.; McDowell, J. C.; Zezas, A.; Kilgard, R. E.

    2009-11-10

    X-ray sources in spiral galaxies can be approximately classified into bulge and disk populations. The bulge (or hard) sources have X-ray colors which are consistent with low-mass X-ray binaries (LMXBs) but the disk sources have softer colors suggesting a different type of source. In this paper, we further study the properties of hard and soft sources by constructing color-segregated X-ray luminosity functions (XLFs) for these two populations. Since the number of sources in any given galaxy is small, we co-added sources from a sample of nearby, face-on spiral galaxies observed by Chandra as a Large Project in Cycle 2. We use simulations to carefully correct the XLF for completeness. The composite hard source XLF is not consistent with a single-power-law fit. At luminosities L{sub x} > 3 x 10{sup 38} erg s{sup -1}, it is well fitted by a power law with a slope that is consistent with that found for sources in elliptical galaxies by Kim and Fabbiano. This supports the suggestion that the hard sources are dominated by LMXBs. In contrast, the high-luminosity XLF of soft sources has a slope similar to the 'universal' high-mass X-ray binary XLF. Some of these sources are stellar-mass black hole binaries accreting at high rates in a thermal/steep power-law state. The softest sources have inferred disk temperatures that are considerably lower than found in galactic black holes binaries. These sources are not well understood, but some may be super-soft ultra-luminous X-ray sources in a quiescent state as suggested by Soria and Ghosh.

  10. Hubble Space Telescope Images of Nearby Luminous Quasars. 2; Results for Eight Quasars and Tests of the Detection Sensitivity

    NASA Technical Reports Server (NTRS)

    Bahcall, John N.; Kirhakos, Sofia; Schneider, Donald P.

    1995-01-01

    galaxies brighter than, on average, about L*, would have been detected. These upper limits, or possible detections, are consistent with, for example, the eight luminous quasars studied in this paper, occurring in host galaxies that have a Shechter luminosity function with a lower cutoff in the range 0.01-0.1 L*. Tests are performed to determine if our failure to detect, in some cases, luminous host galaxies could be an artifact caused by our analysis procedures. These tests include comparing the measured point-spread function (PSF) for our HST observations with the PSFs used in previous ground-based studies of host galaxies, measuring the fluctuations in the sky signals that were subtracted from the quasar images, evaluating empirically the effects of using different stellar PSFs in the analysis, carrying out the subtraction of the stellar (nuclear) source in different ways, creating and analyzing artificial active galactic nuclei (AGNs) with known surface brightnesses, and fitting the observed quasar light to an analytic model that includes a host galaxy.

  11. A NEW MODEL FOR DARK MATTER HALOS HOSTING QUASARS

    SciTech Connect

    Cen, Renyue; Safarzadeh, Mohammadtaher

    2015-01-10

    A new model for quasar-hosting dark matter halos, meeting two physical conditions, is put forth. First, significant interactions are taken into consideration to trigger quasar activities. Second, satellites in very massive halos at low redshift are removed from consideration due to their deficiency in cold gas. We analyze the Millennium Simulation to find halos that meet these two conditions and simultaneously match two-point auto-correlation functions of quasars and cross-correlation functions between quasars and galaxies at z = 0.5-3.2. The masses of the quasar hosts found decrease with decreasing redshift, with the mass thresholds being [(2-5) × 10{sup 12}, (2-5) × 10{sup 11}, (1-3) × 10{sup 11}] M {sub ☉} for median luminosities of ∼[10{sup 46}, 10{sup 46}, 10{sup 45}] erg s{sup –1} at z = (3.2, 1.4, 0.53), respectively, an order of magnitude lower than those inferred based on halo occupation distribution modeling. In this model, quasar hosts are primarily massive central halos at z ≥ 2-3 but increasingly dominated by lower mass satellite halos experiencing major interactions toward lower redshift. However, below z = 1, satellite halos in groups more massive than ∼2 × 10{sup 13} M {sub ☉} do not host quasars. Whether for central or satellite halos, imposing the condition of significant interactions substantially boosts the clustering strength compared to the total population with the same mass cut. The inferred lifetimes of quasars at z = 0.5-3.2 of 3-30 Myr are in agreement with observations. Quasars at z ∼ 2 would be hosted by halos of mass ∼5 × 10{sup 11} M {sub ☉} in this model, compared to ∼3 × 10{sup 12} M {sub ☉} previously thought, which would help reconcile with the observed, otherwise puzzling high covering fractions for Lyman limit systems around quasars.

  12. Effect of Spectral Index Distribution on Estimating the AGN Radio Luminosity Function

    NASA Astrophysics Data System (ADS)

    Yuan, Zunli; Wang, Jiancheng; Zhou, Ming; Mao, Jirong

    2016-10-01

    In this paper, we scrutinize the effect of spectral index distribution on estimating the active galactic nucleus radio luminosity function (RLF) by a Monte Carlo method. We find that the traditional bivariate RLF estimators can cause bias in varying degrees. The bias is especially pronounced for the flat-spectrum radio sources whose spectral index distribution is more scattered. We believe that the bias is caused because the K-corrections complicate the truncation boundary on the L-z plane of the sample, but the traditional bivariate RLF estimators have difficulty dealing with this boundary condition properly. We suggest that the spectral index distribution should be incorporated into the RLF analysis process to obtain a robust estimation. This drives the need for a trivariate function of the form Φ(α, z, L), which we show provides an accurate basis for measuring the RLF.

  13. The luminosity function of cluster galaxies: relations among M_1_, M^*^ and the morphological type.

    NASA Astrophysics Data System (ADS)

    Trevese, D.; Cirimele, G.; Appodia, B.

    1996-11-01

    A study of the luminosity function of 36 Abell clusters of galaxies has been carried out using photographic plates obtained with the Palomar 1.2 m Schmidt telescope. The relation between the magnitude M_1_ of the brightest cluster member and the Schechter function parameter M^*^ has been analyzed. A positive correlation between M^*^ and M_1_ is found. However clusters appear segregated in the M_1_-M^*^ plane according to their Rood & Sastry class in such a way that on average M_1_ becomes brighter while M^*^ becomes fainter going from late to early Rood & Sastry and also Bautz & Morgan classes. Also a partial correlation analysis involving the magnitude M_10_ of the 10th brightest galaxy, shows a negative intrinsic correlation between M_1_ and M^*^. These results agree with the cannibalism model for the formation of brightest cluster members, and provide new constraints for theories of cluster formation and evolution.

  14. Constraints on the age and evolution of the Galaxy from the white dwarf luminosity function

    NASA Technical Reports Server (NTRS)

    Wood, M. A.

    1992-01-01

    The white dwarf disk luminosity function is explored using observational results of Liebert et al. (1988, 1989) as a template for comparison, and the cooling curves of Wood (1990, 1991) as the input basis functions for the integration. The star formation rate over the history of the Galaxy is found to be constant to within an order of magnitude, and the disk age lies in the range 6-13.5 Gyr, where roughly 40 percent of the uncertainty is due to the observational uncertainties. Using the best current estimates as inputs to the integration, the disk ages range from 7.5 to 11 Gyr, i.e., they are substantially younger than most estimates for the halo globular clusters but in reasonable agreement with those for the disk globular clusters and open clusters. The ages of these differing populations, taken together, are consistent with the pressure-supported collapse models of early spiral Galactic evolution.

  15. HOST GALAXIES OF LUMINOUS TYPE 2 QUASARS AT z {approx} 0.5

    SciTech Connect

    Liu Xin; Greene, Jenny E.; Strauss, Michael A.; Zakamska, Nadia L.; Krolik, Julian H.; Heckman, Timothy M.

    2009-09-10

    We present deep Gemini GMOS optical spectroscopy of nine luminous quasars at redshifts z {approx} 0.5, drawn from the Sloan Digital Sky Survey type 2 quasar sample. Our targets were selected to have high intrinsic luminosities (M{sub V} < -26 mag) as indicated by the [O III] {lambda}5007 A emission-line luminosity (L[{sub OIII}]). Our sample has a median black hole mass of {approx}10{sup 8.8} M{sub sun} inferred assuming the local M {sub BH}-{sigma}{sub *} relation and a median Eddington ratio of {approx}0.7, using stellar velocity dispersions {sigma}{sub *} measured from the G band. We estimate the contamination of the stellar continuum from scattered quasar light based on the strength of broad H{beta}, and provide an empirical calibration of the contamination as a function of L {sub [OIII]}; the scattered-light fraction is {approx}30% of L{sub 5100} for objects with L {sub [OIII]} = 10{sup 9.5} L{sub sun}. Population synthesis indicates that young poststarburst populations (<0.1 Gyr) are prevalent in luminous type 2 quasars, in addition to a relatively old population (>1 Gyr) which dominates the stellar mass. Broad emission complexes around He II {lambda}4686 A with luminosities up to 10{sup 8.3} L{sub sun} are unambiguously detected in three out of the nine targets, indicative of Wolf-Rayet (WR) populations. Population synthesis shows that {approx}5 Myr poststarburst populations contribute substantially to the luminosities (>50% of L{sub 5100}) of all three objects with WR detections. We find two objects with double cores and four with close companions. Our results may suggest that luminous type 2 quasars trace an early stage of galaxy interaction, perhaps responsible for both the quasar and the starburst activity.

  16. Clustering of intermediate redshift quasars using the final SDSS III-BOSS sample

    NASA Astrophysics Data System (ADS)

    Eftekharzadeh, Sarah; Myers, Adam D.; White, Martin; Weinberg, David H.; Schneider, Donald P.; Shen, Yue; Font-Ribera, Andreu; Ross, Nicholas P.; Paris, Isabelle; Streblyanska, Alina

    2015-11-01

    We measure the two-point clustering of spectroscopically confirmed quasars from the final sample of the Baryon Oscillation Spectroscopic Survey (BOSS) on comoving scales of 4 ≲ s ≲ 22 h-1 Mpc. The sample covers 6950 deg2 [ ˜ 19 (h- 1Gpc)3] and, over the redshift range 2.2 ≤ z ≤ 2.8, contains 55 826 homogeneously selected quasars, which is twice as many as in any similar work. We deduce bQ = 3.54 ± 0.10; the most precise measurement of quasar bias to date at these redshifts. This corresponds to a host halo mass of ˜2 × 1012 h-1 M⊙ with an implied quasar duty cycle of ˜1 per cent. The real-space projected correlation function is well fitted by a power law of index 2 and correlation length r0 = (8.12 ± 0.22) h- 1 Mpc over scales of 4 ≲ rp ≲ 25 h-1 Mpc. To better study the evolution of quasar clustering at moderate redshift, we extend the redshift range of our study to z ˜ 3.4 and measure the bias and correlation length of three subsamples over 2.2 ≤ z ≤ 3.4. We find no significant evolution of r0 or bias over this range, implying that the host halo mass of quasars decreases somewhat with increasing redshift. We find quasar clustering remains similar over a decade in luminosity, contradicting a scenario in which quasar luminosity is monotonically related to halo mass at z ≈ 2.5. Our results are broadly consistent with previous BOSS measurements, but they yield more precise constraints based upon a larger and more uniform data set.

  17. Effects of variability of X-ray binaries on the X-ray luminosity functions of Milky Way

    NASA Astrophysics Data System (ADS)

    Islam, Nazma; Paul, Biswajit

    2016-08-01

    The X-ray luminosity functions of galaxies have become a useful tool for population studies of X-ray binaries in them. The availability of long term light-curves of X-ray binaries with the All Sky X-ray Monitors opens up the possibility of constructing X-ray luminosity functions, by also including the intensity variation effects of the galactic X-ray binaries. We have constructed multiple realizations of the X-ray luminosity functions (XLFs) of Milky Way, using the long term light-curves of sources obtained in the 2-10 keV energy band with the RXTE-ASM. The observed spread seen in the value of slope of both HMXB and LMXB XLFs are due to inclusion of variable luminosities of X-ray binaries in construction of these XLFs as well as finite sample effects. XLFs constructed for galactic HMXBs in the luminosity range 1036-1039 erg/sec is described by a power-law model with a mean power-law index of -0.48 and a spread due to variability of HMXBs as 0.19. XLFs constructed for galactic LMXBs in the luminosity range 1036-1039 erg/sec has a shape of cut-off power-law with mean power-law index of -0.31 and a spread due to variability of LMXBs as 0.07.

  18. Global survey of star clusters in the Milky Way. V. Integrated JHKS magnitudes and luminosity functions

    NASA Astrophysics Data System (ADS)

    Kharchenko, N. V.; Piskunov, A. E.; Schilbach, E.; Röser, S.; Scholz, R.-D.

    2016-01-01

    Aims: In this study we determine absolute integrated magnitudes in the J,H,KS passbands for Galactic star clusters from the Milky Way Star Clusters survey. In the wide solar neighbourhood, we derive the open cluster luminosity function (CLF) for different cluster ages. Methods: The integrated magnitudes are based on uniform cluster membership derived from the 2MAst catalogue (a merger of the PPMXL and 2MASS) and are computed by summing up the individual luminosities of the most reliable cluster members. We discuss two different techniques of constructing the CLF, a magnitude-limited and a distance-limited approach. Results: Absolute J,H,KS integrated magnitudes are obtained for 3061 open clusters, and 147 globular clusters. The integrated magnitudes and colours are accurate to about 0.8 and 0.2 mag, respectively. Based on the sample of open clusters we construct the general cluster luminosity function in the solar neighbourhood in the three passbands. In each passband the CLF shows a linear part covering a range of 6 to 7 mag at the bright end. The CLFs reach their maxima at an absolute magnitude of -2 mag, then drop by one order of magnitude. During cluster evolution, the CLF changes its slope within tight, but well-defined limits. The CLF of the youngest clusters has a steep slope of about 0.4 at bright magnitudes and a quasi-flat portion for faint clusters. For the oldest population, we find a flatter function with a slope of about 0.2. The CLFs at Galactocentric radii smaller than that of the solar circle differ from those in the direction of the Galactic anti-centre. The CLF in the inner area is flatter and the cluster surface density higher than the local one. In contrast, the CLF is somewhat steeper than the local one in the outer disk, and the surface density is lower. The corresponding catalogue of integrated magnitudes is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc

  19. THE FAINT END OF THE LUMINOSITY FUNCTION AND LOW SURFACE BRIGHTNESS GALAXIES

    SciTech Connect

    Geller, Margaret J.; Kurtz, Michael J.; Fabricant, Daniel G.; Diaferio, Antonaldo; Dell'Antonio, Ian P. E-mail: mkurtz@cfa.harvard.edu E-mail: adiaferio@cfa.harvard.edu

    2012-04-15

    Smithsonian Hectospec Lensing Survey (SHELS) is a dense redshift survey covering a 4 deg{sup 2} region to a limiting R = 20.6. In the construction of the galaxy catalog and in the acquisition of spectroscopic targets, we paid careful attention to the survey completeness for lower surface brightness dwarf galaxies. Thus, although the survey covers a small area, it is a robust basis for computation of the slope of the faint end of the galaxy luminosity function to a limiting M{sub R} = -13.3 + 5log h. We calculate the faint-end slope in the R band for the subset of SHELS galaxies with redshifts in the range 0.02 {<=}z < 0.1, SHELS{sub 0.1}. This sample contains 532 galaxies with R < 20.6 and with a median surface brightness within the half-light radius of SB{sub 50,R} = 21.82 mag arcsec{sup -2}. We used this sample to make one of the few direct measurements of the dependence of the faint end of the galaxy luminosity function on surface brightness. For the sample as a whole the faint-end slope, {alpha} = -1.31 {+-} 0.04, is consistent with both the Blanton et al. analysis of the Sloan Digital Sky Survey and the Liu et al. analysis of the COSMOS field. This consistency is impressive given the very different approaches of these three surveys. A magnitude-limited sample of 135 galaxies with optical spectroscopic redshifts with mean half-light surface brightness, SB{sub 50,R} {>=} 22.5 mag arcsec{sup -2} is unique to SHELS{sub 0.1}. The faint-end slope is {alpha}{sub 22.5} = -1.52 {+-} 0.16. SHELS{sub 0.1} shows that lower surface brightness objects dominate the faint-end slope of the luminosity function in the field, underscoring the importance of surface brightness limits in evaluating measurements of the faint-end slope and its evolution.

  20. Fifty Years of Quasars

    NASA Astrophysics Data System (ADS)

    Kellermann, Kenneth I.

    2013-01-01

    Although the extragalactic nature of quasars was discussed as early as 1960, it was dismissed largely because of preconceived ideas about what appeared to be an unrealistically high luminosity. Following the 1962 occultations of the strong radio source 3C 273 at Parkes, and the subsequent identification with an apparent stellar object, Maartin Schmidt recognized that the relatively simple hydrogen line Balmer series spectrum implied a redshift of 0.16 leading to the general acceptance of the quasars as being extragalactic origin and the most luminous objects in the Universe. Subsequent radio and optical measurements quickly led to the identification of other quasars with increasingly large redshifts. However, claims for a more local population continued for at least several decades confused perhaps by the recognition of the much larger class of radio quiet quasars and active galactic nuclei (AGN), and the uncertain connection with Seyfert galaxies and Zwicky’s compact galaxies. Curiously, 3C 273, which is one of the brightest extragalactic extragalactic sources in the sky, was first catalogued in 1959 and the mag 13 optical counterpart was known at least as early as 1887. Although, since 1960, much fainter optical counterparts were being routinely identified using accurate radio interferometer positions, 3C273 eluded identification until the series of lunar occultations by Cyril Hazard and others were used to determine the position and morphology of the radio source.

  1. The WARPS Survey - VIII. Evolution of the galaxy cluster X-ray Luminosity Function

    NASA Astrophysics Data System (ADS)

    Koens, L. A.; Maughan, B. J.; Jones, L. R.; Ebeling, H.; Horner, D. J.; Perlman, E. S.; Phillipps, S.; Scharf, C. A.

    2013-11-01

    We present measurements of the galaxy cluster X-ray Luminosity Function (XLF) from the Wide Angle ROSAT Pointed Survey (WARPS) and quantify its evolution. WARPS is a serendipitous survey of the central region of ROSAT pointed observations and was carried out in two phases (WARPS-I and WARPS-II). The results here are based on a final sample of 124 clusters, complete above a flux limit of 6.5 × 10-14 erg cm-2 s-1, with members out to redshift z ˜ 1.05, and a sky coverage of 70.9 deg2. We find significant evidence for negative evolution of the XLF, which complements the majority of X-ray cluster surveys. To quantify the suggested evolution, we perform a maximum likelihood analysis and conclude that the evolution is driven by a decreasing number density of high-luminosity clusters with redshift, while the bulk of the cluster population remains nearly unchanged out to redshift z ≈ 1.1, as expected in a low-density universe. The results are found to be insensitive to a variety of sources of systematic uncertainty that affect the measurement of the XLF and determination of the survey selection function. We perform a Bayesian analysis of the XLF to fully account for uncertainties in the local XLF on the measured evolution, and find that the detected evolution remains significant at the 95 per cent level. We observe a significant excess of clusters in the WARPS at 0.1 < z < 0.3 and LX ≈ 2 × 1043 erg s-1 compared with the reference low-redshift XLF, or our Bayesian fit to the WARPS data. We find that the excess cannot be explained by sample variance, or Eddington bias, and is unlikely to be due to problems with the survey selection function.

  2. The galaxy UV luminosity function at z ≃ 2-4; new results on faint-end slope and the evolution of luminosity density

    NASA Astrophysics Data System (ADS)

    Parsa, Shaghayegh; Dunlop, James S.; McLure, Ross J.; Mortlock, Alice

    2016-03-01

    We present a new, robust measurement of the evolving rest-frame ultraviolet (UV) galaxy luminosity function (LF) over the key redshift range from z ≃ 2 to z ≃ 4. Our results are based on the high dynamic range provided by combining the Hubble Ultra Deep Field (HUDF), CANDELS/GOODS-South, and UltraVISTA/COSMOS surveys. We utilize the unparalleled multifrequency photometry available in this survey `wedding cake' to compile complete galaxy samples at z ≃ 2, 3, 4 via photometric redshifts (calibrated against the latest spectroscopy) rather than colour-colour selection, and to determine accurate rest-frame UV absolute magnitudes (M1500) from spectral energy distribution (SED) fitting. Our new determinations of the UV LF extend from M1500 ≃ -22 (AB mag) down to M1500 = -14.5, -15.5 and -16 at z ≃ 2, 3 and 4, respectively (thus, reaching ≃ 3-4 mag fainter than previous blank-field studies at z ≃ 2,3). At z ≃ 2, 3, we find a much shallower faint-end slope (α = -1.32 ± 0.03) than reported in some previous studies (α ≃ -1.7), and demonstrate that this new measurement is robust. By z ≃ 4, the faint-end slope has steepened slightly, to α = -1.43 ± 0.04, and we show that these measurements are consistent with the overall evolutionary trend from z = 0 to 8. Finally, we find that while characteristic number density (φ*) drops from z ≃ 2 to z ≃ 4, characteristic luminosity (M*) brightens by ≃ 1 mag. This, combined with the new flatter faint-end slopes, has the consequence that UV luminosity density (and hence unobscured star formation density) peaks at z ≃ 2.5-3, when the Universe was ≃ 2.5 Gyr old.

  3. The initial mass function for massive stars in the Magellanic Clouds. 3: Luminosity and mass functions for 14 OB associations

    NASA Technical Reports Server (NTRS)

    Hill, Robert J.; Madore, Barry F.; Freedman, Wendy L.

    1994-01-01

    We have used UBV photometry of stars in 14 associations in the Large and Small Magellanic Clouds (LMC/SMS) (Hill, Madore, & Freedman) to derive luminosity and mass functions for the most massive stars. The main-sequence luminosity functions for the associations are quite similar, having an average slope of s = 0.03 +/- 0.06. The mass functions for the associations have slopes that span similar ranges about a common mean for both the LMC and SMC and there is no strong evidence for a significant variation in the slopes from one association to another. Accordingly, metal abundance does not appear to have a strong effect on the initial mass function (IMF), at least for the range in metallicity observed between the Magellanic Clouds. The average slope of the IMF for the Magellanic Cloud associations is Gamma = -2.0 +/- 0.5 for M greater than 9 Solar Masses. The range in the derived slopes is more likely due to the large uncertainties associated with the calculations of the mass functions, rather than to real variations in the IMF. There may be some evidence for a decrease in the slope of the IMF at masses below 9 Solar Masses, but incompleteness and the larger photometric errors associated with the faintest stars make this conclusion tentative.

  4. Characterizing the Properties of Clusters of Galaxies As a Function of Luminosity and Redshift

    SciTech Connect

    Andersson, K.; Peterson, J.R.; Madejski, G.; Goobar, A.; /Stockholm U. /Stockholm U., OKC

    2009-02-24

    We report the application of the new Monte Carlo method, Smoothed Particle Inference (SPI, described in a pair of companion papers), towards analysis and interpretation of X-ray observations of clusters of galaxies with the XMM-Newton satellite. Our sample consists of publicly available well-exposed observations of clusters at redshifts z > 0.069, totaling 101 objects. We determine the luminosity and temperature structure of the X-ray emitting gas, with the goal to quantify the scatter and the evolution of the L{sub X} - T relation, as well as to investigate the dependence on cluster substructure with redshift. This work is important for the establishment of the potential robustness of mass estimates from X-ray data which in turn is essential towards the use of clusters for measurements of cosmological parameters. We use the luminosity and temperature maps derived via the SPI technique to determine the presence of cooling cores, via measurements of luminosity and temperature contrast. The L{sub X}-T relation is investigated, and we confirm that L{sub X} {proportional_to} T{sup 3}. We find a weak redshift dependence ({proportional_to} (1 + z){sup {beta}{sub LT}}, {beta}{sub LT} = 0.50 {+-} 0.34), in contrast to some Chandra results. The level of dynamical activity is established using the 'power ratios' method, and we compare our results to previous application of this method to Chandra data for clusters. We find signs of evolution in the P{sub 3}/P{sub 0} power ratio. A new method, the 'temperature two-point correlation function', is proposed. This method is used to determine the 'power spectrum' of temperature fluctuations in the X-ray emitting gas as a function of spatial scale. We show how this method can be fruitfully used to identify cooling core clusters as well as those with disturbed structures, presumably due to on-going or recent merger activity.

  5. High-Redshift QSOs in the SWIRE Survey and the z~3 QSO Luminosity Function

    NASA Astrophysics Data System (ADS)

    Siana, Brian; Polletta, Maria del Carmen; Smith, Harding E.; Lonsdale, Carol J.; Gonzalez-Solares, Eduardo; Farrah, Duncan; Babbedge, Tom S. R.; Rowan-Robinson, Michael; Surace, Jason; Shupe, David; Fang, Fan; Franceschini, Alberto; Oliver, Seb

    2008-03-01

    We use a simple optical/infrared (IR) photometric selection of high-redshift QSOs that identifies a Lyman break in the optical photometry and requires a red IR color to distinguish QSOs from common interlopers. The search yields 100 z ~ 3 (U-dropout) QSO candidates with 19 < r' < 22 over 11.7 deg2 in the ELAIS-N1 (EN1) and ELAIS-N2 (EN2) fields of the Spitzer Wide-area Infrared Extragalactic (SWIRE) Legacy Survey. The z ~ 3 selection is reliable, with spectroscopic follow-up of 10 candidates confirming that they are all QSOs at 2.83 < z < 3.44. We find that our z ~ 4 (g'-dropout) sample suffers from both unreliability and incompleteness but present seven previously unidentified QSOs at 3.50 < z < 3.89. Detailed simulations show our z ~ 3 completeness to be ~80%-90% from 3.0 < z < 3.5, significantly better than the ~30%-80% completeness of the SDSS at these redshifts. The resulting luminosity function extends 2 mag fainter than SDSS and has a faint-end slope of β = - 1.42 +/- 0.15, consistent with values measured at lower redshift. Therefore, we see no evidence for evolution of the faint-end slope of the QSO luminosity function. Including the SDSS QSO sample, we have now directly measured the space density of QSOs responsible for ~70% of the QSO UV luminosity density at z ~ 3. We derive a maximum rate of H I photoionization from QSOs at z ~ 3.2, Γ = 4.8 × 10-13 s-1, about half of the total rate inferred through studies of the Lyα forest. Therefore, star-forming galaxies and QSOs must contribute comparably to the photoionization of H I in the intergalactic medium at z ~ 3. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

  6. The HerMES submillimetre local and low-redshift luminosity functions

    NASA Astrophysics Data System (ADS)

    Marchetti, L.; Vaccari, M.; Franceschini, A.; Arumugam, V.; Aussel, H.; Béthermin, M.; Bock, J.; Boselli, A.; Buat, V.; Burgarella, D.; Clements, D. L.; Conley, A.; Conversi, L.; Cooray, A.; Dowell, C. D.; Farrah, D.; Feltre, A.; Glenn, J.; Griffin, M.; Hatziminaoglou, E.; Heinis, S.; Ibar, E.; Ivison, R. J.; Nguyen, H. T.; O'Halloran, B.; Oliver, S. J.; Page, M. J.; Papageorgiou, A.; Pearson, C. P.; Pérez-Fournon, I.; Pohlen, M.; Rigopoulou, D.; Roseboom, I. G.; Rowan-Robinson, M.; Schulz, B.; Scott, Douglas; Seymour, N.; Shupe, D. L.; Smith, A. J.; Symeonidis, M.; Valtchanov, I.; Viero, M.; Wang, L.; Wardlow, J.; Xu, C. K.; Zemcov, M.

    2016-02-01

    We used wide-area surveys over 39 deg2 by the HerMES (Herschel Multi-tiered Extragalactic Survey) collaboration, performed with the Herschel Observatory SPIRE multiwavelength camera, to estimate the low-redshift, 0.02 < z < 0.5, monochromatic luminosity functions (LFs) of galaxies at 250, 350 and 500 μm. Within this redshift interval, we detected 7087 sources in five independent sky areas, ˜40 per cent of which have spectroscopic redshifts, while for the remaining objects photometric redshifts were used. The SPIRE LFs in different fields did not show any field-to-field variations beyond the small differences to be expected from cosmic variance. SPIRE flux densities were also combined with Spitzer photometry and multiwavelength archival data to perform a complete spectral energy distribution fitting analysis of SPIRE detected sources to calculate precise k-corrections, as well as the bolometric infrared (IR; 8-1000 μm) LFs and their low-z evolution from a combination of statistical estimators. Integration of the latter prompted us to also compute the local luminosity density and the comoving star formation rate density (SFRD) for our sources, and to compare them with theoretical predictions of galaxy formation models. The LFs show significant and rapid luminosity evolution already at low redshifts, 0.02 < z < 0.2, with L_{IR}^{*} ∝ (1+z)^{6.0± 0.4} and Φ _{IR}^{*} ∝ (1+z)^{-2.1± 0.4}, L_{250}^{*} ∝ (1+z)^{5.3± 0.2} and Φ _{250}^{*} ∝ (1+z)^{-0.6± 0.4} estimated using the IR bolometric and the 250 μm LFs, respectively. Converting our IR LD estimate into an SFRD assuming a standard Salpeter initial mass function and including the unobscured contribution based on the UV dust-uncorrected emission from local galaxies, we estimate an SFRD scaling of SFRD0 + 0.08z, where SFRD0 ≃ (1.9 ± 0.03) × 10-2 [M⊙ Mpc-3] is our total SFRD estimate at z ˜ 0.02.

  7. The X-ray luminosity function of active galactic nuclei in the redshift interval z=3-5

    NASA Astrophysics Data System (ADS)

    Georgakakis, A.; Aird, J.; Buchner, J.; Salvato, M.; Menzel, M.-L.; Brandt, W. N.; McGreer, I. D.; Dwelly, T.; Mountrichas, G.; Koki, C.; Georgantopoulos, I.; Hsu, L.-T.; Merloni, A.; Liu, Z.; Nandra, K.; Ross, N. P.

    2015-10-01

    We combine deep X-ray survey data from the Chandra observatory and the wide-area/shallow XMM-XXL field to estimate the active galactic nuclei (AGN) X-ray luminosity function in the redshift range z = 3-5. The sample consists of nearly 340 sources with either photometric (212) or spectroscopic (128) redshift in the above range. The combination of deep and shallow survey fields also provides a luminosity baseline of three orders of magnitude, LX(2-10 keV) ≈ 1043-1046 erg s- 1 at z > 3. We follow a Bayesian approach to determine the binned AGN space density and explore their evolution in a model-independent way. Our methodology properly accounts for Poisson errors in the determination of X-ray fluxes and uncertainties in photometric redshift estimates. We demonstrate that the latter is essential for unbiased measurement of space densities. We find that the AGN X-ray luminosity function evolves strongly between the redshift intervals z = 3-4 and z = 4-5. There is also suggestive evidence that the amplitude of this evolution is luminosity dependent. The space density of AGN with LX(2-10 keV) < 1045 erg s- 1 drops by a factor of 5 between the redshift intervals above, while the evolution of brighter AGN appears to be milder. Comparison of our X-ray luminosity function with that of ultraviolet (UV)/optical selected quasi-stellar objects at similar redshifts shows broad agreement at bright luminosities, LX(2-10 keV) > 1045 erg s- 1. At fainter luminosities X-ray surveys measure higher AGN space densities. The faint-end slope of UV/optical luminosity functions, however, is steeper than for X-ray selected AGN. This implies that the Type I AGN fraction increases with decreasing luminosity at z > 3, opposite to trends established at lower redshift. We also assess the significance of AGN in keeping the hydrogen ionized at high redshift. Our X-ray luminosity function yields ionizing photon rate densities that are insufficient to keep the Universe ionized at redshift z > 4. A

  8. A Complete K-band Luminosity Function of the Central 30 PC

    NASA Astrophysics Data System (ADS)

    Philipp, S.; Mezger, P. G.; Zylka, R.

    1999-06-01

    We have obtained a K band mosaic image of an area Δα times Δ δ ~650'' times 710'' centered approximately on Sgr A*. With a detection limit of SK' ~100 μ Jy and a completeness limit of ~2000 μ Jy our source counts will only be complete for early O-stars, Supergiants and the most luminous red Giants; less luminous stars will merge into an unresolved background continuum. Special care was taken in our observing procedure to recover all of this continuum emission. 6.1 times 104 individual sources were separated from the background continuum by fitting them with modified Lorentzian distributions. For the low-luminosity sources we construct a model K-band luminosity function (KLF) based on a Salpeter IMF, which is compared with the KLF of Baade's Window after readjustment to match the stellar surface density in the mosaic. We obtain the following results: The emission of both point like sources (interpreted as luminous stars) and an unresolved continuum (interpreted as low-mass main sequence (MS) stars) can be fitted by a KLF ~ SK'α consisting of four power-law approximations with different exponents α: The modeled sectors which relate to MS stars have the functional dependences ~ SK'-0.6 and SK' -0.8; the observed KLF, which relates to Giants and Supergiants becomes gradually steeper. Compared to the KLF of Baades Window (Tiede et al., 1995) the KLF of the mosaic shows a clear overabundance of stars with high K band flux densities which is strongest within the central 24'' (~1 pc).

  9. Luminosity function of [OII] emission-line galaxies in the MassiveBlack-II simulation

    DOE PAGES

    Park, KwangHo; Khandai, Nishikanta; Matteo, Tiziana Di; Ho, Shirley; Croft, Rupert; Wilkins, Stephen M.; Feng, Yu

    2015-09-18

    We examine the luminosity function (LF) of [OII] emission-line galaxies in the high-resolution cosmological simulation MassiveBlack-II (MBII). From the spectral energy distribution of each galaxy, we select a sub-sample of star-forming galaxies at 0.06 ≤ z ≤ 3.0 using the [OII] emission line luminosity L([OII]). We confirm that the specific star formation rate matches that in the Galaxy And Mass Assembly survey. We show that the [OII] LF at z = 1.0 from the MBII shows good agreement with the LFs from several surveys below L([OII]) = 1043.0 erg s–1 while the low redshifts (z ≤ 0.3) show an excessmore » in the prediction of bright [OII] galaxies, but still displaying a good match with observations below L([OII]) = 1041.6 erg s–1. Based on the validity in reproducing the properties of [OII] galaxies at low redshift (z ≤ 1), we forecast the evolution of the [OII] LF at high redshift (z ≤ 3), which can be tested by upcoming surveys such as the Hobby-Eberly Telescope Dark Energy Experiment and Dark Energy Spectroscopic Instrument. The slopes of the LFs at bright and faint ends range from –3 to –2 showing minima at z = 2. The slope of the bright end evolves approximately as (z + 1)–1 at z ≤ 2 while the faint end evolves as ~3(z + 1)–1 at 0.6 ≤ z ≤ 2. In addition, a similar analysis is applied for the evolution of [OIII] LFs, which is to be explored in the forthcoming survey Wide-Field InfraRed Survey Telescope-Astrophysics Focused Telescope Assets. As a result, we show that the auto-correlation function of [OII] and [OIII] emitting galaxies shows a rapid evolution from z = 2 to 1.« less

  10. Quasar feedback and the origin of radio emission in radio-quiet quasars

    NASA Astrophysics Data System (ADS)

    Zakamska, Nadia L.; Greene, Jenny E.

    2014-07-01

    We analyse Sloan Digital Sky Survey spectra of 568 obscured luminous quasars. The [O III] λ5007 Å emission line shows blueshifts and blue excess, indicating that some of the narrow-line gas is undergoing an organized outflow. The velocity width containing 90 per cent of line power ranges from 370 to 4780 km s-1, suggesting outflow velocities up to ˜2000 km s-1, and is strongly correlated with the radio luminosity among the radio-quiet quasars. We propose that radio emission in radio-quiet quasars is due to relativistic particles accelerated in the shocks within the quasar-driven outflows; star formation in quasar hosts is insufficient to explain the observed radio emission. The median radio luminosity of the sample of νLν[1.4 GHz] = 1040 erg s-1 suggests a median kinetic luminosity of the quasar-driven wind of Lwind = 3 × 1044 erg s-1, or about 4 per cent of the estimated median bolometric luminosity Lbol = 8 × 1045 erg s-1. Furthermore, the velocity width of [O III] is positively correlated with mid-infrared luminosity, which suggests that outflows are ultimately driven by the radiative output of the quasar. Emission lines characteristic of shocks in quasi-neutral medium increase with the velocity of the outflow, which we take as evidence of quasar-driven winds propagating into the interstellar medium of the host galaxy. Quasar feedback appears to operate above the threshold luminosity of Lbol ˜ 3 × 1045 erg s-1.

  11. The Century Survey Galactic Halo Project. II. Global Properties and the Luminosity Function of Field Blue Horizontal Branch Stars

    NASA Astrophysics Data System (ADS)

    Brown, Warren R.; Geller, Margaret J.; Kenyon, Scott J.; Kurtz, Michael J.; Allende Prieto, Carlos; Beers, Timothy C.; Wilhelm, Ronald

    2005-09-01

    We discuss a 175 deg2 spectroscopic survey for blue horizontal branch (BHB) stars in the Galactic halo. We use the Two Micron All Sky Survey (2MASS) and the Sloan Digital Sky Survey (SDSS) to select BHB candidates, and we find that the 2MASS and SDSS color selection is 38% and 50% efficient, respectively, for BHB stars. Our samples include one likely runaway B7 star 6 kpc below the Galactic plane. The global properties of the BHB samples are consistent with membership in the halo population: the median metallicity is [Fe/H]=-1.7, the velocity dispersion is 108 km s-1, and the mean Galactic rotation of the BHB stars 3 kpc<|z|<15 kpc is -4+/-30 km s-1. We discuss the theoretical basis of the Preston, Shectman, and Beers MV-color relation for BHB stars and conclude that the intrinsic shape of the BHB MV-color relation results from the physics of stars on the horizontal branch. We calculate the luminosity function for the field BHB star samples using the maximum likelihood method of Efstathiou and coworkers, which is unbiased by density variations. The field BHB luminosity function exhibits a steep rise at bright luminosities, a peak between 0.8luminosities. We compare the field BHB luminosity functions with the luminosity functions derived from 16 different globular cluster BHBs. Kolmogorov-Smirnov tests suggest that field BHB stars and BHB stars in globular clusters share a common distribution of luminosities, with the exception of globular clusters with extended BHBs.

  12. The local stellar luminosity function and mass-to-light ratio in the near-infrared

    NASA Astrophysics Data System (ADS)

    Just, A.; Fuchs, B.; Jahreiß, H.; Flynn, C.; Dettbarn, C.; Rybizki, J.

    2015-07-01

    A new sample of stars, representative of the solar neighbourhood luminosity function (LF), is constructed from the Hipparcos catalogue and the Fifth Catalogue of Nearby Stars. We have cross-matched to sources in the Two Micron All Sky Survey catalogue so that for all stars individually determined near-infrared (NIR) photometry is available on a homogeneous system (typically Ks). The spatial completeness of the sample has been carefully determined by statistical methods, and the NIR LF of the stars has been derived by direct star counts. We find a local volume luminosity of 0.121 ± 0.004 LK⊙ pc-3, corresponding to a volumetric mass-to-light ratio (M/L) of M/L_K = 0.31 ± 0.02 {M}_{⊙}/L_{K⊙}, where giants contribute 80 per cent to the light but less than 2 per cent to the stellar mass. We derive the surface brightness of the solar cylinder with the help of a vertical disc model. We find a surface brightness of 99 LK⊙ pc-2 with an uncertainty of approximately 10 per cent. This corresponds to an M/L for the solar cylinder of M/L_K = 0.34 {M}_{⊙}/L_{K⊙}. The M/L for the solar cylinder is only 10 per cent larger than the local value despite the fact that the local population has a much larger contribution of young stars. It turns out that the effective scaleheights of the lower main sequence carrying most of the mass is similar to that of the giants, which are dominating the NIR light. The corresponding colour for the solar cylinder is V - K = 2.89 mag compared to the local value of V - K = 2.46 mag. An extrapolation of the local surface brightness to the whole Milky Way yields a total luminosity of MK = -24.2 mag. The Milky Way falls in the range of K band Tully-Fisher relations from the literature.

  13. A MULTIVARIATE FIT LUMINOSITY FUNCTION AND WORLD MODEL FOR LONG GAMMA-RAY BURSTS

    SciTech Connect

    Shahmoradi, Amir

    2013-04-01

    It is proposed that the luminosity function, the rest-frame spectral correlations, and distributions of cosmological long-duration (Type-II) gamma-ray bursts (LGRBs) may be very well described as a multivariate log-normal distribution. This result is based on careful selection, analysis, and modeling of LGRBs' temporal and spectral variables in the largest catalog of GRBs available to date: 2130 BATSE GRBs, while taking into account the detection threshold and possible selection effects. Constraints on the joint rest-frame distribution of the isotropic peak luminosity (L{sub iso}), total isotropic emission (E{sub iso}), the time-integrated spectral peak energy (E{sub p,z}), and duration (T{sub 90,z}) of LGRBs are derived. The presented analysis provides evidence for a relatively large fraction of LGRBs that have been missed by the BATSE detector with E{sub iso} extending down to {approx}10{sup 49} erg and observed spectral peak energies (E{sub p} ) as low as {approx}5 keV. LGRBs with rest-frame duration T{sub 90,z} {approx}< 1 s or observer-frame duration T{sub 90} {approx}< 2 s appear to be rare events ({approx}< 0.1% chance of occurrence). The model predicts a fairly strong but highly significant correlation ({rho} = 0.58 {+-} 0.04) between E{sub iso} and E{sub p,z} of LGRBs. Also predicted are strong correlations of L{sub iso} and E{sub iso} with T{sub 90,z} and moderate correlation between L{sub iso} and E{sub p,z}. The strength and significance of the correlations found encourage the search for underlying mechanisms, though undermine their capabilities as probes of dark energy's equation of state at high redshifts. The presented analysis favors-but does not necessitate-a cosmic rate for BATSE LGRBs tracing metallicity evolution consistent with a cutoff Z/Z{sub Sun} {approx} 0.2-0.5, assuming no luminosity-redshift evolution.

  14. UNIFICATION OF LUMINOUS TYPE 1 QUASARS THROUGH C IV EMISSION

    SciTech Connect

    Richards, Gordon T.; Kruczek, Nicholas E.; Deo, Rajesh P.; Kratzer, Rachael M.; Gallagher, S. C.; Hall, Patrick B.; Hewett, Paul C.; Leighly, Karen M.; Shen, Yue

    2011-05-15

    Using a sample of {approx}30,000 quasars from the 7th Data Release of the Sloan Digital Sky Survey, we explore the range of properties exhibited by high-ionization, broad emission lines, such as C IV {lambda}1549. Specifically, we investigate the anti-correlation between continuum luminosity and emission-line equivalent width (the Baldwin Effect (BEff)) and the 'blueshifting' of the high-ionization emission lines with respect to low-ionization emission lines. Employing improved redshift determinations from Hewett and Wild, the blueshift of the C IV emission line is found to be nearly ubiquitous, with a mean shift of {approx}810 km s{sup -1} for radio-quiet (RQ) quasars and {approx}360 km s{sup -1} for radio-loud (RL) quasars. The BEff is present in both RQ and RL samples. We consider these phenomena within the context of an accretion disk-wind model that is modulated by the nonlinear correlation between ultraviolet and X-ray continuum luminosity. Composite spectra are constructed as a function of C IV emission-line properties in an attempt to reveal empirical relationships between different line species and the continuum. Within a two-component disk+wind model of the broad emission-line region (BELR), where the wind filters the continuum seen by the disk component, we find that RL quasars are consistent with being dominated by the disk component, while broad absorption line quasars are consistent with being dominated by the wind component. Some RQ objects have emission-line features similar to RL quasars; they may simply have insufficient black hole (BH) spin to form radio jets. Our results suggest that there could be significant systematic errors in the determination of L{sub bol} and BH mass that make it difficult to place these findings in a more physical context. However, it is possible to classify quasars in a paradigm where the diversity of BELR parameters is due to differences in an accretion disk wind between quasars (and over time); these differences are

  15. PHOTOMETRIC PROPERTIES AND LUMINOSITY FUNCTION OF NEARBY MASSIVE EARLY-TYPE GALAXIES

    SciTech Connect

    He, Y. Q.; Xia, X. Y.; Hao, C. N.; Jing, Y. P.; Mao, S.; Li, Cheng

    2013-08-10

    We perform photometric analyses of a bright early-type galaxy sample with 2949 galaxies (M{sub r} < -22.5 mag) in the redshift range of 0.05-0.15, drawn from the Sloan Digital Sky Survey (SDSS) DR7 with morphological classification from Galaxy Zoo 1. We measure the Petrosian and isophotal magnitudes, as well as the corresponding half-light radius for each galaxy. We find that for the brightest galaxies (M{sub r} < -23 mag), our Petrosian magnitudes and isophotal magnitudes to 25 mag arcsec{sup -2} and 1% of the sky brightness are on average 0.16 mag, 0.20 mag, and 0.26 mag brighter than the SDSS Petrosian values, respectively. In the first case, the underestimations are caused by overestimations in the sky background by the SDSS PHOTO algorithm, while the latter two are also due to deeper photometry. Similarly, the typical half-light radii (r{sub 50}) measured by the SDSS algorithm are smaller than our measurements. As a result, the bright end of the r-band luminosity function is found to decline more slowly than previous works. Our measured luminosity densities at the bright end are more than one order of magnitude higher than those of Blanton et al., and the stellar mass densities at M{sub *} {approx} 5 Multiplication-Sign 10{sup 11} M{sub Sun} and M{sub *} {approx} 10{sup 12} M{sub Sun} are a few tenths and a factor of a few higher than those of Bernardi et al. These results may significantly alleviate the tension in the assembly of massive galaxies between observations and predictions of the hierarchical structure formation model.

  16. The rest-frame K-band luminosity function of galaxies in clusters to z = 1.3

    SciTech Connect

    De Propris, R; Stanford, S A; Eisenhardt, P R; Holden, B P; Rosati, P

    2007-03-20

    We derive the rest-frame K-band luminosity function for galaxies in 32 clusters at 0.6 < z < 1.3 using deep 3.6 {micro}m and 4.5 {micro}m imaging from the Spitzer Space Telescope InfraRed Array Camera (IRAC). The luminosity functions approximate the stellar mass function of the cluster galaxies. Their dependence on redshift indicates that massive cluster galaxies (to the characteristic luminosity M*{sub K}) are fully assembled at least at z {approx} 1.3 and that little significant accretion takes place at later times. The existence of massive, highly evolved galaxies at these epochs is likely to represent a significant challenge to theories of hierarchical structure formation where such objects are formed by the late accretion of spheroidal systems at z < 1.

  17. Optical spectroscopy and the UV luminosity function of galaxies in the Abell 1367, Coma and Virgo clusters

    NASA Astrophysics Data System (ADS)

    Cortese, L.; Gavazzi, G.; Iglesias-Paramo, J.; Boselli, A.; Carrasco, L.

    2003-04-01

    Optical spectroscopy of 93 galaxies, 60 projected in the direction of Abell 1367, 21 onto the Coma cluster and 12 on Virgo, is reported. The targets were selected because they were detected in previous Hα , UV or r' surveys. The present observations bring to 100% the redshift completeness of Hα selected galaxies in the Coma region and to 75% in Abell 1367. All observed galaxies except one show Hα emission and belong to the clusters. This confirms previous determinations of the Hα luminosity function of the two clusters that were based on the assumption that all Hα detected galaxies were cluster members. Using the newly obtained data we re-determine the UV luminosity function of Coma and we compute for the first time the UV luminosity function of A1367. Their faint end slopes remain uncertain (-2.00luminosity function will be alpha ~ -1.35, in agreement with the UV luminosity function of the field (Sullivan et al. \\cite{Sullivan}) and with the Hα luminosity functions of the two clusters (Iglesias-Paramo et al. \\cite{lha}). We discover a point-like Hα source in the Virgo cluster, associated with the giant galaxy VCC873, possibly an extragalactic HII region similar to the one recently observed in Virgo by Gerhard et al. (\\cite{Gerhard}). Based on observations obtained with the Loiano telescope belonging to the University of Bologna (Italy), with the G. Haro telescope of the INAOE (Mexico) and with the Calar Alto observatory operated by the Centro Astronomico Hispano Aleman (Spain).

  18. Carbon-rich giants in the HR diagram and their luminosity function

    NASA Astrophysics Data System (ADS)

    Bergeat, J.; Knapik, A.; Rutily, B.

    2002-08-01

    The luminosity function (LF) of nearly 300 Galactic carbon giants is derived. Adding BaII giants and various related objects, about 370 objects are located in the RGB and AGB portions of the theoretical HR diagram. As intermediate steps, (1) bolometric corrections are calibrated against selected intrinsic color indices; (2) the diagram of photometric coefficients 1/2 vs. astrometric true parallaxes varpi are interpreted in terms of ranges of photospheric radii for every photometric group; (3) coefficients CR and CL for bias-free evaluation of mean photospheric radii and mean luminosities are computed. The LF of Galactic carbon giants exhibits two maxima corresponding to the HC-stars of the thick disk and to the CV-stars of the old thin disk respectively. It is discussed and compared to those of carbon stars in the Magellanic Clouds and Galactic bulge. The HC-part is similar to the LF of the Galactic bulge, reinforcing the idea that the Bulge and the thick disk are part of the same dynamical component. The CV-part looks similar to the LF of the Large Magellanic Cloud (LMC), but the former is wider due to the substantial errors on HIPPARCOS parallaxes. The obtained mean luminosities increase with increasing radii and decreasing effective temperatures, along the HC-CV sequence of photometric groups, except for HC0, the earliest one. This trend illustrates the RGB- and AGB-tracks of low- and intermediate-mass stars for a range in metallicities. From a comparison with theoretical tracks in the HR diagram, the initial masses Mi range from about 0.8 to 4.0 Msun for carbon giants, with possibly larger masses for a few extreme objects. A large range of metallicities is likely, from metal-poor HC-stars classified as CH stars on the grounds of their spectra (a spheroidal component), to near-solar compositions of many CV-stars. Technetium-rich carbon giants are brighter than the lower limit Mbol =~ -3.6+/- 0.4 and centered at =~ -4.7+0.6-0.9 at about =~ (2935

  19. The luminosity function of galactic X-ray sources - A cutoff and a 'standard candle'

    NASA Technical Reports Server (NTRS)

    Margon, B.; Ostriker, J. P.

    1973-01-01

    Analysis of the 2- to 10-kev luminosity distribution of 36 X-ray sources in the Local Group having known or estimated distances, showing that there exists a luminosity cutoff of approximately 10 to the 37.7th ergs/sec in agreement with the theoretical (Eddington) limit for the luminosity of an approximately 1 solar mass star. Furthermore, among the complete sample of high-luminosity sources, there appears to be a statistically significant group of X-ray 'standard candles' at (within less than 0.8 mag) the critical luminosity. This finding (which is in agreement with the self-consistent mass flow accretion models) presents the possibility that X-ray sources may be used as extragalactic distance indicators in the next generation of X-ray astronomy experiments.

  20. Discovery of a bright quasar without a massive host galaxy.

    PubMed

    Magain, Pierre; Letawe, Géraldine; Courbin, Frédéric; Jablonka, Pascale; Jahnke, Knud; Meylan, Georges; Wisotzki, Lutz

    2005-09-15

    A quasar is thought to be powered by the infall of matter onto a supermassive black hole at the centre of a massive galaxy. Because the optical luminosity of quasars exceeds that of their host galaxy, disentangling the two components can be difficult. This led in the 1990s to the controversial claim of the discovery of 'naked' quasars. Since then, the connection between quasars and galaxies has been well established. Here we report the discovery of a quasar lying at the edge of a gas cloud, whose size is comparable to that of a small galaxy, but whose spectrum shows no evidence for stars. The gas in the cloud is excited by the quasar itself. If a host galaxy is present, it is at least six times fainter than would normally be expected for such a bright quasar. The quasar is interacting dynamically with a neighbouring galaxy, whose gas might be feeding the black hole.

  1. The XXL Survey. II. The bright cluster sample: catalogue and luminosity function

    NASA Astrophysics Data System (ADS)

    Pacaud, F.; Clerc, N.; Giles, P. A.; Adami, C.; Sadibekova, T.; Pierre, M.; Maughan, B. J.; Lieu, M.; Le Fèvre, J. P.; Alis, S.; Altieri, B.; Ardila, F.; Baldry, I.; Benoist, C.; Birkinshaw, M.; Chiappetti, L.; Démoclès, J.; Eckert, D.; Evrard, A. E.; Faccioli, L.; Gastaldello, F.; Guennou, L.; Horellou, C.; Iovino, A.; Koulouridis, E.; Le Brun, V.; Lidman, C.; Liske, J.; Maurogordato, S.; Menanteau, F.; Owers, M.; Poggianti, B.; Pomarède, D.; Pompei, E.; Ponman, T. J.; Rapetti, D.; Reiprich, T. H.; Smith, G. P.; Tuffs, R.; Valageas, P.; Valtchanov, I.; Willis, J. P.; Ziparo, F.

    2016-06-01

    Context. The XXL Survey is the largest survey carried out by the XMM-Newton satellite and covers a total area of 50 square degrees distributed over two fields. It primarily aims at investigating the large-scale structures of the Universe using the distribution of galaxy clusters and active galactic nuclei as tracers of the matter distribution. The survey will ultimately uncover several hundreds of galaxy clusters out to a redshift of ~2 at a sensitivity of ~10-14 erg s-1 cm-2 in the [0.5-2] keV band. Aims: This article presents the XXL bright cluster sample, a subsample of 100 galaxy clusters selected from the full XXL catalogue by setting a lower limit of 3 × 10-14 erg s-1 cm-2 on the source flux within a 1' aperture. Methods: The selection function was estimated using a mixture of Monte Carlo simulations and analytical recipes that closely reproduce the source selection process. An extensive spectroscopic follow-up provided redshifts for 97 of the 100 clusters. We derived accurate X-ray parameters for all the sources. Scaling relations were self-consistently derived from the same sample in other publications of the series. On this basis, we study the number density, luminosity function, and spatial distribution of the sample. Results: The bright cluster sample consists of systems with masses between M500 = 7 × 1013 and 3 × 1014 M⊙, mostly located between z = 0.1 and 0.5. The observed sky density of clusters is slightly below the predictions from the WMAP9 model, and significantly below the prediction from the Planck 2015 cosmology. In general, within the current uncertainties of the cluster mass calibration, models with higher values of σ8 and/or ΩM appear more difficult to accommodate. We provide tight constraints on the cluster differential luminosity function and find no hint of evolution out to z ~ 1. We also find strong evidence for the presence of large-scale structures in the XXL bright cluster sample and identify five new superclusters. Based on

  2. The 5-10 keV AGN luminosity function at 0.01 < z < 4.0

    NASA Astrophysics Data System (ADS)

    Fotopoulou, S.; Buchner, J.; Georgantopoulos, I.; Hasinger, G.; Salvato, M.; Georgakakis, A.; Cappelluti, N.; Ranalli, P.; Hsu, L. T.; Brusa, M.; Comastri, A.; Miyaji, T.; Nandra, K.; Aird, J.; Paltani, S.

    2016-03-01

    The active galactic nuclei (AGN) X-ray luminosity function traces actively accreting supermassive black holes and is essential for the study of the properties of the AGN population, black hole evolution, and galaxy-black hole coevolution. Up to now, the AGN luminosity function has been estimated several times in soft (0.5-2 keV) and hard X-rays (2-10 keV). AGN selection in these energy ranges often suffers from identification and redshift incompleteness and, at the same time, photoelectric absorption can obscure a significant amount of the X-ray radiation. We estimate the evolution of the luminosity function in the 5-10 keV band, where we effectively avoid the absorbed part of the spectrum, rendering absorption corrections unnecessary up to NH ~ 1023 cm-2. Our dataset is a compilation of six wide, and deep fields: MAXI, HBSS, XMM-COSMOS, Lockman Hole, XMM-CDFS, AEGIS-XD, Chandra-COSMOS, and Chandra-CDFS. This extensive sample of ~1110 AGN (0.01 < z < 4.0, 41 < log Lx < 46) is 98% redshift complete with 68% spectroscopic redshifts. For sources lacking a spectroscopic redshift estimation we use the probability distribution function of photometric redshift estimation specifically tuned for AGN, and a flat probability distribution function for sources with no redshift information. We use Bayesian analysis to select the best parametric model from simple pure luminosity and pure density evolution to more complicated luminosity and density evolution and luminosity-dependent density evolution (LDDE). We estimate the model parameters that describe best our dataset separately for each survey and for the combined sample. We show that, according to Bayesian model selection, the preferred model for our dataset is the LDDE. Our estimation of the AGN luminosity function does not require any assumption on the AGN absorption and is in good agreement with previous works in the 2-10 keV energy band based on X-ray hardness ratios to model the absorption in AGN up to redshift three

  3. The Norma cluster (ACO3627) - II. The near-infrared Ks-band luminosity function

    NASA Astrophysics Data System (ADS)

    Skelton, R. E.; Woudt, P. A.; Kraan-Korteweg, R. C.

    2009-07-01

    A deep Ks-band photometric catalogue of galaxies at the core of the rich, nearby Norma cluster (ACO3627) is presented. The survey covers about 45 × 45arcmin2 (slightly less than 1/3 Abell radius), which corresponds to ~0.8h-270Mpc2 at the adopted distance (vCMB/H0) of 70h-170Mpc 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 Ks-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.

  4. The optical luminosity function of gamma-ray bursts deduced from ROTSE-III observations

    SciTech Connect

    Cui, X. H.; Wu, X. F.; Wei, J. J.; Yuan, F.; Zheng, W. K.; Liang, E. W.; Akerlof, C. W.; McKay, T. A.; Ashley, M. C. B.; Flewelling, H. A.; Göǧüş, E.; Güver, T.; Kızıloǧlu, Ü.; Pandey, S. B.; Rykoff, E. S.; Rujopakarn, W.; Schaefer, B. E.; Wheeler, J. C.; Yost, S. A. E-mail: xfwu@pmo.ac.cn E-mail: fang.yuan@anu.edu.au E-mail: lew@gxu.edu.cn

    2014-11-10

    We present the optical luminosity function (LF) of gamma-ray bursts (GRBs) estimated from a uniform sample of 58 GRBs from observations with the Robotic Optical Transient Search Experiment III (ROTSE-III). Our GRB sample is divided into two sub-samples: detected afterglows (18 GRBs) and those with upper limits (40 GRBs). We derive R-band fluxes for these two sub-samples 100 s after the onset of the burst. The optical LFs at 100 s are fitted by assuming that the co-moving GRB rate traces the star formation rate. While fitting the optical LFs using Monte Carlo simulations, we take into account the detection function of ROTSE-III. We find that the cumulative distribution of optical emission at 100 s is well described by an exponential rise and power-law decay, a broken power law,and Schechter LFs. A single power-law (SPL) LF, on the other hand, is ruled out with high confidence.

  5. Luminosity function of [OII] emission-line galaxies in the MassiveBlack-II simulation

    SciTech Connect

    Park, KwangHo; Khandai, Nishikanta; Matteo, Tiziana Di; Ho, Shirley; Croft, Rupert; Wilkins, Stephen M.; Feng, Yu

    2015-09-18

    We examine the luminosity function (LF) of [OII] emission-line galaxies in the high-resolution cosmological simulation MassiveBlack-II (MBII). From the spectral energy distribution of each galaxy, we select a sub-sample of star-forming galaxies at 0.06 ≤ z ≤ 3.0 using the [OII] emission line luminosity L([OII]). We confirm that the specific star formation rate matches that in the Galaxy And Mass Assembly survey. We show that the [OII] LF at z = 1.0 from the MBII shows good agreement with the LFs from several surveys below L([OII]) = 1043.0 erg s–1 while the low redshifts (z ≤ 0.3) show an excess in the prediction of bright [OII] galaxies, but still displaying a good match with observations below L([OII]) = 1041.6 erg s–1. Based on the validity in reproducing the properties of [OII] galaxies at low redshift (z ≤ 1), we forecast the evolution of the [OII] LF at high redshift (z ≤ 3), which can be tested by upcoming surveys such as the Hobby-Eberly Telescope Dark Energy Experiment and Dark Energy Spectroscopic Instrument. The slopes of the LFs at bright and faint ends range from –3 to –2 showing minima at z = 2. The slope of the bright end evolves approximately as (z + 1)–1 at z ≤ 2 while the faint end evolves as ~3(z + 1)–1 at 0.6 ≤ z ≤ 2. In addition, a similar analysis is applied for the evolution of [OIII] LFs, which is to be explored in the forthcoming survey Wide-Field InfraRed Survey Telescope-Astrophysics Focused Telescope Assets. As a result, we show that the auto-correlation function of [OII] and [OIII] emitting galaxies shows a rapid evolution from z = 2 to 1.

  6. Discovery of three z > 6.5 quasars in the VISTA kilo-degree infrared galaxy (VIKING) survey

    SciTech Connect

    Venemans, B. P.; Findlay, J. R.; Sutherland, W. J.; De Rosa, G.; McMahon, R. G.; González-Solares, E. A.; Lewis, J. R.; Simcoe, R.; Kuijken, K.

    2013-12-10

    Studying quasars at the highest redshifts can constrain models of galaxy and black hole formation, and it also probes the intergalactic medium in the early universe. Optical surveys have to date discovered more than 60 quasars up to z ≅ 6.4, a limit set by the use of the z-band and CCD detectors. Only one z ≳ 6.4 quasar has been discovered, namely the z = 7.08 quasar ULAS J1120+0641, using near-infrared imaging. Here we report the discovery of three new z ≳ 6.4 quasars in 332 deg{sup 2} of the Visible and Infrared Survey Telescope for Astronomy Kilo-degree Infrared Galaxy (VIKING) survey, thus extending the number from 1 to 4. The newly discovered quasars have redshifts of z = 6.60, 6.75, and 6.89. The absolute magnitudes are between –26.0 and –25.5, 0.6-1.1 mag fainter than ULAS J1120+0641. Near-infrared spectroscopy revealed the Mg II emission line in all three objects. The quasars are powered by black holes with masses of ∼(1-2) × 10{sup 9} M {sub ☉}. In our probed redshift range of 6.44 < z < 7.44 we can set a lower limit on the space density of supermassive black holes of ρ(M {sub BH} > 10{sup 9} M {sub ☉}) > 1.1 × 10{sup –9} Mpc{sup –3}. The discovery of three quasars in our survey area is consistent with the z = 6 quasar luminosity function when extrapolated to z ∼ 7. We do not find evidence for a steeper decline in the space density of quasars with increasing redshift from z = 6 to z = 7.

  7. Galaxy Luminosity Function of the Dynamically Young Abell 119 Cluster: Probing the Cluster Assembly

    NASA Astrophysics Data System (ADS)

    Lee, Youngdae; Rey, Soo-Chang; Hilker, Michael; Sheen, Yun-Kyeong; Yi, Sukyoung K.

    2016-05-01

    We present the galaxy luminosity function (LF) of the Abell 119 cluster down to {M}r˜ -14 mag based on deep images in the u, g, and r bands taken by using MOSAIC II CCD mounted on the Blanco 4 m telescope at the CTIO. The cluster membership was accurately determined based on the radial velocity information and on the color-magnitude relation for bright galaxies and the scaling relation for faint galaxies. The overall LF exhibits a bimodal behavior with a distinct dip at r˜ 18.5 mag ({M}r˜ -17.8 mag), which is more appropriately described by a two-component function. The shape of the LF strongly depends on the clustercentric distance and on the local galaxy density. The LF of galaxies in the outer, low-density region exhibits a steeper slope and more prominent dip compared with that of counterparts in the inner, high-density region. We found evidence for a substructure in the projected galaxy distribution in which several overdense regions in the Abell 119 cluster appear to be closely associated with the surrounding, possible filamentary structure. The combined LF of the overdense regions exhibits a two-component function with a distinct dip, while the LF of the central region is well described by a single Schechter function. We suggest that, in the context of the hierarchical cluster formation scenario, the observed overdense regions are the relics of galaxy groups, retaining their two-component LFs with a dip, which acquired their shapes through a galaxy merging process in group environments, before they fall into a cluster.

  8. Toward a Prescription for Feedback from Quasar Outflows

    NASA Astrophysics Data System (ADS)

    Ganguly, Rajib; Bourjaily, M.; Munsell, J.; Brotherton, M. S.; Bhattacharjee, A.; Runnoe, J.; Charlton, J. C.; Eracleous, M.

    2011-01-01

    Models have shown that quasars are a crucial ingredient in the evolution of massive galaxies. Outflows play a key role in the story of quasars and their host galaxies, by helping regulate the accretion process, the star-formation rate and mass of the host galaxy (i.e., feedback). The prescription for modeling outflows as a contributor to feedback requires knowledge of the outflow velocity, distance, geometry, and column density. In particular, we need to understand how these depend on physical parameters and how much is determined stochastically (and with what distribution). For this purpose, we are examining a sample of 14000 z=1.7-2.0 quasars from the Sloan Digital Sky Survey. This redshift range permits the following from the SDSS spectra: (1) separation of objects that do and do not exhibit outflows; (2) classification/measurement of outflow properties (ionization, velocity, velocity width); and (3) estimates of the quasar black hole mass. To this, we are adding photometry from GALEX, 2MASS, and ROSAT in an effort to characterize more fully the quasar SEDs. ROSAT photometry provides estimates of the level of soft X-ray absorption, which helps regulate the velocity of outflows. GALEX photometry samples the extreme ultraviolet range where several high ionization species, that may be present in the outflows, absorb light. 2MASS photometry samples the rest-frame optical, where the effects of absorption and dust reddening are minimal, yield better estimates of the bolometric luminosity (hence, Eddington ratio). In this poster, we will present preliminary measurements of the amount of absorption in the soft X-ray and extreme ultraviolet bands as a function of both outflow properties and quasar physical properties. This material is based upon work supported by the National Aeronautics and Space Administration under Grant No. 09-ADP09-0016 issued through the Astrophysics Data Analysis Program.

  9. A possible bias on the estimate of Lbol/Ledd in AGN as a function of luminosity and redshift

    NASA Astrophysics Data System (ADS)

    Lamastra, A.; Matt, G.; Perola, G. C.

    2006-12-01

    Context: .The BH mass (and the related Eddington ratio, l = L_bol/L_edd) in broad line AGN is usually evaluated by combining estimates (often indirect) of the BLR radius and of the FWHM of the broad lines, under the assumption that the BLR clouds are in Keplerian motion around the BH. Such an evaluation depends on the geometry of the BLR. There are two major options for the BLR configuration: spherically symmetric or "flattened". In the latter case the inclination to the line of sight becomes a relevant parameter. Aims: .This paper is devoted to evaluate the bias on the estimate of the Eddington ratio when a spherical geometry is assumed (more generally when inclination effects are ignored), while the actual configuration is "flattened", as some evidence suggests. This is done as a function of luminosity and redshift, on the basis of recent results which show the existence of a correlation between the fraction of obscured AGN and these two parameters up to at least z=2.5 (date at larger redshifts being insufficient). Methods: .The assumed BLR velocity field is akin to the "generalized thick disk" proposed by Collin et al. (2006, A&A, 456, 75). Assuming an isotropic orientation in the sky, the mean value of the bias is calculated as a function of luminosity and redshift. Results: .It is demonstrated that, on average, the Eddington ratio obtained assuming a spherical geometry is underestimated for high luminosities, and overestimated for low luminosities. This bias converges for all luminosities at z about 2.7, while nothing can be said on this bias at larger redshifts due to the lack of data. The effects of the bias, averaged over the luminosity function of broad line AGN, have been calculated. The results imply that the bias associated with the a-sphericity of the BLR make even worse the discrepancy between the observations and the predictions of evolutionary models.

  10. Exploration of quasars with the Gaia mission

    NASA Astrophysics Data System (ADS)

    Proft, Svea; Wambsganss, Joachim

    2015-01-01

    We analyze the opportunities in and limits to investigating quasars with the Gaia satellite by studying Gaia's low- and high-resolution quasar spectra, with consideration of their signal-to-noise ratios. Furthermore, we explore bright quasars from the Sloan Digital Sky Survey with broad emission lines (BELs) redshifted into the spectral range of Gaia's Radial Velocity Spectrograph (RVS). We find that Gaia low-resolution spectra of quasars enable a determination of equivalent widths, continuum variability, and the Baldwin effect. Additionally, it will be feasible to analyze BEL reverberation mapping with Gaia data for a small sample of objects. These quasars should have a high cadence of measurements or higher time lags due to large redshifts, high quasar luminosities, or selected low-ionization lines. More than 500 known quasars will also get high-resolution spectra of individual BELs in the small wavelength range of the RVS. This allows an investigation of broad emission line shapes and their variabilities to get information on the spatial structure and kinematics of the broad line region. We identify six known variable SDSS quasars with BELs in the RVS that have interesting spectra for a potential intrinsic line variability investigation. However, the signal-to-noise ratio of the RVS is too small for studying narrow and broad absorption lines in quasar spectra.

  11. THE EVOLUTION OF THE DUSTY TORUS COVERING FACTOR IN QUASARS

    SciTech Connect

    Gu Minfeng

    2013-08-20

    We have assembled a large sample of 5996 quasars at 2.0 {<=} z {<=} 2.4 (high-z) or 0.7 {<=} z {<=} 1.1 (low-z) from the Sloan Digital Sky Survey (SDSS) ninth and seventh data release and quasar catalogs. The spectral energy distributions of quasars were constructed by collecting WISE, UKIDSS, and GALEX photometric data in addition to SDSS data, from which the IR luminosity at 1-7 {mu}m and bolometric luminosity at 1100 A-1 {mu}m were calculated. A red tail is clearly seen in the distribution of the spectral index over 1100 A-1 {mu}m for both the high-z and low-z sources; this tail is likely due to red or reddened quasars. The covering factor (CF) of the dusty torus is estimated as the ratio of the IR luminosity to the bolometric luminosity. We find significant anti-correlations between the CF and the bolometric luminosity, in both the high-z and low-z quasars; however, these two groups follow different tracks. At overlapping bolometric luminosities, the CF of high-z quasars is systematically larger than those of low-z quasars, implying an evolution of the CF with redshift.

  12. Revisiting the axion bounds from the Galactic white dwarf luminosity function

    SciTech Connect

    Bertolami, M.M. Miller; Melendez, B.E.; Althaus, L.G.

    2014-10-01

    It has been shown that the shape of the luminosity function of white dwarfs (WDLF) is a powerful tool to check for the possible existence of DFSZ-axions, a proposed but not yet detected type of weakly interacting particles. With the aim of deriving new constraints on the axion mass, we compute in this paper new theoretical WDLFs on the basis of WD evolving models that incorporate the feedback of axions on the thermal structure of the white dwarf. We find that the impact of the axion emission into the neutrino emission can not be neglected at high luminosities M{sub  Bol}∼< 8) and that the axion emission needs to be incorporated self-consistently into the evolution of the white dwarfs when dealing with axion masses larger than m{sub a} cos {sup 2}β∼> 5 meV (i.e. axion-electron coupling constant g{sub ae}∼> 1.4× 10{sup -13}). We went beyond previous works by including 5 different derivations of the WDLF in our analysis. Then we have performed χ{sup 2}-tests to have a quantitative measure of the agreement between the theoretical WDLFs — computed under the assumptions of different axion masses and normalization methods --- and the observed WDLFs of the Galactic disk. While all the WDLF studied in this work disfavour axion masses in the range suggested by asteroseismology m{sub a} cos {sup 2}β∼> 10 meV; g{sub ae}∼> 2.8× 10{sup -13}) lower axion masses can not be discarded from our current knowledge of the WDLF of the Galactic Disk. A larger set of completely independent derivations of the WDLF of the galactic disk as well as a detailed study of the uncertainties of the theoretical WDLFs is needed before quantitative constraints on the axion-electron coupling constant can be made.

  13. REVEALING PROBABLE UNIVERSAL FEATURES IN THE LOWER RED GIANT BRANCH LUMINOSITY FUNCTIONS OF GALACTIC GLOBULAR CLUSTERS

    SciTech Connect

    Kravtsov, V. V.

    2009-06-15

    This paper aims at demonstrating, for the first time, very probable universal peculiarities of the evolution of stars in the lower red giant branch (RGB) of Galactic globular clusters (GCs), reflected in two corresponding dips in the luminosity functions (LFs). By relying on the database of Hubble Space Telescope photometry of GCs, we analyze the lower RGB LFs of a sample of 18 GCs in a wide metallicity range, {delta}[Fe/H] {approx} 1.9 dex. We first show that in the F555W-(F439W-F555W) color-magnitude diagrams (CMDs), the lower RGB of GCs, except for the most metal-poor of them, frequently shows an apparent 'knee'. It reveals itself as a fairly abrupt change of the RGB slope. At the same luminosity level, the RGB LFs show a feature in the form of a more or less pronounced dip. We find that the magnitude difference between the RGB base and the given feature is, on average, around {delta} F555W{sup dip} {sub base}{approx} 1.4 mag. It shows a marginal variation with metallicity, if any, comparable to the error. At the same time, the magnitude difference between the dip and the RGB bump, {delta} F555W{sup bump} {sub dip}, decreases with increasing metallicity and falls within the range 0.8 {approx}< {delta} F555W{sup bump} {sub dip} {approx}< 1.7 mag. Generalized LFs (GLFs) have been obtained for three subsamples of GCs within limited metallicity ranges and with different horizontal branch (HB) morphology. They reproduce the 'knee-related' dip that is statistically significant in two of the GLFs. This feature turns out to be more pronounced in the GLFs of GCs with either the blue or red HB morphology than with the intermediate one. The same GLFs also reveal an additional probable universal dip. It shows up below the RGB bump at {delta} F555W slightly increasing from {approx}0.3 to {approx}0.5 mag with increasing metallicity. Also, the statistical significance of this 'prebump' dip increases, on average, toward higher metallicity. Except for the well known RGB bump, no

  14. Complete Hard X-Ray Surveys, AGN Luminosity Functions and the X-Ray Background

    NASA Technical Reports Server (NTRS)

    Tueller, Jack

    2011-01-01

    AGN are believed to make up most of the Cosmic X-Ray Background (CXB) above a few keV, but this background cannot be fully resolved at energies less than 10 keV due to absorption. The Swift/BAT and INTEGRAL missions are performing the first complete hard x-ray surveys with minimal bias due to absorption. The most recent results for both missions will be presented. Although the fraction of the CXB resolved by these surveys is small, it is possible to derive unbiased number counts and luminosity functions for AGN in the local universe. The survey energy range from 15-150 keV contains the important reflection and cutoff spectral features dominate the shape of the AGN contribution to the CXB. Average spectral characteristics of survey detected AGN will be presented and compared with model distributions. The numbers of hard x-ray blazars detected in these surveys are finally sufficient to estimate this important component's contribution the cosmic background. Constraints on CXB models and their significance will be discussed.

  15. Linking the fate of massive black hole binaries to the active galactic nuclei luminosity function

    NASA Astrophysics Data System (ADS)

    Dotti, M.; Merloni, A.; Montuori, C.

    2015-04-01

    Massive black hole binaries are naturally predicted in the context of the hierarchical model of structure formation. The binaries that manage to lose most of their angular momentum can coalesce to form a single remnant. In the last stages of this process, the holes undergo an extremely loud phase of gravitational wave emission, possibly detectable by current and future probes. The theoretical effort towards obtaining a coherent physical picture of the binary path down to coalescence is still underway. In this paper, for the first time, we take advantage of observational studies of active galactic nuclei evolution to constrain the efficiency of gas-driven binary decay. Under conservative assumptions we find that gas accretion towards the nuclear black holes can efficiently lead binaries of any mass forming at high redshift (≳2) to coalescence within the current time. The observed `downsizing' trend of the accreting black hole luminosity function further implies that the gas inflow is sufficient to drive light black holes down to coalescence, even if they bind in binaries at lower redshifts, down to z ≈ 0.5 for binaries of ˜107 M⊙, and z ≈ 0.2 for binaries of ˜106 M⊙. This has strong implications for the detection rates of coalescing black hole binaries of future space-based gravitational wave experiments.

  16. Effect of primordial non-Gaussianities on the far-UV luminosity function of high-redshift galaxies: implications for cosmic reionization

    NASA Astrophysics Data System (ADS)

    Chevallard, Jacopo; Silk, Joseph; Nishimichi, Takahiro; Habouzit, Melanie; Mamon, Gary A.; Peirani, Sébastien

    2015-01-01

    Understanding how the intergalactic medium (IGM) was reionized at z ≳ 6 is one of the big challenges of current high-redshift astronomy. It requires modelling the collapse of the first astrophysical objects (Pop III stars, first galaxies) and their interaction with the IGM, while at the same time pushing current observational facilities to their limits. The observational and theoretical progress of the last few years have led to the emergence of a coherent picture in which the budget of hydrogen-ionizing photons is dominated by low-mass star-forming galaxies, with little contribution from Pop III stars and quasars. The reionization history of the Universe therefore critically depends on the number density of low-mass galaxies at high redshift. In this work, we explore how changes in the cosmological model, and in particular in the statistical properties of initial density fluctuations, affect the formation of early galaxies. Following Habouzit et al. (2014), we run five different N-body simulations with Gaussian and (scale-dependent) non-Gaussian initial conditions, all consistent with Planck constraints. By appealing to a phenomenological galaxy formation model and to a population synthesis code, we compute the far-UV galaxy luminosity function down to MFUV = -14 at redshift 7 ≤ z ≤ 15. We find that models with strong primordial non-Gaussianities on ≲ Mpc scales show a far-UV luminosity function significantly enhanced (up to a factor of 3 at z = 14) in low-mass galaxies. We adopt a reionization model calibrated from state-of-the-art hydrodynamical simulations and show that such scale-dependent non-Gaussianities leave a clear imprint on the Universe reionization history and electron Thomson scattering optical depth τe. Although current uncertainties in the physics of reionization and on the determination of τe still dominate the signatures of non-Gaussianities, our results suggest that τe could ultimately be used to constrain the statistical properties

  17. Liners and Low Luminosity AGN in the ROSAT Database

    NASA Technical Reports Server (NTRS)

    Elvis, Martin; West, Donald K. (Technical Monitor)

    2003-01-01

    This program has led to a series of papers being written and published in the Astrophysical Journal. Together these papers try to explain major parts of the LINER and low luminosity AGN puzzle. One paper ('Accretion Disk Instabilities, Cold Dark Matter Models, and Their Role in Quasar Evolution', Hatziminaoglou E., Siemiginowska A., & Elvis M., 2001, ApJ, 547, 90) describes an analytical model for the evolution of the quasar luminosity function. By combining the Press-Schechter formalism for the masses of initial structures with the luminosity distribution for a population of single mass black holes given by an unstable accretion disk an almost complete end-to-end physics-based model of quasar evolution is produced. In this model black holes spend 75% of their time in a low accretion state (at L(Edd)). This low state population of black holes is likely to be observed as the LINER and low luminosity AGNs in the local universe. Another paper ('Broad Emission Line Regions in AGN: the Link with the Accretion Power', Nicastro F., 2000, ApJ Letters, 530, L65) gives a physical basis for why low state black holes appear as LINERS. By linking the Lightman-Eardley instability in an accretion disk to the ori.gin of a wind that contains the broad emission line cloud material this model explains the large widths seen in these lines as being the Keplerian velocity of the disk at the instability radius. For LINERS the key is that below an accretion rate of 10(exp -3)M(sub Edd)the Lightman-Eardley instability falls within the innermost stable orbit of the disk, and so leaves the entire disk stable. No wind occurs, and so no broad emission lines are seen. Most LINERS are likely to be black holes in this low state. Tests of this model are being considered.

  18. Dark-ages reionization and galaxy formation simulation - IV. UV luminosity functions of high-redshift galaxies

    NASA Astrophysics Data System (ADS)

    Liu, Chuanwu; Mutch, Simon J.; Angel, P. W.; Duffy, Alan R.; Geil, Paul M.; Poole, Gregory B.; Mesinger, Andrei; Wyithe, J. Stuart B.

    2016-10-01

    In this paper, we present calculations of the UV luminosity function (LF) from the Dark-ages Reionization And Galaxy-formation Observables from Numerical Simulations project, which combines N-body, semi-analytic and seminumerical modelling designed to study galaxy formation during the Epoch of Reionization. Using galaxy formation physics including supernova feedback, the model naturally reproduces the UV LFs for high-redshift star-forming galaxies from z ˜ 5 through to z ˜ 10. We investigate the luminosity-star formation rate (SFR) relation, finding that variable SFR histories of galaxies result in a scatter around the median relation of 0.1-0.3 dex depending on UV luminosity. We find close agreement between the model and observationally derived SFR functions. We use our calculated luminosities to investigate the LF below current detection limits, and the ionizing photon budget for reionization. We predict that the slope of the UV LF remains steep below current detection limits and becomes flat at MUV ≳ -14. We find that 48 (17) per cent of the total UV flux at z ˜ 6 (10) has been detected above an observational limit of MUV ˜ -17, and that galaxies fainter than MUV ˜ -17 are the main source of ionizing photons for reionization. We investigate the luminosity-stellar mass relation, and find a correlation for galaxies with MUV < -14 that has the form M_{ast } ∝ 10^{-0.47M_UV}, in good agreement with observations, but which flattens for fainter galaxies. We determine the luminosity-halo mass relation to be M_vir ∝ 10^{-0.35M_UV}, finding that galaxies with MUV = -20 reside in host dark matter haloes of 1011.0±0.1 M⊙ at z ˜ 6, and that this mass decreases towards high redshift.

  19. The road to quasars

    NASA Astrophysics Data System (ADS)

    Kellermann, K. I.

    2015-03-01

    Although the extragalactic nature of 3C 48 and other quasi stellar radio sources was discussed as early as 1960 by John Bolton and others, it was rejected largely because of preconceived ideas about what appeared to be unrealistically high radio and optical luminosities. Not until the 1962 occultations of the strong radio source 3C 273 at Parkes, which led Maarten Schmidt to identify 3C 273 with an apparent stellar object at a redshift of 0.16, was the true nature understood. Successive radio and optical measurements quickly led to the identification of other quasars with increasingly large redshifts and the general, although for some decades not universal, acceptance of quasars as the very luminous nuclei of galaxies. Curiously, 3C 273, which is one of the strongest extragalactic sources in the sky, was first cataloged in 1959 and the magnitude 13 optical counterpart was observed at least as early as 1887. Since 1960, much fainter optical counterparts were being routinely identified using accurate radio interferometer positions which were measured primarily at the Caltech Owens Valley Radio Observatory. However, 3C 273 eluded identification until the series of lunar occultation observations led by Cyril Hazard. Although an accurate radio position had been obtained earlier with the OVRO interferometer, inexplicably 3C 273 was initially misidentified with a faint galaxy located about an arc minute away from the true quasar position.

  20. The Luminosity and Stellar Mass Functions of Red W1-W2 Galaxies

    NASA Astrophysics Data System (ADS)

    O'Connor, J. A.; Rosenberg, J. L.; Satyapal, S.; Secrest, N. J.

    2016-08-01

    We present a study of nearby galaxies as a function of their [3.4]-[4.6] colour. Galaxies that are red in their [3.4]-[4.6] colour contain heated dust and the reddest systems ([3.4]-[4.6] > 0.5) are classified as AGN by some selection criteria. The sample discussed here includes nearby galaxies selected from the Sloan Digital Sky Survey (SDSS) that are also in the Wide-field Infrared Survey Explorer (WISE) catalogue. We calculate the number density of galaxies, in the form of the luminosity and mass functions, using the V/Vmax method and a Stepwise Maximum Likelihood method that has been modified to account for the additional colour selection. The reddest galaxies which have [3.4]-[4.6] > 0.8 and are sometimes classified as AGN by their colour, make up 0.2% of nearby galaxies. However, the reddest galaxies are a rising fraction of the low mass galaxy population. Identifying the lowest mass (M < 108M⊙) red ([3.4]-[4.6] > 0.8) galaxies as AGN is surprising given that none are optical AGN or composites, in contrast with their more massive (M > 1010M⊙) red galaxy counterparts that are dominated by optical AGN and composites (86.4%). We also show that these low mass red galaxies are associated with higher specific star formation rates than their bluer counterparts. While the properties of this relatively rare segment of nearby low-mass galaxies are intriguing, particularly if they are associated with AGN activity, there is not yet enough evidence to determine whether it is AGN or unusual star formation that is driving red colours in these systems.

  1. The Optical Luminosity Function of Void Galaxies in the SDSS and ALFALFA Surveys

    NASA Astrophysics Data System (ADS)

    Moorman, Crystal M.; Vogeley, Michael S.; Hoyle, Fiona; Pan, Danny C.; Haynes, Martha P.; Giovanelli, Riccardo

    2015-09-01

    We measure the r-band galaxy luminosity function (LF) across environments over the redshift range 0 < z < 0.107 using the Sloan Digital Sky Survey (SDSS). We divide our sample into galaxies residing in large-scale voids (void galaxies) and those residing in denser regions (wall galaxies). The best-fitting Schechter parameters for void galaxies are {log}{{{Φ }}}*=-3.40+/- 0.03 log(Mpc-3), {M}* = -19.88 ± 0.05, and α = -1.20 ± 0.02. For wall galaxies, the best-fitting parameters are {log}{{{Φ }}}*=-2.86+/- 0.02 log(Mpc-3), {M}* = -20.80 ± 0.03, and α = -1.16 ± 0.01. We find a shift in the characteristic magnitude, {M}*, toward fainter magnitudes for void galaxies and find no significant difference between the faint-end slopes of the void and wall galaxy LFs. We investigate how low-surface-brightness selection effects can affect the galaxy LF. To attempt to examine a sample of galaxies that is relatively free of surface-brightness selection effects, we compute the optical galaxy LF of galaxies detected by the blind H i survey Arecibo Legacy Fast ALFA (ALFALFA). We find that the global LF of the ALFALFA sample is not well fit by a Schechter function because of the presence of a wide dip in the LF around Mr = -18 and an upturn at fainter magnitudes (α ˜ -1.47). We compare the H i selected r-band LF to various LFs of optically selected populations to determine where the H i selected optical LF obtains its shape. We find that sample selection plays a large role in determining the shape of the LF.

  2. The luminosity and stellar mass functions of red W1-W2 galaxies

    NASA Astrophysics Data System (ADS)

    O'Connor, J. A.; Rosenberg, J. L.; Satyapal, S.; Secrest, N. J.

    2016-11-01

    We present a study of nearby galaxies as a function of their [3.4]-[4.6] colour. Galaxies that are red in their [3.4]-[4.6] colour contain heated dust and the reddest systems ([3.4]-[4.6] > 0.5) are classified as active galactic nuclei (AGN) by some selection criteria. The sample discussed here includes nearby galaxies selected from the Sloan Digital Sky Survey (SDSS) that are also in the Wide-field Infrared Survey Explorer (WISE) catalogue. We calculate the number density of galaxies, in the form of the luminosity and mass functions, using the V/Vmax method and a stepwise maximum likelihood method that has been modified to account for the additional colour selection. The reddest galaxies which have [3.4]-[4.6] > 0.8 and are sometimes classified as AGN by their colour make up 0.2 per cent of nearby galaxies. However, the reddest galaxies are a rising fraction of the low-mass galaxy population. Identifying the lowest mass (M < 108 M⊙) red ([3.4]-[4.6] > 0.8) galaxies as AGN is surprising given that none are optical AGN or composites, in contrast with their more massive (M > 1010 M⊙) red galaxy counterparts that are dominated by optical AGN and composites (86.4 per cent). We also show that these low-mass red galaxies are associated with higher specific star formation rates than their bluer counterparts. While the properties of this relatively rare segment of nearby low-mass galaxies are intriguing, particularly if they are associated with AGN activity, there is not yet enough evidence to determine whether it is AGN or unusual star formation that is driving red colours in these systems.

  3. Planetary Nebulae in the Solar Neighbourhood: Statistics, Distance Scale and Luminosity Function

    NASA Astrophysics Data System (ADS)

    Frew, David J.

    2008-07-01

    An accurate census of the nearest planetary nebulae (PNe) is needed for calculations of the total number, space density, scale height, and birth rate of PNe in the Galaxy, to understand the dynamics of an evolving nebula and its relationship to the cooling history of the central star, and also to provide an unbiased sample to investigate the frequency of binary central stars and their role in the formation and shaping of these objects. This study presents the most refined volume-limited survey of PNe known to date. Integrated H-alpha fluxes for over 400 mostly evolved PNe are presented, based primarily on data from the Southern H-alpha Sky Survey Atlas (SHASSA) and the Virginia Tech Spectral-Line Survey (VTSS). Aperture photometry on the digital images was performed to extract H-alpha+[NII] fluxes. The [NII] contribution was then de-convolved using literature data, new data from slit spectra, or spectrophotometric data from the Wisconsin H-Alpha Mapper (WHAM) also obtained as part of this project. Comparison with previous work shows that the flux scale presented here has no significant zero-point error. The H-alpha fluxes are used to determine new Zanstra temperatures for those PNe with accurate central star photometry, calculating surface-brightness distances for each PN in the sample, and in conjunction with accurate [OIII] fluxes, new absolute PN magnitudes for delineating the faint end of the PN luminosity function. A spectroscopic survey of a range of MASH PNe is also presented. New emission-line intensities for 60 PNe are given, including a preliminary discussion of the chemical abundances of this sample. New distances have been determined for a large number of PNe, by either critically examining the literature, or by deriving new extinction and kinematic distances where suitable. For all PNe not amenable to these approaches, distances were estimated from a new H-alpha surface brightness-radius (SB-r) relation. The Hα SB-r relation covers >6 dex in SB, and

  4. The ACS Virgo Cluster Survey. XII. The Luminosity Function of Globular Clusters in Early-Type Galaxies

    NASA Astrophysics Data System (ADS)

    Jordán, Andrés; McLaughlin, Dean E.; Côté, Patrick; Ferrarese, Laura; Peng, Eric W.; Mei, Simona; Villegas, Daniela; Merritt, David; Tonry, John L.; West, Michael J.

    2007-07-01

    We analyze the luminosity function of the globular clusters (GCs) belonging to the early-type galaxies observed in the ACS Virgo Cluster Survey. We have obtained maximum likelihood estimates for a Gaussian representation of the globular cluster luminosity function (GCLF) for 89 galaxies. We have also fit the luminosity functions with an ``evolved Schechter function'', which is meant to reflect the preferential depletion of low-mass GCs, primarily by evaporation due to two-body relaxation, from an initial Schechter mass function similar to that of young massive clusters in local starbursts and mergers. We find a highly significant trend of the GCLF dispersion σ with galaxy luminosity, in the sense that the GC systems in smaller galaxies have narrower luminosity functions. The GCLF dispersions of our Galaxy and M31 are quantitatively in keeping with this trend, and thus the correlation between σ and galaxy luminosity would seem more fundamental than older notions that the GCLF dispersion depends on Hubble type. We show that this narrowing of the GCLF in a Gaussian description is driven by a steepening of the cluster mass function above the classic turnover mass, as one moves to lower luminosity host galaxies. In a Schechter function description, this is reflected by a steady decrease in the value of the exponential cutoff mass scale. We argue that this behavior at the high-mass end of the GC mass function is most likely a consequence of systematic variations of the initial cluster mass function rather than long-term dynamical evolution. The GCLF turnover mass MTO is roughly constant, at MTO~=(2.2+/-0.4)×105 Msolar in bright galaxies, but it decreases slightly (by ~35% on average, with significant scatter) in dwarf galaxies with MB,gal>~-18. It could be important to allow for this effect when using the GCLF as a distance indicator. We show that part, although perhaps not all, of the variation could arise from the shorter dynamical friction timescales in less

  5. Moderate resolution spectrophotometry of high redshift quasars

    NASA Technical Reports Server (NTRS)

    Schneider, Donald P.; Schmidt, Maarten; Gunn, James E.

    1991-01-01

    A uniform set of photometry and high signal-to-noise moderate resolution spectroscopy of 33 quasars with redshifts larger than 3.1 is presented. The sample consists of 17 newly discovered quasars (two with redshifts in excess of 4.4) and 16 sources drawn from the literature. The objects in this sample have r magnitudes between 17.4 and 21.4; their luminosities range from -28.8 to -24.9. Three of the 33 objects are broad absorption line quasars. A number of possible high redshift damped Ly-alpha systems were found.

  6. Luminosity function of low-mass X-ray binaries in the globular cluster system of NGC 1399

    NASA Astrophysics Data System (ADS)

    D'Ago, G.; Paolillo, M.; Fabbiano, G.; Puzia, T. H.; Maccarone, T. J.; Kundu, A.; Goudfrooij, P.; Zepf, S. E.

    2014-07-01

    Aims: We present a study of the faint end of the X-ray luminosity function (XLF) of low-mass X-ray binaries (LMXBs) in the Globular Cluster (GC) system of the cD galaxy NGC 1399. Methods: We performed a stacking experiment on 618 X-ray undetected GCs, in order to verify the presence of faint LMXBs and to constrain the faint-end slope of the GC-LMXBs XLF below the individual detection threshold of 8 × 1037 erg s-1 in the 0.5 - 8 keV band. Results: We obtain a significant X-ray detection for the whole GC sample, as well as for the red and blue GC subpopulations, corresponding to an average luminosity per GC ⟨ LX ⟩ GC of (3.6 ± 1.0) × 1036 erg s-1, (6.9 ± 2.1) × 1036 erg s-1, and (1.7 ± 0.9) × 1036 erg s-1, respectively, for all GCs, red GCs, and blue GCs. If LMXBs in red and blue GCs have the same average intrinsic luminosity, we derive a red/blue ratio ≃3 of GCs hosting LMXBs (2.5 ± 1.0 or 4.1 ± 2.5 depending on the surveyed region); alternatively, assuming the fractions observed for brighter sources, we measure an average X-ray luminosity of LX = (4.3 ± 1.3) × 1037 erg s-1 and LX = (3.4 ± 1.7) × 1037 erg s-1 per red and blue GC-LMXBs, respectively. In the assumption that the XLF follows a power-law distribution, we find that a low-luminosity break is required at LX ≤ 8 × 1037 erg s-1 both in the whole, as well as in the color-selected (red and blue) subsamples. Given the bright-end slopes measured above the X-ray completeness limit, this result is significant at >3σ level. Our best estimates for the faint-end slope are βL = -1.39/-1.38/-1.36 for all/red/blue GC-LMXBs. We also find evidence that the luminosity function becomes steeper at luminosities LX ≳ 3 × 1039 erg s-1, as observed in old ellipticals. Conclusions: If most GCs host a single X-ray binary, we conclude that in NGC 1399 the XLF flattens at low luminosities as observed in other nearer galaxies, and we discuss some consequences of this flattening on LMXBs formation scenarios.

  7. A Survey of z>5.7 Quasars in the Sloan Digital Sky Survey. III. Discovery of Five Additional Quasars

    NASA Astrophysics Data System (ADS)

    Fan, Xiaohui; Hennawi, Joseph F.; Richards, Gordon T.; Strauss, Michael A.; Schneider, Donald P.; Donley, Jennifer L.; Young, Jason E.; Annis, James; Lin, Huan; Lampeitl, Hubert; Lupton, Robert H.; Gunn, James E.; Knapp, Gillan R.; Brandt, W. N.; Anderson, Scott; Bahcall, Neta A.; Brinkmann, Jon; Brunner, Robert J.; Fukugita, Masataka; Szalay, Alexander S.; Szokoly, Gyula P.; York, Donald G.

    2004-08-01

    We present the discovery of five new quasars at z>5.7, selected from the multicolor imaging data of the Sloan Digital Sky Survey (SDSS). Three of them, at redshifts 5.93, 6.07, and 6.22, were selected from ~1700 deg2 of new SDSS Main Survey imaging in the northern Galactic cap. An additional quasar, at redshift 5.85, was discovered by co-adding the data obtained in the Fall Equatorial Stripe in the SDSS Southern Survey Region. The fifth object, at redshift 5.80, is selected from a nonstandard SDSS scan in the southern Galactic cap outside the Main Survey area. The spectrum of SDSS J162331.81+311200.5 (z=6.22) shows a complete Gunn-Peterson trough at zabs>5.95, similar to the troughs detected in the other three z>~6.2 quasars known. We present a composite spectrum of the z>5.7 quasars discovered in the SDSS to date. The average emission-line and continuum properties of z~6 quasars exhibit no significant evolution compared with those at low redshift. Using a complete sample of nine z>5.7 quasars, we find that the density of quasars with M1450<-26.7 at z~6 is (6+/-2)×10-10 Mpc-3 (H0=65 km s-1 Mpc-1, Ω=0.35, and Λ=0.65), consistent with our previous estimates. The luminosity distribution of the sample is fitted with a power-law luminosity function Ψ(L)~L-3.2+/-0.7, somewhat steeper than but consistent with our previous estimates. Based on observations obtained with the Sloan Digital Sky Survey, and with the Apache Point Observatory 3.5 m telescope, which is owned and operated by the Astrophysical Research Consortium; and with the MMT Observatory, a joint facility of the University of Arizona and the Smithsonian Institution, with the University of Arizona 2.3 m Bok Telescope, with the Kitt Peak National Observatory 4 m Mayall Telescope, with the 6.5 m Landon Clay Telescope at the Las Campanas Observatory, a collaboration between the Observatories of the Carnegie Institution of Washington, University of Arizona, Harvard University, the University of Michigan, and

  8. X-ray Luminosity Functions of Young Stars: T Tauri Stars, Pleiades and Hyades

    NASA Astrophysics Data System (ADS)

    Stelzer, B.; Neuhäuser, R.

    We report on coronal activity of pre-main sequence and young main sequence stars in the Taurus region as observed by ROSAT. X-rays of late-type stars are related to magnetic structures in the corona which are produced in a dynamo mechanism, generally described in analogy to the solar case. The details of the heating process and temporal evolution of the dynamo efficiency are not well understood. The sample studied here represents the largest set of X-ray observations in the Taurus region analysed jointly, and provides better sensitivity than the ROSAT All-Sky Survey due to the use of ROSAT pointed PSPC observations. Our stellar sample is composed of T Tauri stars from the Taurus-Auriga region, and late-type stars from the Pleiades and Hyades clusters. The different ages of these regions allow a study of the evolution of coronal X-ray emission during early stellar phases. We analyse and compare the X-ray luminosity functions (XLF) for subgroups of stars from the above regions to learn more about the influence of age, mass and multiplicity on the observed X-ray emission level. The pre-main sequence stage is characterized by two classes of TTS, classical TTS and weak-line TTS, which show different XLF: in the Taurus region weak-line TTS are X-ray brighter than classical TTS. For stars on the main-sequence the X-ray emission declines with increasing mass (or effective temperature), indicating the importance of the convection zone for the stellar dynamo.

  9. Deep Ultraviolet Luminosity Functions at the Infall Region of the Coma Cluster

    NASA Astrophysics Data System (ADS)

    Hammer, D. M.; Hornschemeier, A. E.; Salim, S.; Smith, R.; Jenkins, L.; Mobasher, B.; Miller, N.; Ferguson, H.

    2012-02-01

    We have used deep GALEX observations at the infall region of the Coma cluster to measure the faintest ultraviolet (UV) luminosity functions (LFs) presented for a rich galaxy cluster thus far. The Coma UV LFs are measured to M UV = -10.5 in the GALEX FUV and NUV bands, or 3.5 mag fainter than previous studies, and reach the dwarf early-type galaxy population in Coma for the first time. The Schechter faint-end slopes (α ≈ -1.39 in both GALEX bands) are shallower than reported in previous Coma UV LF studies owing to a flatter LF at faint magnitudes. A Gaussian-plus-Schechter model provides a slightly better parameterization of the UV LFs resulting in a faint-end slope of α ≈ -1.15 in both GALEX bands. The two-component model gives faint-end slopes shallower than α = -1 (a turnover) for the LFs constructed separately for passive and star-forming galaxies. The UV LFs for star-forming galaxies show a turnover at M UV ≈ -14 owing to a deficit of dwarf star-forming galaxies in Coma with stellar masses below M * = 108 M ⊙. A similar turnover is identified in recent UV LFs measured for the Virgo cluster suggesting this may be a common feature of local galaxy clusters, whereas the field UV LFs continue to rise at faint magnitudes. We did not identify an excess of passive galaxies as would be expected if the missing dwarf star-forming galaxies were quenched inside the cluster. In fact, the LFs for both dwarf passive and star-forming galaxies show the same turnover at faint magnitudes. We discuss the possible origin of the missing dwarf star-forming galaxies in Coma and their expected properties based on comparisons to local field galaxies.

  10. Deep UV Luminosity Functions at the Infall Region of the Coma Cluster

    NASA Technical Reports Server (NTRS)

    Hammer, D. M.; Hornschemeier, A. E.; Salim, S.; Smith, R.; Jenkins, L.; Mobasher, B.; Miller, N.; Ferguson, H.

    2011-01-01

    We have used deep GALEX observations at the infall region of the Coma cluster to measure the faintest UV luminosity functions (LFs) presented for a rich galaxy cluster thus far. The Coma UV LFs are measured to M(sub uv) = -10.5 in the GALEX FUV and NUV bands, or 3.5 mag fainter than previous studies, and reach the dwarf early-type galaxy population in Coma for the first time. The Schechter faint-end slopes (alpha approximately equal to -1.39 in both GALEX bands) are shallower than reported in previous Coma UV LF studies owing to a flatter LF at faint magnitudes. A Gaussian-plus-Schechter model provides a slightly better parametrization of the UV LFs resulting in a faint-end slope of alpha approximately equal to -1.15 in both GALEX bands. The two-component model gives faint-end slopes shallower than alpha = -1 (a turnover) for the LFs constructed separately for passive and star forming galaxies. The UV LFs for star forming galaxies show a turnover at M(sub UV) approximately equal to -14 owing to a deficit of dwarf star forming galaxies in Coma with stellar masses below M(sub *) = 10(sup 8) solar mass. A similar turnover is identified in recent UV LFs measured for the Virgo cluster suggesting this may be a common feature of local galaxy clusters, whereas the field UV LFs continue to rise at faint magnitudes. We did not identify an excess of passive galaxies as would be expected if the missing dwarf star forming galaxies were quenched inside the cluster. In fact, the LFs for both dwarf passive and star forming galaxies show the same turnover at faint magnitudes. We discuss the possible origin of the missing dwarf star forming galaxies in Coma and their expected properties based on comparisons to local field galaxies.

  11. The Faint-End of the Galaxy Luminosity Function in the Hydra I Cluster

    NASA Astrophysics Data System (ADS)

    Yamanoi, H.; Tanaka, M.

    2007-05-01

    INTRODUCTION: Dwarf galaxies account for a large share of cluster galaxies and their properties should be closely related to the formation and evolution of clusters. Despite the obvious importance, however, the number of very faint (down to M ˜ -10) cluster samples available to date is limited and properties of such faint galaxies remain unclear. In this study, we aim to reveal very faint-end slopes of galaxy luminosity functions (LFs) in the Hydra I cluster (Abell 1060) at z = 0.0126, in which such very faint galaxies have not been probed yet. OBSERVATIONS: We base our analyses on the data taken with the Suprime-Cam on the Subaru telescope at Mauna Kea. A deep photometric survey was carried out in the B- and Rc-bands. We observed the central region as well as a peripheral region of Hydra I. This is because we aim to investigate the environmental dependence of properties of very faint galaxies. We subtract fore-/background galaxy contamination in the cluster fields and obtain intrinsic LFs of the cluster galaxies. RESULTS AND DISCUSSION: We find that the LFs at the fainter magnitudes have a slightly steeper slope than that reported on the same cluster previously. The slope is flatter at faint magnitudes (M > -14) than that at the brighter magnitudes. This tendency is consistent with a composite LF constructed from several nearby clusters by previous work. Although the LFs in the Hydra central region are similar to those in the peripheral region at M < -14, the LF slope in the peripheral region is slightly flatter than that in the central region in the fainter magnitude range. This means that a larger number of dwarf galaxies reside in denser environments. This tend is seen only in the red galaxy LFs when we separate the Hydra member galaxies into red and blue galaxies. The Hydra I cluster is dominated by red galaxies down to M ˜ -10.

  12. On the faint-end of the high-z galaxy luminosity function

    NASA Astrophysics Data System (ADS)

    Yue, Bin; Ferrara, Andrea; Xu, Yidong

    2016-08-01

    Recent measurements of the Luminosity Function (LF) of galaxies in the Epoch of Reionization (EoR, zlower.5ex buildrel> over ˜ 6) indicate a very steep increase of the number density of low-mass galaxies populating the LF faint-end. However, as star formation in low-mass halos can be easily depressed or even quenched by ionizing radiation, a turnover is expected at some faint UV magnitudes. Using a physically-motivated analytical model, we quantify reionization feedback effects on the LF faint-end shape. We find that if reionization feedback is neglected, the power-law Schechter parameterization characterizing the LF faint-end remains valid up to absolute UV magnitude ˜-9. If instead radiative feedback is strong enough that quenches star formation in halos with circular velocity smaller than 50 km s-1, the LF starts to drop at absolute UV magnitude ˜-15, i.e. slightly below the detection limits of current (unlensed) surveys at z ˜ 5. The LFs may rise again at higher absolute UV magnitude, where, as a result of interplay between reionization process and galaxy formation, most of the galaxy light is from relic stars formed before the EoR. We suggest that the galaxy number counts data, particularly in lensed fields, can put strong constraints on reionization feedback. In models with stronger reionization feedback, stars in galaxies with absolute UV magnitude higher than ˜-13 and smaller than ˜-8 are typically older. Hence, the stellar age - UV magnitude relation can be used as an alternative feedback probe.

  13. On the Radiative Efficiencies, Eddington Ratios, and Duty Cycles of Luminous High-redshift Quasars

    NASA Astrophysics Data System (ADS)

    Shankar, Francesco; Crocce, Martin; Miralda-Escudé, Jordi; Fosalba, Pablo; Weinberg, David H.

    2010-07-01

    We investigate the characteristic radiative efficiency epsilon, Eddington ratio λ, and duty cycle P 0 of high-redshift active galactic nuclei (AGNs), drawing on measurements of the AGN luminosity function at z = 3-6 and, especially, on recent measurements of quasar clustering at z = 3-4.5 from the Sloan Digital Sky Survey. The free parameters of our models are epsilon, λ, and the normalization, scatter, and redshift evolution of the relation between black hole (BH) mass M BH and halo virial velocity V vir. We compute the luminosity function from the implied growth of the BH mass function and the quasar correlation length from the bias of the host halos. We test our adopted formulae for the halo mass function and halo bias against measurements from the large N-body simulation developed by the MICE collaboration. The strong clustering of AGNs observed at z = 3 and, especially, at z = 4 implies that massive BHs reside in rare, massive dark matter halos. Reproducing the observed luminosity function then requires high efficiency epsilon and/or low Eddington ratio λ, with a lower limit (based on 2σ agreement with the measured z = 4 correlation length) epsilon >~ 0.7λ/(1 + 0.7λ), implying epsilon >~ 0.17 for λ>0.25. Successful models predict high duty cycles, P 0 ~ 0.2, 0.5, and 0.9 at z = 3.1, 4.5, and 6, respectively, and they require that the fraction of halo baryons locked in the central BH is much larger than the locally observed value. The rapid drop in the abundance of the massive and rare host halos at z > 7 implies a proportionally rapid decline in the number density of luminous quasars, much stronger than simple extrapolations of the z = 3-6 luminosity function would predict. For example, our most successful model predicts that the highest redshift quasar in the sky with true bolometric luminosity L > 1047.5 erg s-1 should be at z ~ 7.5, and that all quasars with higher apparent luminosities would have to be magnified by lensing.

  14. The SDSS-III BOSS quasar lens survey: discovery of 13 gravitationally lensed quasars

    NASA Astrophysics Data System (ADS)

    More, Anupreeta; Oguri, Masamune; Kayo, Issha; Zinn, Joel; Strauss, Michael A.; Santiago, Basilio X.; Mosquera, Ana M.; Inada, Naohisa; Kochanek, Christopher S.; Rusu, Cristian E.; Brownstein, Joel R.; da Costa, Luiz N.; Kneib, Jean-Paul; Maia, Marcio A. G.; Quimby, Robert M.; Schneider, Donald P.; Streblyanska, Alina; York, Donald G.

    2016-02-01

    We report the discovery of 13 confirmed two-image quasar lenses from a systematic search for gravitationally lensed quasars in the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). We adopted a methodology similar to that used in the SDSS Quasar Lens Search (SQLS). In addition to the confirmed lenses, we report 11 quasar pairs with small angular separations ( ≲ 2 arcsec) confirmed from our spectroscopy, which are either projected pairs, physical binaries, or possibly quasar lens systems whose lens galaxies have not yet been detected. The newly discovered quasar lens system, SDSS J1452+4224 at zs ≈ 4.8 is one of the highest redshift multiply imaged quasars found to date. Furthermore, we have over 50 good lens candidates yet to be followed up. Owing to the heterogeneous selection of BOSS quasars, the lens sample presented here does not have a well-defined selection function.

  15. Quasar redshifts: the intrinsic component

    NASA Astrophysics Data System (ADS)

    Hansen, Peter M.

    2016-09-01

    The large observed redshift of quasars has suggested large cosmological distances and a corresponding enormous energy output to explain the brightness or luminosity as seen at earth. Alternative or complementary sources of redshift have not been identified by the astronomical community. This study examines one possible source of additional redshift: an intrinsic component based on the plasma characteristics of high temperature and high electron density which are believed to be present.

  16. Properties of galaxies at the faint end of the Hα luminosity function at z ~ 0.62

    NASA Astrophysics Data System (ADS)

    Gómez-Guijarro, Carlos; Gallego, Jesús; Villar, Víctor; Rodríguez-Muñoz, Lucía; Clément, Benjamin; Cuby, Jean-Gabriel

    2016-07-01

    Context. Studies measuring the star formation rate density, luminosity function, and properties of star-forming galaxies are numerous. However, it exists a gap at 0.5 < z < 0.8 in Hα-based studies. Aims: Our main goal is to study the properties of a sample of faint Hα emitters at z ~ 0.62. We focus on their contribution to the faint end of the luminosity function and derived star formation rate density, characterising their morphologies and basic photometric and spectroscopic properties. Methods: We use a narrow-band technique in the near-infrared, with a filter centred at 1.06 μm. The data come from ultra-deep VLT/HAWK-I observations in the GOODS-S field with a total of 31.9 h in the narrow-band filter. In addition to our survey, we mainly make use of ancillary data coming from the CANDELS and Rainbow Cosmological Surveys Database, from the 3D-HST for comparison, and also spectra from the literature. We perform a visual classification of the sample and study their morphologies from structural parameters available in CANDELS. In order to obtain the luminosity function, we apply a traditional V/Vmax method and perform individual extinction corrections for each object to accurately trace the shape of the function. Results: Our 28 Hα-selected sample of faint star-forming galaxies reveals a robust faint-end slope of the luminosity function α = - 1.46-0.08+0.16 . The derived star formation rate density at z ~ 0.62 is ρSFR = 0.036-0.008+0.012 M⊙ yr-1 Mpc-3 . The sample is mainly composed of disks, but an important contribution of compact galaxies with Sérsic indexes n ~ 2 display the highest specific star formation rates. Conclusions: The luminosity function at z ~ 0.62 from our ultra-deep data points towards a steeper α when an individual extinction correction for each object is applied. Compact galaxies are low-mass, low-luminosity, and starburst-dominated objects with a light profile in an intermediate stage from early to late types. Based on observations

  17. Hard X-ray luminosity function of tidal disruption events: First results from the MAXI extragalactic survey

    NASA Astrophysics Data System (ADS)

    Kawamuro, Taiki; Ueda, Yoshihiro; Shidatsu, Megumi; Hori, Takafumi; Kawai, Nobuyuki; Negoro, Hitoshi; Mihara, Tatehiro

    2016-08-01

    We derive the first hard X-ray luminosity function (XLF) of stellar tidal disruption events (TDEs) by supermassive black holes (SMBHs), which gives an occurrence rate of TDEs per unit volume as a function of peak luminosity and redshift, utilizing an unbiased sample observed by the Monitor of All-sky X-ray Image (MAXI). On the basis of the light curves characterized by a power-law decay with an index of -5/3, a systematic search using the MAXI data detected four TDEs in the first 37 months of observations, all of which have been found in the literature. To formulate the TDE XLF, we consider the mass function of SMBHs, that of disrupted stars, the specific TDE rate as a function of SMBH mass, and the fraction of TDEs with relativistic jets. We perform an unbinned maximum likelihood fit to the MAXI TDE list and check the consistency with the observed TDE rate in the ROSAT all-sky survey. The results suggest that the intrinsic fraction of the jet-accompanying events is 0.0007%-34%. We confirm that at z ≲ 1.5 the contamination of the hard X-ray luminosity functions of active galactic nuclei by TDEs is not significant and hence that their contribution to the growth of SMBHs is negligible at the redshifts.

  18. THE FAINT-END SLOPE OF THE REDSHIFT 5.7 Ly{alpha} LUMINOSITY FUNCTION

    SciTech Connect

    Henry, Alaina L.; Martin, Crystal L.; Dressler, Alan; McCarthy, Patrick; Sawicki, Marcin

    2012-01-10

    Using new Keck DEIMOS spectroscopy, we examine the origin of the steep number counts of ultra-faint emission-line galaxies recently reported by Dressler et al. We confirm six Ly{alpha} emitters (LAEs), three of which have significant asymmetric line profiles with prominent wings extending 300-400 km s{sup -1} redward of the peak emission. With these six LAEs, we revise our previous estimate of the number of faint LAEs in the Dressler et al. survey. Combining these data with the density of bright LAEs in the Cosmic Evolution Survey and Subaru Deep Field provides the best constraints to date on the redshift 5.7 LAE luminosity function (LF). Schechter function parameters, {phi}* = 4.5 Multiplication-Sign 10{sup -4} Mpc{sup -3}, L* = 9.1 Multiplication-Sign 10{sup 42} erg s{sup -1}, and {alpha} = -1.70, are estimated using a maximum likelihood technique with a model for slit-losses. To place this result in the context of the UV-selected galaxy population, we investigate how various parameterizations of the Ly{alpha} equivalent width distribution, along with the measured UV-continuum LF, affect shape and normalization of the Ly{alpha} LF. The nominal model, which uses z {approx} 6 equivalent widths from the literature, falls short of the observed space density of LAEs at the bright end, possibly indicating a need for higher equivalent widths. This parameterization of the equivalent width distribution implies that as many as 50% of our faintest LAEs should have M{sub UV} > -18.0, rendering them undetectable in even the deepest Hubble Space Telescope surveys at this redshift. Hence, ultra-deep emission-line surveys find some of the faintest galaxies ever observed at the end of the reionization epoch. Such faint galaxies likely enrich the intergalactic medium with metals and maintain its ionized state in the post-reionization era. Observations of these objects provide a glimpse of the building blocks of present-day galaxies at an early time.

  19. The hard X-ray luminosity function of high-redshift (3 < z ≲ 5) active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Vito, F.; Gilli, R.; Vignali, C.; Comastri, A.; Brusa, M.; Cappelluti, N.; Iwasawa, K.

    2014-12-01

    We present the hard-band (2-10 keV) X-ray luminosity function (HXLF) of 0.5-2 keV band selected active galactic nuclei (AGN) at high redshift. We have assembled a sample of 141 AGN at 3 < z ≲ 5 from X-ray surveys of different size and depth, in order to sample different regions in the LX - z plane. The HXLF is fitted in the range log LX ˜ 43-45 with standard analytical evolutionary models through a maximum likelihood procedure. The evolution of the HXLF is well described by a pure density evolution, with the AGN space density declining by a factor of ˜10 from z = 3 to 5. A luminosity-dependent density evolution model, which, normally, best represents the HXLF evolution at lower redshift, is also consistent with the data, but a larger sample of low-luminosity (log LX < 44), high-redshift AGN is necessary to constrain this model. We also estimated the intrinsic fraction of AGN obscured by a column density log NH ≥ 23 to be 0.54 ± 0.05, with no strong dependence on luminosity. This fraction is higher than the value in the Local Universe, suggesting an evolution of the luminous (LX > 1044 erg s-1) obscured AGN fraction from z = 0 to z > 3.

  20. VizieR Online Data Catalog: 2-10keV luminosity function of AGN (Ranalli+, 2016)

    NASA Astrophysics Data System (ADS)

    Ranalli, P.; Koulouridis, E.; Georgantopoulos, I.; Fotopoulou, S.; Hsu, L.-T.; Salvato, M.; Comastri, A.; Pierre, M.; Cappelluti, N.; Carrera, F. J.; Chiappetti, L.; Clerc, N.; Gilli, R.; Iwasawa, K.; Pacaud, F.; Paltani, S.; Plionis, E.; Vignali, C.

    2016-02-01

    The XMM-LSS, XMM-CDFS, and XMM-COSMOS are three surveys with complementary properties in terms of luminosity and redshift coverage. We used these three surveys to derive Bayesian estimates of the unabsorbed luminosity function (LF) of AGN in the 2-10keV band. The LF estimates are presented as a set of samples from the posterior probability distribution of the LF parameters. The LF is parameterised as a double power-law, with either the luminosity and density evolution (LADE) model, or the luminosity-dependent density evolution (LDDE) model. The double power-law is described by Eq.(10) in the paper. The LADE and LDDE models are described by Eqs.(11-14) and Eqs.(15-17), respectively. A Fortran 2008 implementation of these models can be found in file src2/lumf_funcs.f90 of the LFTools package, in the classes doublepowerlaw, ladevol, and lddevol (see the paper). (8 data files).

  1. The Evolution of the Galaxy Rest-Frame Ultraviolet Luminosity Function Over the First Two Billion Years

    NASA Technical Reports Server (NTRS)

    Finkelstein, Steven L.; Ryan, Russell E., Jr.; Papovich, Casey; Dickinson, Mark; Song, Mimi; Somerville, Rachel; Ferguson, Henry C.; Salmon, Brett; Giavalisco, Mauro; Koekomoer, Anton M.; Ashby, Matthew L. N.; Behroozi, Peter; Castellano, Marco; Dunlop, James S.; Faber, Sandy M.; Fazio, Giovanni G.; Fontana, Adriano; Grogin, Norman A.; Hathi, Nimish; Jaacks, Jason; Kocevski, Dale D.; Livermore, Rachael; McLure, Ross J.; Merlin, Emiliano; Rafelski, Marc Alexander

    2014-01-01

    We present a robust measurement and analysis of the rest-frame ultraviolet (UV) luminosity function at z = 4 to 8. We use deep Hubble Space Telescope imaging over the CANDELS/GOODS fields, the Hubble Ultra Deep Field and the Hubble Frontier Field deep parallel observations near the Abell 2744 and MACS J0416.1- 2403 clusters. The combination of these surveys provides an effective volume of 0.6-1.2 ×10(exp 6) Mpc(exp 3) over this epoch, allowing us to perform a robust search for bright (M(sub UV) less than -21) and faint (M(sub UV) = -18) galaxies. We select galaxies using a well-tested photometric redshift technique with careful screening of contaminants, finding a sample of 7446 galaxies at 3.5 less than z less than 8.5, with more than 1000 galaxies at z of approximately 6 - 8. We measure both a stepwise luminosity function for galaxies in our redshift samples, as well as a Schechter function, using a Markov Chain Monte Carlo analysis to measure robust uncertainties. At the faint end our UV luminosity functions agree with previous studies, yet we find a higher abundance of UV-bright galaxies at z of greater than or equal to 6. Our bestfit value of the characteristic magnitude M* is consistent with -21 at z of greater than or equal to 5, different than that inferred based on previous trends at lower redshift. At z = 8, a single power-law provides an equally good fit to the UV luminosity function, while at z = 6 and 7, an exponential cutoff at the bright-end is moderately preferred. We compare our luminosity functions to semi-analytical models, and find that the lack of evolution in M* is consistent with models where the impact of dust attenuation on the bright-end of the luminosity function decreases at higher redshift, though a decreasing impact of feedback may also be possible. We measure the evolution of the cosmic star-formation rate (SFR) density by integrating our observed luminosity functions to M(sub UV) = -17, correcting for dust attenuation, and find that

  2. The Evolution of the Galaxy Rest-frame Ultraviolet Luminosity Function over the First Two Billion Years

    NASA Astrophysics Data System (ADS)

    Finkelstein, Steven L.; Ryan, Russell E., Jr.; Papovich, Casey; Dickinson, Mark; Song, Mimi; Somerville, Rachel S.; Ferguson, Henry C.; Salmon, Brett; Giavalisco, Mauro; Koekemoer, Anton M.; Ashby, Matthew L. N.; Behroozi, Peter; Castellano, Marco; Dunlop, James S.; Faber, Sandy M.; Fazio, Giovanni G.; Fontana, Adriano; Grogin, Norman A.; Hathi, Nimish; Jaacks, Jason; Kocevski, Dale D.; Livermore, Rachael; McLure, Ross J.; Merlin, Emiliano; Mobasher, Bahram; Newman, Jeffrey A.; Rafelski, Marc; Tilvi, Vithal; Willner, S. P.

    2015-09-01

    We present a robust measurement and analysis of the rest-frame ultraviolet (UV) luminosity functions at z = 4-8. We use deep Hubble Space Telescope imaging over the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey/GOODS fields, the Hubble Ultra Deep Field, and the Hubble Frontier Field deep parallel observations near the Abell 2744 and MACS J0416.1-2403 clusters. The combination of these surveys provides an effective volume of 0.6-1.2 × 106 Mpc3 over this epoch, allowing us to perform a robust search for faint ({M}{UV}=-18) and bright (M{}{UV}\\lt -21) high-redshift galaxies. We select candidate galaxies using a well-tested photometric redshift technique with careful screening of contaminants, finding a sample of 7446 candidate galaxies at 3.5 \\lt z \\lt 8.5, with >1000 galaxies at z ≈ 6-8. We measure both a stepwise luminosity function for candidate galaxies in our redshift samples, and a Schechter function, using a Markov Chain Monte Carlo analysis to measure robust uncertainties. At the faint end, our UV luminosity functions agree with previous studies, yet we find a higher abundance of UV-bright candidate galaxies at z ≥slant 6. Our best-fit value of the characteristic magnitude {M}{UV}* is consistent with -21 at z ≥slant 5, which is different than that inferred based on previous trends at lower redshift, and brighter at ˜2σ significance than previous measures at z = 6 and 7. At z = 8, a single power law provides an equally good fit to the UV luminosity function, while at z = 6 and 7 an exponential cutoff at the bright end is moderately preferred. We compare our luminosity functions to semi-analytical models, and find that the lack of evolution in {M}{UV}* is consistent with models where the impact of dust attenuation on the bright end of the luminosity function decreases at higher redshift, although a decreasing impact of feedback may also be possible. We measure the evolution of the cosmic star-formation rate (SFR) density by

  3. The 2-10 keV unabsorbed luminosity function of AGN from the LSS, CDFS, and COSMOS surveys

    NASA Astrophysics Data System (ADS)

    Ranalli, P.; Koulouridis, E.; Georgantopoulos, I.; Fotopoulou, S.; Hsu, L.-T.; Salvato, M.; Comastri, A.; Pierre, M.; Cappelluti, N.; Carrera, F. J.; Chiappetti, L.; Clerc, N.; Gilli, R.; Iwasawa, K.; Pacaud, F.; Paltani, S.; Plionis, E.; Vignali, C.

    2016-05-01

    The XMM-Large scale structure (XMM-LSS), XMM-Cosmological evolution survey (XMM-COSMOS), and XMM-Chandra deep field south (XMM-CDFS) surveys are complementary in terms of sky coverage and depth. Together, they form a clean sample with the least possible variance in instrument effective areas and point spread function. Therefore this is one of the best samples available to determine the 2-10 keV luminosity function of active galactic nuclei (AGN) and their evolution. The samples and the relevant corrections for incompleteness are described. A total of 2887 AGN is used to build the LF in the luminosity interval 1042-1046 erg s-1 and in the redshift interval 0.001-4. A new method to correct for absorption by considering the probability distribution for the column density conditioned on the hardness ratio is presented. The binned luminosity function and its evolution is determined with a variant of the Page-Carrera method, which is improved to include corrections for absorption and to account for the full probability distribution of photometric redshifts. Parametric models, namely a double power law with luminosity and density evolution (LADE) or luminosity-dependent density evolution (LDDE), are explored using Bayesian inference. We introduce the Watanabe-Akaike information criterion (WAIC) to compare the models and estimate their predictive power. Our data are best described by the LADE model, as hinted by the WAIC indicator. We also explore the recently proposed 15-parameter extended LDDE model and find that this extension is not supported by our data. The strength of our method is that it provides unabsorbed, non-parametric estimates, credible intervals for luminosity function parameters, and a model choice based on predictive power for future data. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA member states and NASA.Tables with the samples of the posterior probability distributions

  4. The gamma-ray luminosity function of millisecond pulsars and implications for the GeV excess

    DOE PAGES

    Hooper, Dan; Mohlabeng, Gopolang

    2016-03-29

    It has been proposed that a large population of unresolved millisecond pulsars (MSPs) could potentially account for the excess of GeV-scale gamma-rays observed from the region surrounding the Galactic Center. The viability of this scenario depends critically on the gamma-ray luminosity function of this source population, which determines how many MSPs Fermi should have already detected as resolved point sources. In this paper, we revisit the gamma-ray luminosity function of MSPs, without relying on uncertain distance measurements. Our determination, based on a comparison of models with the observed characteristics of the MSP population, suggests that Fermi should have already detectedmore » a significant number of sources associated with such a hypothesized Inner Galaxy population. As a result, we cannot rule out a scenario in which the MSPs residing near the Galactic Center are systematically less luminous than those present in the Galactic Plane or within globular clusters.« less

  5. Confirmation of a Steep Luminosity Function for Ly alpha Emitters at z 5.7: a Major Component of Reionization

    NASA Technical Reports Server (NTRS)

    Dressler, Alan; Henry, Alaina L.; Martin, Crystal L.; Sawicki, Marcin; McCarthy, Patrick; Villaneuva, Edward

    2014-01-01

    We report the first direct and robust measurement of the faint-end slope of the Ly-alpha emitter (LAE) luminosity function at z = 5.7. Candidate LAEs from a low-spectral-resolution blind search with IMACS on Magellan- Baade were targeted at higher resolution to distinguish high redshift LAEs from foreground galaxies. All but 2 of our 42 single-emission-line systems are fainter than F = 2.0×10(exp-17) ergs s(exp-1) cm(exp-2), making these the faintest emission-lines observed for a z = 5.7 sample with known completeness, an essential property for determining the faint end slope of the LAE luminosity function. We find 13 LAEs as compared to 29 foreground galaxies, in very good agreement with the modeled foreground counts predicted in Dressler et al. (2011a) that had been used to estimate a faint-end slope of alpha = -2.0 for the LAE luminosity function. A 32% LAE fraction, LAE/(LAE+foreground) within the flux interval F = 2-20 × 10(exp-18) ergs s(exp-1) cm(exp-2) constrains the faint end slope of the luminosity function to -1.95 greater than alpha greater than -2.35 (1 delta). We show how this steep LF should provide, to the limit of our observations, more than 20% of the flux necessary to maintain ionization at z = 5.7, with a factor-of-ten extrapolation in flux reaching more than 55%. We suggest that this bodes well for a comparable contribution by similar, low-mass star forming galaxies at higher-redshift - within the reionization epoch at z greater than approximately 7, only 250 Myr earlier - and that such systems provide a substantial, if not dominant, contribution to the late-stage reionization of the IGM.

  6. Mean and extreme radio properties of quasars and the origin of radio emission

    SciTech Connect

    Kratzer, Rachael M.; Richards, Gordon T.

    2015-02-01

    We investigate the evolution of both the radio-loud fraction (RLF) and (using stacking analysis) the mean radio loudness of quasars. We consider how these properties evolve as a function of redshift and luminosity, black hole (BH) mass and accretion rate, and parameters related to the dominance of a wind in the broad emission-line region. We match the FIRST source catalog to samples of luminous quasars (both spectroscopic and photometric), primarily from the Sloan Digital Sky Survey. After accounting for catastrophic errors in BH mass estimates at high redshift, we find that both the RLF and the mean radio luminosity increase for increasing BH mass and decreasing accretion rate. Similarly, both the RLF and mean radio loudness increase for quasars that are argued to have weaker radiation line driven wind components of the broad emission-line region. In agreement with past work, we find that the RLF increases with increasing optical/UV luminosity and decreasing redshift, while the mean radio loudness evolves in the exact opposite manner. This difference in behavior between the mean radio loudness and the RLF in L−z may indicate selection effects that bias our understanding of the evolution of the RLF; deeper surveys in the optical and radio are needed to resolve this discrepancy. Finally, we argue that radio-loud (RL) and radio-quiet (RQ) quasars may be parallel sequences, but where only RQ quasars at one extreme of the distribution are likely to become RL, possibly through slight differences in spin and/or merger history.

  7. FAR-IR/SUBMILLIMETER SPECTROSCOPIC COSMOLOGICAL SURVEYS: PREDICTIONS OF INFRARED LINE LUMINOSITY FUNCTIONS FOR z < 4 GALAXIES

    SciTech Connect

    Spinoglio, Luigi; Dasyra, Kalliopi M.; Gruppioni, Carlotta; Valiante, Elisabetta; Isaak, Kate

    2012-02-01

    Star formation and accretion onto supermassive black holes in the nuclei of galaxies are the two most energetic processes in the universe, producing the bulk of the observed emission throughout its history. We simulated the luminosity functions of star-forming and active galaxies for spectral lines that are thought to be good spectroscopic tracers of either phenomenon, as a function of redshift. We focused on the infrared (IR) and submillimeter domains, where the effects of dust obscuration are minimal. Using three different and independent theoretical models for galaxy formation and evolution, constrained by multi-wavelength luminosity functions, we computed the number of star-forming and active galaxies per IR luminosity and redshift bin. We converted the continuum luminosity counts into spectral line counts using relationships that we calibrated on mid- and far-IR spectroscopic surveys of galaxies in the local universe. Our results demonstrate that future facilities optimized for survey-mode observations, i.e., the Space Infrared telescope for Cosmology and Astrophysics and the Cerro Chajnantor Atacama Telescope, will be able to observe thousands of z > 1 galaxies in key fine-structure lines, e.g., [Si II], [O I], [O III], [C II], in a half-square-degree survey, with 1 hr integration time per field of view. Fainter lines such as [O IV], [Ne V], and H{sub 2} (0-0)S1 will be observed in several tens of bright galaxies at 1 < z < 2, while diagnostic diagrams of active nucleus versus star formation activity will be feasible even for normal z {approx} 1 galaxies. We discuss the new parameter space that these future telescopes will cover and that strongly motivates their construction.

  8. First discoveries of z ˜ 6 quasars with the Kilo-Degree Survey and VISTA Kilo-Degree Infrared Galaxy survey

    NASA Astrophysics Data System (ADS)

    Venemans, B. P.; Verdoes Kleijn, G. A.; Mwebaze, J.; Valentijn, E. A.; Bañados, E.; Decarli, R.; de Jong, J. T. A.; Findlay, J. R.; Kuijken, K. H.; Barbera, F. La; McFarland, J. P.; McMahon, R. G.; Napolitano, N.; Sikkema, G.; Sutherland, W. J.

    2015-11-01

    We present the results of our first year of quasar search in the ongoing ESO public Kilo-Degree Survey (KiDS) and VISTA Kilo-Degree Infrared Galaxy (VIKING) surveys. These surveys are among the deeper wide-field surveys that can be used to uncover large numbers of z ˜ 6 quasars. This allows us to probe a more common population of z ˜ 6 quasars that is fainter than the well-studied quasars from the main Sloan Digital Sky Survey. From this first set of combined survey catalogues covering ˜250 deg2 we selected point sources down to ZAB = 22 that had a very red i - Z (i - Z > 2.2) colour. After follow-up imaging and spectroscopy, we discovered four new quasars in the redshift range 5.8 < z < 6.0. The absolute magnitudes at a rest-frame wavelength of 1450 Å are between -26.6 < M1450 < -24.4, confirming that we can find quasars fainter than M*, which at z = 6 has been estimated to be between M* = -25.1 and M* = -27.6. The discovery of four quasars in 250 deg2 of survey data is consistent with predictions based on the z ˜ 6 quasar luminosity function. We discuss various ways to push the candidate selection to fainter magnitudes and we expect to find about 30 new quasars down to an absolute magnitude of M1450 = -24. Studying this homogeneously selected faint quasar population will be important to gain insight into the onset of the co-evolution of the black holes and their stellar hosts.

  9. HST images of FeLoBAL quasars: Testing quasar-galaxy evolution models

    NASA Astrophysics Data System (ADS)

    Herbst, Hanna; Hamann, Fred; Villforth, Carolin; Caselli, Paola; Koekemoer, Anton M.; Veilleux, Sylvain

    2016-01-01

    We present preliminary results from an HST imaging study of FeLoBAL quasars, which have extremely low-ionization Broad Absorption Line (BAL) outflows and might be a young quasar population based on their red colors, large far-IR luminosities (suggesting high star formation rates), and powerful outflows. Some models of quasar - host galaxy evolution propose a triggering event, such as a merger, to fuel both a burst of star formation and the quasar/AGN activity. These models suggest young quasars are initially obscured inside the dusty starburst until a "blowout" phase, driven by the starburst or quasar outflows like FeLoBALs, ends the star formation and reveals the visibly luminous quasar. Despite the popularity of this evolution scheme, there is little observational evidence to support the role of mergers in triggering AGN or the youth of dust-reddened quasars (such as FeLoBALs) compared to normal blue quasars.Our Cycle 22 HST program is designed to test the youth of FeLoBAL quasars and the connection of FeLoBALs to mergers. We obtain WFC3/IR F160W images of 10 FeLoBAL quasars at redshift z~0.9 (covering ~8500A in the quasar rest frame). We will compare the host galaxy morphologies and merger signatures of FeLoBALs with normal blue quasars (which are older according to the evolution model) and non-AGN galaxies matched in redshift and stellar mass. If FeLoBAL quasars are indeed in a young evolutionary state, close in time to the initial merging event, they should have stronger merger features compared to blue quasars and non-AGN galaxies. Preliminary results suggest that this is not the case - FeLoBAL quasars appear to reside in faint, compact hosts with weak or absent merger signatures. We discuss the implications of these results for galaxy evolution models and other studies of dust-reddened quasar populations.

  10. Luminosity monitor.

    SciTech Connect

    Underwood, D. G.

    1998-07-16

    Luminosity monitors are needed in each experiment doing spin physics at RHIC. They concentrate on the luminosity aspects here because, for example, with a 10{sup {minus}3} raw asymmetry in an experiment, an error of 10{sup {minus}4} in the luminosity is as significant as a 10% polarization error. Because luminosity is a property of how two beams overlap, the luminosity at an interaction region must be measured at that interaction region in order to be relevant to the experiment at that interaction region. The authors will have to do the physics and the luminosity measurements by using labels on the event sums according to the polarization labels on the colliding bunches. Most likely they will not have independent polarization measurement on each bunch, but only on all the filled bunches in a ring, or perhaps all the bunches that are actually used in an experiment. Most analyses can then be handled by using the nine combinations gotten from three kinds of bunches in each ring, +, {minus} and empty bunches. The empty bunches are needed to measure beam-gas background, (and some, like six in a row, are needed for the beam abort). Much of the difficulty comes from the fact that they must use a physics process to represent the luminosity. This process must have kinematic and geometric cuts both to reduce systematics such as beam-gas backgrounds, and to make it representative of the part of the interaction diamond from which the physics events come.

  11. Similarity of ionized gas nebulae around unobscured and obscured quasars

    NASA Astrophysics Data System (ADS)

    Liu, Guilin; Zakamska, Nadia L.; Greene, Jenny E.

    2014-08-01

    Quasar feedback is suspected to play a key role in the evolution of massive galaxies, by removing or reheating gas in quasar host galaxies and thus limiting the amount of star formation. In this paper, we continue our investigation of quasar-driven winds on galaxy-wide scales. We conduct Gemini Integral Field Unit spectroscopy of a sample of luminous unobscured (type 1) quasars, to determine the morphology and kinematics of ionized gas around these objects, predominantly via observations of the [O III] λ5007 Å emission line. We find that ionized gas nebulae extend out to ˜13 kpc from the quasar, that they are smooth and round, and that their kinematics are inconsistent with gas in dynamical equilibrium with the host galaxy. The observed morphological and kinematic properties are strikingly similar to those of ionized gas around obscured (type 2) quasars with matched [O III] luminosity, with marginal evidence that nebulae around unobscured quasars are slightly more compact. Therefore, in samples of obscured and unobscured quasars carefully matched in [O III] luminosity, we find support for the standard geometry-based unification model of active galactic nuclei, in that the intrinsic properties of the quasars, of their hosts and of their ionized gas appear to be very similar. Given the apparent ubiquity of extended ionized regions, we are forced to conclude that either the quasar is at least partially illuminating pre-existing gas or that both samples of quasars are seen during advanced stages of quasar feedback. In the latter case, we may be biased by our [O III]-based selection against quasars in the early `blow-out' phase, for example due to dust obscuration.

  12. The evolution of star formation in quasar host galaxies

    NASA Astrophysics Data System (ADS)

    Serjeant, Stephen; Hatziminaoglou, Evanthia

    2009-07-01

    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 < IAB < -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 <1Jy 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) ~ L0.44+/-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.

  13. X-ray studies of quasars with the Einstein Observatory

    NASA Technical Reports Server (NTRS)

    Tananbaum, H.; Branduardi, G.; Fabbiano, G.; Feigelson, E.; Giacconi, R.; Henry, J. P.; Avni, Y.; Elvis, M.; Pye, J. P.; Soltan, A.

    1979-01-01

    Results of an investigation of the X-ray properties of quasars conducted using the Einstein Observatory (HEAO 2) are reported. The positions, fluxes and luminosities of 35 known quasars were observed by the Einstein high-resolution imaging detector and the imaging proportional counter. Assuming optical redshifts as valid distance indicators, 0.5-4.5 keV X-ray luminosities ranging from 10 to the 43rd to 10 to the 47 ergs/sec are obtained, with evidence of very little cold gas absorption. Flux variability on a time scale of less than 10,000 sec is observed for the quasar OX 169, which implies a mass between 8 x 10 to the 5th and 2 x 10 to the 8th solar masses for the black hole assumed to be responsible for the emission. Preliminary results of the quasar survey also indicate that quasars contribute significantly to the diffuse X-ray background.

  14. HOST GALAXIES OF z = 4 QUASARS

    SciTech Connect

    McLeod, K. K.; Bechtold, Jill E-mail: jbechtold@as.arizona.ed

    2009-10-10

    We have undertaken a project to investigate the host galaxies and environments of a sample of quasars at z approx 4. In this paper, we describe deep near-infrared imaging of 34 targets using the Magellan I and Gemini North telescopes. We discuss in detail special challenges of distortion and nonlinearity that must be addressed when performing point-spread function (PSF) subtraction with data from these telescopes and their IR cameras, especially in very good seeing. We derive black hole masses from emission-line spectroscopy, and we calculate accretion rates from our K{sub s} -band photometry, which directly samples the rest frame B for these objects. We introduce a new isophotal diameter technique for estimating host galaxy luminosities. We report the detection of four host galaxies on our deepest, sharpest images, and present upper limits for the others. We find that if host galaxies passively evolve such that they brighten by 2 mag or more in the rest-frame B band between the present and z = 4, then high-z hosts are less massive at a given black hole mass than are their low-z counterparts. We argue that the most massive hosts plateau at approx<10 L*. We estimate the importance of selection effects on this survey and the subsequent limitations of our conclusions. These results are in broad agreement with recent semianalytical models for the formation of luminous quasars and their host spheroids by mergers of gas-rich galaxies, with significant dissipation, and self-regulation of black hole growth and star formation by the burst of merger-induced quasar activity.

  15. THE LBT BOOeTES FIELD SURVEY. I. THE REST-FRAME ULTRAVIOLET AND NEAR-INFRARED LUMINOSITY FUNCTIONS AND CLUSTERING OF BRIGHT LYMAN BREAK GALAXIES AT Z {approx} 3

    SciTech Connect

    Bian Fuyan; Fan Xiaohui; Jiang Linhua; McGreer, Ian; Dave, Romeel; Dey, Arjun; Green, Richard F.; Maiolino, Roberto; Walter, Fabian; Lee, Kyoung-Soo

    2013-09-01

    We present a deep LBT/LBC U{sub spec}-band imaging survey (9 deg{sup 2}) covering the NOAO Booetes field. A total of 14,485 Lyman break galaxies (LBGs) at z {approx} 3 are selected, which are used to measure the rest-frame UV luminosity function (LF). The large sample size and survey area reduce the LF uncertainties due to Poisson statistics and cosmic variance by {>=}3 compared to previous studies. At the bright end, the LF shows excess power compared to the best-fit Schechter function, which can be attributed to the contribution of z {approx} 3 quasars. We compute the rest-frame near-infrared LF and stellar mass function (SMF) of z {approx} 3 LBGs based on the R-band and [4.5 {mu}m]-band flux relation. We investigate the evolution of the UV LFs and SMFs between z {approx} 7 and z {approx} 3, which supports a rising star formation history in the LBGs. We study the spatial correlation function of two bright LBG samples and estimate their average host halo mass. We find a tight relation between the host halo mass and the galaxy star formation rate (SFR), which follows the trend predicted by the baryonic accretion rate onto the halo, suggesting that the star formation in LBGs is fueled by baryonic accretion through the cosmic web. By comparing the SFRs with the total baryonic accretion rates, we find that cosmic star formation efficiency is about 5%-20% and it does not evolve significantly with redshift, halo mass, or galaxy luminosity.

  16. Quasars as tracers of cosmic flows

    NASA Astrophysics Data System (ADS)

    Modzelewska, J.; Czerny, B.; Bilicki, M.; Hryniewicz, K.; Krupa, M.; Petrogalli, F.; Pych, W.; Kurcz, A.; Udalski, A.

    2016-10-01

    Quasars, as the most luminous persistent sources in the Universe, have broad applications for cosmological studies. In particular, they can be employed to directly measure the expansion history of the Universe, similarly to SNe Ia. The advantage of quasars is that they are numerous, cover a broad range of redshifts, up to z = 7, and do not show significant evolution of metallicity with redshift. The idea is based on the relation between the time delay of an emission line and the continuum, and the absolute monochromatic luminosity of a quasar. For intermediate redshift quasars, the suitable line is Mg II. Between December 2012 and March 2014, we performed five spectroscopic observations of the QSO CTS C30.10 (z = 0.900) using the South African Large Telesope (SALT), supplemented with photometric monitoring, with the aim of determining the variability of the line shape, changes in the total line intensity and in the continuum. We show that the method is very promising.

  17. Crossing the Lyman valley: how many UV-bright high redshift quasars are there?

    NASA Astrophysics Data System (ADS)

    Picard, Alain; Jakobsen, Peter

    1993-09-01

    We present predictions for the appearance of the high redshift quasar population at far-UV (λ <~ 1500A) wavelengths, with an emphasis on assessing the feasibility of carrying out the HeII λ304A equivalent of the Gunn-Peterson test with HST and FUSE. We assume that the shape of the intrinsic extreme-UV spectra of luminous quasars can be described by a simple power law, and combine the quasar evolution models of Schmidt & Green (1983) and Boyle et al. (1988) with the intervening Lyman continuum absorption model of Moller & Jakobsen (1990) in order to calculate the distribution of quasars in apparent far- UV flux and redshift. We present curves giving the predicted total number of observable quasars on the sky as a function of limiting far-UV sensitivity at received HeII λ304A for the redshift range z > 3 accessible with HST and the range 2 < z <3 accessible with FUSE. The steepness of the quasar luminosity function is enhanced by the effects of intervening Lyman continuum absorption, and leads to the number of observable quasars being strongly dependent on the limiting sensitivity and assumed quasar spectrum. Nonetheless, our analysis suggests that a limiting far-UV spectroscopic sensitivity of Flambda_ ~ 1 x 10^16^ ergs s^-1^ cm^2^ A^-1^ is required in order to be able to observe HeII λ304A absorption in the ~10^2^ brightest quasars at redshifts z > 3. This sensitivity cannot currently be reached with the aberrated HST observatory but may be achievable in the future with the COSTAR and STIS instruments. In the lower redshift range 2 < Z < 3, where redshifted HeII λ304A line is accessible with FUSE, the corresponding sensitivity required to reach the ~10^2^ brightest quasars is Flambda_ ~ 1 x 10^-15^ ergs s^-1^ cm^-2^ A^-1^. This sensitivity is below that expected for the prime spectrographic mode of FUSE, but could be achieved in a low resolution mode

  18. Scale-dependent galaxy bias in the Sloan Digital Sky Survey as a function of luminosity and colour

    NASA Astrophysics Data System (ADS)

    Cresswell, James G.; Percival, Will J.

    2009-01-01

    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 < 0.1hMpc-1, but on smaller scales can affect the recovery of Ωmh 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.

  19. SPITZER OBSERVATIONS OF YOUNG RED QUASARS

    SciTech Connect

    Urrutia, Tanya; Lacy, Mark; Spoon, Henrik; Glikman, Eilat; Petric, Andreea; Schulz, Bernhard E-mail: mlacy@nrao.edu E-mail: eilat.glikman@yale.edu E-mail: bschulz@ipac.caltech.edu

    2012-10-01

    We present mid-infrared spectra and photometry of 13 redshift 0.4 < z < 1 dust reddened quasars obtained with Spitzer IRS and MIPS. We compare properties derived from their infrared spectral energy distributions (intrinsic active galactic nucleus (AGN) luminosity and far-infrared luminosity from star formation) to the host luminosities and morphologies from Hubble Space Telescope imaging, and black hole masses estimated from optical and/or near-infrared spectroscopy. Our results are broadly consistent with models in which most dust reddened quasars are an intermediate phase between a merger-driven starburst triggering a completely obscured AGN, and a normal, unreddened quasar. We find that many of our objects have high accretion rates, close to the Eddington limit. These objects tend to fall below the black hole mass-bulge luminosity relation as defined by local galaxies, whereas most of our low accretion rate objects are slightly above the local relation, as typical for normal quasars at these redshifts. Our observations are therefore most readily interpreted in a scenario in which galaxy stellar mass growth occurs first by about a factor of three in each merger/starburst event, followed sometime later by black hole growth by a similar amount. We do not, however, see any direct evidence for quasar feedback affecting star formation in our objects, for example, in the form of a relationship between accretion rate and star formation. Five of our objects, however, do show evidence for outflows in the [O III]5007 A emission line profile, suggesting that the quasar activity is driving thermal winds in at least some members of our sample.

  20. THE INFLUENCE OF RED SPIRAL GALAXIES ON THE SHAPE OF THE LOCAL K-BAND LUMINOSITY FUNCTION

    SciTech Connect

    Bonne, Nicolas J.; Brown, Michael J. I.; Jones, Heath; Pimbblet, Kevin A.

    2015-02-01

    We have determined K-band luminosity functions for 13,325 local universe galaxies as a function of morphology and color (for K {sub tot} ≤ 10.75). Our sample is drawn from the Two Micron All Sky Survey Extended Source Catalog, with all sample galaxies having measured morphologies and distances (including 4219 archival redshift-independent distances). The luminosity function for our total sample is in good agreement with previous works, but is relatively smooth at faint magnitudes (due to bulk flow distance corrections). We investigated the differences due to morphological and color selection using 5417 sample galaxies with NASA Sloan Atlas optical colors and find that red spirals comprise 20%-50% of all spirals with –25 ≤ M{sub K}  < –20. Fainter than M{sub K} = –24, red spirals are as common as early types, explaining the different faint end slopes (α = –0.87 and –1.00 for red and early-types, respectively). While we find red spirals comprise more than 50% of all M{sub K}  < –25 spiral galaxies, they do not dominate the bright end of the overall red galaxy luminosity function, which is dominated by early-type galaxies. The brightest red spirals have ongoing star formation and those without are frequently misclassified as early-types. The faintest ones have an appearance and Sérsic indices consistent with faded disks, rather than true bulge-dominated galaxies.

  1. Quasar Variability in the Mid-Infrared

    NASA Astrophysics Data System (ADS)

    Kozłowski, Szymon; Kochanek, Christopher S.; Ashby, Matthew L. N.; Assef, Roberto J.; Brodwin, Mark; Eisenhardt, Peter R.; Jannuzi, Buell T.; Stern, Daniel

    2016-02-01

    The Decadal IRAC Boötes Survey is a mid-IR variability survey of the ˜9 sq. deg. of the NDWFS Boötes Field and extends the time baseline of its predecessor, the Spitzer Deep, Wide-Field Survey (SDWFS), from 4 to 10 years. The Spitzer Space Telescope visited the field five times between 2004 and 2014 at 3.6 and 4.5 μm. We provide the difference image analysis photometry for a half a million mostly extragalactic sources. In mid-IR color-color plane, sources with quasar colors constitute the largest variability class (75%), 16% of the variable objects have stellar colors and the remaining 9% have the colors of galaxies. Adding the fifth epoch doubles the number of variable active galactic nuclei (AGNs) for the same false positive rates as in SDWFS, or increases the number of sources by 20% while decreasing the false positive rates by factors of 2-3 for the same variability amplitude. We quantify the ensemble mid-IR variability of ˜1500 spectroscopically confirmed AGNs using single power-law structure functions (SFs), which we find to be steeper (index γ ≈ 0.45) than in the optical (γ ≈ 0.3), leading to much lower amplitudes at short time-lags. This provides evidence for large emission regions, smoothing out any fast UV/optical variations, as the origin of infrared quasar variability. The mid-IR AGN SF slope γ seems to be uncorrelated with both the luminosity and rest-frame wavelength, while the amplitude shows an anti-correlation with the luminosity and a correlation with the rest-frame wavelength.

  2. Evolution of the dusty infrared luminosity function from z = 0 to z = 2.3 using observations from Spitzer

    NASA Astrophysics Data System (ADS)

    Magnelli, B.; Elbaz, D.; Chary, R. R.; Dickinson, M.; Le Borgne, D.; Frayer, D. T.; Willmer, C. N. A.

    2011-04-01

    Aims: We derive the evolution of the infrared luminosity function (LF) over the last 4/5ths of cosmic time using deep 24 and 70 μm imaging of the GOODS North and South fields. Methods: We use an extraction technique based on prior source positions at shorter wavelengths to build the 24 and 70 μm source catalogs. The majority (93%) of the sources have a spectroscopic (39%) or a photometric redshift (54%) and, in our redshift range of interest (i.e., 1.3 < z < 2.3) s20% of the sources have a spectroscopic redshift. To extend our study to lower 70 μm luminosities we perform a stacking analysis and we characterize the observed L24/(1 + z) vs. L70/(1 + z) correlation. Using spectral energy distribution (SED) templates which best fit this correlation, we derive the infrared luminosity of individual sources from their 24 and 70 μm luminosities. We then compute the infrared LF at zs1.55 ± 0.25 and zs2.05 ± 0.25. Results: We observe the break in the infrared LF up to zs2.3. The redshift evolution of the infrared LF from z = 1.3 to z = 2.3 is consistent with a luminosity evolution proportional to (1 + z)1.0 ± 0.9 combined with a density evolution proportional to (1 + z)-1.1 ± 1.5. At zs2, luminous infrared galaxies (LIRGs: 1011L⊙ < LIR < 1012 L⊙) are still the main contributors to the total comoving infrared luminosity density of the Universe. At zs2, LIRGs and ultra-luminous infrared galaxies (ULIRGs: 1012L⊙ < LIR) account for s49% and s17% respectively of the total comoving infrared luminosity density of the Universe. Combined with previous results using the same strategy for galaxies at z < 1.3 and assuming a constant conversion between the infrared luminosity and star-formation rate (SFR) of a galaxy, we study the evolution of the SFR density of the Universe from z = 0 to z = 2.3. We find that the SFR density of the Universe strongly increased with redshift from z = 0 to z = 1.3, but is nearly constant at higher redshift out to z = 2.3. As part of the

  3. A Database of Cepheid Distance Moduli and Tip of the Red Giant Branch, Globular Cluster Luminosity Function, Planetary Nebula Luminosity Function, and Surface Brightness Fluctuation Data Useful for Distance Determinations

    NASA Astrophysics Data System (ADS)

    Ferrarese, , Laura; Ford, Holland C.; Huchra, John; Kennicutt, Robert C., Jr.; Mould, Jeremy R.; Sakai, , Shoko; Freedman, Wendy L.; Stetson, Peter B.; Madore, Barry F.; Gibson, Brad K.; Graham, John A.; Hughes, Shaun M.; Illingworth, Garth D.; Kelson, Daniel D.; Macri, Lucas; Sebo, Kim; Silbermann, N. A.

    2000-06-01

    We present a compilation of Cepheid distance moduli and data for four secondary distance indicators that employ stars in the old stellar populations: the planetary nebula luminosity function (PNLF), the globular cluster luminosity function (GCLF), the tip of the red giant branch (TRGB), and the surface brightness fluctuation (SBF) method. The database includes all data published as of 1999 July 15. The main strength of this compilation resides in the fact that all data are on a consistent and homogeneous system: all Cepheid distances are derived using the same calibration of the period-luminosity relation, the treatment of errors is consistent for all indicators, and measurements that are not considered reliable are excluded. As such, the database is ideal for comparing any of the distance indicators considered, or for deriving a Cepheid calibration to any secondary distance indicator, such as the Tully-Fisher relation, the Type Ia supernovae, or the fundamental plane for elliptical galaxies. This task has already been undertaken by Ferrarese et al., Sakai et al., Kelson et al., and Gibson et al. Specifically, the database includes (1) Cepheid distances, extinctions, and metallicities; (2) reddened apparent λ5007 Å magnitudes of the PNLF cutoff; (3) reddened apparent magnitudes and colors of the turnover of the GCLF (in both the V and B bands); (4) reddened apparent magnitudes of the TRGB (in the I band) and V-I colors at 0.5 mag fainter than the TRGB; and (5) reddened apparent surface brightness fluctuation magnitudes measured in Kron-Cousin I, K', and Kshort, and using the F814W filter with the Hubble Space Telescope (HST) WFPC2. In addition, for every galaxy in the database we give reddening estimates from IRAS/DIRBE as well as H I maps, J2000 coordinates, Hubble and T-type morphological classification, apparent total magnitude in B, and systemic velocity.

  4. EDDINGTON-LIMITED ACCRETION AND THE BLACK HOLE MASS FUNCTION AT REDSHIFT 6

    SciTech Connect

    Willott, Chris J.; Crampton, David; Hutchings, John B.; Schade, David; Albert, Loic; Arzoumanian, Doris; Bergeron, Jacqueline; Omont, Alain; Delorme, Philippe; Reyle, Celine

    2010-08-15

    We present discovery observations of a quasar in the Canada-France High-z Quasar Survey (CFHQS) at redshift z = 6.44. We also use near-infrared spectroscopy of nine CFHQS quasars at z {approx} 6 to determine black hole masses. These are compared with similar estimates for more luminous Sloan Digital Sky Survey quasars to investigate the relationship between black hole mass and quasar luminosity. We find a strong correlation between Mg II FWHM and UV luminosity and that most quasars at this early epoch are accreting close to the Eddington limit. Thus, these quasars appear to be in an early stage of their life cycle where they are building up their black hole mass exponentially. Combining these results with the quasar luminosity function, we derive the black hole mass function at z = 6. Our black hole mass function is {approx}10{sup 4} times lower than at z = 0 and substantially below estimates from previous studies. The main uncertainties which could increase the black hole mass function are a larger population of obscured quasars at high redshift than is observed at low redshift and/or a low quasar duty cycle at z = 6. In comparison, the global stellar mass function is only {approx}10{sup 2} times lower at z = 6 than at z = 0. The difference between the black hole and stellar mass function evolution is due to either rapid early star formation which is not limited by radiation pressure as is the case for black hole growth or inefficient black hole seeding. Our work predicts that the black hole mass-stellar mass relation for a volume-limited sample of galaxies declines rapidly at very high redshift. This is in contrast to the observed increase at 4 < z < 6 from the local relation if one just studies the most massive black holes.

  5. Large-scale peculiar velocities through the galaxy luminosity function at z ~ 0.1

    NASA Astrophysics Data System (ADS)

    Feix, Martin; Nusser, Adi; Branchini, Enzo

    2016-10-01

    Peculiar motion introduces systematic variations in the observed luminosity distribution of galaxies. This allows one to constrain the cosmic peculiar velocity field from large galaxy redshift surveys. Using around half a million galaxies from the SDSS Data Release 7 at z ~ 0.1, we demonstrate the applicability of this approach to large datasets and obtain bounds on peculiar velocity moments and σ8, the amplitude of the linear matter power spectrum. Our results are in good agreement with the ΛCDM model and consistent with the previously reported ~ 1% zero-point tilt in the SDSS photometry. Finally, we discuss the prospects of constraining the growth rate of density perturbations by reconstructing the full linear velocity field from the observed galaxy clustering in redshift space.

  6. On the origin of excess cool gas in quasar host haloes

    NASA Astrophysics Data System (ADS)

    Johnson, Sean D.; Chen, Hsiao-Wen; Mulchaey, John S.

    2015-09-01

    Previous observations of quasar host haloes at z ≈ 2 have uncovered large quantities of cool gas that exceed what is found around inactive galaxies of both lower and higher masses. To better understand the source of this excess cool gas, we compiled an exhaustive sample of 195 quasars at z ≈ 1 with constraints on chemically enriched, cool gas traced by Mg II absorption in background quasar spectra from the Sloan Digital Sky Survey. This quasar sample spans a broad range of luminosities from Lbol = 1044.4 to 1046.8 erg s-1 and allows an investigation of whether halo gas properties are connected with quasar properties. We find a strong correlation between luminosity and cool gas covering fraction. In particular, low-luminosity quasars exhibit a mean gas covering fraction comparable to inactive galaxies of similar masses, but more luminous quasars exhibit excess cool gas approaching what is reported previously at z ≈ 2. Moreover, 30-40 per cent of the Mg II absorption occurs at radial velocities of |Δv| > 300 km s-1 from the quasar, inconsistent with gas bound to a typical quasar host halo. The large velocity offsets and observed luminosity dependence of the cool gas near quasars can be explained if the gas arises from: (1) neighbouring haloes correlated through large-scale structure at Mpc scales, (2) feedback from luminous quasars or (3) debris from the mergers thought to trigger luminous quasars. The first of these scenarios is in tension with the lack of correlation between quasar luminosity and clustering while the latter two make distinct predictions that can be tested with additional observations.

  7. A PHYSICAL MODEL FOR THE 0 {approx}< z {approx}< 8 REDSHIFT EVOLUTION OF THE GALAXY ULTRAVIOLET LUMINOSITY AND STELLAR MASS FUNCTIONS

    SciTech Connect

    Tacchella, Sandro; Carollo, C. Marcella; Trenti, Michele

    2013-05-10

    We present a model to understand the redshift evolution of the UV luminosity and stellar mass functions of Lyman break galaxies. Our approach is based on the assumption that the luminosity and stellar mass of a galaxy is related to its dark-matter (DM) halo assembly and gas infall rate. Specifically, galaxies experience a burst of star formation at the halo assembly time, followed by a constant star formation rate, representing a secular star formation activity sustained by steady gas accretion. Star formation from steady gas accretion is the dominant contribution to the galaxy UV luminosity at all redshifts. The model is calibrated by constructing a galaxy luminosity versus halo mass relation at z = 4 via abundance matching. After this luminosity calibration, the model naturally fits the z = 4 stellar mass function, and correctly predicts the evolution of both luminosity and stellar mass functions from z = 0 to z = 8. While the details of star formation efficiency and feedback are hidden within our calibrated luminosity versus halo mass relation, our study highlights that the primary driver of galaxy evolution across cosmic time is the buildup of DM halos, without the need to invoke a redshift-dependent efficiency in converting gas into stars.

  8. Powerful Winds in Extreme RBS quasars (POWER)

    NASA Astrophysics Data System (ADS)

    Piconcelli, Enrico

    2013-10-01

    This proposal aims at studying powerful outflows in ultra-luminous (log Lx >45) Radio-Quiet Quasars (RQQ). We propose to observe four objects extracted from a luminosity limited sample in the ROSAT Bright Survey for a full orbit (130 ks) each. Both models and observations suggest that the efficiency of driving energetic outflows increases with the AGN luminosity. Therefore, our targets are potentially the best objects to hunt for very powerful outflows expected in the AGN/galaxy feedback scenario. Our observations represent the first attempt ever to obtain deep, high-resolution-driven spectroscopy of a representative sample of RQQ in this high-luminosity regime.

  9. Binary black hole merger rates inferred from luminosity function of ultra-luminous X-ray sources

    NASA Astrophysics Data System (ADS)

    Inoue, Yoshiyuki; Tanaka, Yasuyuki T.; Isobe, Naoki

    2016-10-01

    The Advanced Laser Interferometer Gravitational-Wave Observatory (aLIGO) has detected direct signals of gravitational waves (GWs) from GW150914. The event was a merger of binary black holes whose masses are 36^{+5}_{-4} M_{{⊙}} and 29^{+4}_{-4} M_{{⊙}}. Such binary systems are expected to be directly evolved from stellar binary systems or formed by dynamical interactions of black holes in dense stellar environments. Here we derive the binary black hole merger rate based on the nearby ultra-luminous X-ray source (ULX) luminosity function (LF) under the assumption that binary black holes evolve through X-ray emitting phases. We obtain the binary black hole merger rate as 5.8(tULX/0.1 Myr)- 1λ- 0.6exp ( - 0.30λ) Gpc- 3 yr- 1, where tULX is the typical duration of the ULX phase and λ is the Eddington ratio in luminosity. This is coincident with the event rate inferred from the detection of GW150914 as well as the predictions based on binary population synthesis models. Although we are currently unable to constrain the Eddington ratio of ULXs in luminosity due to the uncertainties of our models and measured binary black hole merger event rates, further X-ray and GW data will allow us to narrow down the range of the Eddington ratios of ULXs. We also find the cumulative merger rate for the mass range of 5 M⊙ ≤ MBH ≤ 100 M⊙ inferred from the ULX LF is consistent with that estimated by the aLIGO collaboration considering various astrophysical conditions such as the mass function of black holes.

  10. THE VERY FAINT END OF THE UV LUMINOSITY FUNCTION OVER COSMIC TIME: CONSTRAINTS FROM THE LOCAL GROUP FOSSIL RECORD

    SciTech Connect

    Weisz, Daniel R.; Johnson, Benjamin D.; Conroy, Charlie

    2014-10-10

    We present a new technique to estimate the evolution of the very faint end of the UV luminosity function (LF) out to z ∼ 5. Measured star formation histories (SFHs) from the fossil record of Local Group (LG) galaxies are used to reconstruct the LF down to M {sub UV} ∼–5 at z ∼ 5 and M {sub UV} ∼–1.5 at z < 1. Such faint limits are well beyond the current observational limits and are likely to remain beyond the limits of next-generation facilities. The reconstructed LFs, when combined with direct measurements of the LFs at higher luminosity, are well-fit by a standard Schechter function with no evidence of a break to the faintest limits probed by this technique. The derived faint-end slope, α, steepens from ≈ – 1.2 at z < 1 to ≈ – 1.6 at 4 < z < 5. We test the effects of burstiness in the SFHs and find the recovered LFs to be only modestly affected. Incompleteness corrections for the faintest LG galaxies and the (unlikely) possibility of significant luminosity-dependent destruction of dwarf galaxies between high redshift and the present epoch are important uncertainties. These and other uncertainties can be mitigated with more detailed modeling and future observations. The reconstructed faint end LF from the fossil record can therefore be a powerful and complementary probe of the high-redshift faint galaxies believed to play a key role in the reionization of the universe.

  11. QUASARS PROBING QUASARS. IV. JOINT CONSTRAINTS ON THE CIRCUMGALACTIC MEDIUM FROM ABSORPTION AND EMISSION

    SciTech Connect

    Hennawi, Joseph F.; Prochaska, J. Xavier

    2013-03-20

    We have constructed a sample of 29 close projected quasar pairs where the background quasar spectrum reveals absorption from optically thick H I gas associated with the foreground quasar. These unique sightlines allow us to study the quasar circumgalactic medium (CGM) in absorption and emission simultaneously, because the background quasar pinpoints large concentrations of gas where Ly{alpha} emission, resulting from quasar-powered fluorescence, resonant Ly{alpha} scattering, and/or cooling radiation, is expected. A sensitive search (1{sigma} surface-brightness limits of SB{sub Ly{alpha}}{approx_equal}3 Multiplication-Sign 10{sup -18} erg s{sup -1} cm{sup -2} arcsec{sup -2}) for diffuse Ly{alpha} emission in the environments of the foreground (predominantly radio-quiet) quasars is conducted using Gemini/GMOS and Keck/LRIS slit spectroscopy. We fail to detect large-scale {approx}100 kpc Ly{alpha} emission, either at the location of the optically thick absorbers or in the foreground quasar halos, in all cases except a single system. We interpret these non-detections as evidence that the gas detected in absorption is shadowed from the quasar UV radiation due to obscuration effects, which are frequently invoked in unified models of active galactic nuclei. Small-scale R {approx}< 50 kpc extended Ly{alpha} nebulosities are detected in 34% of our sample, which are likely the high-redshift analogs of the extended emission-line regions (EELRs) commonly observed around low-redshift (z < 0.5) quasars. This may be fluorescent recombination radiation from a population of very dense clouds with a low covering fraction illuminated by the quasar. We also detect a compact high rest-frame equivalent width (W{sub Ly{alpha}} > 50 A) Ly{alpha}-emitter with luminosity L{sub Ly{alpha}} = 2.1 {+-} 0.32 Multiplication-Sign 10{sup 41} erg s{sup -1} at small impact parameter R = 134 kpc from one foreground quasar, and argue that it is more likely to result from quasar-powered fluorescence

  12. Host Galaxies of Luminous Type 2 Quasars at z ~ 0.5

    NASA Astrophysics Data System (ADS)

    Liu, Xin; Zakamska, Nadia L.; Greene, Jenny E.; Strauss, Michael A.; Krolik, Julian H.; Heckman, Timothy M.

    2009-09-01

    We present deep Gemini GMOS optical spectroscopy of nine luminous quasars at redshifts z ~ 0.5, drawn from the Sloan Digital Sky Survey type 2 quasar sample. Our targets were selected to have high intrinsic luminosities (MV < -26 mag) as indicated by the [O III] λ5007 Å emission-line luminosity (L [O III]). Our sample has a median black hole mass of ~108.8 M sun inferred assuming the local M BH-σ* relation and a median Eddington ratio of ~0.7, using stellar velocity dispersions σ* measured from the G band. We estimate the contamination of the stellar continuum from scattered quasar light based on the strength of broad Hβ, and provide an empirical calibration of the contamination as a function of L [O III]; the scattered-light fraction is ~30% of L 5100 for objects with L [O III] = 109.5 L sun. Population synthesis indicates that young poststarburst populations (<0.1 Gyr) are prevalent in luminous type 2 quasars, in addition to a relatively old population (>1 Gyr) which dominates the stellar mass. Broad emission complexes around He II λ4686 Å with luminosities up to 108.3 L sun are unambiguously detected in three out of the nine targets, indicative of Wolf-Rayet (WR) populations. Population synthesis shows that ~5 Myr poststarburst populations contribute substantially to the luminosities (>50% of L 5100) of all three objects with WR detections. We find two objects with double cores and four with close companions. Our results may suggest that luminous type 2 quasars trace an early stage of galaxy interaction, perhaps responsible for both the quasar and the starburst activity. Based, in part, on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada

  13. A Survey of z ~ 6 Quasars in the Sloan Digital Sky Survey Deep Stripe. I. A Flux-Limited Sample at zAB < 21

    NASA Astrophysics Data System (ADS)

    Jiang, Linhua; Fan, Xiaohui; Annis, James; Becker, Robert H.; White, Richard L.; Chiu, Kuenley; Lin, Huan; Lupton, Robert H.; Richards, Gordon T.; Strauss, Michael A.; Jester, Sebastian; Schneider, Donald P.

    2008-03-01

    We present the discovery of five quasars at z ~ 6 selected from 260 deg2 of the Sloan Digital Sky Survey (SDSS) southern survey, a deep imaging survey obtained by repeatedly scanning a stripe along the celestial equator. The five quasars with 20 < zAB < 21 are 1-2 magnitudes fainter than the luminous z ~ 6 quasars discovered in the SDSS main survey. One of them was independently discovered by the UKIRT Infrared Deep Sky Survey. These quasars, combined with another z ~ 6 quasar known in this region, make a complete flux-limited quasar sample at zAB < 21. The sample spans the redshift range 5.85 <= z <= 6.12 and the luminosity range -26.5 <= M 1450 <= -25.4 (H 0 = 70 km s-1 Mpc-1, Ω m = 0.3, and ΩΛ = 0.7). We use the 1/Va method to determine that the comoving quasar spatial density at langzrang = 6.0 and langM 1450rang = -25.8 is (5.0 ± 2.1) × 10-9 Mpc-3 mag-1. We model the bright-end quasar luminosity function (QLF) at z ~ 6 as a power law Φ(L 1450) vprop L β 1450. The slope β calculated from a combination of our sample and the luminous SDSS quasar sample is -3.1 ± 0.4, significantly steeper than the slope of the QLF at z ~ 4. Based on the derived QLF, we find that the quasar/active galactic nucleus (AGN) population cannot provide enough photons to ionize the intergalactic medium (IGM) at z ~ 6 unless the IGM is very homogeneous and the luminosity (L*1450) at which the QLF power law breaks is very low. Based on observations obtained with the Sloan Digital Sky Survey, which is owned and operated by the Astrophysical Research Consortium; the MMT Observatory, a joint facility of the University of Arizona and the Smithsonian Institution; the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile; the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration, and was made possible by the generous financial

  14. A Hubble Diagram for Quasars

    NASA Astrophysics Data System (ADS)

    Risaliti, G.; Lusso, E.

    2015-12-01

    We present a new method to test the ΛCDM cosmological model and to estimate cosmological parameters based on the nonlinear relation between the ultraviolet and X-ray luminosities of quasars. We built a data set of 1138 quasars by merging several samples from the literature with X-ray measurements at 2 keV and SDSS photometry, which was used to estimate the extinction-corrected 2500 Å flux. We obtained three main results: (1) we checked the nonlinear relation between X-ray and UV luminosities in small redshift bins up to z˜ 6, confirming that the relation holds at all redshifts with the same slope; (2) we built a Hubble diagram for quasars up to z˜ 6, which is well matched to that of supernovae in the common z = 0-1.4 redshift interval and extends the test of the cosmological model up to z˜ 6; and (3) we showed that this nonlinear relation is a powerful tool for estimating cosmological parameters. Using the present data and assuming a ΛCDM model, we obtain {{{Ω }}}M = 0.22{}-0.08+0.10 and {{{Ω }}}{{Λ }} = 0.92{}-0.30+0.18 ({{{Ω }}}M = 0.28 ± 0.04 and {{{Ω }}}{{Λ }} = 0.73 +/- 0.08 from a joint quasar-SNe fit). Much more precise measurements will be achieved with future surveys. A few thousand SDSS quasars already have serendipitous X-ray observations from Chandra or XMM-Newton, and at least 100,000 quasars with UV and X-ray data will be made available by the extended ROentgen Survey with an Imaging Telescope Array all-sky survey in a few years. The Euclid, Large Synoptic Survey Telescope, and Advanced Telescope for High ENergy Astrophysics surveys will further increase the sample size to at least several hundred thousand. Our simulations show that these samples will provide tight constraints on the cosmological parameters and will allow us to test for possible deviations from the standard model with higher precision than is possible today.

  15. Understanding the near infrared spectrum of quasars

    NASA Astrophysics Data System (ADS)

    Hernán-Caballero, Antonio; Hatziminaoglou, Evanthia; Alonso-Herrero, Almudena; Mateos, Silvia

    2016-08-01

    The rest-frame near infrared (NIR) is a key spectral range for understanding the physics of AGN, but progress has been hindered by the difficulty in defining the NIR spectrum of the accretion disk and removing contamination from stellar emission in the host galaxy. In this talk I will present the analysis of a sample of 85 luminous (L3µm>10^45.5 erg/s) quasars with rest-frame NIR spectroscopy from AKARI and Spitzer/IRS. Their high luminosity allows a direct determination of the NIR shape of the quasar spectrum clean from host galaxy emission. We find that the entire UV-to-MIR SED can be accurately reproduced with a semi-empirical disk+dust model that uses a single template for the accretion disk and two blackbody components (hot and warm) for the dust. The observed diversity in individual SEDs can be accounted for by varying levels of extinction affecting the disk component and differences in the relative luminosities of the disk and dust components. We present a new quasar template [0.1-10µm] as well as separate templates for the disk and dust components, and conclude that previous templates based on less luminous quasars suffer from contamination by stellar emission in the host galaxy, which accounts for up to ~30% of the flux at 1µm. We also perform the first ever measurement of the Paschen_α emission in a large sample of luminous quasars and find that the Paschen_α to optical continuum luminosity ratio is boosted in our sample compared to less luminous quasars.

  16. Covering factors of the dusty obscurers in radio-loud and radio-quiet quasars

    NASA Astrophysics Data System (ADS)

    Gupta, Maitrayee; Sikora, Marek; Nalewajko, Krzysztof

    2016-09-01

    We compare covering factors of circumnuclear dusty obscurers in radio-loud and radio-quiet quasars. The radio-loud quasars are represented by a sample of FR II quasars obtained by cross-matching a catalog of the FR II radio sources selected by van Velzen et al. with the SDSS DR7 catalog of quasars. Covering factors of FR II quasars are compared with covering factors of the radio-quiet quasars matched with them in redshift, black hole mass, and Eddington-ratio. We found that covering factors, proxied by the infrared-to-bolometric luminosity ratio, are on average slightly smaller in FR II quasars than in radio-quiet quasars, however, this difference is statistically significant only for the highest Eddington ratios. For both samples, no statistically significant dependence of a median covering factor on Eddington ratio, black hole mass, nor redshift can be claimed.

  17. Constraining the Warm Dark Matter Particle Mass through Ultra-deep UV Luminosity Functions at z=2

    NASA Astrophysics Data System (ADS)

    Menci, N.; Sanchez, N. G.; Castellano, M.; Grazian, A.

    2016-02-01

    We compute the mass function of galactic dark matter halos for different values of the warm dark matter (WDM) particle mass mX and compare it with the number density of ultra-faint galaxies derived from the deepest UV luminosity function available so far at redshift z ≈ 2. The magnitude limit MUV = -13 reached by such observations allows us to probe the WDM mass functions down to scales close to or smaller than the half-mass mode mass scale ˜109 M⊙. This allowed for an efficient discrimination among predictions for different mX which turn out to be in practice independent of the star formation efficiency η adopted to associate the observed UV luminosities of galaxies to the corresponding dark matter halo masses. Adopting a conservative approach to take into account the existing theoretical uncertainties in the galaxy halo mass function, we obtain a robust limit mX ≥ 1.8 keV for the mass of thermal relic WDM particles when comparing with the measured abundance of the faintest galaxies, while mX ≥ 1.5 keV is obtained when we compare with the Schechter fit to the observed luminosity function. The corresponding lower limit for sterile neutrinos depends on the modeling of the production mechanism; for instance msterile ≳ 4 keV holds for the Shi-Fuller mechanism. We discuss the impact of observational uncertainties on the above bound on mX. In the cold dark matter (CDM) limit {m}X\\gg 1 {{keV}} we recover the generic CDM result that very inefficient star formation efficiency is required to match the observed galaxy abundances. As a baseline for comparison with forthcoming observational results from the Hubble Space Telescope Frontier Field project, we provide predictions for the number density of faint galaxies with MUV = -13 for different values of the WDM particle mass and of the star formation efficiency η, which are valid up to z ≈ 4.

  18. Blue outliers among intermediate redshift quasars

    NASA Astrophysics Data System (ADS)

    Marziani, P.; Sulentic, J. W.; Stirpe, G. M.; Dultzin, D.; Del Olmo, A.; Martínez-Carballo, M. A.

    2016-01-01

    [OIII]λ 5007 "blue outliers"—that are suggestive of outflows in the narrow line region of quasars—appear to be much more common at intermediate z (high luminosity) than at low z. About 40~% of quasars in a Hamburg ESO intermediate z sample of 52 sources qualify as "blue outliers" (i.e., quasars with [OIII]λλ 4959,5007 lines showing large systematic blueshifts with respect to rest frame). We discuss major findings on what has become an intriguing field in active galactic nuclei research and stress the relevance of "blue outliers" to feedback and host galaxy evolution.

  19. The black hole spins of quasars

    NASA Astrophysics Data System (ADS)

    You, Bei; Cao, Xinwu

    2016-02-01

    We present the estimates of the black hole spins of five quasars. The peaks of the spectra of the accretion discs surrounding massive black holes in quasars are in the far-UV or soft X-ray band, which are usually not observed. However, in the disc corona model, the soft photons from the disc are Comptonized to high energy in the hot corona, and the hard X-ray spectra (luminosity and spectral shape) contain the information of the incident spectra from the disc. The values of black hole spin parameter a are inferred from the spectral fitting, which spread over a large range, ~ -0.94 to 0.998.

  20. M dwarfs in the Local Milky Way: The Field Low-Mass Stellar Luminosity and Mass Functions

    SciTech Connect

    Bochanski, Jr, John J.

    2008-01-01

    Modern sky surveys, such as the Sloan Digital Sky Survey (SDSS) and the Two-Micron All Sky Survey, have revolutionized how Astronomy is done. With millions of photometric and spectroscopic observations, global observational properties can be studied with unprecedented statistical significance. Low-mass stars dominate the local Milky Way, with tens of millions observed by SDSS within a few kpc. Thus, they make ideal tracers of the Galactic potential, and the thin and thick disks. In this thesis dissertation, I present my efforts to characterize the local low-mass stellar population, using a collection of observations from the Sloan Digital Sky Survey (SDSS). First, low-mass stellar template spectra were constructed from the co-addition of thousands of SDSS spectroscopic observations. These template spectra were used to quantify the observable changes introduced by chromospheric activity and metallicity. Furthermore, the average ugriz colors were measured as a function of spectral type. Next, the local kinematic structure of the Milky Way was quantified, using a special set of SDSS spectroscopic observations. Combining proper motions and radial velocities (measured using the spectral templates), along with distances, the full UVW space motions of over 7000 low-mass stars along one line of sight were computed. These stars were also separated kinematically to investigate other observational differences between the thin and thick disks. Finally, this dissertation details a project designed to measure the luminosity and mass functions of low-mass stars. Using a new technique optimized for large surveys, the field luminosity function (LF) and local stellar density profile are measured simultaneously. The sample size used to estimate the LF is nearly three orders of magnitude larger than any previous study, offering a definitive measurement of this quantity. The observed LF is transformed into a mass function (MF) and compared to previous studies.

  1. The Far-Infrared Luminosity Function and Star Formation Rate Density for Dust Obscured Galaxies in the Bootes Field

    NASA Astrophysics Data System (ADS)

    Calanog, Jae Alyson; Wardlow, J. L.; Fu, H.; Cooray, A. R.; HerMES

    2013-01-01

    We present the far-Infrared (FIR) luminosity function (LF) and the star-formation rate density (SFRD) for dust-obscured galaxies (DOGs) in the Bootes field at redshift 2. These galaxies are selected by having a large rest frame mid-IR to UV flux density ratio ( > 1000) and are expected to be some of the most luminous and heavily obscured galaxies in the Universe at this epoch. Photometric redshifts for DOGs are estimated from optical and mid-IR data using empirically derived low resolution spectral templates for AGN and galaxies. We use HerMES Herschel-SPIRE data to fit a modified blackbody to calculate the FIR luminosity (LFIR) and dust temperature (Td) for all DOGs individually detected in SPIRE maps. A stacking analyses was implemented to measure a median sub-mm flux of undetected DOGs. We find that DOGs have LIR and Td that are similar with the sub-millimeter galaxy (SMG) population, suggesting these two populations are related. The DOG LF and SFRD at 2 are calculated and compared to SMGs.

  2. Millisecond pulsars and the Galactic Center gamma-ray excess: the importance of luminosity function and secondary emission

    NASA Astrophysics Data System (ADS)

    Petrović, Jovana; Serpico, Pasquale D.; Zaharijas, Gabrijela

    2015-02-01

    Several groups of authors have analyzed Fermi LAT data in a region around the Galactic Center finding an unaccounted gamma-ray excess over diffuse backgrounds in the GeV energy range. It has been argued that it is difficult or even impossible to explain this diffuse emission by the leading astrophysical candidates—millisecond pulsars (MSPs). Here we provide a new estimate of the contribution to the excess by a population of yet unresolved MSP located in the bulge of the Milky Way. We simulate this population with the GALPLOT package by adopting a parametric approach, with the range of free parameters gauged on the MSP characteristics reported by the second pulsar catalogue (2PC). We find that the conclusions strongly depend on the details of the MSP luminosity function (in particular, its high luminosity end) and other explicit or tacit assumptions on the MSP statistical properties, which we discuss. Notably, for the first time we study the importance of the possible secondary emission of the MSPs in the Galactic Center, i.e. the emission via inverse Compton losses of electrons injected in the interstellar medium. Differently from a majority of other authors, we find that within current uncertainties a large if not dominant contribution of MSPs to the excess cannot be excluded. We also show that the sensitivities of future instruments or possibly already of the latest LAT data analysis (Pass 8) provide good perspectives to test this scenario by resolving a significant number of MSPs.

  3. Are extremely luminous far-infrared galaxies the result of merging quasar cores

    NASA Astrophysics Data System (ADS)

    Norris, R. P.

    1990-11-01

    Extremely Luminous far-infrared galaxies (ELFs) are a class of galaxy discovered independently by several groups. The class is characterized by a quasar-like total luminosity (1011 to 1013 solar luminosity) which is radiated almost entirely in the far-infrared. It has been suggested that obscured quasar cores may be responsible for generating this luminosity. Here the author demonstrates that ELFs appear in several guises which can be characterized by the number of quasar cores they contain (zero, one or two). The author develops a unified model to account for these differences.

  4. The quasar clustering and its evolution in a semi-analytic model based on ultra high-resolution N-body simulations

    NASA Astrophysics Data System (ADS)

    Oogi, Taira; Enoki, Motohiro; Ishiyama, Tomoaki; Kobayashi, Masakazu A. R.; Makiya, Ryu; Nagashima, Masahiro

    We investigate clustering properties of quasars using a new version of our semi-analytic model of galaxy and quasar formation with state-of-the-art cosmological N-body simulations (Ishiyama et al. 2015; Oogi et al. 2015). We assume that a major merger of galaxies triggers quasar activity. We find that the quasar bias does not depend significantly on the quasar luminosity, similar to observed trends. This result reflects the fact that quasars with a fixed luminosity have various Eddington ratios and thus have various host halo masses that primarily determine the quasar bias. The quasar bias increases with redshift, which is in qualitative agreement with observations. Our bias value is lower than the observed values at high redshifts, implying that we need some mechanisms that make quasars inactive in low-mass haloes and/or that make them more active in high-mass haloes.

  5. C IV emission-line properties and systematic trends in quasar black hole mass estimates

    NASA Astrophysics Data System (ADS)

    Coatman, Liam; Hewett, Paul C.; Banerji, Manda; Richards, Gordon T.

    2016-09-01

    Black hole masses are crucial to understanding the physics of the connection between quasars and their host galaxies and measuring cosmic black hole-growth. At high redshift, z ≳ 2.1, black hole masses are normally derived using the velocity width of the C IV λ λ1548, 1550 broad emission line, based on the assumption that the observed velocity widths arise from virial-induced motions. In many quasars, the C IV emission line exhibits significant blue asymmetries (`blueshifts') with the line centroid displaced by up to thousands of km s-1 to the blue. These blueshifts almost certainly signal the presence of strong outflows, most likely originating in a disc wind. We have obtained near-infrared spectra, including the Hα λ6565 emission line, for 19 luminous (LBol = 46.5-47.5 erg s-1) Sloan Digital Sky Survey quasars, at redshifts 2 < z < 2.7, with C IV emission lines spanning the full range of blueshifts present in the population. A strong correlation between C IV velocity width and blueshift is found and, at large blueshifts, >2000 km s-1, the velocity widths appear to be dominated by non-virial motions. Black hole masses, based on the full width at half-maximum of the C IV emission line, can be overestimated by a factor of 5 at large blueshifts. A larger sample of quasar spectra with both C IV and H β, or Hα, emission lines will allow quantitative corrections to C IV-based black hole masses as a function of blueshift to be derived. We find that quasars with large C IV blueshifts possess high Eddington luminosity ratios and that the fraction of high-blueshift quasars in a flux-limited sample is enhanced by a factor of approximately 4 relative to a sample limited by black hole mass.

  6. The Sloan Digital Sky Survey Quasar Catalog. 4. Fifth Data Release

    SciTech Connect

    Schneider, Donald P.; Hall, Patrick B.; Richards, Gordon T.; Strauss, Michael A.; Vanden Berk, Daniel E.; Anderson, Scott F.; Brandt, W.N.; Fan, Xiao-Hui; Jester, Sebastian; Gray, Jim; Gunn, James E.; /Penn State U., Astron. Astrophys. /York U., Canada /Johns Hopkins U. /Princeton U. Observ. /Washington U., Seattle, Astron. Dept. /Arizona U., Astron. Dept. - Steward Observ. /Southampton U. /Heidelberg, Max Planck Inst. Astron. /Microsoft, BARC /Chicago U. /Adler Planetarium, Chicago

    2007-04-01

    We present the fourth edition of the Sloan Digital Sky Survey (SDSS) Quasar Catalog. The catalog contains 77,429 objects; this is an increase of over 30,000 entries since the previous edition. The catalog consists of the objects in the SDSS Fifth Data Release that have luminosities larger than M{sub i} = -22.0 (in a cosmology with H{sub 0} = 70 km s{sup -1} Mpc{sup -1}, {Omega}{sub M} = 0.3, and {Omega}{sub {Lambda}} = 0.7), have at least one emission line with FWHM larger than 1000 km s{sup -1} or have interesting/complex absorption features, are fainter than i {approx} 15.0, and have highly reliable redshifts. The area covered by the catalog is {approx} 5740 deg{sup 2}. The quasar redshifts range from 0.08 to 5.41, with a median value of 1.48; the catalog includes 891 quasars at redshifts greater than four, of which 36 are at redshifts greater than five. Approximately half of the catalog quasars have i < 19; nearly all have i < 21. For each object the catalog presents positions accurate to better than 0.2-minutes rms per coordinate, five-band (ugriz) CCD-based photometry with typical accuracy of 0.03 mag, and information on the morphology and selection method. The catalog also contains basic radio, near-infrared, and X-ray emission properties of the quasars, when available, from other large-area surveys. The calibrated digital spectra cover the wavelength region 3800-9200 {angstrom} at a spectral resolution of {approx_equal} 2000; the spectra can be retrieved from the public database using the information provided in the catalog. The average SDSS colors of quasars as a function of redshift, derived from the catalog entries, are presented in tabular form. Approximately 96% of the objects in the catalog were discovered by the SDSS.

  7. Quasars and their emission lines as cosmological probes

    NASA Astrophysics Data System (ADS)

    Marziani, Paola; Sulentic, Jack W.

    2014-10-01

    Quasars are the most luminous sources in the Universe. They are currently observed out to redshift z≈7 when the Universe was less than one tenth of its present age. Since their discovery 50 years ago astronomers have dreamed of using them as standard candles. Unfortunately quasars cover a very large range (8 dex) of luminosity making them far from standard. We briefly review several methods that can potentially exploit quasars properties and allow us to obtain useful constraints on principal cosmological parameters. Using our 4D Eigenvector 1 formalism we have found a way to effectively isolate quasars radiating near the Eddington limit. If the Eddington ratio is known, under several assumptions it is possible to derive distance independent luminosities. We discuss the main statistical and systematic errors involved, and whether these “standard Eddington candles” can be actually used to constrain cosmological models.

  8. Improvements in the X-ray luminosity function and constraints on the cosmological parameters from X-ray luminous clusters

    NASA Astrophysics Data System (ADS)

    Del Popolo, A.; Costa, V.; Lanzafame, G.

    2010-05-01

    Aims: We improve the current constraints on Ω_m, the dark-energy equation-of-state parameter, w, and σ_8, obtained from measurements of the X-ray luminosity function of galaxy clusters, namely MACS, the local BCS, and the REFLEX galaxy cluster samples with luminosities L > 3 × 1044 erg/s in the 0.1-2.4 keV band. Methods: To this aim, we use Tinker and collaborators mass function instead of Jenkins and collaborators and the mass-luminosity relationship obtained by Del Popolo and collaborators. Results: Using the same methods and priors as Mantz and collaborators, we find Ω_m = 0.28+0.05-0.04 and σ_8 = 0.78+0.04-0.05, for a ΛCDM universe, while the result of Mantz and collaborators gives less tight constraints Ω_m = 0.28+0.11-0.07 and σ_8 = 0.78+0.11-0.13. In the case of a wCDM model, we find Ω_m = 0.27+0.07-0.06, σ_8 = 0.81+0.05-0.06 and w = -1.3+0.3-0.4, while in Mantz and collaborators they are again less tight Ω_m = 0.24+0.15-0.07, σ_8 = 0.85+0.13-0.20 and w = -1.4+0.4-0.7. Combining the XLF analysis with the fgas+CMB+SNIa data set results in the constraint Ω_m = 0.269 ± 0.012, σ_8 = 0.81 ± 0.021 and w = -1.02 ± 0.04, to be compared with Mantz and collaborators, Ω_m = 0.269 ± 0.016, σ_8 = 0.82 ± 0.03 and w = -1.02 ± 0.06. The tightness of the last constraints obtained by Mantz and collaborators, are fundamentally due to the tightness of the fgas+CMB+SNIa constraints and not to their XLF analysis. Our findings, consistent with w = -1, lend additional support to the cosmological-constant model.

  9. The bivariate brightness function of galaxies and a demonstration of the impact of surface brightness selection effects on luminosity function estimations

    NASA Astrophysics Data System (ADS)

    Cross, Nicholas; Driver, Simon P.

    2002-01-01

    In this paper we fit an analytic function to the bivariate brightness distribution (BBD) of galaxies. It is a combination of the classical Schechter Function convolved with a Gaussian distribution in surface brightness: thus incorporating the luminosity-surface brightness correlation as seen in many recent data sets. We fit this function to a recent measurement of the BBD based on 45000 galaxies from the Two-Degree Field Galaxy Redshift Survey. The parameters for the best-fitting model are φ*=(0.0206+/-0.0009)h3Mpc-3, Mbj*-5logh=(-19.72+/-0.04)mag, α=-1.05+/-0.02, βμ=0.281+/-0.007, μe,bj*=(22.45+/-0.01)magarcsec-2 and σμ=0.517+/-0.006. φ*, Mbj* and α equate to the conventional Schechter parameters. βμ is the slope of the luminosity-surface brightness correlation, μe,bj* is the characteristic effective surface brightness at Mbj* and σμ is the width of the Gaussian. Using a BBF we explore the impact of the limiting detection isophote on classical measures of the galaxy luminosity distribution. We demonstrate that if isophotal magnitudes are used then errors of ΔMbj*~0.62mag, Δφ*~26 per cent and Δα~0.04 are likely for μlim,bj=24.0magarcsec-2. If Gaussian corrected magnitudes are used these change to ΔMbj*~0.38mag, Δφ*~11 per cent and Δα<0.01 for μlim,bj=24.0magarcsec-2. Hence while the faint-end slope, α, appears fairly robust to surface brightness issues, both the M* and φ* values are highly dependent. The range over which these parameters were seen to vary is fully consistent with the scatter in the published values, reproducing the range of observed luminosity densities (1.1luminosity function within the errors for μlim,bj=24.0magarcsec-2. We conclude that surface brightness selection effects are primarily responsible for this variation. After due consideration of these effects, we derive a value of jbj=2.16× 108hLsolarMpc-3.

  10. Rest-frame optical properties of luminous, radio-selected broad absorption line quasars

    NASA Astrophysics Data System (ADS)

    Runnoe, Jessie C.; Ganguly, R.; Brotherton, M. S.; DiPompeo, M. A.

    2013-08-01

    We have obtained Infrared Telescope Facility/SpeX spectra of eight moderate-redshift (z = 0.7-2.4), radio-selected (log R* ≈ 0.4-1.9) broad absorption line (BAL) quasars. The spectra cover the rest-frame optical band. We compare the optical properties of these quasars to those of canonically radio-quiet (log R* ≲ 1) BAL quasars at similar redshifts and to low-redshift quasars from the Palomar-Green catalogue. As with previous studies of BAL quasars, we find that [O III] λ5007 is weak, and optical Fe II emission is strong, a rare combination in canonically radio-loud (log R* ≳ 1) quasars. With our measurements of the optical properties, particularly the Balmer emission-line widths and the continuum luminosity, we have used empirical scaling relations to estimate black hole masses and Eddington ratios. These lie in the range (0.4-2.6) × 109 M⊙ and 0.1-0.9, respectively. Despite their comparatively extreme radio properties relative to most BAL quasars, their optical properties are quite consistent with those of radio-quiet BAL quasars and dissimilar to those of radio-loud non-BAL quasars. While BAL quasars generally appear to have low values of [O III] λ5007/Fe II an extreme of `Eigenvector 1', the Balmer line widths and Eddington ratios do not appear to significantly differ from those of unabsorbed quasars at similar redshifts and luminosities.

  11. The Most Powerful Cosmic Telescopes for Constraining the Faint-end Slope of the z > 7 Luminosity Function

    NASA Astrophysics Data System (ADS)

    Ammons, Stephen; Wong, K. C.; Zabludoff, A. I.; Keeton, C. R.; French, D.

    2012-01-01

    It is likely that intergalactic hydrogen was reionized by redshifts of 6 < z < 10, but it is not known whether the flux density of UV photons from the earliest galaxies was sufficient to do so. Measurements of the faint end slope of the luminosity function at these redshifts can help to address this question. I explore the use of the densest galaxy fields to lens faint objects into detectability, increasing source counts and providing improved constraints on dlog N / dlog L. First, I present galaxy spectroscopy for the first two dense beams identified from the SDSS. We have now confirmed that these beams have integrated masses of 3-4 x 1015 solar masses, surpassing even the most massive single cluster lensing fields. This increased mass should result in 50-1000% more detected sources at z > 7 than other current methods with equivalent exposure time. Second, I compare the high-redshift detection efficiencies of lensing and blank fields including realistic assumptions for the intrinsic sizes and morphologies of sources at z > 7. We find that there are heretofore uncorrected biases introduced by lensing due to the difficulty of detecting faint, highly elongated objects at high magnification. To interpret high-redshift, magnified number counts correctly, incompleteness due to this bias must be addressed with lensing simulations. The correction for incompleteness near the detection limit may exceed a factor of ten. Including finite source size and realistic shape assumptions, luminosity function slopes must be steeper than -dlog N / dlog L 2 at the faint end for cosmic telescopes to surpass blank field surveys in z > 7 detection efficiency. Prepared by LLNL under Contract DE-AC52-07NA27344.

  12. HST luminosity functions of the globular clusters M10, M22, and M55. A comparison with other clusters

    NASA Astrophysics Data System (ADS)

    Piotto, G.; Zoccali, M.

    1999-05-01

    From a combination of deep Hubble Space Telescope V and I images with groundbased images in the same bands, we have obtained color-magnitude diagrams of M10, M22, and M55, extending from just above the hydrogen burning limit to the tip of the red giant branch, down to the white dwarf cooling sequence. We have used the color-magnitude arrays to extract main sequence luminosity functions (LFs) from the turnoff to m ~ 0.13m_sun. The LFs of M10 is significantly steeper than that for the other two clusters. The difference cannot be due to a difference in metallicity. A comparison with the LFs from Piotto et al. (1997), shows a large spread in the LF slopes. This spread is also present in the local mass functions (MFs) obtained from the observed LFs using different theoretical mass-luminosity relations. The dispersion in the MF slopes remains also after removing the mass segregation effects by using multimass King-Michie models. The globular cluster MF slopes are also flatter than the MF slope of the field stars and of the Galactic clusters in the same mass interval. We interpret the MF slope dispersion and the MF flatness as an evidence of dynamical evolution which makes the present day globular cluster stellar MFs different from the initial MFs. The slopes of the present day MFs exclude that the low mass star can be dynamically relevant for the Galactic globular clusters. Based on HST observations retrieved from the ESO ST-ECF Archive, and on observations made at the European Southern Observatory, La Silla, Chile, and at the JKT telescope at La Palma, Islas Canarias.

  13. DECOMPOSING STAR FORMATION AND ACTIVE GALACTIC NUCLEUS WITH SPITZER MID-INFRARED SPECTRA: LUMINOSITY FUNCTIONS AND CO-EVOLUTION

    SciTech Connect

    Fu Hai; Scoville, N. Z.; Yan Lin; Capak, P.; Aussel, H.; Le Floc'h, E.; Salvato, M.; Kartaltepe, J. S.; Frayer, D. T.; Sanders, D. B.; Sheth, K.; Taniguchi, Y.

    2010-10-10

    We present Spitzer 7-38 {mu}m spectra for a 24 {mu}m flux-limited sample of galaxies at z {approx} 0.7 in the COSMOS field. The detailed high-quality spectra allow us to cleanly separate star formation (SF) and active galactic nucleus (AGN) in individual galaxies. We first decompose mid-infrared luminosity functions (LFs). We find that the SF 8 {mu}m and 15 {mu}m LFs are well described by Schechter functions. AGNs dominate the space density at high luminosities, which leads to the shallow bright-end slope of the overall mid-infrared LFs. The total infrared (8-1000 {mu}m) LF from 70 {mu}m selected galaxies shows a shallower bright-end slope than the bolometrically corrected SF 15 {mu}m LF, owing to the intrinsic dispersion in the mid-to-far-infrared spectral energy distributions. We then study the contemporary growth of galaxies and their supermassive black holes (BHs). Seven of the thirty-one luminous infrared galaxies with Spitzer spectra host luminous AGNs, implying an AGN duty cycle of 23% {+-} 9%. The time-averaged ratio of BH accretion rate and SF rate matches the local M{sub BH} - M{sub bulge} relation and the M{sub BH} - M{sub host} relation at z {approx} 1. These results favor co-evolution scenarios in which BH growth and intense SF happen in the same event but the former spans a shorter lifetime than the latter. Finally, we compare our mid-infrared spectroscopic selection with other AGN identification methods and discuss candidate Compton-thick AGNs in the sample. While only half of the mid-infrared spectroscopically selected AGNs are detected in X-ray, {approx}90% of them can be identified with their near-infrared spectral indices.

  14. The Rise of Dwarfs and the Fall of Giants: Galaxy Formation Feedback Signatures in the Halo Satellite Luminosity Function

    NASA Astrophysics Data System (ADS)

    Cooray, Asantha; Cen, Renyue

    2005-11-01

    The observed luminosity function (LF) of satellite galaxies shows several interesting features that require a better understanding of gas-thermodynamic processes and feedback effects related to reionization and galaxy formation. In galaxy clusters, the abundance of dwarf galaxies is consistent with the expectation based on the subhalo mass function, whereas in galaxy groups, a relatively small abundance of dwarfs is expected based on models of photoionization. In all halo systems, however, there is a dip in the abundance of galaxies with luminosities in the range ~2×108 Lsolar to 1010 Lsolar, corresponding to subhalo mass scales between ~5×1010 Msolar and a few times 1011 Msolar. Photoionization from reionization has been used to explain statistics of the dwarf population, with larger systems forming prior to, and smaller systems forming subsequent to, reionization. The observed dip in the LF is an imprint of small dwarf galaxies (<~2×108 Lsolar) that formed prior to reionization. The galactic winds powered by supernovae in these dwarf galaxies propagate energy and metals to large distances such that the intergalactic medium is uniformly enriched to a level of 10-3 Zsolar. The associated energy raises the intergalactic medium temperature and the Jeans mass to a range 1010-1011 Msolar at z~3.4-6.0. Because the epoch of nonlinearity for halos in this mass range is at z>=3.4-4.4, their gas content, hence star formation, is greatly suppressed on average and leads to the observed dip in the observed LF at z=0.

  15. DES J0454–4448: Discovery of the first luminous z ≥ 6 quasar from the Dark Energy Survey

    SciTech Connect

    Reed, S. L.

    2015-10-28

    We present the first results of a survey for high-redshift, z ≥ 6, quasars using izY multicolour photometric observations from the Dark Energy Survey (DES). Here we report the discovery and spectroscopic confirmation of the zAB, YAB = 20.2, 20.2 (M1450 = –26.5) quasar DES J0454–4448 with a redshift of z = 6.09±0.02 based on the onset of the Ly α forest and an H i near zone size of 4.1+1.1–1.2 proper Mpc. The quasar was selected as an i-band drop out with i–z = 2.46 and zAB < 21.5 from an area of ~300 deg2. It is the brightest of our 43 candidates and was identified for spectroscopic follow-up solely based on the DES i–z and z–Y colours. The quasar is detected by WISE and has W1AB = 19.68. The discovery of one spectroscopically confirmed quasar with 5.7 < z < 6.5 and zAB ≤ 20.2 is consistent with recent determinations of the luminosity function at z ~ 6. DES when completed will have imaged ~5000 deg2 to YAB = 23.0 (5σ point source) and we expect to discover 50–100 new quasars with z > 6 including 3–10 with z > 7 dramatically increasing the numbers of quasars currently known that are suitable for detailed studies.

  16. DES J0454–4448: Discovery of the first luminous z ≥ 6 quasar from the Dark Energy Survey

    DOE PAGES

    Reed, S. L.

    2015-10-28

    We present the first results of a survey for high-redshift, z ≥ 6, quasars using izY multicolour photometric observations from the Dark Energy Survey (DES). Here we report the discovery and spectroscopic confirmation of the zAB, YAB = 20.2, 20.2 (M1450 = –26.5) quasar DES J0454–4448 with a redshift of z = 6.09±0.02 based on the onset of the Ly α forest and an H i near zone size of 4.1+1.1–1.2 proper Mpc. The quasar was selected as an i-band drop out with i–z = 2.46 and zAB < 21.5 from an area of ~300 deg2. It is the brightestmore » of our 43 candidates and was identified for spectroscopic follow-up solely based on the DES i–z and z–Y colours. The quasar is detected by WISE and has W1AB = 19.68. The discovery of one spectroscopically confirmed quasar with 5.7 < z < 6.5 and zAB ≤ 20.2 is consistent with recent determinations of the luminosity function at z ~ 6. DES when completed will have imaged ~5000 deg2 to YAB = 23.0 (5σ point source) and we expect to discover 50–100 new quasars with z > 6 including 3–10 with z > 7 dramatically increasing the numbers of quasars currently known that are suitable for detailed studies.« less

  17. ISOCAM observations of the rho Ophiuchi cloud: Luminosity and mass functions of the pre-main sequence embedded cluster

    NASA Astrophysics Data System (ADS)

    Bontemps, S.; André, P.; Kaas, A. A.; Nordh, L.; Olofsson, G.; Huldtgren, M.; Abergel, A.; Blommaert, J.; Boulanger, F.; Burgdorf, M.; Cesarsky, C. J.; Cesarsky, D.; Copet, E.; Davies, J.; Falgarone, E.; Lagache, G.; Montmerle, T.; Pérault, M.; Persi, P.; Prusti, T.; Puget, J. L.; Sibille, F.

    2001-06-01

    We present the results of the first extensive mid-infrared (IR) imaging survey of the rho Ophiuchi embedded cluster, performed with the ISOCAM camera on board the ISO satellite. The main rho Ophiuchi molecular cloud L1688, as well as the two secondary clouds L1689N and L1689S, have been completely surveyed for point sources at 6.7 mu m and 14.3 mu m. A total of 425 sources are detected in ~ 0.7 deg2, including 16 Class I, 123 Class II, and 77 Class III young stellar objects (YSOs). Essentially all of the mid-IR sources coincide with near-IR sources, but a large proportion of them are recognized for the first time as YSOs. Our dual-wavelength survey allows us to identify essentially all the YSOs with IR excess in the embedded cluster down to Fnu ~ 10-15 mJy. It more than doubles the known population of Class II YSOs and represents the most complete census to date of newly formed stars in the rho Ophiuchi central region. There are, however, reasons to believe that several tens of Class III YSOs remain to be identified below Lstar ~ 0.2 Lsolar. The mid-IR luminosities of most ( ~ 65%) Class II objects are consistent with emission from purely passive circumstellar disks. The stellar luminosity function of the complete sample of Class II YSOs is derived with good accuracy down to Lstar ~ 0.03 Lsolar. It is basically flat (in logarithmic units) below Lstar ~ 2 Lsolar, exhibits a possible local maximum at Lstar ~ 1.5 Lsolar, and sharply falls off at higher luminosities. A modeling of the luminosity function, using available pre-main sequence tracks and plausible star formation histories, allows us to derive the mass distribution of the Class II YSOs which arguably reflects the initial mass function (IMF) of the embedded cluster. After correction for the presence of unresolved binary systems, we estimate that the IMF in rho Ophiuchi is well described by a two-component power law with a low-mass index of -0.35+/-0.25, a high-mass index of -1.7 (to be compared with the

  18. Spectroscopic CCD surveys for quasars at large redshift. II - A Pfuei transit survey

    NASA Technical Reports Server (NTRS)

    Schmidt, Maarten; Schneider, Donald P.; Gunn, James E.

    1986-01-01

    A CCD transit survey has been carried out with the 200 in. telescope of a strip of sky 5 arcmin wide and 9 hr long. Direct images and slitless spectra of over 43,000 objects were obtained on two successive nights. An automatic search for emission lines of given minimum equivalent width and signal-to-noise ratio yielded 52 candidate sources. Slit spectra revealed that 24 were emission-line galaxies with z less than 0.4 and eight were quasars with 2 between 1.00 and 2.76. The number of quasars detect agrees with that predicted from luminosity function models for z less than 2.9. The models also indicate that between 30 and 62 quasars with z less than 2.9 should have been found in this survey, but none were detected. This result reconfirms that there is a redshift cutoff near or below redshift three. The apparent conflict of this measurement with the known existence of dozens of quasars with redshifts larger than three is discussed.

  19. The X-Ray Luminosity Function of M37 and the Evolution of Coronal Activity in Low-mass Stars

    NASA Astrophysics Data System (ADS)

    Núñez, Alejandro; Agüeros, Marcel A.

    2016-10-01

    We use a 440.5 ks Chandra observation of the ≈500 Myr old open cluster M37 to derive the X-ray luminosity functions of its ≤1.2 {M}ȯ stars. Combining detections of 162 M37 members with upper limits for 160 non-detections, we find that its G, K, and M stars have a similar median (0.5–7 keV) X-ray luminosity {L}{{X}}={10}29.0 {erg} {{{s}}}-1, whereas the {L}{{X}}-to-bolometric-luminosity ratio ({L}{{X}}/{L}{bol}) indicates that M stars are more active than G and K stars by ≈ 1 order of magnitude at 500 Myr. To characterize the evolution of magnetic activity in low-mass stars over their first ≈ 600 {{Myr}}, we consolidate X-ray and optical data from the literature for stars in six other open clusters: from youngest to oldest they are, the Orion Nebula Cluster (ONC), NGC 2547, NGC 2516, the Pleiades, NGC 6475, and the Hyades. For these, we homogenize the conversion of instrumental count rates to {L}{{X}} by applying the same one-temperature emission model as for M37, and obtain masses using the same empirical mass-absolute magnitude relation (except for the ONC). We find that for G and K stars X-ray activity decreases ≈ 2 orders of magnitude over their first 600 Myr, and for M stars, ≈1.5. The decay rate of the median {L}{{X}} follows the relation {L}{{X}}\\propto {t}b, where b=-0.61+/- 0.12 for G stars, ‑0.82 ± 0.16 for K stars, and ‑0.40 ± 0.17 for M stars. In {L}{{X}}/{L}{bol} space, the slopes are ‑0.68 ± 0.12, ‑0.81 ± 0.19, and ‑0.61 ± 0.12, respectively. These results suggest that for low-mass stars the age-activity relation steepens after ≈ 625 {{Myr}}, consistent with the faster decay in activity observed in solar analogs at t\\gt 1 {{Gyr}}.

  20. Dissecting the Quasar Main Sequence: Insight from Host Galaxy Properties

    NASA Astrophysics Data System (ADS)

    Sun, Jiayi; Shen, Yue

    2015-05-01

    The diverse properties of broad-line quasars appear to follow a well-defined main sequence along which the optical Fe ii strength increases. It has been suggested that this sequence is mainly driven by the Eddington ratio (L/LEdd) of the black hole (BH) accretion. Shen & Ho demonstrated with quasar clustering analysis that the average BH mass decreases with increasing Fe ii strength when quasar luminosity is fixed, consistent with this suggestion. Here we perform an independent test by measuring the stellar velocity dispersion σ* (hence, the BH mass via the M-σ* relation) from decomposed host spectra in low-redshift Sloan Digital Sky Survey quasars. We found that at fixed quasar luminosity, σ* systematically decreases with increasing Fe ii strength, confirming that the Eddington ratio increases with Fe ii strength. We also found that at fixed luminosity and Fe ii strength, there is little dependence of σ* on the broad Hβ FWHM. These new results reinforce the framework that the Eddington ratio and orientation govern most of the diversity seen in broad-line quasar properties.

  1. DISSECTING THE QUASAR MAIN SEQUENCE: INSIGHT FROM HOST GALAXY PROPERTIES

    SciTech Connect

    Sun, Jiayi; Shen, Yue

    2015-05-01

    The diverse properties of broad-line quasars appear to follow a well-defined main sequence along which the optical Fe ii strength increases. It has been suggested that this sequence is mainly driven by the Eddington ratio (L/L{sub Edd}) of the black hole (BH) accretion. Shen and Ho demonstrated with quasar clustering analysis that the average BH mass decreases with increasing Fe ii strength when quasar luminosity is fixed, consistent with this suggestion. Here we perform an independent test by measuring the stellar velocity dispersion σ{sub *} (hence, the BH mass via the M–σ{sub *} relation) from decomposed host spectra in low-redshift Sloan Digital Sky Survey quasars. We found that at fixed quasar luminosity, σ{sub *} systematically decreases with increasing Fe ii strength, confirming that the Eddington ratio increases with Fe ii strength. We also found that at fixed luminosity and Fe ii strength, there is little dependence of σ{sub *} on the broad Hβ FWHM. These new results reinforce the framework that the Eddington ratio and orientation govern most of the diversity seen in broad-line quasar properties.

  2. The near-to-mid infrared spectrum of quasars

    NASA Astrophysics Data System (ADS)

    Hernán-Caballero, Antonio; Hatziminaoglou, Evanthia; Alonso-Herrero, Almudena; Mateos, Silvia

    2016-08-01

    We analyse a sample of 85 luminous (log (νLν(3µm)/erg s-1)>45.5) quasars with restframe ˜2-11 µm spectroscopy from AKARI and Spitzer. Their high luminosity allows a direct determination of the near-infrared quasar spectrum free from host galaxy emission. A semi-empirical model consisting of a single template for the accretion disk and two blackbodies for the dust emission successfully reproduces the 0.1-10 µm spectral energy distributions (SEDs). Excess emission at 1-2 µm over the best-fitting model suggests that hotter dust is necessary in addition to the ˜1200 K blackbody and the disk to reproduce the entire near-infrared spectrum. Variation in the extinction affecting the disk and in the relative strength of the disk and dust components accounts for the diversity of individual SEDs. Quasars with higher dust-to-disk luminosity ratios show slightly redder infrared continua and less prominent silicate emission. We find no luminosity dependence in the shape of the average infrared quasar spectrum. We generate a new quasar template that covers the restframe range 0.1-11 µm, and separate templates for the disk and dust components. Comparison with other infrared quasar composites suggests that previous ones are less reliable in the 2-4 µm range. Our template is the first one to provide a detailed view of the infrared emission on both sides of the 4 µm bump.

  3. THE UDF05 FOLLOW-UP OF THE HUBBLE ULTRA DEEP FIELD. III. THE LUMINOSITY FUNCTION AT z {approx} 6

    SciTech Connect

    Su Jian; Stiavelli, Massimo; Bergeron, Eddie; Bradley, Larry; Dahlen, Tomas; Ferguson, Henry C.; Koekemoer, Anton; Lucas, Ray A.; Panagia, Nino; Pavlovsky, Cheryl; Oesch, Pascal; Carollo, Marcella; Lilly, Simon; Trenti, Michele; Giavalisco, Mauro; Mobasher, Bahram

    2011-09-10

    In this paper, we present a derivation of the rest-frame 1400 A luminosity function (LF) at redshift six from a new application of the maximum likelihood method by exploring the five deepest Hubble Space Telescope/Advanced Camera for Surveys (HST/ACS) fields, i.e., the Hubble Ultra Deep Field, two UDF05 fields, and two Great Observatories Origins Deep Survey fields. We work on the latest improved data products, which makes our results more robust than those of previous studies. We use unbinned data and thereby make optimal use of the information contained in the data set. We focus on the analysis to a magnitude limit where the completeness is larger than 50% to avoid possibly large errors in the faint end slope that are difficult to quantify. We also take into account scattering in and out of the dropout sample due to photometric errors by defining for each object a probability that it belongs to the dropout sample. We find the best-fit Schechter parameters to the z {approx} 6 LF are {alpha} = 1.87 {+-} 0.14, M{sub *} = -20.25 {+-} 0.23, and {phi}{sub *} = 1.77{sup +0.62}{sub -0.49} x 10{sup -3} Mpc{sup -3}. Such a steep slope suggests that galaxies, especially the faint ones, are possibly the main sources of ionizing photons in the universe at redshift six. We also combine results from all studies at z {approx} 6 to reach an agreement in the 95% confidence level that -20.45 < M{sub *} < -20.05 and -1.90 < {alpha} < -1.55. The luminosity density has been found not to evolve significantly between z {approx} 6 and z {approx} 5, but considerable evolution is detected from z {approx} 6 to z {approx} 3.

  4. DO QUASAR BROAD-LINE VELOCITY WIDTHS ADD ANY INFORMATION TO VIRIAL BLACK HOLE MASS ESTIMATES?

    SciTech Connect

    Croom, Scott M.

    2011-08-01

    We examine how much information measured broad-line widths add to virial black hole (BH) mass estimates for flux-limited samples of quasars. We do this by comparing the BH mass estimates to those derived by randomly reassigning the quasar broad-line widths to different objects and re-calculating the BH mass. For 9000 BH masses derived from the H{beta} line we find that the distributions of original and randomized BH masses in the M{sub BH}-redshift plane and the M{sub BH}-luminosity plane are formally identical. A two-dimensional Kolmogorov-Smirnov test does not find a difference at >90% confidence. For the Mg II line (32,000 quasars) we do find very significant differences between the randomized and original BH masses, but the amplitude of the difference is still small. The difference for the C IV line (14,000 quasars) is 2{sigma}-3{sigma} and again the amplitude of the difference is small. Subdividing the data into redshift and luminosity bins we find that the median absolute difference in BH mass between the original and randomized data is 0.025, 0.01, and 0.04 dex for H{beta}, Mg II, and C IV, respectively. The maximum absolute difference is always {<=}0.1 dex. We investigate whether our results are sensitive to corrections to Mg II virial masses, such as those suggested by Onken and Kollmeier. These corrections do not influence our results, other than to reduce the significance of the difference between original and randomized BH masses to only 1{sigma}-2{sigma} for Mg II. Moreover, we demonstrate that the correlation between mass residuals and Eddington ratio discussed by Onken and Kollmeier is more directly attributable to the slope of the relation between H{beta} and Mg II line width. The implication is that the measured quasar broad-line velocity widths provide little extra information, after allowing for the mean velocity width. In this case virial estimates are equivalent to M{sub BH}{proportional_to}L{sup {alpha}}, with L/L{sub Edd

  5. Quasars in the MAMBO blank field survey

    NASA Astrophysics Data System (ADS)

    Voss, H.; Bertoldi, F.; Carilli, C.; Owen, F. N.; Lutz, D.; Holdaway, M.; Ledlow, M.; Menten, K. M.

    2006-03-01

    Our MAMBO 1.2 mm blank field imaging survey of ~0.75 sqd has uncovered four unusually bright sources, with flux densities between 10 and 90 mJy, all located in the Abell 2125 field. The three brightest are flat spectrum radio sources with bright optical and X-ray counterparts. Their mm and radio flux densities are variable on timescales of months. Their X-ray luminosities classify them as quasars. The faintest of the four mm bright sources appears to be a bright, radio-quiet starburst at z˜3, similar to the sources seen at lower flux densities in the MAMBO and SCUBA surveys. It may also host a mildly obscured AGN of quasar-like X-ray luminosity. The three non-thermal mm sources imply an areal density of flat spectrum radio sources higher by at least 7 compared with that expected from an extrapolation of the lower frequency radio number counts.

  6. The luminosity function at the end of the main sequence: Results of a deep, large-area, CCD survey for cool dwarfs

    NASA Technical Reports Server (NTRS)

    Kirkpatrick, J. Davy; Mcgraw, John T.; Hess, Thomas R.; Liebert, James; Mccarthy, Donald W., Jr.

    1994-01-01

    The luminosity function at the end of the main sequence is determined from V, R, and I data taken by the charge coupled devices (CCD)/Transit Instrument, a dedicated telescope surveying an 8.25 min wide strip of sky centered at delta = +28 deg, thus sampling Galactic latitudes of +90 deg down to -35 deg. A selection of 133 objects chosen via R - I and V - I colors has been observed spectroscopically at the 4.5 m Multiple Mirror Telescope to assess contributions by giants and subdwarfs and to verify that the reddest targets are objects of extremely late spectral class. Eighteen dwarfs of type M6 or later have been discovered, with the latest being of type M8.5. Data used for the determination of the luminosity function cover 27.3 sq. deg down to a completeness limit of R = 19.0. This luminosity function, computed at V, I, and bolometric magnitudes, shows an increase at the lowest luminosities, corresponding to spectral types later than M6- an effect suggested in earlier work by Reid & Gilmore and Legget & Hawkins. When the luminosity function is segregated into north Galactic and south Galactic portions, it is found that the upturn at faint magnitudes exists only in the southern sample. In fact, no dwarfs with M(sub I) is greater than or equal to 12.0 are found within the limiting volume of the 19.4 sq deg northern sample, in stark contrast to the smaller 7.9 sq deg area at southerly latitudes where seven such dwarfs are found. This fact, combined with the fact that the Sun is located approximately 10-40 pc north of the midplane, suggests that the latest dwarfs are part of a young population with a scale height much smaller than the 350 pc value generally adopted for other M dwarfs. These objects comprise a young population either because the lower metallicities prevelant at earlier epochs inhibited the formation of late M dwarfs or because the older counterparts of this population have cooled beyond current detection limits. The latter scenario would hold if these

  7. The LBT Boötes Field Survey. I. The Rest-frame Ultraviolet and Near-infrared Luminosity Functions and Clustering of Bright Lyman Break Galaxies at Z ~ 3

    NASA Astrophysics Data System (ADS)

    Bian, Fuyan; Fan, Xiaohui; Jiang, Linhua; McGreer, Ian; Dey, Arjun; Green, Richard F.; Maiolino, Roberto; Walter, Fabian; Lee, Kyoung-Soo; Davé, Romeel

    2013-09-01

    We present a deep LBT/LBC U spec-band imaging survey (9 deg2) covering the NOAO Boötes field. A total of 14,485 Lyman break galaxies (LBGs) at z ~ 3 are selected, which are used to measure the rest-frame UV luminosity function (LF). The large sample size and survey area reduce the LF uncertainties due to Poisson statistics and cosmic variance by >=3 compared to previous studies. At the bright end, the LF shows excess power compared to the best-fit Schechter function, which can be attributed to the contribution of z ~ 3 quasars. We compute the rest-frame near-infrared LF and stellar mass function (SMF) of z ~ 3 LBGs based on the R-band and [4.5 μm]-band flux relation. We investigate the evolution of the UV LFs and SMFs between z ~ 7 and z ~ 3, which supports a rising star formation history in the LBGs. We study the spatial correlation function of two bright LBG samples and estimate their average host halo mass. We find a tight relation between the host halo mass and the galaxy star formation rate (SFR), which follows the trend predicted by the baryonic accretion rate onto the halo, suggesting that the star formation in LBGs is fueled by baryonic accretion through the cosmic web. By comparing the SFRs with the total baryonic accretion rates, we find that cosmic star formation efficiency is about 5%-20% and it does not evolve significantly with redshift, halo mass, or galaxy luminosity. Based on data acquired using the Large Binocular Telescope (LBT). The LBT is an international collaboration among institutions in the United States, Italy, and Germany. LBT Corporation partners are: The University of Arizona on behalf of the Arizona university system; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; The Ohio State University, and The Research Corporation, on behalf of The University of Notre Dame, University of Minnesota, and University

  8. Quasar Selection in the Optical + MIR

    NASA Astrophysics Data System (ADS)

    Richards, Gordon T.; Myers, Adam D.; Peters, Christina M.

    2015-01-01

    We identify 885,503 type 1 quasar candidates to i<22 using the combination of optical and mid-IR photometry. Optical photometry is taken from SDSS-III, while mid-IR photometry comes from a combination of data from ALLWISE and several large-area Spitzer-IRAC fields. Selection was based on a training sample of 157,701 spectroscopically-confirmed type 1 quasars with both optical and mid-IR data. Of these candidates, 306,686 lack spectroscopic confirmation, including 8665 quasar candidates with 3.53.5 than the traditional mid-IR selection ``wedges'' and to 2.2quasars than the SDSS-III/BOSS project. This catalog paves the way for luminosity-dependent clustering investigations of large numbers of faint, high-redshift quasars. This work was supported in part by NASA-ADAP grant NNX12AI49G.

  9. A POPULATION OF DUST-RICH QUASARS AT z {approx} 1.5

    SciTech Connect

    Dai, Y. Sophia; Elvis, Martin; Huang Jiasheng; Fazio, Giovanni; Trichas, Markos; Bergeron, Jacqueline; Omont, Alain; Bock, Jamie; Vieira, Joaquin D.; Cooray, Asantha; Hatziminaoglou, Evanthia; Ibar, Edo; Magdis, Georgios E.; Rigopoulou, Dimitra; Oliver, Seb J.; Page, Mathew J.; Symeonidis, Myrto; Perez-Fournon, Ismael; Roseboom, Isaac G.; Scott, Douglas; and others

    2012-07-01

    We report Herschel SPIRE (250, 350, and 500 {mu}m) detections of 32 quasars with redshifts 0.5 {<=}z < 3.6 from the Herschel Multi-tiered Extragalactic Survey (HerMES). These sources are from a MIPS 24 {mu}m flux-limited sample of 326 quasars in the Lockman Hole Field. The extensive multi-wavelength data available in the field permit construction of the rest-frame spectral energy distributions (SEDs) from ultraviolet to the mid-infrared for all sources, and to the far-infrared (FIR) for the 32 objects. Most quasars with Herschel FIR detections show dust temperatures in the range of 25-60 K, with a mean of 34 K. The FIR luminosities range from 10{sup 11.3} to 10{sup 13.5} L{sub Sun }, qualifying most of their hosts as ultra- or hyper-luminous infrared galaxies. These FIR-detected quasars may represent a dust-rich population, but with lower redshifts and fainter luminosities than quasars observed at {approx}1 mm. However, their FIR properties cannot be predicted from shorter wavelengths (0.3-20 {mu}m, rest frame), and the bolometric luminosities derived using the 5100 A index may be underestimated for these FIR-detected quasars. Regardless of redshift, we observed a decline in the relative strength of FIR luminosities for quasars with higher near-infrared luminosities.

  10. An Ultra-luminous Quasar at z = 5.363 with a Ten Billion Solar Mass Black Hole and a Metal-rich DLA at z ∼ 5

    NASA Astrophysics Data System (ADS)

    Wang, Feige; Wu, Xue-Bing; Fan, Xiaohui; Yang, Jinyi; Cai, Zheng; Yi, Weimin; Zuo, Wenwen; Wang, Ran; McGreer, Ian D.; Ho, Luis C.; Kim, Minjin; Yang, Qian; Bian, Fuyan; Jiang, Linhua

    2015-07-01

    We report the discovery of an ultra-luminous quasar J030642.51+185315.8 (hereafter J0306+1853) at redshift 5.363, which hosts a supermassive black hole with {M}{BH}=(1.07+/- 0.27)× {10}10 {M}ȯ . With an absolute magnitude {M}1450=-28.92 and a bolometric luminosity {L}{bol}∼ 3.4× {10}14{L}ȯ , J0306+1853 is one of the most luminous objects in the early universe. It is not likely to be a beamed source based on its small flux variability, low radio loudness, and normal broad emission lines. In addition, a z=4.986 damped Lyα system (DLA) with [{{M}}/{{H}}]=-1.3+/- 0.1, among the most metal-rich DLAs at z≳ 5, is detected in the absorption spectrum of this quasar. This ultra-luminous quasar puts strong constraints on the bright end of the quasar luminosity function and massive end of the black hole mass function. It will provide a unique laboratory for the study of BH growth and the co-evolution between a BH and the host galaxy with multi-wavelength follow-up observations. The future high-resolution spectra will give more insight into the DLA and other absorption systems along the line of sight of J0306+1853.

  11. Ultra-faint ultraviolet galaxies at z ∼ 2 behind the lensing cluster A1689: The luminosity function, dust extinction, and star formation rate density

    SciTech Connect

    Alavi, Anahita; Siana, Brian; Freeman, William R.; Dominguez, Alberto; Richard, Johan; Stark, Daniel P.; Robertson, Brant; Scarlata, Claudia; Teplitz, Harry I.; Rafelski, Marc; Kewley, Lisa

    2014-01-10

    We have obtained deep ultraviolet imaging of the lensing cluster A1689 with the WFC3/UVIS camera onboard the Hubble Space Telescope in the F275W (30 orbits) and F336W (4 orbits) filters. These images are used to identify z ∼ 2 star-forming galaxies via their Lyman break, in the same manner that galaxies are typically selected at z ≥ 3. Because of the unprecedented depth of the images and the large magnification provided by the lensing cluster, we detect galaxies 100× fainter than previous surveys at this redshift. After removing all multiple images, we have 58 galaxies in our sample in the range –19.5 < M {sub 1500} < –13 AB mag. Because the mass distribution of A1689 is well constrained, we are able to calculate the intrinsic sensitivity of the observations as a function of source plane position, allowing for accurate determinations of effective volume as a function of luminosity. We fit the faint-end slope of the luminosity function to be α = –1.74 ± 0.08, which is consistent with the values obtained for 2.5 < z < 6. Notably, there is no turnover in the luminosity function down to M {sub 1500} = –13 AB mag. We fit the UV spectral slopes with photometry from existing Hubble optical imaging. The observed trend of increasingly redder slopes with luminosity at higher redshifts is observed in our sample, but with redder slopes at all luminosities and average reddening of (E(B – V)) = 0.15 mag. We assume the stars in these galaxies are metal poor (0.2 Z {sub ☉}) compared to their brighter counterparts (Z {sub ☉}), resulting in bluer assumed intrinsic UV slopes and larger derived values for dust extinction. The total UV luminosity density at z ∼ 2 is 4.31{sub −0.60}{sup +0.68}×10{sup 26} erg s{sup –1} Hz{sup –1} Mpc{sup –3}, more than 70% of which is emitted by galaxies in the luminosity range of our sample. Finally, we determine the global star formation rate density from UV-selected galaxies at z ∼ 2 (assuming a constant dust

  12. A study of the discrepant QSO X-ray luminosity function from the HEAO-2 data archive

    NASA Technical Reports Server (NTRS)

    Margon, B.

    1984-01-01

    An in-progress investigation aimed at characterizing the X-ray luminosity of very faint QSOs is described. More than 100 faint, previously uncataloged QSOs which lie in areas imaged in X rays at very high sensitivity were discovered.

  13. GALAXIES IN FILAMENTS HAVE MORE SATELLITES: THE INFLUENCE OF THE COSMIC WEB ON THE SATELLITE LUMINOSITY FUNCTION IN THE SDSS

    SciTech Connect

    Guo, Quan; Libeskind, N. I.; Tempel, E.

    2015-02-20

    We investigate whether the satellite luminosity function (LF) of primary galaxies identified in the Sloan Digital Sky Survey (SDSS) depends on whether the host galaxy is in a filament or not. Isolated primary galaxies are identified in the SDSS spectroscopic sample, and potential satellites (that are up to four magnitudes fainter than their hosts) are searched for in the much deeper photometric sample. Filaments are constructed from the galaxy distribution by the Bisous process. Isolated primary galaxies are divided into two subsamples: those in filaments and those not in filaments. We examine the stacked mean satellite LF of both the filament and nonfilament samples and find that, on average, the satellite LF of galaxies in filaments is significantly higher than those of galaxies not in filaments. The filamentary environment can increase the abundance of the brightest satellites (M {sub sat.} < M {sub prim.} + 2.0) by a factor of ∼2 compared with nonfilament isolated galaxies. This result is independent of the primary galaxy magnitude, although the satellite LF of galaxies in the faintest magnitude bin is too noisy to determine if such a dependence exists. Because our filaments are extracted from a spectroscopic flux-limited sample, we consider the possibility that the difference in satellite LF is due to a redshift, color, or environmental bias, finding these to be insufficient to explain our result. The dependence of the satellite LF on the cosmic web suggests that the filamentary environment may have a strong effect on the efficiency of galaxy formation.

  14. Common envelope mechanisms: constraints from the X-ray luminosity function of high-mass X-ray binaries

    SciTech Connect

    Zuo, Zhao-Yu; Li, Xiang-Dong E-mail: lixd@nju.edu.cn

    2014-12-10

    We use the measured X-ray luminosity function (XLF) of high-mass X-ray binaries (HMXBs) in nearby star-forming galaxies to constrain the common envelope (CE) mechanisms, which play a key role in governing the binary evolution. We find that the XLF can be reproduced quite closely under both CE mechanisms usually adopted, i.e., the α{sub CE} formalism and the γ algorithm, with a reasonable range of parameters considered. Provided that the parameter combination is the same, the γ algorithm is likely to produce more HMXBs than the α{sub CE} formalism, by a factor of up to ∼10. In the framework of the α{sub CE} formalism, a high value of α{sub CE} is required to fit the observed XLF, though it does not significantly affect the global number of the HMXB populations. We present the detailed components of the HMXB populations under the γ algorithm and compare them with those in Zuo et al. and observations. We suggest the distinct observational properties, as well as period distributions of HMXBs, may provide further clues to discriminate between these two types of CE mechanisms.

  15. C-M diagram and luminosity function of the Galactic globular cluster NGC 7099. I. Photographic photometry

    SciTech Connect

    Piotto, G.; Rosino, L.; Capaccioli, M.; Ortolani, S.; Alcaino, G.

    1987-08-01

    New photographic photometry of about 4400 stars in the field of the Galactic globular cluster NGC 7099 = M30 is presented. A C-M diagram and a luminosity function are obtained from this photometry. The distance modulus is estimated at 14.5 + or - 0.5 assuming V(HB) = 15.11 + or - 0.10 and E(B-V) = 0.03 + or - 0.03. The metallicity is (Fe/H) = 1.9 + or - 0.3 based on the dereddened color index (B-V)0,g = 0.71 + or - 0.03. The theoretical isochrones of VandenBerg and Bell (1985) give a better fit to the observations assuming (Fe/H) = -1.8, (m-M)V = 14.6, and E(B-V) = 0.02. A fair fit is also obtained using isochrones of low iron content with an oxygen enhancement of 0.7. From the fit, an age of 17 + or - 4 Gyr is deduced. 41 references.

  16. Galaxies in Filaments have More Satellites: The Influence of the Cosmic Web on the Satellite Luminosity Function in the SDSS

    NASA Astrophysics Data System (ADS)

    Guo, Quan; Tempel, E.; Libeskind, N. I.

    2015-02-01

    We investigate whether the satellite luminosity function (LF) of primary galaxies identified in the Sloan Digital Sky Survey (SDSS) depends on whether the host galaxy is in a filament or not. Isolated primary galaxies are identified in the SDSS spectroscopic sample, and potential satellites (that are up to four magnitudes fainter than their hosts) are searched for in the much deeper photometric sample. Filaments are constructed from the galaxy distribution by the Bisous process. Isolated primary galaxies are divided into two subsamples: those in filaments and those not in filaments. We examine the stacked mean satellite LF of both the filament and nonfilament samples and find that, on average, the satellite LF of galaxies in filaments is significantly higher than those of galaxies not in filaments. The filamentary environment can increase the abundance of the brightest satellites (M sat. < M prim. + 2.0) by a factor of ~2 compared with nonfilament isolated galaxies. This result is independent of the primary galaxy magnitude, although the satellite LF of galaxies in the faintest magnitude bin is too noisy to determine if such a dependence exists. Because our filaments are extracted from a spectroscopic flux-limited sample, we consider the possibility that the difference in satellite LF is due to a redshift, color, or environmental bias, finding these to be insufficient to explain our result. The dependence of the satellite LF on the cosmic web suggests that the filamentary environment may have a strong effect on the efficiency of galaxy formation.

  17. OPTIMAL TIME-SERIES SELECTION OF QUASARS

    SciTech Connect

    Butler, Nathaniel R.; Bloom, Joshua S.

    2011-03-15

    We present a novel method for the optimal selection of quasars using time-series observations in a single photometric bandpass. Utilizing the damped random walk model of Kelly et al., we parameterize the ensemble quasar structure function in Sloan Stripe 82 as a function of observed brightness. The ensemble model fit can then be evaluated rigorously for and calibrated with individual light curves with no parameter fitting. This yields a classification in two statistics-one describing the fit confidence and the other describing the probability of a false alarm-which can be tuned, a priori, to achieve high quasar detection fractions (99% completeness with default cuts), given an acceptable rate of false alarms. We establish the typical rate of false alarms due to known variable stars as {approx}<3% (high purity). Applying the classification, we increase the sample of potential quasars relative to those known in Stripe 82 by as much as 29%, and by nearly a factor of two in the redshift range 2.5 < z < 3, where selection by color is extremely inefficient. This represents 1875 new quasars in a 290 deg{sup 2} field. The observed rates of both quasars and stars agree well with the model predictions, with >99% of quasars exhibiting the expected variability profile. We discuss the utility of the method at high redshift and in the regime of noisy and sparse data. Our time-series selection complements well-independent selection based on quasar colors and has strong potential for identifying high-redshift quasars for Baryon Acoustic Oscillations and other cosmology studies in the LSST era.

  18. Wide Field Multiband Imaging of Low Redshift Quasar Environments

    NASA Astrophysics Data System (ADS)

    Scott, Jennifer E.; Rafiee, Alireza; Bechtold, Jill; Ellingson, Erica; Thibodeau, Christopher; Richmond, Michael

    2015-02-01

    We present photometry of the large-scale environments of a sample of 12 broad line active galactic nuclei (AGNs) with 0.06 < z < 0.37 from deep images in the Sloan Digital Sky Survey u, g, r, and i filters taken with the 90Prime prime focus camera on the Steward Observatory Bok Telescope. We measure galaxy clustering around these AGNs using two standard techniques: correlation amplitude (B gq) and the two point correlation function. We find average correlation amplitudes for the 10 radio-quiet objects in the sample equal to (9 ± 18, 144 ± 114, -39 ± 56, 295 ± 260) Mpc1.77 in (u, g, r, i), all consistent with the expectation from galaxy clustering. Using a ratio of the galaxy-quasar cross-correlation function to the galaxy autocorrelation function, we calculate the relative bias of galaxies and AGNs, b gq. The bias in the u band, b gq = 3.08 ± 0.51 is larger compared to that calculated in the other bands, but it does not correlate with AGN luminosity, black hole mass, or AGN activity via the luminosity of the [O III] emission line. Thus ongoing nuclear accretion activity is not reflected in the large scale environments from ~10 h -1 kpc to ~0.5 h -1 Mpc and may indicate a non-merger mode of AGN activity and/or a significant delay between galaxy mergers and nuclear activity in this sample of mostly radio-quiet quasars.

  19. Quasar Classification Using Color and Variability

    NASA Astrophysics Data System (ADS)

    Peters, Christina M.; Richards, Gordon

    2015-08-01

    We use the Non-parametric Bayesian Classification Kernel Density Estimation (NBC KDE) quasar selection algorithm (Richards et al. 2004) to identify 36,569 type 1 quasar candidates in the Sloan Digital Sky Survey (SDSS) Stripe 82 field using the combination of optical photometry and variability. 5-band coadded optical photometry is taken from the SDSS-I/II to a depth of r ~ 22.4; from these data variability parameters are calculated by fitting the structure function of each object in each band with a power law using 10 to >100 observations for timescales from ~1 day to ~8 years. Selection was based on a training sample of 13,221 spectroscopically-confirmed type 1 quasars from SDSS-I/II and the Baryon Oscillation Spectroscopic Survey (BOSS). Using variability alone, colors alone, and combining variability and colors we achieve 91%, 93%, and 97% quasar completeness and 98%, 98%, and 97% efficiency respectively, with particular improvement in the selection of quasars at 2.7 < z < 3.5 where quasars and stars have similar optical colors. The 23,043 quasar candidates that are not spectroscopically confirmed reach a depth of coadd i ~ 22: 0 and 21,380 (92.8%) are dimmer than coadded i -band magnitude of 20.2, the cut off for spectroscopic follow-up for SDSSDR7.

  20. The role of cluster mergers and travelling shocks in shaping the Hα luminosity function at z ˜ 0.2: `sausage' and `toothbrush' clusters

    NASA Astrophysics Data System (ADS)

    Stroe, Andra; Sobral, David; Röttgering, Huub J. A.; van Weeren, Reinout J.

    2014-02-01

    The most extreme cluster mergers can lead to massive cluster-wide travelling shock waves. The CIZA J2242.8+5301 (`sausage') and 1RXS J0603.3+4213 (`toothbrush') clusters (z ˜ 0.2) host enormous radio-emitting shocks with simple geometry. We investigate the role of mergers and shocks in shaping the Hα luminosity function, using custom-made narrow-band filters matching the cluster redshifts mounted on the Isaac Newton Telescope. We surveyed ˜0.28 deg2 for each cluster and found 181 line emitters in the `sausage' (volume of 3.371 × 103 Mpc3 for Hα at z = 0.1945) and 141 in the `toothbrush' (4.546 × 103 Mpc3 for Hα at z = 0.225), out of which 49 (`sausage') and 30 (`toothbrush') are expected to be Hα. We build luminosity functions for the field-of-view down to an average limiting star formation rate of 0.14 M⊙ yr-1, find good agreement with field luminosity functions at z = 0.2, but significant differences between the shapes of the luminosity functions for the two clusters. We discover extended, tens-of-kpc-wide Hα haloes in galaxies neighbouring relics, which were possibly disrupted by the passage of the shock wave. By comparing the `sausage' cluster with blank fields and other clusters, we also uncover an order of magnitude boost (at 9σ level) in the normalization φ* of the luminosity function in the relic areas. Our results suggest that cluster mergers may play an important role in the evolution of cluster galaxies through shock-induced star formation.

  1. Gamma-ray luminosity and photon index evolution of FSRQ blazars and contribution to the gamma-ray background

    SciTech Connect

    Singal, J.; Ko, A.; Petrosian, V.

    2014-05-10

    We present the redshift evolutions and distributions of the gamma-ray luminosity and photon spectral index of flat spectrum radio quasar (FSRQ) type blazars, using non-parametric methods to obtain the evolutions and distributions directly from the data. The sample we use for analysis consists of almost all FSRQs observed with a greater than approximately 7σ detection threshold in the first-year catalog of the Fermi Gamma-ray Space Telescope's Large Area Telescope, with redshifts as determined from optical spectroscopy by Shaw et al. We find that FSQRs undergo rapid gamma-ray luminosity evolution, but negligible photon index evolution, with redshift. With these evolutions accounted for we determine the density evolution and luminosity function of FSRQs and calculate their total contribution to the extragalactic gamma-ray background radiation, resolved and unresolved, which is found to be 16(+10/–4)%, in agreement with previous studies.

  2. The massive end of the luminosity and stellar mass functions and clustering from CMASS to SDSS: evidence for and against passive evolution

    NASA Astrophysics Data System (ADS)

    Bernardi, M.; Meert, A.; Sheth, R. K.; Huertas-Company, M.; Maraston, C.; Shankar, F.; Vikram, V.

    2016-02-01

    We describe the luminosity function, based on Sérsic fits to the light profiles, of CMASS galaxies at z ˜ 0.55. Compared to previous estimates, our Sérsic-based reductions imply more luminous, massive galaxies, consistent with the effects of Sérsic- rather than Petrosian or de Vaucouleur-based photometry on the Sloan Digital Sky Survey (SDSS) main galaxy sample at z ˜ 0.1. This implies a significant revision of the high-mass end of the correlation between stellar and halo mass. Inferences about the evolution of the luminosity and stellar mass functions depend strongly on the assumed, and uncertain, k + e corrections. In turn, these depend on the assumed age of the population. Applying k + e corrections taken from fitting the models of Maraston et al. to the colours of both SDSS and CMASS galaxies, the evolution of the luminosity and stellar mass functions appears impressively passive, provided that the fits are required to return old ages. However, when matched in comoving number- or luminosity-density, the SDSS galaxies are less strongly clustered compared to their counterparts in CMASS. This rules out the passive evolution scenario, and, indeed, any minor merger scenarios which preserve the rank ordering in stellar mass of the population. Potential incompletenesses in the CMASS sample would further enhance this mismatch. Our analysis highlights the virtue of combining clustering measurements with number counts.

  3. Spectroscopic CCD surveys for quasars at large redshift. I - A deep PFUEI survey. [Prime Focus Universal Extragalactic Instrument

    NASA Technical Reports Server (NTRS)

    Schmidt, M.; Schneider, D. P.; Gunn, J. E.

    1986-01-01

    A survey for faint quasars has been conducted using slitless spectroscopy with the PFUEI at the 200 inch (5 m) telescope. The survey covers a total of 0.91 sq deg in 113 fields at galactic latitudes above 30 deg. Calibrated spectra in the range 4500-7200 A were obtained for more than 9000 objects. Emission-line candidates were selected on the basis of two criteria: the equivalent width must exceed 50 A, and the signal-to-noise ratio of the detection of the line versus the sky background should be larger than 7. Among 45 candidates so selected, subsequent slit spectroscopy confirmed 27 emission-line objects. Among these, 17 are emission-line galaxies with redshifts in the range 0.04-0.31, and 10 are quasars with redshifts between 0.91 and 2.66. The well-defined selection criteria for these objects, together with the distribution of rest frame equivalent widths of the emission lines, allow derivation of the area of sky covered as a function of the continuum limiting magnitude. The observed number of quasars in the redshift range 0.7-2.7 agrees well with that predicted by the luminosity function models published by Schmidt and Green in 1983. It is concluded that quasars with an absolute magnitude of M(B) = -25 suffer a redshift cutoff near or below a redshift of 3.

  4. THE Pa{alpha} LUMINOSITY FUNCTION OF H II REGIONS IN NEARBY GALAXIES FROM HST/NICMOS

    SciTech Connect

    Liu Guilin; Calzetti, Daniela; Kennicutt, Robert C. Jr.; Schinnerer, Eva; Sofue, Yoshiaki; Komugi, Shinya; Egusa, Fumi; Scoville, Nicholas Z.

    2013-07-20

    The H II region luminosity function (LF) is an important tool for deriving the birthrates and mass distribution of OB associations and is an excellent tracer of the newly formed massive stars and associations. To date, extensive work (predominantly in H{alpha}) has been done from the ground, which is hindered by dust extinction and the severe blending of adjacent (spatially or in projection) H II regions. Reliably measuring the properties of H II regions requires a linear resolution <40 pc, but analyses satisfying this requirement have been done only in a handful of galaxies, so far. As the first space-based work using a galaxy sample, we have selected 12 galaxies from our HST/NICMOS Pa{alpha} survey and studied the LF and size distribution of H II regions both in individual galaxies and cumulatively, using a virtually extinction-free tracer of the ionizing photon rate. The high angular resolution and low sensitivity to diffuse emission of NICMOS also offer an advantage over ground-based imaging by enabling a higher degree of de-blending of the H II regions. We do not confirm the broken power-law LFs found in ground-based studies. Instead, we find that the LFs, both individual and co-added, follow a single power law dN(L)/dln L{proportional_to}L {sup -1}, are consistent with the mass function of star clusters in nearby galaxies, and are in agreement with the results of the existing analyses with Hubble Space Telescope (HST) data. The individual and co-added size distributions of H II regions are both roughly consistent with dN(D)/dln D{proportional_to}D {sup -3}, but the power-law scaling is probably contaminated by blended regions or complexes.

  5. Correlaciones cruzadas quasar-galaxia y AGN-galaxia

    NASA Astrophysics Data System (ADS)

    Martínez, H. J.; Merchán, M. E.; Valotto, C. A.; García Lambas, D.

    We compute quasar-galaxy and AGN-galaxy cross-correlation functions for samples taken from the Véron-Cetty & Véron (1998) catalog of quasars and active galaxies, using tracer galaxies taken from the Edinburgh/Durham Southern Catalog. The sample of active galaxy targets shows positive correlation at projected separations rp < 6 h-1 ~Mpc consistent with the usual power-law. On the other hand, we do not find a statistically significant positive quasar-galaxy correlation signal except in the range 3 h-1 Mpc < rp < 6 h-1 Mpc where we find similar AGN-galaxy and quasar-galaxy correlation amplitudes. At separations rp<3~h-1 ~Mpc a strong decline of quasar-galaxy correlations is observed, suggesting a significant local influence of quasars in galaxy formation. In an attempt to reproduce the observed cross-correlation between quasars and galaxies, we have performed CDM cosmological hydrodynamical simulations and tested the viability of a scenario based on the model developed by Silk & Rees (1998). In this scheme a fraction of the energy released by quasars is considered to be transferred into the baryonic component of the intergalactic medium in the form of winds. The results of the simulations suggest that the shape of the observed quasar-galaxy cross-correlation function could be understood in a scenario where a substantial amount of energy is transferred to the medium at the redshift of maximum quasar activity.

  6. Magnification of light from many distant quasars by gravitational lenses.

    PubMed

    Wyithe, J Stuart B; Loeb, Abraham

    2002-06-27

    Exceptionally bright quasars with redshifts up to z = 6.28 have recently been discovered. Quasars are thought to be powered by the accretion of gas onto supermassive black holes at the centres of galaxies. Their maximum (Eddington) luminosity depends on the mass of the black hole, and the brighter quasars are inferred to have black holes with masses of more than a few billion solar masses. The existence of such massive black holes poses a challenge to models for the formation of structures in the early Universe, as it requires their formation within one billion years of the Big Bang. Here we show that up to one-third of known quasars with z approximately equal to 6 will have had their observed flux magnified by a factor of ten or more, as a consequence of gravitational lensing by galaxies along the line of sight. The inferred abundance of quasar host galaxies, as well as the luminosity density provided by the quasars, has therefore been substantially overestimated.

  7. A Long-Term Space Astrophysics Research Program: The Evolution of the Quasar Continuum

    NASA Technical Reports Server (NTRS)

    Elvis, M.; Oliversen, Ronald K. (Technical Monitor)

    2002-01-01

    Four papers have been written. One reports on the major study funded by this grant: a pan-chromatic study of the quasar continuum at redshift 3. Two others make use of the quasar continuum shapes to find the minimum total accretion luminosity of the Universe, and hence the efficiency and spin of supermassive black holes; the second shows that the reemission of absorbed quasar radiation alleviates a major problem with galaxy formation and the FIR background. The last paper recognizes the role quasars may play in the initial formation of dust in the early Universe.

  8. FIRST-2MASS RED QUASARS: TRANSITIONAL OBJECTS EMERGING FROM THE DUST

    SciTech Connect

    Glikman, Eilat; Urrutia, Tanya; Lacy, Mark; Djorgovski, S. George; Mahabal, Ashish; Myers, Adam D.; Ross, Nicholas P.; Petitjean, Patrick; Ge, Jian; Schneider, Donald P.; York, Donald G.

    2012-09-20

    We present a sample of 120 dust-reddened quasars identified by matching radio sources detected at 1.4 GHz in the Faint Images of the Radio Sky at Twenty Centimeters survey with the near-infrared Two Micron All Sky Survey catalog and color-selecting red sources. Optical and/or near-infrared spectroscopy provide broad wavelength sampling of their spectral energy distributions that we use to determine their reddening, characterized by E(B - V). We demonstrate that the reddening in these quasars is best described by Small-Magellanic-Cloud-like dust. This sample spans a wide range in redshift and reddening (0.1 {approx}< z {approx}< 3, 0.1 {approx}< E(B - V) {approx}< 1.5), which we use to investigate the possible correlation of luminosity with reddening. At every redshift, dust-reddened quasars are intrinsically the most luminous quasars. We interpret this result in the context of merger-driven quasar/galaxy co-evolution where these reddened quasars are revealing an emergent phase during which the heavily obscured quasar is shedding its cocoon of dust prior to becoming a 'normal' blue quasar. When correcting for extinction, we find that, depending on how the parent population is defined, these red quasars make up {approx}< 15%-20% of the luminous quasar population. We estimate, based on the fraction of objects in this phase, that its duration is 15%-20% as long as the unobscured, blue quasar phase.

  9. The extended ROSAT-ESO Flux Limited X-ray Galaxy Cluster Survey (REFLEX II). IV. X-ray luminosity function and first constraints on cosmological parameters

    NASA Astrophysics Data System (ADS)

    Böhringer, Hans; Chon, Gayoung; Collins, Chris A.

    2014-10-01

    The X-ray luminosity function that is closely related to the cluster mass function is an important statistic of the census of galaxy clusters in our Universe. It is also an important means to probe the cosmological model of our Universe. Based on our recently completed REFLEX II cluster sample comprising 910 galaxy clusters with redshifts we construct the X-ray luminosity function of galaxy clusters for the nearby Universe and discuss its implications. We derived the X-ray luminosity function of the REFLEX II clusters on the basis of a precisely constructed selection function for the full sample and for several redshift slices from z = 0 to z = 0.4. In this redshift interval we find no significant signature of redshift evolution of the luminosity function. We provide the results of fits of a parameterized Schechter function and extensions of it which provide a reasonable characterization of the data. We also use a model for structure formation and galaxy cluster evolution to compare the observed X-ray luminosity function with the theoretical predictions for different cosmological models. The most interesting constraints can be derived for the cosmological parameters Ωm and σ8. We explore the influence of several model assumptions on which our analysis is based. We find that the scaling relation of X-ray luminosity and mass introduces the largest systematic uncertainty. From the statistical uncertainty alone we can constrain the matter density parameter, Ωm ~ 0.27 ± 0.03 and the amplitude parameter of the matter density fluctuations, σ8 ~ 0.80 ± 0.03. Marginalizing over the most important uncertainties, the normalisation and slope of the LX - M scaling relation, we have larger error bars and a result of Ωm ~ 0.29 ± 0.04 and σ8 ~ 0.77 ± 0.07 (1σ confidence limits). We compare our results with those of the SZ-cluster survey provided by the Planck mission and we find very good agreement with the results using Planck clusters as cosmological probes, but there

  10. Possible evolution of supermassive black holes from FRI quasars

    NASA Astrophysics Data System (ADS)

    Kim, Matthew I.; Christian, Damian J.; Garofalo, David; D'Avanzo, Jaclyn

    2016-08-01

    We explore the question of the rapid buildup of black hole mass in the early universe employing a growing black hole mass-based determination of both jet and disc powers predicted in recent theoretical work on black hole accretion and jet formation. Despite simplified, even artificial assumptions about accretion and mergers, we identify an interesting low probability channel for the growth of one billion solar mass black holes within hundreds of millions of years of the big bang without appealing to super Eddington accretion. This result is made more compelling by the recognition of a connection between this channel and an end product involving active galaxies with FRI radio morphology but weaker jet powers in mildly sub-Eddington accretion regimes. While FRI quasars have already been shown to occupy a small region of the available parameter space for black hole feedback in the paradigm, we further suggest that the observational dearth of FRI quasars is also related to their connection to the most massive black hole growth due to both these FRIs high redshifts and relative weakness. Our results also allow us to construct the AGN (active galactic nucleus) luminosity function at high redshift, that agree with recent studies. In short, we produce a connection between the unexplained paucity of a given family of AGNs and the rapid growth of supermassive black holes, two heretofore seemingly unrelated aspects of the physics of AGNs.

  11. The Extreme Ultraviolet Variability of Quasars

    NASA Astrophysics Data System (ADS)

    Punsly, Brian; Marziani, Paola; Zhang, Shaohua; Muzahid, Sowgat; O’Dea, Christopher P.

    2016-10-01

    We study the extreme ultraviolet (EUV) variability (rest frame wavelengths 500–920 Å) of high-luminosity quasars using Hubble Space Telescope (HST) (low to intermediate redshift sample) and Sloan Digital sky Survey (SDSS) (high redshift sample) archives. The combined HST and SDSS data indicates a much more pronounced variability when the sampling time between observations in the quasar rest frame is \\gt 2× {10}7 {{s}} compared to \\lt 1.5× {10}7 s. Based on an excess variance analysis, for time intervals \\lt 2× {10}7 {{s}} in the quasar rest frame, 10% of the quasars (4/40) show evidence of EUV variability. Similarly, for time intervals \\gt 2× {10}7 {{s}} in the quasar rest frame, 55% of the quasars (21/38) show evidence of EUV variability. The propensity for variability does not show any statistically significant change between 2.5× {10}7 {{s}} and 3.16× {10}7 {{s}} (1 year). The temporal behavior is one of a threshold time interval for significant variability as opposed to a gradual increase on these timescales. A threshold timescale can indicate a characteristic spatial dimension of the EUV region. We explore this concept in the context of the slim disk models of accretion. We find that for rapidly spinning black holes, the radial infall time to the plunge region of the optically thin surface layer of the slim disk that is responsible for the preponderance of the EUV flux emission (primarily within 0–7 black hole radii from the inner edge of the disk) is consistent with the empirically determined variability timescale.

  12. Herschel-ATLAS Galaxy Counts and High-redshift Luminosity Functions: The Formation of Massive Early-type Galaxies

    NASA Astrophysics Data System (ADS)

    Lapi, A.; González-Nuevo, J.; Fan, L.; Bressan, A.; De Zotti, G.; Danese, L.; Negrello, M.; Dunne, L.; Eales, S.; Maddox, S.; Auld, R.; Baes, M.; Bonfield, D. G.; Buttiglione, S.; Cava, A.; Clements, D. L.; Cooray, A.; Dariush, A.; Dye, S.; Fritz, J.; Herranz, D.; Hopwood, R.; Ibar, E.; Ivison, R.; Jarvis, M. J.; Kaviraj, S.; López-Caniego, M.; Massardi, M.; Michałowski, M. J.; Pascale, E.; Pohlen, M.; Rigby, E.; Rodighiero, G.; Serjeant, S.; Smith, D. J. B.; Temi, P.; Wardlow, J.; van der Werf, P.

    2011-11-01

    Exploiting the Herschel Astrophysical Terahertz Large Area Survey Science Demonstration Phase survey data, we have determined the luminosity functions (LFs) at rest-frame wavelengths of 100 and 250 μm and at several redshifts z >~ 1, for bright submillimeter galaxies with star formation rates (SFRs) >~ 100 M ⊙ yr-1. We find that the evolution of the comoving LF is strong up to z ≈ 2.5, and slows down at higher redshifts. From the LFs and the information on halo masses inferred from clustering analysis, we derived an average relation between SFR and halo mass (and its scatter). We also infer that the timescale of the main episode of dust-enshrouded star formation in massive halos (M H >~ 3 × 1012 M ⊙) amounts to ~7 × 108 yr. Given the SFRs, which are in the range of 102-103 M ⊙ yr-1, this timescale implies final stellar masses of the order of 1011-1012 M ⊙. The corresponding stellar mass function matches the observed mass function of passively evolving galaxies at z >~ 1. The comparison of the statistics for submillimeter and UV-selected galaxies suggests that the dust-free, UV bright phase is >~ 102 times shorter than the submillimeter bright phase, implying that the dust must form soon after the onset of star formation. Using a single reference spectral energy distribution (SED; the one of the z ≈ 2.3 galaxy SMM J2135-0102), our simple physical model is able to reproduce not only the LFs at different redshifts >1 but also the counts at wavelengths ranging from 250 μm to ≈1 mm. Owing to the steepness of the counts and their relatively broad frequency range, this result suggests that the dispersion of submillimeter SEDs of z > 1 galaxies around the reference one is rather small. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  13. Cosmology with AGN: can we use quasars as standard candles?

    NASA Astrophysics Data System (ADS)

    Risaliti, G.

    2016-06-01

    The non-linear relation between X-ray and UV luminosity in quasars can be used to estimate their distance. Recently, we have shown that despite the large dispersion of the relation, a Hubble Diagram made of large samples of quasars can provide unique constraints on cosmology at high redshift. Furthermore, the dispersion of the relation is heavily affected by measurement errors: until now we have used serendipitous X-ray observations, but dedicated observations would significantly increase the precision of the distance estimates. I discuss the future role of XMM in this new field, showing (1) the fundamental contribution of the Serendipitous Source Catalogue and of large surveys, and (2) the breakthrough advancements we may achieve with the observation of a large number of SDSS quasars at high redshift: every 12-15 quasars observed at z~3 would be equivalent to discovering a supernova at that redshift.

  14. AN INFRARED EXCESS IDENTIFIED IN RADIO-LOUD BROAD ABSORPTION LINE QUASARS

    SciTech Connect

    DiPompeo, M. A.; Runnoe, J. C.; Brotherton, M. S.; Myers, A. D.

    2013-01-10

    If broad absorption line (BAL) quasars represent a high-covering-fraction evolutionary state (even if this is not the sole factor governing the presence of BALs), it is expected that they should show an excess of mid-infrared radiation compared to normal quasars. Some previous studies have suggested that this is not the case. We perform the first analysis of the IR properties of radio-loud BAL quasars, using IR data from WISE and optical (rest-frame ultraviolet) data from SDSS, and compare the BAL quasar sample with a well-matched sample of unabsorbed quasars. We find a statistically significant excess in the mid- to near-infrared luminosities of BAL quasars, particularly at rest-frame wavelengths of 1.5 and 4 {mu}m. Our sample was previously used to show that BALs are observed along many lines of sight toward quasars, but with an overabundance of more edge-on sources, suggesting that orientation factors into the appearance of BALs. The evidence here-of a difference in IR luminosities between BAL quasars and unabsorbed quasars-can be ascribed to evolution. This suggests that a merging of the current BAL paradigms is needed to fully describe the class.

  15. DES J0454-4448: discovery of the first luminous z ≥ 6 quasar from the Dark Energy Survey

    SciTech Connect

    Reed, S. L.; McMahon, R. G.; Banerji, M.; Becker, G. D.; Gonzalez-Solares, E.; Martini, P.; Ostrovski, F.; Rauch, M.; Abbott, T.; Abdalla, F. B.; Allam, S.; Benoit-Levy, A.; Bertin, E.; Buckley-Geer, E.; Burke, D.; Carnero Rosell, A.; da Costa, L. N.; D'Andrea, C.; DePoy, D. L.; Desai, S.; Diehl, H. T.; Doel, P.; Cunha, C. E.; Estrada, J.; Evrard, A. E.; Fausti Neto, A.; Finley, D. A.; Fosalba, P.; Frieman, J.; Gruen, D.; Honscheid, K.; James, D.; Kent, S.; Kuehn, K.; Kuropatkin, N.; Lahav, O.; Maia, M. A. G.; Makler, M.; Marshall, J.; Merritt, K.; Miquel, R.; Mohr, J.; Nord, B.; Ogando, R.; Plazas, A.; Romer, K.; Roodman, A.; Rykoff, E.; Sako, M.; Sanchez, E.; Santiago, B.; Schubnell, M.; Sevilla, I.; Smith, C.; Soares-Santos, M.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thomas, D.; Tucker, D.; Walker, A.; Wechsler, R. H.

    2015-10-28

    We present the first results of a survey for high-redshift, z ≥ 6, quasars using izY multicolour photometric observations from the Dark Energy Survey (DES). Here we report the discovery and spectroscopic confirmation of the zAB, YAB = 20.2, 20.2 (M1450 = -26.5) quasar DES J0454-4448 with a redshift of z = 6.09±0.02 based on the onset of the Ly α forest and an H I near zone size of 4.1+1.1-1.2 proper Mpc. The quasar was selected as an i-band drop out with i-z = 2.46 and zAB < 21.5 from an area of ~300 deg2. It is the brightest of our 43 candidates and was identified for spectroscopic follow-up solely based on the DES i-z and z-Y colours. The quasar is detected by WISE and has W1AB = 19.68. The discovery of one spectroscopically confirmed quasar with 5.7 < z < 6.5 and zAB ≤ 20.2 is consistent with recent determinations of the luminosity function at z ~ 6. DES when completed will have imaged ~5000 deg2 to YAB = 23.0 (5σ point source) and we expect to discover 50–100 new quasars with z > 6 including 3–10 with z > 7 dramatically increasing the numbers of quasars currently known that are suitable for detailed studies.

  16. Exploratory Chandra Observation of the Ultraluminous Quasar SDSS J010013.02+280225.8 at Redshift 6.30

    NASA Astrophysics Data System (ADS)

    Ai, Yanli; Dou, Liming; Fan, Xiaohui; Wang, Feige; Wu, Xue-Bing; Bian, Fuyan

    2016-06-01

    We report exploratory Chandra observations of the ultraluminous quasar SDSS J010013.02+280225.8 at redshift 6.30. The quasar is clearly detected by Chandra with a possible component of extended emission. The rest-frame 2–10 keV luminosity is {9.0}-4.5+9.1 × 1045 erg s‑1 with an inferred photon index of Γ = {3.03}-0.70+0.78. This quasar is X-ray bright, with an inferred X-ray-to-optical flux ratio {α }{ox} = -{1.22}-0.05+0.07, higher than the values found in other quasars of comparable ultraviolet luminosity. The properties inferred from this exploratory observation indicate that this ultraluminous quasar might be growing with super-Eddington accretion and probably viewed with a small inclination angle. Deep X-ray observations will help to probe the plausible extended emission and better constrain the spectral features for this ultraluminous quasar.

  17. Distributions of Quasar Hosts on the Galaxy Main Sequence Plane

    NASA Astrophysics Data System (ADS)

    Zhang, Zhoujian; Shi, Yong; Rieke, George H.; Xia, Xiaoyang; Wang, Yikang; Sun, Bingqing; Wan, Linfeng

    2016-03-01

    The relation between star formation rates (SFRs) and stellar masses, i.e., the galaxy main sequence, is a useful diagnostic of galaxy evolution. We present the distributions relative to the main sequence of 55 optically selected PG and 12 near-IR-selected Two Micron All Sky Survey (2MASS) quasars at z ≤ 0.5. We estimate the quasar host stellar masses from Hubble Space Telescope or ground-based AO photometry, and the SFRs through the mid-infrared aromatic features and far-IR photometry. We find that PG quasar hosts more or less follow the main sequence defined by normal star-forming galaxies while 2MASS quasar hosts lie systematically above the main sequence. PG and 2MASS quasars with higher nuclear luminosities seem to have higher specific SFRs (sSFRs), although there is a large scatter. No trends are seen between sSFRs and SMBH masses, Eddington ratios, or even morphology types (ellipticals, spirals, and mergers). Our results could be placed in an evolutionary scenario with quasars emerging during the transition from ULIRGs/mergers to ellipticals. However, combined with results at higher redshift, they suggest that quasars can be widely triggered in normal galaxies as long as they contain abundant gas and have ongoing star formation.

  18. A census of quasar-intrinsic absorption in the Hubble Space Telescope archive: systems from high-resolution echelle spectra

    NASA Astrophysics Data System (ADS)

    Ganguly, Rajib; Lynch, Ryan S.; Charlton, Jane C.; Eracleous, Michael; Tripp, Todd M.; Palma, Christopher; Sembach, Kenneth R.; Misawa, Toru; Masiero, Joseph R.; Milutinovic, Nikola; Lackey, Benjamin D.; Jones, Therese M.

    2013-10-01

    We present a census of zabs ≲ 2 intrinsic (those showing partial coverage) and associated (zabs ˜ zem) quasar absorption-line systems detected in the Hubble Space Telescope archive of Space Telescope Imaging Spectrograph echelle spectra. This work complements the Misawa et al. survey of 2 < zem < 4 quasars that selects systems using similar techniques. We confirm the existence of so-called strong N V intrinsic systems (where the equivalent width of H I Lyα is small compared to N V λ1238) presented in that work, but find no convincing cases of `strong C IV' intrinsic systems at low redshift/luminosity. Moreover, we also report on the existence of `strong O VI' systems. From a comparison of partial coverage results as a function of ion, we conclude that systems selected by the N V ion have the highest probability of being intrinsic. By contrast, the C IV and O VI ions are poor selectors. Of the 30 O VI systems tested, only two of the systems in the spectrum on 3C 351 show convincing evidence for partial coverage. However, there is an ˜3σ excess in the number of absorbers near the quasar redshift (|Δv| ≤ 5000 km s-1) over absorbers at large redshift differences. In at least two cases, the associated O VI systems are known not to arise close to the accretion disc of the quasar.

  19. A molecular line scan in the Hubble deep field north: Constraints on the co luminosity function and the cosmic H{sub 2} density

    SciTech Connect

    Walter, F.; Decarli, R.; Da Cunha, E.; Sargent, M.; Dickinson, M.; Daddi, E.; Riechers, D.; Ellis, R.; Stark, D.; Weiner, B.; Aravena, M.; Bell, E.; Bertoldi, F.; Cox, P.; Downes, D.; Neri, R.; Lentati, L.; Maiolino, R.; Menten, K. M.; and others

    2014-02-20

    We present direct constraints on the CO luminosity function at high redshift and the resulting cosmic evolution of the molecular gas density, ρ{sub H{sub 2}}(z), based on a blind molecular line scan in the Hubble Deep Field North (HDF-N) using the IRAM Plateau de Bure Interferometer. Our line scan of the entire 3 mm window (79-115 GHz) covers a cosmic volume of ∼7000 Mpc{sup 3}, and redshift ranges z < 0.45, 1.01 < z < 1.89 and z > 2. We use the rich multiwavelength and spectroscopic database of the HDF-N to derive some of the best constraints on CO luminosities in high redshift galaxies to date. We combine the blind CO detections in our molecular line scan (presented in a companion paper) with stacked CO limits from galaxies with available spectroscopic redshifts (slit or mask spectroscopy from Keck and grism spectroscopy from the Hubble Space Telescope) to give first blind constraints on high-z CO luminosity functions and the cosmic evolution of the H{sub 2} mass density ρ{sub H{sub 2}}(z) out to redshifts z ∼ 3. A comparison to empirical predictions of ρ{sub H{sub 2}}(z) shows that the securely detected sources in our molecular line scan already provide significant contributions to the predicted ρ{sub H{sub 2}}(z) in the redshift bins (z) ∼ 1.5 and (z) ∼ 2.7. Accounting for galaxies with CO luminosities that are not probed by our observations results in cosmic molecular gas densities ρ{sub H{sub 2}}(z) that are higher than current predictions. We note, however, that the current uncertainties (in particular the luminosity limits, number of detections, as well as cosmic volume probed) are significant, a situation that is about to change with the emerging ALMA observatory.

  20. Fifty Years of Quasars: Physical Insights and Potential for Cosmology

    NASA Astrophysics Data System (ADS)

    Sulentic, J. W.; Marziani, P.; Dultzin, D.; D'Onofrio, M.; del Olmo, A.

    2014-12-01

    Last year (2013) was more or less the 50th anniversary of the discovery of quasars. It is an interesting time to review what we know (and don't know) about them both empirically and theoretically. These compact sources involving line emitting plasma show extraordinary luminosities extending to one thousand times that of our Milky Way in emitting volumes of a few solar system diameters (log Lboi= 44.0 - 48.0 erg s-1: D=1-3 light months ~ 103 - 104 gravitational radii). The advent of 8-10 meter class telescopes enables us to study them spectroscopically in ever greater detail. In 2000 we introduced a 4D Eigenvector 1 parameters space involving optical, UV and X- ray measures designed to serve as a 4D equivalent of the 2D H-R diagram so important for depicting the diversity of stellar types and evolutionary states. This diagram has revealed a principal sequence of quasars distinguished by Eddington ratio (proportional to the accretion rate per unit mass). Thus while stellar differences are primarily driven by the mass of a star, quasar differences are apparently driven by the ratio of luminosity-to-mass. Out of this work has emerged the concept of two quasars populations A and B separated at Eddington ratio around 0.2 which maximizes quasar multispectral differences. The mysterious 8% of quasars that are radio-loud belong to population B which are the lowest accretors with the largest black hole masses. Finally we consider the most extreme population A quasars which are the highest accretors and in some cases are among the youngest quasars. We describe how these sources might be exploited as standard candles for cosmology.

  1. THE BRIGHTEST OF REIONIZING GALAXIES SURVEY: CONSTRAINTS ON THE BRIGHT END OF THE z {approx} 8 LUMINOSITY FUNCTION

    SciTech Connect

    Bradley, L. D.; Stiavelli, M.; Pirzkal, N.; Trenti, M.; Oesch, P. A.; Bouwens, R. J.; Shull, J. M.; Holwerda, B. W.

    2012-12-01

    We report the discovery of 33 Lyman-break galaxy candidates at z {approx} 8 detected in Hubble Space Telescope Wide Field Camera 3 (WFC3) imaging as part of the Brightest of Reionizing Galaxies (BoRG) pure-parallel survey. The ongoing BoRG survey currently has the largest area (274 arcmin{sup 2}) with Y {sub 098} (or Y {sub 105}), J {sub 125}, and H {sub 160} band coverage needed to search for z {approx} 8 galaxies, about three times the current CANDELS area, and slightly larger than what will be the final CANDELS wide component with Y {sub 105} data (required to select z {approx} 8 sources). Our sample of 33 relatively bright Y {sub 098}-dropout galaxies have J {sub 125}-band magnitudes between 25.5 and 27.4 mag. This is the largest sample of bright (J {sub 125} {approx}< 27.4) z {approx} 8 galaxy candidates presented to date. Combining our data set with the Hubble Ultra-Deep Field data set, we constrain the rest-frame ultraviolet galaxy luminosity function at z {approx} 8 over the widest dynamic range currently available. The combined data sets are well fitted by a Schechter function, i.e., {phi} (L) = {phi}{sub *} (L/L{sub *}){sup {alpha}} e{sup -(}L{sup /L{sub *})}, without evidence for an excess of sources at the bright end. At 68% confidence, for h = 0.7 we derive {phi}{sub *} = (4.3{sup +3.5} {sub -2.1}) Multiplication-Sign 10{sup -4} Mpc{sup -3}, M {sub *} = -20.26{sup +0.29} {sub -0.34}, and a very steep faint-end slope {alpha} = -1.98{sup +0.23} {sub -0.22}. While the best-fit parameters still have a strong degeneracy, especially between {phi}{sub *} and M {sub *}, our improved coverage at the bright end has reduced the uncertainty of the faint-end power-law slope at z {approx} 8 compared to the best previous determination at {+-}0.4. With a future expansion of the BoRG survey, combined with planned ultradeep WFC3/IR observations, it will be possible to further reduce this uncertainty and clearly demonstrate the steepening of the faint-end slope compared

  2. The Luminosity Function and Star Formation Rate Between Redshifts of 0.07 and 1.47 for Narrow-band Emitters in the Subaru Deep Field

    NASA Astrophysics Data System (ADS)

    Ly, Chun; Malkan, M.; Kashikawa, N.; Shimasaku, K.; Doi, M.; Nagao, T.; Iye, M.; Kodama, T.; Morokuma, T.; Motohara, K.

    2006-06-01

    Subaru Deep Field line-emitting galaxies in four narrow-band filters at low and intermediate redshifts are presented. Broad-band colors, follow-up optical spectroscopy, and multiple narrow-band filters are used to distinguish Hα, [OII], and [OIII] emitters between redshifts of 0.07 and 1.47 to construct their averaged rest-frame optical-to-UV SED and luminosity functions. These luminosity functions are derived down to faint magnitudes, which allows for a more accurate determination of the faint end slope. With a large (N 200-900) sample for each redshift interval, a Schechter profile is fitted to each luminosity function. Prior to dust extinction corrections, the [OIII] and [OII] luminosity functions reported in this paper agree reasonably well with those of Hippelein et al (2003). The z=0.066-0.092 Hα LF agrees with those of Jones & Bland-Hawthorn (2001), but for z=0.24 and 0.40, their number density is higher by a factor of two or more. The z=0.08 Hα LF, which reaches two orders of magnitude fainter than Gallego et al. (1995), is steeper by 25%. This indicates that there are more low luminosity star-forming galaxies for z<0.1 than predicted. The faint end slope α and φ* show a strong evolution with redshift while L* show little evolution. The evolution in α indicates that low-luminosity galaxies have a stronger evolution compared to brighter ones. Integrated star formation rate densities are derived via Hα for 0.07function of redshift, is seen for 0.4

  3. Hubble Space Telescope Imaging of Post-starburst Quasars

    NASA Astrophysics Data System (ADS)

    Cales, S. L.; Brotherton, M. S.; Shang, Zhaohui; Bennert, Vardha Nicola; Canalizo, G.; Stoll, R.; Ganguly, R.; Vanden Berk, D.; Paul, C.; Diamond-Stanic, A.

    2011-11-01

    We present images of 29 post-starburst quasars (PSQs) from a Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) Wide Field Channel Snapshot program. These broadlined active galactic nuclei (AGNs) possess the spectral signatures of massive (M burst ~ 1010 M sun), moderate-aged stellar populations (hundreds of Myr). Thus, their composite nature provides insight into the AGN-starburst connection. We measure quasar-to-host galaxy light contributions via semi-automated two-dimensional light profile fits of point-spread-function-subtracted images. We examine the host morphologies and model the separate bulge and disk components. The HST/ACS-F606W images reveal an equal number of spiral (13/29) and early-type (13/29) hosts, with the remaining three hosts having indeterminate classifications. AGNs hosted by early-type galaxies have on average greater luminosity than those hosted by spiral galaxies. Disturbances such as tidal tails, shells, star-forming knots, and asymmetries are seen as signposts of interaction/merger activity. Disturbances like these were found in 17 of the 29 objects and are evenly distributed among early-type and spiral galaxies. Two of these systems are clearly merging with their companions. Compared to other AGNs of similar luminosity and redshift, these PSQs have a higher fraction of early-type hosts and disturbances. Our most luminous objects with disturbed early-type host galaxies appear to be consistent with merger products. Thus, these luminous galaxies may represent a phase in an evolutionary scenario for merger-driven activity. Our less luminous objects appear to be consistent with Seyfert galaxies not requiring triggering by major mergers. Many of these Seyferts are barred spiral galaxies.

  4. HUBBLE SPACE TELESCOPE IMAGING OF POST-STARBURST QUASARS

    SciTech Connect

    Cales, S. L.; Brotherton, M. S.; Shang Zhaohui; Bennert, Vardha Nicola; Canalizo, G.; Stoll, R.; Ganguly, R.; Vanden Berk, D.; Paul, C.; Diamond-Stanic, A. E-mail: mbrother@uwyo.edu E-mail: bennert@physics.ucsb.edu E-mail: stoll@astronomy.ohio-state.edu E-mail: daniel.vandenberk@email.stvincent.edu E-mail: aleks@ucsd.edu

    2011-11-10

    We present images of 29 post-starburst quasars (PSQs) from a Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) Wide Field Channel Snapshot program. These broadlined active galactic nuclei (AGNs) possess the spectral signatures of massive (M{sub burst} {approx} 10{sup 10} M{sub sun}), moderate-aged stellar populations (hundreds of Myr). Thus, their composite nature provides insight into the AGN-starburst connection. We measure quasar-to-host galaxy light contributions via semi-automated two-dimensional light profile fits of point-spread-function-subtracted images. We examine the host morphologies and model the separate bulge and disk components. The HST/ACS-F606W images reveal an equal number of spiral (13/29) and early-type (13/29) hosts, with the remaining three hosts having indeterminate classifications. AGNs hosted by early-type galaxies have on average greater luminosity than those hosted by spiral galaxies. Disturbances such as tidal tails, shells, star-forming knots, and asymmetries are seen as signposts of interaction/merger activity. Disturbances like these were found in 17 of the 29 objects and are evenly distributed among early-type and spiral galaxies. Two of these systems are clearly merging with their companions. Compared to other AGNs of similar luminosity and redshift, these PSQs have a higher fraction of early-type hosts and disturbances. Our most luminous objects with disturbed early-type host galaxies appear to be consistent with merger products. Thus, these luminous galaxies may represent a phase in an evolutionary scenario for merger-driven activity. Our less luminous objects appear to be consistent with Seyfert galaxies not requiring triggering by major mergers. Many of these Seyferts are barred spiral galaxies.

  5. The Pan-STARRS1 z>6 quasar survey: More than 100 quasars within the first Gyr of the universe

    NASA Astrophysics Data System (ADS)

    Walter, Fabian; Banados, Eduardo; Venemans, Bram; Decarli, Roberto; Farina, Emanuele; Mazzucchelli, Chiara; Fan, Xiaohui; Chambers, Kenneth C.

    2016-01-01

    Quasars are the most luminous non-transient sources in the Universe. As such, they are ideal probes of the redshift range z=6-7, a critical phase in cosmic history, when the Universe is emerging from the dark ages. Over the last three years we have exploited the Pan-STARRS1 survey, more than doubling the number of known z>5.5 quasars (tripling the number of z>6 quasars in the southern sky, and discovering 4 of the 9 quasars known at z>6.5). This seach significantly extended the sampled parameter space in terms of quasar luminosities and redshift coverage. Pioneering studies already demostrate the intrumental role of QSOs in probing the very early phases of galaxy formation and black hole growth within 1 Gyr from the Big Bang: a) billion solar masses black holes are already in place, b) they are surrounded by massive reservoirs of cold gas, and c) the neutral fraction of the intergalactic medium rapidly drops after z~6, thus marking the end of the epoch of reionization. Our significantly enlarged sample marks the transition phase from studies of individual sources to statistical studies of the high-z quasar population. We present some of the comprehensive multiwavelength characterization of the high-z quasar population and their environment (our on-going efforts include deep NIR spectroscopy, ALMA, NOEMA, HST, Spitzer, and JVLA observations).

  6. A Long-Term Space Astrophysics Research Program. The Evolution of the Quasar Continuum

    NASA Technical Reports Server (NTRS)

    Elvis, M.

    1998-01-01

    The grant "The Evolution of the Quasar Continuum" resulted in over 53 published referred papers and conference proceedings. The more significant of these papers are listed below, and abstracts are attached. The papers address a wide range of issues involving the evolution of quasars, their electromagnetic emissions, and their environment, from nearby low luminosity Seyfert galaxies to quasars at the highest redshifts. Primarily observational in content the work nonetheless included theoretical studies of quasar accretion disks that attempt to explain the observed time variability of quasars, and the overall 'demographics' of the quasar population. The work carried out under this grant has laid a strong foundation for ongoing and future research with AXAF, HST and other new facilities.

  7. THE RADIO PROPERTIES OF TYPE 2 QUASARS

    SciTech Connect

    Lal, Dharam Vir; Ho, Luis C.

    2010-03-15

    This paper presents the first high-resolution and high-sensitivity study of the radio properties of optically selected type 2 quasars. We used the Very Large Array at 8.4 GHz to observe 59 sources drawn from the Sloan Digital Sky Survey sample of Zakamska et al.. The detection rate of our survey is 59% (35/59), comparable to the detection rate in FIRST at 1.4 GHz. Ongoing star formation, although present, contributes negligible radio emission at the current sensitivity limit. Comparing the radio powers with the [O III] {lambda}5007 luminosities, we find that roughly 15% {+-} 5% of the sample can be considered radio loud. Intriguingly, the vast majority of the detected sources in our sample fall in a region intermediate between those traditionally occupied by radio loud and radio quiet quasars. Moreover, most of these 'radio intermediate' sources tend to have flat or inverted radio spectra, which we speculate may be caused by free-free absorption by ionized gas in the narrow-line region. The incidence of flat-spectrum sources in type 2 quasars appears to be much higher than in type 1 quasars, in apparent violation of the simple orientation-based unified model for active galaxies.

  8. The luminosity function of star clusters in 20 star-forming galaxies based on Hubble legacy archive photometry

    SciTech Connect

    Whitmore, Bradley C.; Bowers, Ariel S.; Lindsay, Kevin; Ansari, Asna; Evans, Jessica; Chandar, Rupali; Larsen, Soeren

    2014-04-01

    Luminosity functions (LFs) have been determined for star cluster populations in 20 nearby (4-30 Mpc), star-forming galaxies based on Advanced Camera for Surveys source lists generated by the Hubble Legacy Archive (HLA). These cluster catalogs provide one of the largest sets of uniform, automatically generated cluster candidates available in the literature at present. Comparisons are made with other recently generated cluster catalogs demonstrating that the HLA-generated catalogs are of similar quality, but in general do not go as deep. A typical cluster LF can be approximated by a power law, dN/dL∝L {sup α}, with an average value for α of –2.37 and rms scatter = 0.18 when using the F814W ('I') band. A comparison of fitting results based on methods that use binned and unbinned data shows good agreement, although there may be a systematic tendency for the unbinned (maximum likelihood) method to give slightly more negative values of α for galaxies with steeper LFs. We find that galaxies with high rates of star formation (or equivalently, with the brightest or largest numbers of clusters) have a slight tendency to have shallower values of α. In particular, the Antennae galaxy (NGC 4038/39), a merging system with a relatively high star formation rate (SFR), has the second flattest LF in the sample. A tentative correlation may also be present between Hubble type and values of α, in the sense that later type galaxies (i.e., Sd and Sm) appear to have flatter LFs. Hence, while there do appear to be some weak correlations, the relative similarity in the values of α for a large number of star-forming galaxies suggests that, to first order, the LFs are fairly universal. We examine the bright end of the LFs and find evidence for a downturn, although it only pertains to about 1% of the clusters. Our uniform database results in a small scatter (≈0.4 to 0.5 mag) in the correlation between the magnitude of the brightest cluster (M {sub brightest}) and log of the number

  9. X-RAY ABSORPTION OF HIGH-REDSHIFT QUASARS

    SciTech Connect

    Eitan, Assaf; Behar, Ehud E-mail: behar@physics.technion.ac.il

    2013-09-01

    The soft X-ray photoelectric absorption of high-z quasars has been known for two decades, but has no unambiguous astrophysical context. We construct the largest sample to date of 58 high-redshift quasars (z > 0.45) selected from the XMM-Newton archive based on a high photon count criterion (>1800). We measure the optical depth {tau} at 0.5 keV and find that 43% of the quasars show significant absorption. We aim to find which physical parameters of the quasars, e.g., redshift, radio luminosity, radio loudness, or X-ray luminosity, drive their observed absorption. We compare the absorption behavior with redshift with the pattern expected if the diffuse intergalactic medium (IGM) is responsible for the observed absorption. We also compare the absorption with a comparison sample of gamma-ray burst (GRB) X-ray afterglows. Although the z > 2 quasar opacity is consistent with diffuse IGM absorption, many intermediate-z (0.45 < z < 2) quasars are not sufficiently absorbed for this scenario, and are appreciably less absorbed than GRBs. Only 10/37 quasars at z < 2 are absorbed, and only 5/30 radio-quiet quasars are absorbed. We find a weak correlation between {tau} and z, and an even weaker correlation between {tau} and radio luminosity. These findings lead to the conclusion that although a diffuse IGM origin for the quasar absorption is unlikely, the optical depth does seem to increase with redshift, roughly as (1 + z){sup 2.2{+-}0.6}, tending to {tau} Almost-Equal-To 0.4 at high redshifts, similar to the high-z GRBs. This result can be explained by an ionized and clumpy IGM at z < 2, and a cold, diffuse IGM at higher redshift. If, conversely, the absorption occurs at the quasar, and owing to the steep L{sub x} {proportional_to}(1 + z){sup 7.1{+-}0.5} correlation in the present sample, the host column density scales as N{sub H}{proportional_to}L{sub x}{sup 0.7{+-}0.1}.

  10. Characterizing Quasar Outflows I: Sample, Spectral Measurements

    NASA Astrophysics Data System (ADS)

    Ganguly, Rajib; Christenson, D. H.; Richmond, J. M.; Derseweh, J. A.; Robbins, J. M.; Townsend, S. L.; Stark, M. A.

    2012-05-01

    Galaxy evolution models have shown that quasars are a crucial ingredient in the evolution of massive galaxies. Outflows play a key role in the story of quasars and their host galaxies, by helping regulate the accretion process, the star-formation rate and mass of the host galaxy (i.e., feedback). The prescription for modeling outflows as a contributor to feedback requires knowledge of the outflow velocity, geometry, and column density. In particular, we need to understand how these depend on physical parameters and how much is determined stochastically (and with what distribution). For this purpose, we are examining a sample of 11000 z=1.7-2.0 quasars from the Sloan Digital Sky Survey. This redshift range permits the following from the SDSS spectra: (1) separation of objects that do and do not exhibit outflows; (2) classification/measurement of outflow properties (ionization, velocity, velocity width); and (3) measurements of UV emission line and continuum parameters. In this poster, we subjectively divide these quasars into four categories: broad absorption-line quasars (2700 objects), associated absorption-line quasars (1700 objects), reddened quasars (160 objects), and unabsorbed/unreddened quasars (6300 objects). We present measurements of the absorption (velocities, velocity widths, equivalent widths), composite spectral profiles of outflows as a function of velocity, as well as measurements of the continuum and CIV, MgII, and FeII emission-line properties. In accompanying posters, we add photometry from the rest-frame X-ray (ROSAT and Chandra), EUV (GALEX), optical (2MASS), and infrared (WISE) bands to complete the SED. The continuum and emission-line measurements from the SDSS spectra and accompanying photometry provides estimates on the black hole masses, bolometric luminsosities, and SED. We consider empirically how these affect the outflow properties. This material is based upon work supported by the National Aeronautics and Space Administration under

  11. A Markov Chain Monte Carlo Software Package to Constrain the Evolution of Luminosity Functions, Test SED Models, and Simulate Future Surveys

    NASA Astrophysics Data System (ADS)

    Kurinsky, Noah; Sajina, Anna

    2014-06-01

    We present a novel simulation and fitting program which employs MCMC to constrain the spectral energy distribution makeup and luminosity function evolution required to produce a given mutli-wavelength survey. This tool employs a multidimensional color-color diagnostic to determine goodness of fit, and simulates observational sources of error such as flux-limits and instrumental noise. Our goals in designing this tool were to a) use it to study Infrared surveys and test SED template models, and b) create it in such a way as to make it usable in any electromagnetic regime for any class of sources to which any luminosity functional form can be prescribed.I will discuss our specific use of the program to characterize a survey from the Herschel SPIRE HerMES catalog, including implications for our luminosity function and SED models. I will also briefly discuss the ways we envision using it for simulation and application to other surveys, and I will demonstrate the degree to which its reusability can serve to enrich a wide range of analyses.

  12. UV Luminosity Functions at Redshifts z ˜ 4 to z ˜ 10: 10,000 Galaxies from HST Legacy Fields

    NASA Astrophysics Data System (ADS)

    Bouwens, R. J.; Illingworth, G. D.; Oesch, P. A.; Trenti, M.; Labbé, I.; Bradley, L.; Carollo, M.; van Dokkum, P. G.; Gonzalez, V.; Holwerda, B.; Franx, M.; Spitler, L.; Smit, R.; Magee, D.

    2015-04-01

    The remarkable Hubble Space Telescope (HST) data sets from the CANDELS, HUDF09, HUDF12, ERS, and BoRG/HIPPIES programs have allowed us to map the evolution of the rest-frame UV luminosity function (LF) from z˜ 10 to z˜ 4. We develop new color criteria that more optimally utilize the full wavelength coverage from the optical, near-IR, and mid-IR observations over our search fields, while simultaneously minimizing the incompleteness and eliminating redshift gaps. We have identified 5859, 3001, 857, 481, 217, and 6 galaxy candidates at z˜ 4, z˜ 5, z˜ 6, z˜ 7, z˜ 8, and z˜ 10, respectively, from the ˜1000 arcmin2 area covered by these data sets. This sample of >10,000 galaxy candidates at z≥slant 4 is by far the largest assembled to date with HST. The selection of z ˜ 4-8 candidates over the five CANDELS fields allows us to assess the cosmic variance; the largest variations are at z≥slant 7. Our new LF determinations at z˜ 4 and z˜ 5 span a 6 mag baseline and reach to -16 AB mag. These determinations agree well with previous estimates, but the larger samples and volumes probed here result in a more reliable sampling of \\gt {{L}*} galaxies and allow us to reassess the form of the UV LFs. Our new LF results strengthen our earlier findings to 3.4σ significance for a steeper faint-end slope of the UV LF at z\\gt 4, with α evolving from α =-1.64+/- 0.04 at z˜ 4 to α =-2.06+/- 0.13 at z˜ 7 (and α =-2.02+/- 0.23 at z˜ 8), consistent with that expected from the evolution of the halo mass function. We find less evolution in the characteristic magnitude M* from z˜ 7 to z˜ 4; the observed evolution in the LF is now largely represented by changes in {{φ }*}. No evidence for a non-Schechter-like form to the z ˜ 4-8 LFs is found. A simple conditional LF model based on halo growth and evolution in the M/L ratio (\\propto {{(1+z)}-1.5}) of halos provides a good representation of the observed evolution. Based on observations obtained with Mega

  13. Low-redshift quasars in the SDSS Stripe 82. The local environments

    NASA Astrophysics Data System (ADS)

    Karhunen, K.; Kotilainen, J. K.; Falomo, R.; Bettoni, D.

    2014-06-01

    We study the environments of low-redshift (z < 0.5) quasars based on a large and homogeneous data set from the Stripe 82 region of the Sloan Digital Sky Survey (SDSS). We have compared the <1 Mpc scale environments of 302 quasars that were resolved in our recent study to those of 288 inactive galaxies with closely matched redshifts. Crucially, the luminosities of the inactive galaxies and the quasar host galaxies are also closely matched, unlike in most previous studies. The environmental overdensities were studied by measuring the number density of galaxies within a projected distance of 200 kpc to 1 Mpc. The galaxy number density of the quasar environments is comparable to that of the inactive galaxies with similar luminosities, both classes of objects showing significant excess compared to the background galaxy density for distances <400 kpc. There is no significant dependence of the galaxy number density on redshift, quasar or host galaxy luminosity, black hole mass or radio loudness. This suggests that the fuelling and triggering of the nuclear activity is only weakly dependent on the local environment of quasars, and the quasar phase may be a short-lived common phase in the life cycle of all massive galaxies.

  14. The Next Generation Virgo Cluster Survey (NGVS). XIII. The Luminosity and Mass Function of Galaxies in the Core of the Virgo Cluster and the Contribution from Disrupted Satellites

    NASA Astrophysics Data System (ADS)

    Ferrarese, Laura; Côté, Patrick; Sánchez-Janssen, Rúben; Roediger, Joel; McConnachie, Alan W.; Durrell, Patrick R.; MacArthur, Lauren A.; Blakeslee, John P.; Duc, Pierre-Alain; Boissier, S.; Boselli, Alessandro; Courteau, Stéphane; Cuillandre, Jean-Charles; Emsellem, Eric; Gwyn, S. D. J.; Guhathakurta, Puragra; Jordán, Andrés; Lançon, Ariane; Liu, Chengze; Mei, Simona; Mihos, J. Christopher; Navarro, Julio F.; Peng, Eric W.; Puzia, Thomas H.; Taylor, James E.; Toloba, Elisa; Zhang, Hongxin

    2016-06-01

    We present measurements of the galaxy luminosity and stellar mass function in a 3.71 deg2 (0.3 Mpc2) area in the core of the Virgo Cluster, based on {u}\\ast griz data from the Next Generation Virgo Cluster Survey (NGVS). The galaxy sample—which consists of 352 objects brighter than M g = ‑9.13 mag, the 50% completeness limit of the survey—reaches 2.2 mag deeper than the widely used Virgo Cluster Catalog and at least 1.2 mag deeper than any sample previously used to measure the luminosity function in Virgo. Using a Bayesian analysis, we find a best-fit faint-end slope of α = ‑1.33 ± 0.02 for the g-band luminosity function; consistent results are found for the stellar mass function and the luminosity function in the other four NGVS bandpasses. We discuss the implications for the faint-end slope of adding 92 ultracompact dwarfs (UCDs)—previously compiled by the NGVS in this region—to the galaxy sample, assuming that UCDs are the stripped remnants of nucleated dwarf galaxies. Under this assumption, the slope of the luminosity function (down to the UCD faint magnitude limit, M g = ‑9.6 mag) increases dramatically, up to α = ‑1.60 ± 0.06 when correcting for the expected number of disrupted non-nucleated galaxies. We also calculate the total number of UCDs and globular clusters that may have been deposited in the core of Virgo owing to the disruption of satellites, both nucleated and non-nucleated. We estimate that ˜150 objects with M g ≲ ‑9.6 mag and that are currently classified as globular clusters might, in fact, be the nuclei of disrupted galaxies. We further estimate that as many as 40% of the (mostly blue) globular clusters in the Virgo core might once have belonged to such satellites; these same disrupted satellites might have contributed ˜40% of the total luminosity in galaxies observed in the core region today. Finally, we use an updated Local Group galaxy catalog to provide a new measurement of the luminosity function of Local Group

  15. The Next Generation Virgo Cluster Survey (NGVS). XIII. The Luminosity and Mass Function of Galaxies in the Core of the Virgo Cluster and the Contribution from Disrupted Satellites

    NASA Astrophysics Data System (ADS)

    Ferrarese, Laura; Côté, Patrick; Sánchez-Janssen, Rúben; Roediger, Joel; McConnachie, Alan W.; Durrell, Patrick R.; MacArthur, Lauren A.; Blakeslee, John P.; Duc, Pierre-Alain; Boissier, S.; Boselli, Alessandro; Courteau, Stéphane; Cuillandre, Jean-Charles; Emsellem, Eric; Gwyn, S. D. J.; Guhathakurta, Puragra; Jordán, Andrés; Lançon, Ariane; Liu, Chengze; Mei, Simona; Mihos, J. Christopher; Navarro, Julio F.; Peng, Eric W.; Puzia, Thomas H.; Taylor, James E.; Toloba, Elisa; Zhang, Hongxin

    2016-06-01

    We present measurements of the galaxy luminosity and stellar mass function in a 3.71 deg2 (0.3 Mpc2) area in the core of the Virgo Cluster, based on {u}\\ast griz data from the Next Generation Virgo Cluster Survey (NGVS). The galaxy sample—which consists of 352 objects brighter than M g = -9.13 mag, the 50% completeness limit of the survey—reaches 2.2 mag deeper than the widely used Virgo Cluster Catalog and at least 1.2 mag deeper than any sample previously used to measure the luminosity function in Virgo. Using a Bayesian analysis, we find a best-fit faint-end slope of α = -1.33 ± 0.02 for the g-band luminosity function; consistent results are found for the stellar mass function and the luminosity function in the other four NGVS bandpasses. We discuss the implications for the faint-end slope of adding 92 ultracompact dwarfs (UCDs)—previously compiled by the NGVS in this region—to the galaxy sample, assuming that UCDs are the stripped remnants of nucleated dwarf galaxies. Under this assumption, the slope of the luminosity function (down to the UCD faint magnitude limit, M g = -9.6 mag) increases dramatically, up to α = -1.60 ± 0.06 when correcting for the expected number of disrupted non-nucleated galaxies. We also calculate the total number of UCDs and globular clusters that may have been deposited in the core of Virgo owing to the disruption of satellites, both nucleated and non-nucleated. We estimate that ˜150 objects with M g ≲ -9.6 mag and that are currently classified as globular clusters might, in fact, be the nuclei of disrupted galaxies. We further estimate that as many as 40% of the (mostly blue) globular clusters in the Virgo core might once have belonged to such satellites; these same disrupted satellites might have contributed ˜40% of the total luminosity in galaxies observed in the core region today. Finally, we use an updated Local Group galaxy catalog to provide a new measurement of the luminosity function of Local Group satellites

  16. A Survey of z>5.8 Quasars in the Sloan Digital Sky Survey. I. Discovery of Three New Quasars and the Spatial Density of Luminous Quasars at z~6

    NASA Astrophysics Data System (ADS)

    Fan, Xiaohui; Narayanan, Vijay K.; Lupton, Robert H.; Strauss, Michael A.; Knapp, Gillian R.; Becker, Robert H.; White, Richard L.; Pentericci, Laura; Leggett, S. K.; Haiman, Zoltán; Gunn, James E.; Ivezić, Željko; Schneider, Donald P.; Anderson, Scott F.; Brinkmann, J.; Bahcall, Neta A.; Connolly, Andrew J.; Csabai, István; Doi, Mamoru; Fukugita, Masataka; Geballe, Tom; Grebel, Eva K.; Harbeck, Daniel; Hennessy, Gregory; Lamb, Don Q.; Miknaitis, Gajus; Munn, Jeffrey A.; Nichol, Robert; Okamura, Sadanori; Pier, Jeffrey R.; Prada, Francisco; Richards, Gordon T.; Szalay, Alex; York, Donald G.

    2001-12-01

    We present the results from a survey of i-dropout objects selected from ~1550 deg2 of multicolor imaging data from the Sloan Digital Sky Survey to search for luminous quasars at z>~5.8. Objects with i*-z*>2.2 and z*<20.2 are selected, and follow-up J-band photometry is used to separate L- and T-type cool dwarfs from high-redshift quasars. We describe the discovery of three new quasars, SDSSp J083643.85+005453.3 (z=5.82), J130608.26+035626.3 (z=5.99), and J103027.10+052455.0 (z=6.28). The quasar SDSSp J083643.85+005453.3 is a radio source with flux of 1.1 mJy at 20 cm. The spectra of all three quasars show strong and broad Lyα+N V emission lines and very strong Lyα forest absorption, with a mean continuum decrement DA>0.90. The ARC 3.5 m spectrum of SDSSp J103027.10+052455.0 shows that over a range of ~300 Å immediately blueward of the Lyα emission, the average transmitted flux is only 0.003+/-0.020 times that of the continuum level, consistent with zero flux over a ~300 Å range of the Lyα forest region and suggesting a tentative detection of the complete Gunn-Peterson trough. The existence of strong metal lines in the quasar spectra suggests early metal enrichment in the quasar environment. The three new objects, together with the previously published z=5.8 quasar SDSSp J104433.04-012502.2, form a complete color-selected flux-limited sample at z>~5.8. We estimate the selection function of this sample, taking into account the estimated variations in the quasar spectral energy distribution, as well as observational photometric errors. We find that at z=6, the comoving density of luminous quasars at M1450<-26.8 (H0=50 km s-1 Mpc-1, Ω=1) is 1.1×10-9 Mpc-3. This is a factor of ~2 lower than that at z~5 and is consistent with an extrapolation of the observed quasar evolution at z<5. Using the current sample, we discuss the constraint on the shape of the quasar luminosity function and the implications for the contribution of quasars to the ionizing background at z

  17. Discovery of low-redshift X-ray selected quasars - New clues to the QSO phenomenon

    NASA Technical Reports Server (NTRS)

    Grindlay, J. E.; Forman, W. R.; Steiner, J. E.; Canizares, C. R.; Mcclintock, J. E.

    1980-01-01

    The identification of six X-ray sources discovered by the Einstein Observatory with X-ray quasars is reported, and the properties of these X-ray selected quasars are discussed. The four high-latitude fields of 1 sq deg each in which the Einstein imaging proportional counter detected serendipitous X-ray sources at intermediate exposures of 10,000 sec were observed by 4-m and 1.5-m telescopes, and optical sources with uv excesses and emission line spectra typical of many low-redshift quasars and Seyfert 1 galaxies were found within the 1-arcsec error boxes of the X-ray sources. All six quasars identified were found to be radio quiet, with low redshift and relatively faint optical magnitudes, and to be similar in space density, colors and magnitude versus redshift relation to an optically selected sample at the same mean magnitude. X-ray luminosity was found to be well correlated with both continuum and broad-line emission luminosities for the known radio-quiet quasars and Seyfert 1 galaxies, and it was observed that the five objects with the lowest redshifts have very similar X-ray/optical luminosity ratios despite tenfold variations in X-ray luminosity. It is concluded that photoionization by a continuum extending to X-ray energies is the dominant excitation mechanism in radio-quiet quasars.

  18. Quasar Dust Factories.

    NASA Astrophysics Data System (ADS)

    Marengo, Massimo; Elvis, Martin; Karovska, Margarita

    We show that quasars are naturally copious producers of dust, assuming only that the quasar broad emission lines (BELs) are produced by gas clouds that are part of an outflowing wind. These BEL clouds have large initial densities (ne ˜109 - 1011 cm-3) so that as they expand quasi-adiabatically they cool from an initial T = 104 K to a dust-capable T = 103 K, and reduce their pressures from ˜0.1 dyn cm-2 to ˜ 10-3 -10-5 dyn cm-2.. This places the expanded BEL clouds in the (T,P) dust forming regime of late-type giants extended atmospheres, both static and pulsing. The result applies whether the clouds have C/O abundance ratio greater or lower than 1. Photo-destruction of the grains by the quasar UV/X-ray continuum is not important, as the BEL clouds reach these conditions several parsecs from the quasar nucleus, well below the dust evaporation temperature. This result offers a new insight for the strong link between quasars and dust, and for the heavy obscuration around many quasars. It also introduces a new means of forming dust at early cosmological times, and a direct mechanism for the injection of such dust in the intergalactic medium. Since dust at high z is found only by observing quasars, our result allows far less dust to be present at early epochs, since dust only need be present where a quasar is, rather than the quasar illuminating pre-existing dust which would then need to be present in all galaxies at high z. See astro-ph/0202002 or ApJ 576, L107 (2002).

  19. How Similar are the Properties of Quasars with Nearly Identical Ultraviolet Spectra?

    NASA Astrophysics Data System (ADS)

    Rochais, Thomas; Singh, Vikram; Chick, William; Maithil, Jaya; Sutter, Jessica; Brotherton, Michael S.; Shang, Zhaohui

    2016-09-01

    The spectrum of a quasar contains important information about its properties. Thus, it can be expected that two quasars with similar spectra will have similar properties, but just how similar has not before been quantified. Here we compare the ultraviolet spectra of a sample of 5553 quasars from Data Release 7 of the Sloan Digital Sky Survey, focusing on the 1350 Å ≤λ ≤ 2900 Å rest-frame region which contains prominent emission lines from Si IV, O IV], C IV, C III], and Mg II species. We use principal component analysis to determine the dominant components of spectral variation, as well as to quantitatively measure spectral similarity. As suggested by both the Baldwin effect and modified Baldwin effect, quasars with similar spectra have similar properties: bolometric luminosity, Eddington fraction, and black hole mass. The latter two quantities are calculated from the luminosity in conjunction with spectral features, and the variation between quasars with virtually identical spectra (which we call doppelgangers) is driven by the variance in the luminosity plus measurement uncertainties. In the doppelgangers the luminosity differences show 1σ uncertainties of 57% (or 0.63 magnitudes) and ˜70% 1σ uncertainties for mass and Eddington fraction. Much of the difference in luminosities may be attributable to time lags between the spectral lines and the continuum. Furthermore, we find that suggestions that the mostly highly accreting quasars should be better standard candles than other quasars are not bourne out for doppelgangers. Finally, we discuss the implications for using quasars as cosmological probes and the nature of the first two spectral principal components.

  20. Quasars as a Tracer of Large-scale Structures in the Distant Universe

    NASA Astrophysics Data System (ADS)

    Song, Hyunmi; Park, Changbom; Lietzen, Heidi; Einasto, Maret

    2016-08-01

    We study the dependence of the number density and properties of quasars on the background galaxy density using the currently largest spectroscopic data sets of quasars and galaxies. We construct a galaxy number density field smoothed over the variable smoothing scale of between approximately 10 and 20 h -1 Mpc over the redshift range 0.46 < z < 0.59 using the Sloan Digital Sky Survey (SDSS) Data Release 12 (DR12) Constant MASS galaxies. The quasar sample is prepared from the SDSS-I/II DR7. We examine the correlation of incidence of quasars with the large-scale background density and the dependence of quasar properties such as bolometric luminosity, black hole mass, and Eddington ratio on the large-scale density. We find a monotonic correlation between the quasar number density and large-scale galaxy number density, which is fitted well with a power-law relation, {n}Q\\propto {ρ }G0.618. We detect weak dependences of quasar properties on the large-scale density such as a positive correlation between black hole mass and density, and a negative correlation between luminosity and density. We discuss the possibility of using quasars as a tracer of large-scale structures at high redshifts, which may be useful for studies of the growth of structures in the high-redshift universe.

  1. The z = 9-10 galaxy population in the Hubble Frontier Fields and CLASH surveys: the z = 9 luminosity function and further evidence for a smooth decline in ultraviolet luminosity density at z≥ 8

    NASA Astrophysics Data System (ADS)

    McLeod, D. J.; McLure, R. J.; Dunlop, J. S.

    2016-07-01

    We present the results of a search for z = 9-10 galaxies within the first eight pointings of the Hubble Frontier Fields (HFF) survey and 20 cluster fields from the Cluster Lensing And Supernova survey with Hubble (CLASH) survey. Combined with our previous analysis of the Hubble Ultra Deep Field, we have now completed a search for z = 9-10 galaxies over ≃ 130 arcmin2, spread across 29 Hubble Space Telescope Wide Field Camera 3/IR pointings. We confine our primary search for high-redshift candidates in this imaging to the uniformly deep, relatively low magnification regions (i.e. σ160 > 30 AB mag for HFF and σ160 > 28.8 AB mag for CLASH in 0.5-arcsec apertures). We unveil a sample of 33 galaxy candidates at zphot ≥ 8.4, five of which have primary photometric redshift solutions in the range 9.6 < zphot < 11.2. The improved statistics and reduced cosmic variance provided by our new sample allows a more accurate determination of the ultraviolet (UV)-selected galaxy luminosity function (LF) at z ≃ 9. Our new results strengthen our previous conclusion that the LF appears to evolve smoothly from z = 8 to 9, an evolution which can be equally well modelled by a factor of ≃ 2 drop in density, or a dimming of ≃ 0.5 mag in M⋆. Moreover, we are able to place initial constraints on the z = 10 LF, finding that the number density at M1500 ≃ -19.7 is log (φ ) = -4.1^{+0.2}_{-0.3}, a factor of ≃ 2 lower than at z = 9. Finally, we use our new results to revisit the issue of the decline in UV luminosity density (ρUV) at z ≥ 8. We conclude that the data continue to support a smooth decline in ρUV over the redshift interval 6 < z < 10, in agreement with simple models of early galaxy evolution driven by the growth in the underlying dark matter halo mass function.

  2. QUASARS PROBING QUASARS. VI. EXCESS H I ABSORPTION WITHIN ONE PROPER Mpc OF z ∼ 2 QUASARS

    SciTech Connect

    Prochaska, J. Xavier; Cantalupo, Sebastiano; Lau, Marie Wingyee; Bovy, Jo; Djorgovski, S. G.; Ellison, Sara L.; Martin, Crystal L.; Simcoe, Robert A.

    2013-10-20

    With close pairs of quasars at different redshifts, a background quasar sightline can be used to study a foreground quasar's environment in absorption. We use a sample of 650 projected quasar pairs to study the H I Lyα absorption transverse to luminous, z ∼ 2 quasars at proper separations of 30 kpc < R < 1 Mpc. In contrast to measurements along the line-of-sight, regions transverse to quasars exhibit enhanced H I Lyα absorption and a larger variance than the ambient intergalactic medium, with increasing absorption and variance toward smaller scales. Analysis of composite spectra reveals excess absorption characterized by a Lyα equivalent width profile W = 2.3 Å (R /100 kpc){sup –0.46}. We also observe a high (≅ 60%) covering factor of strong, optically thick H I absorbers (H I column N{sub H{sub I}}>10{sup 17.3} cm{sup -2}) at separations R < 200 kpc, which decreases to ∼20% at R ≅ 1 Mpc, but still represents a significant excess over the cosmic average. This excess of optically thick absorption can be described by a quasar-absorber cross-correlation function ξ{sub QA}(r) = (r/r{sub 0}){sup γ} with a large correlation length r{sub 0} = 12.5{sup +2.7}{sub -1.4} h{sup -1} Mpc (comoving) and γ=1.68{sup +0.14}{sub -0.30}. The H I absorption measured around quasars exceeds that of any previously studied population, consistent with quasars being hosted by massive dark matter halos M{sub halo} ≈ 10{sup 12.5} M{sub ☉} at z ∼ 2.5. The environments of these massive halos are highly biased toward producing optically thick gas, and may even dominate the cosmic abundance of Lyman limit systems and hence the intergalactic opacity to ionizing photons at z ∼ 2.5. The anisotropic absorption around quasars implies the transverse direction is much less likely to be illuminated by ionizing radiation than the line-of-sight.

  3. Testing quasar unification: radiative transfer in clumpy winds

    NASA Astrophysics Data System (ADS)

    Matthews, J. H.; Knigge, C.; Long, K. S.; Sim, S. A.; Higginbottom, N.; Mangham, S. W.

    2016-05-01

    Various unification schemes interpret the complex phenomenology of quasars and luminous active galactic nuclei (AGN) in terms of a simple picture involving a central black hole, an accretion disc and an associated outflow. Here, we continue our tests of this paradigm by comparing quasar spectra to synthetic spectra of biconical disc wind models, produced with our state-of-the-art Monte Carlo radiative transfer code. Previously, we have shown that we could produce synthetic spectra resembling those of observed broad absorption line (BAL) quasars, but only if the X-ray luminosity was limited to 1043 erg s-1. Here, we introduce a simple treatment of clumping, and find that a filling factor of ˜0.01 moderates the ionization state sufficiently for BAL features to form in the rest-frame UV at more realistic X-ray luminosities. Our fiducial model shows good agreement with AGN X-ray properties and the wind produces strong line emission in, e.g., Lyα and C IV 1550 Å at low inclinations. At high inclinations, the spectra possess prominent LoBAL features. Despite these successes, we cannot reproduce all emission lines seen in quasar spectra with the correct equivalent-width ratios, and we find an angular dependence of emission line equivalent width despite the similarities in the observed emission line properties of BAL and non-BAL quasars. Overall, our work suggests that biconical winds can reproduce much of the qualitative behaviour expected from a unified model, but we cannot yet provide quantitative matches with quasar properties at all viewing angles. Whether disc winds can successfully unify quasars is therefore still an open question.

  4. Unusual high-redshift radio broad absorption-line quasar 1624+3758

    NASA Astrophysics Data System (ADS)

    Benn, C. R.; Carballo, R.; Holt, J.; Vigotti, M.; González-Serrano, J. I.; Mack, K.-H.; Perley, R. A.

    2005-07-01

    We present observations of the most radio-luminous broad absorption-line (BAL) quasar known, 1624+3758, at redshift z= 3.377. The quasar has several unusual properties. (1) The FeII UV191 1787-Åemission line is very prominent. (2) The BAL trough (BALnicity index 2990 km s-1) is detached by 21000 km s-1 and extends to velocity v=-29000 km s-1. There are additional intrinsic absorbers at -1900 and -2800 km s-1. (3) The radio rotation measure of the quasar, 18350 rad m-2, is the second highest known. The radio luminosity is P1.4GHz= 4.3 × 1027 W Hz-1 (H0= 50 km s-1 Mpc-1, q0= 0.5) and the radio loudness is R*= 260. The radio source is compact and the radio spectrum is GHz-peaked, consistent with it being relatively young. The width of the CIV emission line, in conjunction with the total optical luminosity, implies a black hole mass MBH~ 109Msolar, L/LEddington~ 2. The high Eddington ratio and the radio-loudness place this quasar in one corner of Boroson's two-component scheme for the classification of active galactic nuclei, implying a very high accretion rate, and this may account for some of the unusual observed properties. The v=-1900km s-1 absorber is a possible Lyman-limit system, with N(HI) = 4 × 1018 cm-2, and a covering factor of 0.7. A complex mini-BAL absorber at v=-2200 to -3400 km s-1 is detected in each of CIV, NV and OVI. The blue and red components of the CIV doublet happen to be unblended, allowing both the covering factor and optical depth to be determined as a function of velocity. Variation of the covering factor with velocity dominates the form of the mini-BAL, with the absorption being saturated (e-τ~ 0) over most of the velocity range. The velocity dependence of the covering factor and the large velocity width imply that the mini-BAL is intrinsic to the quasar. There is some evidence of line-locking between velocity components in the CIV mini-BAL, suggesting that radiation pressure plays a role in accelerating the outflow.

  5. Galaxy Clustering Around Nearby Luminous Quasars

    NASA Technical Reports Server (NTRS)

    Fisher, Karl B.; Bahcall, John N.; Kirhakos, Sofia; Schneider, Donald P.

    1996-01-01

    We examine the clustering of galaxies around a sample of 20 luminous low redshift (z approx. less than 0.30) quasars observed with the Wide Field Camera-2 on the Hubble Space Telescope (HST). The HST resolution makes possible galaxy identification brighter than V = 24.5 and as close as 1 min or 2 min to the quasar. We find a significant enhancement of galaxies within a projected separation of approx. less than 100 1/h kpc of the quasars. If we model the QSO/galaxy correlation function as a power law with a slope given by the galaxy/galaxy correlation function, we find that the ratio of the QSO/galaxy to galaxy/galaxy correlation functions is 3.8 +/- 0.8. The galaxy counts within r less than 15 1/h kpc of the quasars are too high for the density profile to have an appreciable core radius (approx. greater than 100 1/h kpc). Our results reinforce the idea that low redshift quasars are located preferentially in groups of 10-20 galaxies rather than in rich clusters. We see no significant difference in the clustering amplitudes derived from radio-loud and radio-quiet subsamples.

  6. Quasar target selection fiber efficiency

    SciTech Connect

    Newberg, H.; Yanny, B.

    1996-05-01

    We present estimates of the efficiency for finding QSOs as a function of limiting magnitude and galactic latitude. From these estimates, we have formulated a target selection strategy that should net 80,000 QSOs in the north galactic cap with an average of 70 fibers per plate, not including fibers reserved for high-redshift quasars. With this plan, we expect 54% of the targets to be QSOs. The North Galactic Cap is divided into two zones of high and low stellar density. We use about five times as many fibers for QSO candidates in the half of the survey with the lower stellar density as we use in the half with higher stellar density. The current plan assigns 15% of the fibers to FIRST radio sources; if these are not available, those fibers would be allocated to lower probability QSO sources, dropping the total number of QSOs by a small factor (5%). We will find about 17,000 additional quasars in the southern strips, and maybe a few more at very high redshift. Use was made of two data sets: the star and quasar simulated test data generated by Don Schneider, and the data from UJFN plate surveys by Koo (1986) and Kron (1980). This data was compared to results from the Palomar-Green Survey and a recent survey by Pat Osmer and collaborators.

  7. Tracing a high redshift cosmic web with quasar systems

    NASA Astrophysics Data System (ADS)

    Einasto, Maret; Tago, Erik; Lietzen, Heidi; Park, Changbom; Heinämäki, Pekka; Saar, Enn; Song, Hyunmi; Liivamägi, Lauri Juhan; Einasto, Jaan

    2014-08-01

    Context. To understand the formation, evolution, and present-day properties of the cosmic web we need to study it at low and high redshifts. Aims: We trace the cosmic web at redshifts that range from 1.0 ≤ z ≤ 1.8 by using the quasar (QSO) data from the SDSS DR7 QSO catalogue. Methods: We apply a friend-of-friend algorithm to the quasar and random catalogues to determine systems at a series of linking length and analyse richness and sizes of these systems. Results: At the linking lengths l ≤ 30 h-1 Mpc, the number of quasar systems is larger than the number of systems detected in random catalogues, and the systems themselves have smaller diameters than random systems. The diameters of quasar systems are comparable to the sizes of poor galaxy superclusters in the local Universe. The richest quasar systems have four members. The mean space density of quasar systems, ≈ 10-7 (h-1 Mpc)-3, is close to the mean space density of local rich superclusters. At intermediate linking lengths (40 ≤ l ≤ 70 h-1 Mpc), the richness and length of quasar systems are similar to those derived from random catalogues. Quasar system diameters are similar to the sizes of rich superclusters and supercluster chains in the local Universe. The percolating system, which penetrate the whole sample volume appears in a quasar sample at a smaller linking length than in random samples (85 h-1 Mpc). At the linking length 70 h-1 Mpc, the richest systems of quasars have diameters exceeding 500 h-1 Mpc. Quasar luminosities in systems are not correlated with the system richness. Conclusions: Quasar system catalogues in our web pages and at the Strasbourg Astronomical Data Center (CDS) serve as a database for searching superclusters of galaxies and for tracing the cosmic web at high redshifts. Appendix A is available in electronic form at http://www.aanda.orgThe catalogues are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc

  8. Quasar feedback revealed by giant molecular outflows

    NASA Astrophysics Data System (ADS)

    Feruglio, C.; Maiolino, R.; Piconcelli, E.; Menci, N.; Aussel, H.; Lamastra, A.; Fiore, F.

    2010-07-01

    In the standard scenario for galaxy evolution young star-forming galaxies transform into red bulge-dominated spheroids, where star formation has been quenched. To explain this transformation, a strong negative feedback generated by accretion onto a central super-massive black hole is often invoked. The depletion of gas resulting from quasar-driven outflows should eventually stop star-formation across the host galaxy and lead the black hole to “suicide” by starvation. Direct observational evidence for a major quasar feedback onto the host galaxy is still missing, because outflows previously observed in quasars are generally associated with the ionized component of the gas, which only accounts for a minor fraction of the total gas content, and typically occurrs in the central regions. We used the IRAM PdB Interferometer to observe the CO(1-0) transition in Mrk 231, the closest quasar known. Thanks to the wide band we detected broad wings of the CO line, with velocities of up to 750 km s-1 and spatially resolved on the kpc scale. These broad CO wings trace a giant molecular outflow of about 700 M_⊙/year, far larger than the ongoing star-formation rate (~200 M_⊙/year) observed in the host galaxy. This wind will totally expel the cold gas reservoir in Mrk 231 in about 107 yrs, therefore halting the star-formation activity on the same timescale. The inferred kinetic energy in the molecular outflow is ~1.2 × 1044 erg/s, corresponding to a few percent of the AGN bolometric luminosity, which is very close to the fraction expected by models ascribing quasar feedback to highly supersonic shocks generated by radiatively accelerated nuclear winds. Instead, the contribution by the SNe associated with the starburst fall short by several orders of magnitude to account for the kinetic energy observed in the outflow. The direct observational evidence for quasar feedback reported here provides solid support to the scenarios ascribing the observed properties of local massive

  9. Quasars: A Progress Report.

    ERIC Educational Resources Information Center

    Weedman, Daniel

    1988-01-01

    Reports on some of the discoveries over the last quarter century regarding quasars including spectra and energy sources, formation and evolution, and cosmological probes. Describes some of the fundamental mysteries that remain. (CW)

  10. High Redshift Quasars

    NASA Technical Reports Server (NTRS)

    Elvis, Martin S.

    1996-01-01

    The report for this period includes three papers: 'Associated Absorption at Low and High Redshift'; 'Strong X-ray Absorption in a Broad Absorption Line Quasar: PHL5200'; and 'ASCA and ROSAT X-ray Spectra of High-Redshift Radio-Loud Quasars'. The first gives examples from both low and high redshift for combining information on absorbing material in active galactic nuclei from both x-ray and the UV. The second presents ASCA observations of the z = 1.98 prototype broad absorption line quasar (BALQSO): PHL 5200, detected with both the solid-state imaging spectrometers and the gas imaging spectometers. The third paper presents results on the x-ray properties of 9 high-redshift radio-loud quasars observed by ASCA and ROSAT, including ASCA observations of S5 0014+81 (z = 3.38) and S5 0836+71 (z = 2.17) and ROSAT observations of PKS 2126-158.

  11. STELLAR POPULATIONS IN THE CENTRAL 0.5 pc OF THE GALAXY. I. A NEW METHOD FOR CONSTRUCTING LUMINOSITY FUNCTIONS AND SURFACE-DENSITY PROFILES

    SciTech Connect

    Do, T.; Martinez, G. D.; Lu, J. R.; Ghez, A. M.; Morris, M. R.; Yelda, S.; Wright, S. A.; Matthews, K.

    2013-02-20

    We present new high angular resolution near-infrared spectroscopic observations of the nuclear star cluster surrounding the Milky Way's central supermassive black hole. Using the integral-field spectrograph OSIRIS on Keck II behind the laser-guide-star adaptive optics system, this spectroscopic survey enables us to separate early-type (young, 4-6 Myr) and late-type (old, >1 Gyr) stars with a completeness of 50% down to K' = 15.5 mag, which corresponds to {approx}10 M {sub Sun} for the early-type stars. This work increases the radial extent of reported OSIRIS/Keck measurements by more than a factor of three from 4'' to 14'' (0.16 to 0.56 pc), along the projected disk of young stars. For our analysis, we implement a new method of completeness correction using a combination of star-planting simulations and Bayesian inference. We assign probabilities for the spectral type of every source detected in deep imaging down to K' = 15.5 mag using information from spectra, simulations, number counts, and the distribution of stars. The inferred radial surface-density profiles, {Sigma}(R){proportional_to}R {sup -{Gamma}}, for the young stars and late-type giants are consistent with earlier results ({Gamma}{sub early} = 0.93 {+-} 0.09, {Gamma}{sub late} = 0.16 {+-} 0.07). The late-type surface-density profile is approximately flat out to the edge of the survey. While the late-type stellar luminosity function is consistent with the Galactic bulge, the completeness-corrected luminosity function of the early-type stars has significantly more young stars at faint magnitudes compared with previous surveys with similar depth. This luminosity function indicates that the corresponding mass function of the young stars is likely less top-heavy than that inferred from previous surveys.

  12. Quasars and gravitational lenses.

    PubMed

    Turner, E L

    1984-03-23

    Despite the expenditure of large amounts of telescope time and other resources, most of the fundamental questions concerning quasi-stellar objects (quasars) remain unanswered. A complex phenomenology of radio, infrared, optical, and x-ray properties has accumulated but has not yielded even a satisfactory classification system. The large red shifts (distances) of quasars make them very valuable tools for studying cosmology and the properties of intervening matter in the Universe through observations of absorption lines and gravitational lenses.

  13. Quasar variability measurements with SDSS repeated imaging and POSS data

    NASA Astrophysics Data System (ADS)

    Ivezic, Ž.; Lupton, R. H.; Juric, M.; Anderson, S.; Hall, P. B.; Richards, G. T.; Rockosi, C. M.; vanden Berk, D. E.; Turner, E. L.; Knapp, G. R.; Gunn, J. E.; Schlegel, D.; Strauss, M. A.; Schneider, D. P.

    2004-11-01

    We analyze the properties of quasar variability using repeated SDSS imaging data in five UV-to-far red photometric bands, accurate to 0.02 mag, for ˜13,000 spectroscopically confirmed quasars. The observed time lags span the range from 3 hours to over 3 years, and constrain the quasar variability for rest-frame time lags of up to two years, and at rest-frame wavelengths from 1000Å to 6000Å. We demonstrate that ˜66,000 SDSS measurements of magnitude differences can be described within the measurement noise by a simple function of only three free parameters. The addition of POSS data constrains the long-term behavior of quasar variability and provides evidence for a turn-over in the structure function. This turn-over indicates that the characteristic time scale for optical variability of quasars is of the order 1 year.

  14. The He II Proximity Effect and The Lifetime of Quasars

    NASA Astrophysics Data System (ADS)

    Khrykin, I. S.; Hennawi, J. F.; McQuinn, M.; Worseck, G.

    2016-06-01

    The lifetime of quasars is fundamental for understanding the growth of supermassive black holes, and is an important ingredient in models of the reionization of the intergalactic medium (IGM). However, despite various attempts to determine quasar lifetimes, current estimates from a variety of methods are uncertain by orders of magnitude. This work combines cosmological hydrodynamical simulations and 1D radiative transfer to investigate the structure and evolution of the He ii Lyα proximity zones around quasars at z ≃ 3-4. We show that the time evolution in the proximity zone can be described by a simple analytical model for the approach of the He ii fraction {x}{He{{II}}}(t) to ionization equilibrium, and use this picture to illustrate how the transmission profile depends on the quasar lifetime, quasar UV luminosity, and the ionization state of Helium in the ambient IGM (i.e., the average He ii fraction, or equivalently the metagalactic He ii ionizing background). A significant degeneracy exists between the lifetime and the average He ii fraction, however the latter can be determined from measurements of the He ii Lyα optical depth far from quasars, allowing the lifetime to be measured. We advocate stacking existing He ii quasar spectra at z ˜ 3, and show that the shape of this average proximity zone profile is sensitive to lifetimes as long as ˜30 Myr. At higher redshift z ˜ 4 where the He ii fraction is poorly constrained, degeneracies will make it challenging to determine these parameters independently. Our analytical model for He ii proximity zones should also provide a useful description of the properties of H i proximity zones around quasars at z ≃ 6-7.

  15. THE FIRST HIGH-REDSHIFT QUASAR FROM Pan-STARRS

    SciTech Connect

    Morganson, Eric; De Rosa, Gisella; Decarli, Roberto; Walter, Fabian; Rix, Hans-Walter; Chambers, Ken; Burgett, William; Flewelling, Heather; Hodapp, Klaus; Kaiser, Nick; Magnier, Eugene; Sweeney, Bill; Waters, Christopher; McGreer, Ian; Fan, Xiaohui; Greiner, Jochen; Price, Paul

    2012-06-15

    We present the discovery of the first high-redshift (z > 5.7) quasar from the Panoramic Survey Telescope and Rapid Response System 1 (Pan-STARRS1 or PS1). This quasar was initially detected as an i{sub P1} dropout in PS1, confirmed photometrically with the SAO Wide-field InfraRed Camera at Arizona's Multiple Mirror Telescope (MMT) and the Gamma-Ray Burst Optical/Near-Infrared Detector at the MPG 2.2 m telescope in La Silla. The quasar was verified spectroscopically with the MMT Spectrograph, Red Channel and the Cassegrain Twin Spectrograph at the Calar Alto 3.5 m telescope. Its near-infrared spectrum was taken at the Large Binocular Telescope Observatory (LBT) with the LBT Near-Infrared Spectroscopic Utility with Camera and Integral Field Unit for Extragalactic Research. It has a redshift of 5.73, an AB z{sub P1} magnitude of 19.4, a luminosity of 3.8 Multiplication-Sign 10{sup 47} erg s{sup -1}, and a black hole mass of 6.9 Multiplication-Sign 10{sup 9} M{sub Sun }. It is a broad absorption line quasar with a prominent Ly{beta} peak and a very blue continuum spectrum. This quasar is the first result from the PS1 high-redshift quasar search that is projected to discover more than 100 i{sub P1} dropout quasars and could potentially find more than 10 z{sub P1} dropout (z > 6.8) quasars.

  16. A Luminosity Function of Ly(alpha)-Emitting Galaxies at Z [Approx. Equal to] 4.5(Sup 1),(Sup 2)

    NASA Technical Reports Server (NTRS)

    Dawson, Steve; Rhoads, James E.; Malhotra, Sangeeta; Stern, Daniel; Wang, JunXian; Dey, Arjun; Spinrad, Hyron; Jannuzi, Buell T.

    2007-01-01

    We present a catalog of 59 z [approx. equal to] 4:5 Ly(alpha)-emitting galaxies spectroscopically confirmed in a campaign of Keck DEIMOS follow-up observations to candidates selected in the Large Are (LALA) narrowband imaging survey.We targeted 97 candidates for spectroscopic follow-up; by accounting for the variety of conditions under which we performed spectroscopy, we estimate a selection reliability of approx.76%. Together with our previous sample of Keck LRIS confirmations, the 59 sources confirmed herein bring the total catalog to 73 spectroscopically confirmed z [approx. equal to] 4:5 Ly(alpha)- emitting galaxies in the [approx. equal to] 0.7 deg(exp 2) covered by the LALA imaging. As with the Keck LRIS sample, we find that a nonnegligible fraction of the co rest-frame equivalent widths (W(sub lambda)(sup rest)) that exceed the maximum predicted for normal stellar populations: 17%-31%(93%confidence) of the detected galaxies show (W(sub lambda)(sup rest)) 12%-27% (90% confidence) show (W(sub lambda)(sup rest)) > 240 A. We construct a luminosity function of z [approx. equal to] 4.5 Ly(alpha) emission lines for comparison to Ly(alpha) luminosity function < 6.6. We find no significant evidence for Ly(alpha) luminosity function evolution from z [approx. equal to] 3 to z [approx. equal to] 6. This result supports the conclusion that the intergalactic me largely reionized from the local universe out to z [approx. equal to] 6.5. It is somewhat at odds with the pronounced drop in the cosmic star formation rate density recently measured between z approx. 3 an z approx. 6 in continuum-selected Lyman-break galaxies, and therefore potentially sheds light on the relationship between the two populations.

  17. Discovery of eight z ∼ 6 quasars from Pan-STARRS1

    SciTech Connect

    Bañados, E.; Venemans, B. P.; Morganson, E.; Decarli, R.; Walter, F.; Rix, H.-W.; Farina, E. P.; Chambers, K. C.; Morgan, J. S.; Burgett, W. S.; Kaiser, N.; Kudritzki, R.-P.; Fan, X.; McGreer, I.; Jiang, L.; De Rosa, G.; Simcoe, R.; Weiß, A.; Price, P. A.; Greiner, J.; and others

    2014-07-01

    High-redshift quasars are currently the only probes of the growth of supermassive black holes and potential tracers of structure evolution at early cosmic time. Here we present our candidate selection criteria from the Panoramic Survey Telescope and Rapid Response System 1 and follow-up strategy to discover quasars in the redshift range 5.7 ≲ z ≲ 6.2. With this strategy we discovered eight new 5.7 ≤ z ≤ 6.0 quasars, increasing the number of known quasars at z > 5.7 by more than 10%. We additionally recovered 18 previously known quasars. The eight quasars presented here span a large range of luminosities (–27.3 ≤ M {sub 1450} ≤ –25.4; 19.6 ≤ z {sub P1} ≤ 21.2) and are remarkably heterogeneous in their spectral features: half of them show bright emission lines whereas the other half show a weak or no Lyα emission line (25% with rest-frame equivalent width of the Lyα +N V line lower than 15 Å). We find a larger fraction of weak-line emission quasars than in lower redshift studies. This may imply that the weak-line quasar population at the highest redshifts could be more abundant than previously thought. However, larger samples of quasars are needed to increase the statistical significance of this finding.

  18. The Most Luminous z ~ 9-10 Galaxy Candidates Yet Found: The Luminosity Function, Cosmic Star-formation Rate, and the First Mass Density Estimate at 500 Myr

    NASA Astrophysics Data System (ADS)

    Oesch, P. A.; Bouwens, R. J.; Illingworth, G. D.; Labbé, I.; Smit, R.; Franx, M.; van Dokkum, P. G.; Momcheva, I.; Ashby, M. L. N.; Fazio, G. G.; Huang, J.-S.; Willner, S. P.; Gonzalez, V.; Magee, D.; Trenti, M.; Brammer, G. B.; Skelton, R. E.; Spitler, L. R.

    2014-05-01

    We present the discovery of four surprisingly bright (H 160 ~ 26-27 mag AB) galaxy candidates at z ~ 9-10 in the complete HST CANDELS WFC3/IR GOODS-N imaging data, doubling the number of z ~ 10 galaxy candidates that are known, just ~500 Myr after the big bang. Two similarly bright sources are also detected in a reanalysis of the GOODS-S data set. Three of the four galaxies in GOODS-N are significantly detected at 4.5σ-6.2σ in the very deep Spitzer/IRAC 4.5 μm data, as is one of the GOODS-S candidates. Furthermore, the brightest of our candidates (at z = 10.2 ± 0.4) is robustly detected also at 3.6 μm (6.9σ), revealing a flat UV spectral energy distribution with a slope β = -2.0 ± 0.2, consistent with demonstrated trends with luminosity at high redshift. Thorough testing and use of grism data excludes known low-redshift contamination at high significance, including single emission-line sources, but as-yet unknown low redshift sources could provide an alternative solution given the surprising luminosity of these candidates. Finding such bright galaxies at z ~ 9-10 suggests that the luminosity function for luminous galaxies might evolve in a complex way at z > 8. The cosmic star formation rate density still shows, however, an order-of-magnitude increase from z ~ 10 to z ~ 8 since the dominant contribution comes from low-luminosity sources. Based on the IRAC detections, we derive galaxy stellar masses at z ~ 10, finding that these luminous objects are typically 109 M ⊙. This allows for a first estimate of the cosmic stellar mass density at z ~ 10 resulting in log _{10}\\rho _{*} = 4.7^{+0.5}_{-0.8} M ⊙ Mpc-3 for galaxies brighter than M UV ~ -18. The remarkable brightness, and hence luminosity, of these z ~ 9-10 candidates will enable deep spectroscopy to determine their redshift and nature, and highlights the opportunity for the James Webb Space Telescope to map the buildup of galaxies at redshifts much earlier than z ~ 10. Based on data obtained with the

  19. Herschel ATLAS: The cosmic star formation history of quasar host galaxies

    NASA Astrophysics Data System (ADS)

    Serjeant, S.; Bertoldi, F.; Blain, A. W.; Clements, D. L.; Cooray, A.; Danese, L.; Dunlop, J.; Dunne, L.; Eales, S.; Falder, J.; Hatziminaoglou, E.; Hughes, D. H.; Ibar, E.; Jarvis, M. J.; Lawrence, A.; Lee, M. G.; Michałowski, M.; Negrello, M.; Omont, A.; Page, M.; Pearson, C.; van der Werf, P. P.; White, G.; Amblard, A.; Auld, R.; Baes, M.; Bonfield, D. G.; Burgarella, D.; Buttiglione, S.; Cava, A.; Dariush, A.; de Zotti, G.; Dye, S.; Frayer, D.; Fritz, J.; Gonzalez-Nuevo, J.; Herranz, D.; Ivison, R. J.; Lagache, G.; Leeuw, L.; Lopez-Caniego, M.; Maddox, S.; Pascale, E.; Pohlen, M.; Rigby, E.; Rodighiero, G.; Samui, S.; Sibthorpe, B.; Smith, D. J. B.; Temi, P.; Thompson, M.; Valtchanov, I.; Verma, A.

    2010-07-01

    We present a derivation of the star formation rate per comoving volume of quasar host galaxies, derived from stacking analyses of far-infrared to mm-wave photometry of quasars with redshifts 0 < z < 6 and absolute I-band magnitudes -22 > IAB > -32 We use the science demonstration observations of the first ~16 deg2 from the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) in which there are 240 quasars from the Sloan Digital Sky Survey (SDSS) and a further 171 from the 2dF-SDSS LRG and QSO (2SLAQ) survey. We supplement this data with a compilation of data from IRAS, ISO, Spitzer, SCUBA and MAMBO. H-ATLAS alone statistically detects the quasars in its survey area at >5σ at 250,350 and 500 μm. From the compilation as a whole we find striking evidence of downsizing in quasar host galaxy formation: low-luminosity quasars with absolute magnitudes in the range -22 > IAB > -24 have a comoving star formation rate (derived from 100 μm rest-frame luminosities) peaking between redshifts of 1 and 2, while high-luminosity quasars with IAB < -26 have a maximum contribution to the star formation density at z ~ 3. The volume-averaged star formation rate of -22 > IAB > -24 quasars evolves as (1 + z)2.3±0.7 at z < 2, but the evolution at higher luminosities is much faster reaching (1 + z)10±1 at -26 > IAB > -28. We tentatively interpret this as a combination of a declining major merger rate with time and gas consumption reducing fuel for both black hole accretion and star formation. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia with important participation from NASA.