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 0.07

The ugrizYJHK luminosity distributions and densities from the combined MGC, SDSS and UKIDSS LAS data sets

NASA Astrophysics Data System (ADS)

Hill, David T.; Driver, Simon P.; Cameron, Ewan; Cross, Nicholas; Liske, Jochen; Robotham, Aaron

2010-05-01

We combine data from the Millennium Galaxy Catalogue, Sloan Digital Sky Survey and UKIRT Infrared Deep Sky Survey Large Area Survey to produce ugrizYJHK luminosity functions and densities from within a common, low-redshift volume (z < 0.1, ~ 71000h-31 Mpc3 for L* systems) with 100 per cent spectroscopic completeness. In the optical the fitted Schechter functions are comparable in shape to those previously reported values but with higher normalizations (typically 0, 30, 20, 15, 5 per cent higher φ* values in u, g, r, i, z, respectively, over those reported by the SDSS team). We attribute these to differences in the redshift ranges probed, incompleteness and adopted normalization methods. In the near-IR (NIR) we find significantly different Schechter function parameters (mainly in the M* values) to those previously reported and attribute this to the improvement in the quality of the imaging data over previous studies. This is the first homogeneous measurement of the extragalactic luminosity density which fully samples both the optical and NIR regimes. Unlike previous compilations that have noted a discontinuity between the optical and NIR regimes our homogeneous data set shows a smooth cosmic spectral energy distribution (CSED). After correcting for dust attenuation we compare our CSED to the expected values based on recent constraints on the cosmic star formation history and the initial mass function.

Radio Identification of Millimeter-Bright Galaxies Detected in the AzTEC/ASTE Blank Field Survey

NASA Astrophysics Data System (ADS)

Hatsukade, Bunyo; Kohno, Kotaro; White, Glenn; Matsuura, Shuji; Hanami, Hitoshi; Shirahata, Mai; Nakanishi, Kouichiro; Hughes, David; Tamura, Yoichi; Iono, Daisuke; Wilson, Grant; Yun, Min

2008-10-01

We propose a deep 1.4-GHz imaging of millimeter-bright sources in the AzTEC/ASTE 1.1-mm blank field survey of AKARI Deep Field-South. The AzTEC/ASTE uncovered 37 sources, which are possibly at z > 2. We have obtained multi-wavelength data in this field, but the large beam size of AzTEC/ASTE (30 arcsec) prevents us from identifying counterparts. The aim of this proposal is to identify radio counterparts with higher-angular resolution. This enables us (i) To identifying optical/IR counterparts. It enables optical spectroscopy to determine precise redshifts, allowing us to derive SFRs, luminosity functions, clustering properties, mass of dark matter halos, etc. (ii) To constrain luminosity evolutions of SMGs by comparing of 1.4-GHz number counts (and luminosity functions) with luminosity evolution models. (iii) To estimate photometric redshifts from 1.4-GHz and 1.1-mm data using the radio-FIR flux correlation. In case of non-detection, we can put deep lower limits (3 sigma limit of z > 3). These information lead to the study of evolutionary history of SMGs, their relationship with other galaxy populations, contribution to the cosmic star formation history and the infrared background.

The Coma Cluster Luminosity Function from Ultraviolet to Near-Infrared

NASA Astrophysics Data System (ADS)

Andreon, S.; Cuillandre, J.-C.; Pello, R.

The Coma cluster luminosity function (LF) from ultraviolet (2000 AA ) to the near-infrared (H band) is summarized. In the UV the LF is very steep, much steeper than in the optical. The steep Coma UV LF implies that faint and bright galaxies give similar contributions to the total UV flux and to the total metal production rate. The ComaUV LF is dominated in number and luminosity by blue galaxies, which are often faint in the optical. Therefore the Coma UV LF is dominated by star forming galaxies, not by massive and large galaxies. The optical Coma LF is relatively steep (alpha=-1.4) over the 11 magnitudes sampled, but its slope and shape depend on considered filter and magnitude. We found a clear steeping of the FL going from B to R bands, indicative of the presence of a large number of red dwarfs, as faint as three bright globular clusters. Furthermore, using Hubble Space Telescope images, we discover that blends of globular clusters, not resolved in individual components due to seeing, look like dwarf galaxies when observed from the ground and are numerous and bright. The existence of these fake extended sources increases the steepness of the LF at faint magnitudes, if not deal on. This concern affects previous deep probing of the luminosity function, but not the present work. The near-infrared LF wa s computed on a near-infrared selected sample of galaxies which photometry is complete down to the typical dwarf (M* +5) luminosity. The Coma LF can be described by a Schechter function with intermediate slope (alpha sim-1.3), plus a dip at MH~-22 mag. The shape of the Coma LF in H band is quite similar to th e one found in the B band. The similarity of the LF in the optical and H bands implies that in the central region of Coma there is no new population of galaxies which is too faint to be observed in the optical band (because dust enshrouded, for instance), down to the magnitudes of dwarfs. The exponential cut of the LF at the bright end is in good agreement with the one derived from shallower near-infrared samples o f galaxies, both in clusters and in the field. The faint end of the LF, reaching MH~-19 mag (roughly MB~ -15), is steep, but less than previously suggested from shallower near-infrared observations of an adjacent region in the Coma cluster.

The Cool White Dwarf Luminosity Function and the Age of the Galactic Disk

NASA Astrophysics Data System (ADS)

Leggett, S. K.; Ruiz, Maria Teresa; Bergeron, P.

1998-04-01

We present new optical and infrared data for the cool white dwarfs in the proper motion sample of Liebert, Dahn, & Monet. Stellar properties--surface chemical composition, effective temperature, radius, surface gravity, mass, and luminosity--are determined from these data by using the model atmospheres of Bergeron, Saumon, & Wesemael. The space density contribution is calculated for each star and the luminosity function (LF) for cool white dwarfs is determined. Comparing the LF to the most recent cooling sequences by Wood implies that the age of the local region of the Galactic disk is 8 +/- 1.5 Gyr. This result is consistent with the younger ages now being derived for the globular clusters and the universe itself.

The UV Luminosity Function at 6 < z < 10 from the Hubble Frontier Fields

NASA Astrophysics Data System (ADS)

Livermore, Rachael C.; Finkelstein, Steven L.; Lotz, Jennifer M.

2017-01-01

The Hubble Frontier Fields program has obtained deep optical and near-infrared Hubble Space Telescope imaging of six galaxy clusters and associated parallel fields. The depth of the imaging (m_AB ~ 29) means we can identify faint galaxies at z > 6, and those in the cluster fields also benefit from magnification due to strong gravitational lensing that allows us to reach intrinsic absolute magnitudes of M_UV ~ -12.5 at z ~ 6. Here, we present the UV luminosity functions at 6 < z < 10 from the complete Hubble Frontier Fields data, revealing a steep faint-end slope that extends to the limits of the data. The lack of any apparent turnover in the luminosity functions means that faint galaxies in the early Universe may have provided sufficient ionizing radiation to sustain reionization.

The X-Ray Background and the AGN Luminosity Function

NASA Astrophysics Data System (ADS)

Hasinger, G.

The deepest X-ray surveys performed with ROSAT were able to resolve as much as 70-80% of the 1-2 keV X-ray background into resolved sources. Optical follow-up observations were able to identify the majority of faint X-ray sources as active galactic nuclei (AGN) out to redshifts of 4.5 as well as a sizeable fraction as groups of galaxies out to redshifts of 0.7. A new population of X-ray luminous, optically innocent narrow emission line galaxies (NELGs) at the faintest X-ray fluxes is still a matter of debate, most likely many of them are also connected to AGN. First deep surveys with the Japanese ASCA satellite give us a glimpse of the harder X-ray background where the bulk of the energy density resides. Future X-ray observatories (XMM and AXAF) will be able to resolve the harder X-ray background. For the first time we are now in a position to study the cosmological evolution of the X-ray luminosity function of AGN, groups of galaxies and galaxies and simultaneously constrain their total luminosity output over cosmic time.

The light up and early evolution of high redshift Supermassive Black Holes

NASA Astrophysics Data System (ADS)

Comastri, Andrea; Brusa, Marcella; Aird, James; Lanzuisi, Giorgio

2016-07-01

The known AGN population at z > 6 is made by luminous optical QSO hosting Supermassive Black Holes (M > 10 ^{9}solar masses), likely to represent the tip of the iceberg of the luminosity and mass function. According to theoretical models for structure formation, Massive Black Holes (M _{BH} 10^{4-7} solar masses) are predicted to be abundant in the early Universe (z > 6). The majority of these lower luminosity objects are expected to be obscured and severely underepresented in current optical near-infrared surveys. The detection of such a population would provide unique constraints on the Massive Black Holes formation mechanism and subsequent growth and is within the capabilities of deep and large area ATHENA surveys. After a summary of the state of the art of present deep XMM and Chandra surveys, at z >3-6 also mentioning the expectations for the forthcoming eROSITA all sky survey; I will present the observational strategy of future multi-cone ATHENA Wide Field Imager (WFI) surveys and the expected breakthroughs in the determination of the luminosity function and its evolution at high (> 4) and very high (>6) redshifts.

VizieR Online Data Catalog: Luminosity and redshift of galaxies from WISE/SDSS (Toba+, 2014)

NASA Astrophysics Data System (ADS)

Toba, Y.; Oyabu, S.; Matsuhara, H.; Malkan, M. A.; Gandhi, P.; Nakagawa, T.; Isobe, N.; Shirahata, M.; Oi, N.; Ohyama, Y.; Takita, S.; Yamauchi, C.; Yano, K.

2017-07-01

We selected 12 and 22 um flux-limited galaxies based on the WISE (Cat. II/311) and SDSS (Cat. II/294) catalogs, and these galaxies were then classified into five types according to their optical spectroscopic information in the SDSS catalog. For spectroscopically classified galaxies, we constructed the luminosity functions using the 1/Vmax method, considering the detection limit of the WISE and SDSS catalogs. (1 data file).

Efficiency of Synchrotron Radiation from Rotation-powered Pulsars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kisaka, Shota; Tanaka, Shuta J., E-mail: kisaka@phys.aoyama.ac.jp, E-mail: sjtanaka@center.konan-u.ac.jp

2017-03-01

Synchrotron radiation is widely considered to be the origin of the pulsed non-thermal emissions from rotation-powered pulsars in optical and X-ray bands. In this paper, we study the synchrotron radiation emitted by the created electron and positron pairs in the pulsar magnetosphere to constrain the energy conversion efficiency from the Poynting flux to the particle energy flux. We model two pair creation processes, two-photon collision, which efficiently works in young γ -ray pulsars (≲10{sup 6} year), and magnetic pair creation, which is the dominant process to supply pairs in old pulsars (≳10{sup 6} year). Using the analytical model, we derivemore » the maximum synchrotron luminosity as a function of the energy conversion efficiency. From the comparison with observations, we find that the energy conversion efficiency to the accelerated particles should be an order of unity in the magnetosphere, even though we make a number of the optimistic assumptions to enlarge the synchrotron luminosity. In order to explain the luminosity of the non-thermal X-ray/optical emission from pulsars with low spin-down luminosity L {sub sd} ≲ 10{sup 34} erg s{sup −1}, non-dipole magnetic field components should be dominant at the emission region. For the γ -ray pulsars with L {sub sd} ≲ 10{sup 35} erg s{sup −1}, observed γ -ray to X-ray and optical flux ratios are much higher than the flux ratio between curvature and the synchrotron radiations. We discuss some possibilities such as the coexistence of multiple accelerators in the magnetosphere as suggested from the recent numerical simulation results. The obtained maximum luminosity would be useful to select observational targets in X-ray and optical bands.« less

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ikeda, H.; Matsuoka, K.; Kajisawa, M.

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. Inmore » 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.« less

Planetary nebulae as standard candles. IV - A test in the Leo I group

NASA Technical Reports Server (NTRS)

Ciardullo, Robin; Jacoby, George H.; Ford, Holland C.

1989-01-01

In this paper, PN are used to determine accurate distances to three galaxies in the Leo I group - The E0 giant elliptical NGC 3379, its optical companion, the SB0 spiral NGC 3384, and the smaller E6 elliptical NGC 3377. In all three galaxies, the luminosity-specific PN number densities are roughly the same, and the derived stellar death rates are in remarkable agreement with the predictions of stellar evolution theory. It is shown that the shape of the forbidden O III 5007 A PN luminosity function is the same in each galaxy and indistinguishable from that observed in M31 and M81. It is concluded that the PN luminosity function is an excellent standard candle for early-type galaxies.

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.

Challenges in Finding AGNs in the Low Luminosity Regime

NASA Astrophysics Data System (ADS)

Satyapal, Shobita; Abel, Nick; Secrest, Nathan; Singh, Amrit; Ellison, Sara

2016-08-01

Low luminosity AGNs are an important component of the AGN population. They are often found in the lowest mass galaxies or galaxies that lack classical bulges, a demographic that places important constraints to models of supermassive black hole seed formation and merger-free models of AGN fueling. The detection of AGNs in this low luminosity regime is challenging both because star formation in the host galaxy can dominate the optical spectrum and gas and dust can obscure the central engine at both optical and X-ray wavelengths. Thus while mid-infrared color selection and X-ray observations at energies <10 keV are often powerful tools in uncovering optically unidentified AGNs at higher luminosities, this is not the case in the low luminosity regime. In this talk, I will review the effectiveness of uncovering AGNs in the low luminosity regime using multiwavength investigations, with a focus on infrared spectroscopic signatures.

First operational experience with DORIS II

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nesemann, H.; Wille, K.

1983-08-01

DORIS II is a completely new designed e/sup +/-e/sup -/ storage ring with a mini-beta scheme. After first runs with a 8 cm optic, the vertical amplitude functions in the interaction points were reduced to 4 cm. This yielded luminosities of L = 1.5 X 10/sup 31/ cm/sup -2/sec/sup -1/ with 2 X 27 mA at E = 5 GeV. Because of the short injection time, an integrated luminosity of more than 600 nb/sup -1/ per day has been obtained.

Galaxy And Mass Assembly (GAMA): bivariate functions of Hα star-forming galaxies

NASA Astrophysics Data System (ADS)

Gunawardhana, M. L. P.; Hopkins, A. M.; Taylor, E. N.; Bland-Hawthorn, J.; Norberg, P.; Baldry, I. K.; Loveday, J.; Owers, M. S.; Wilkins, S. M.; Colless, M.; Brown, M. J. I.; Driver, S. P.; Alpaslan, M.; Brough, S.; Cluver, M.; Croom, S.; Kelvin, L.; Lara-López, M. A.; Liske, J.; López-Sánchez, A. R.; Robotham, A. S. G.

2015-02-01

We present bivariate luminosity and stellar mass functions of Hα star-forming galaxies drawn from the Galaxy And Mass Assembly (GAMA) survey. While optically deep spectroscopic observations of GAMA over a wide sky area enable the detection of a large number of 0.001 < SFRHα (M⊙ yr-1) < 100 galaxies, the requirement for an Hα detection in targets selected from an r-band magnitude-limited survey leads to an incompleteness due to missing optically faint star-forming galaxies. Using z < 0.1 bivariate distributions as a reference we model the higher-z distributions, thereby approximating a correction for the missing optically faint star-forming galaxies to the local star formation rate (SFR) and M densities. Furthermore, we obtain the r-band luminosity functions (LFs) and stellar mass functions of Hα star-forming galaxies from the bivariate LFs. As our sample is selected on the basis of detected Hα emission, a direct tracer of ongoing star formation, this sample represents a true star-forming galaxy sample, and is drawn from both photometrically classified blue and red subpopulations, though mostly from the blue population. On average 20-30 per cent of red galaxies at all stellar masses are star forming, implying that these galaxies may be dusty star-forming systems.

Mini Survey of SDSS [OIII] AGN with Swift: Testing the Hypothesis that L(sub [OIII]) Traces AGN Luminosity

NASA Technical Reports Server (NTRS)

2007-01-01

The number of AGN and their luminosity distribution are crucial parameters for our understanding of the AGN phenomenon. Recent work strongly suggests every massive galaxy has a central black hole. However most of these objects either are not radiating or have been very difficult to detect We are now in the era of large surveys, and the luminosity function (LF] of AGN has been estimated in various ways. In the X-ray band. Chandra and XMM surveys have revealed that the LF of hard X-ray selected AGN shows a strong luminosity-dependent evolution with a dramatic break towards low L(sub x) (at all z). This is seen for all types of AGN, but is stronger for the broad-line objects. In sharp contrast, the local LF of optically-selected samples shows no such break and no differences between narrow and broad-line objects. If as been suggested, hard X ray and optical emission line can both can be fair indicators of AGN activity, it is important to first understand how reliable these characteristics are if we hope to understand the apparent discrepancy in the LFs.

Analytical N beam position monitor method

NASA Astrophysics Data System (ADS)

Wegscheider, A.; Langner, A.; Tomás, R.; Franchi, A.

2017-11-01

Measurement and correction of focusing errors is of great importance for performance and machine protection of circular accelerators. Furthermore LHC needs to provide equal luminosities to the experiments ATLAS and CMS. High demands are also set on the speed of the optics commissioning, as the foreseen operation with β*-leveling on luminosity will require many operational optics. A fast measurement of the β -function around a storage ring is usually done by using the measured phase advance between three consecutive beam position monitors (BPMs). A recent extension of this established technique, called the N-BPM method, was successfully applied for optics measurements at CERN, ALBA, and ESRF. We present here an improved algorithm that uses analytical calculations for both random and systematic errors and takes into account the presence of quadrupole, sextupole, and BPM misalignments, in addition to quadrupolar field errors. This new scheme, called the analytical N-BPM method, is much faster, further improves the measurement accuracy, and is applicable to very pushed beam optics where the existing numerical N-BPM method tends to fail.

Optical excess of dim isolated neutron stars

NASA Astrophysics Data System (ADS)

Ertan, Ü.; Çalışkan, Ş.; Alpar, M. A.

2017-09-01

The optical excess in the spectra of dim isolated neutron stars (XDINs) is a significant fraction of their rotational energy loss rate. This is strikingly different from the situation in isolated radio pulsars. We investigate this problem in the framework of the fallback disc model. The optical spectra can be powered by magnetic stresses on the innermost disc matter, as the energy dissipated is emitted as blackbody radiation mainly from the inner rim of the disc. In the fallback disc model, XDINs are the sources evolving in the propeller phase with similar torque mechanisms. In this model, the ratio of the total magnetic work that heats up the inner disc matter is expected to be similar for different XDINs. Optical luminosities that are calculated consistently with the optical spectra and the theoretical constraints on the inner disc radii give very similar ratios of the optical luminosity to the rotational energy loss rate for all these sources. These ratios indicate that a significant fraction of the magnetic torque heats up the disc matter while the remaining fraction expels disc matter from the system. For XDINs, the contribution of heating by X-ray irradiation to the optical luminosity is negligible in comparison with the magnetic heating. The correlation we expect between the optical luminosities and the rotational energy loss rates of XDINs can be a property of the systems with low X-ray luminosities, in particular those in the propeller phase.

A Physical Model for the Evolving Ultraviolet Luminosity Function of High Redshift Galaxies and their Contribution to the Cosmic Reionization

NASA Astrophysics Data System (ADS)

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

2014-04-01

We present a physical model for the evolution of the ultraviolet (UV) luminosity function of high-redshift galaxies, taking into account in a self-consistent way their chemical evolution and the associated evolution of dust extinction. Dust extinction is found to increase fast with halo mass. A strong correlation between dust attenuation and halo/stellar mass for UV selected high-z galaxies is thus predicted. The model yields good fits of the UV and Lyman-α (Lyα) line luminosity functions at all redshifts at which they have been measured. The weak observed evolution of both luminosity functions between z = 2 and z = 6 is explained as the combined effect of the negative evolution of the halo mass function; of the increase with redshift of the star formation efficiency due to the faster gas cooling; and of dust extinction, differential with halo mass. The slope of the faint end of the UV luminosity function is found to steepen with increasing redshift, implying that low luminosity galaxies increasingly dominate the contribution to the UV background at higher and higher redshifts. The observed range of the UV luminosities at high z implies a minimum halo mass capable of hosting active star formation M crit <~ 109.8 M ⊙, which is consistent with the constraints from hydrodynamical simulations. From fits of Lyα line luminosity functions, plus data on the luminosity dependence of extinction, and from the measured ratios of non-ionizing UV to Lyman-continuum flux density for samples of z ~= 3 Lyman break galaxies and Lyα emitters, we derive a simple relationship between the escape fraction of ionizing photons and the star formation rate. It implies that the escape fraction is larger for low-mass galaxies, which are almost dust-free and have lower gas column densities. Galaxies already represented in the UV luminosity function (M UV <~ -18) can keep the universe fully ionized up to z ~= 6. This is consistent with (uncertain) data 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, τes, 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 crit ~= 108.5 M ⊙, implying that the UV luminosity functions extend to M UV ~= -13, although the corresponding τes is still on the low side of CMB-based estimates.

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.

ROSAT all-sky survey on the Einstein EMSS sample

NASA Technical Reports Server (NTRS)

Maccacaro, Tomasso

1992-01-01

The cosmological evolution and the luminosity function (XLF) of X ray selected Active Galactic Nuclei (AGN's) are discussed. The sample used is extracted from the Einstein Observatory Extended Medium Sensitivity Surveys (EMSS) and consists of more than 420 objects. Preliminary results from the ROSAT All-Sky Survey data confirm the correctness of the optical identification of the EMSS sources, thus giving confidence to the results obtained from the analysis of the AGN's sample. The XLF observed at different redshifts (up to z approx. 2) gives direct evidence of cosmological evolution. Data have been analyzed within the framework of luminosity evolution models and the two most common evolutionary forms, L sub x(Z) = L sub x(0) x e(sup Cr) and L sub x(Z) = L sub x(0) x (1 + z)(exp C), have been considered. Luminosity dependent evolution is required if the evolution function has the exponential form, whereas the simpler pure luminosity evolution model is still acceptable if the evolution function has the power law form. Using the whole sample of objects the number-counts and the de-evolved (z = 0) XLF have been derived. A comparison of the EMSS data with preliminary ROSAT results presented at this meeting indicates an overall agreement.

SPECIAL ISSUE ON OPTICAL PROCESSING OF INFORMATION: Optical signal-processing systems based on anisotropic media

NASA Astrophysics Data System (ADS)

Kiyashko, B. V.

1995-10-01

Partially coherent optical systems for signal processing are considered. The transfer functions are formed in these systems by interference of polarised light transmitted by an anisotropic medium. It is shown that such systems can perform various integral transformations of both optical and electric signals, in particular, two-dimensional Fourier and Fresnel transformations, as well as spectral analysis of weak light sources. It is demonstrated that such systems have the highest luminosity and vibration immunity among the systems with interference formation of transfer functions. An experimental investigation is reported of the application of these systems in the processing of signals from a linear hydroacoustic antenna array, and in measurements of the optical spectrum and of the intrinsic noise.

Far-infrared emission and star formation in spiral galaxies

NASA Technical Reports Server (NTRS)

Trinchieri, G.; Fabbiano, G.; Bandiera, R.

1989-01-01

The correlations between the emission in the far-IR, H-alpha, and blue in a sample of normal spiral galaxies are investigated. It is found that the luminosities in these three bands are all tightly correlated, although both the strength of the correlations and their functional dependencies are a function of the galaxies' morphological types. The best-fit power laws to these correlations are different for the comparison of different quantities and deviate significantly from linearity in some cases, implying the presence of additional emission mechanisms not related to the general increase of luminosity with galactic mass. Clear evidence is found of two independent effects in the incidence of warm far-IR emission in late-type spirals. One is a luminosity effect shown by the presence of excess far-IR relative to H-alpha or optical emission in the more luminous galaxies. The other is a dependence on widespread star-formation activity.

On the X-ray spectrum of the volume emissivity arising from Abell clusters

NASA Technical Reports Server (NTRS)

Stottlemyer, A. R.; Boldt, E. A.

1984-01-01

HEAO 1 A-2 X-ray spectra (2-15 keV) for an optically selected sample of Abell clusters of galaxies with z less than 0.1 have been analyzed to determine the energy dependence of the cosmological X-ray volume emissivity arising from such clusters. This spectrum is well fitted by an isothermal-bremsstrahlung model with kT = 7.4 + or - 1.5 KeV. This result is a test of the isothermal-volume-emissivity spectrum to be inferred from the conjecture that all contributing clusters may be characterized by kT = 7 keV, as assumed by McKee et al. (1980) in estimating the underlying luminosity function for the same sample. Although satisfied at the statistical level indicated, the analysis of a low-luminosity subsample suggests that this assumption of identical isothermal spectra would lead to a systematic error for a more statistically precise determination of the luminosity function's form.

Associating Fast Radio Bursts with Extragalactic Radio Sources: General Methodology and a Search for a Counterpart to FRB 170107

NASA Astrophysics Data System (ADS)

Eftekhari, T.; Berger, E.; Williams, P. K. G.; Blanchard, P. K.

2018-06-01

The discovery of a repeating fast radio burst (FRB) has led to the first precise localization, an association with a dwarf galaxy, and the identification of a coincident persistent radio source. However, further localizations are required to determine the nature of FRBs, the sources powering them, and the possibility of multiple populations. Here we investigate the use of associated persistent radio sources to establish FRB counterparts, taking into account the localization area and the source flux density. Due to the lower areal number density of radio sources compared to faint optical sources, robust associations can be achieved for less precise localizations as compared to direct optical host galaxy associations. For generally larger localizations that preclude robust associations, the number of candidate hosts can be reduced based on the ratio of radio-to-optical brightness. We find that confident associations with sources having a flux density of ∼0.01–1 mJy, comparable to the luminosity of the persistent source associated with FRB 121102 over the redshift range z ≈ 0.1–1, require FRB localizations of ≲20″. We demonstrate that even in the absence of a robust association, constraints can be placed on the luminosity of an associated radio source as a function of localization and dispersion measure (DM). For DM ≈1000 pc cm‑3, an upper limit comparable to the luminosity of the FRB 121102 persistent source can be placed if the localization is ≲10″. We apply our analysis to the case of the ASKAP FRB 170107, using optical and radio observations of the localization region. We identify two candidate hosts based on a radio-to-optical brightness ratio of ≳100. We find that if one of these is indeed associated with FRB 170107, the resulting radio luminosity (1029‑ 4 × 1030 erg s‑1 Hz‑1, as constrained from the DM value) is comparable to the luminosity of the FRB 121102 persistent source.

On the Mass and Luminosity Functions of Tidal Disruption Flares: Rate Suppression due to Black Hole Event Horizons

NASA Astrophysics Data System (ADS)

van Velzen, S.

2018-01-01

The tidal disruption of a star by a massive black hole is expected to yield a luminous flare of thermal emission. About two dozen of these stellar tidal disruption flares (TDFs) may have been detected in optical transient surveys. However, explaining the observed properties of these events within the tidal disruption paradigm is not yet possible. This theoretical ambiguity has led some authors to suggest that optical TDFs are due to a different process, such as a nuclear supernova or accretion disk instabilities. Here we present a test of a fundamental prediction of the tidal disruption event scenario: a suppression of the flare rate due to the direct capture of stars by the black hole. Using a recently compiled sample of candidate TDFs with black hole mass measurements, plus a careful treatment of selection effects in this flux-limited sample, we confirm that the dearth of observed TDFs from high-mass black holes is statistically significant. All the TDF impostor models we consider fail to explain the observed mass function; the only scenario that fits the data is a suppression of the rate due to direct captures. We find that this suppression can explain the low volumetric rate of the luminous TDF candidate ASASSN-15lh, thus supporting the hypothesis that this flare belongs to the TDF family. Our work is the first to present the optical TDF luminosity function. A steep power law is required to explain the observed rest-frame g-band luminosity, {dN}/{{dL}}g\\propto {L}g-2.5. The mean event rate of the flares in our sample is ≈ 1× {10}-4 galaxy‑1 yr‑1, consistent with the theoretically expected tidal disruption rate.

A Model for Protostellar Cluster Luminosities and the Impact on the CO–H2 Conversion Factor

NASA Astrophysics Data System (ADS)

Gaches, Brandt A. L.; Offner, Stella S. R.

2018-02-01

We construct a semianalytic model to study the effect of far-ultraviolet (FUV) radiation on gas chemistry from embedded protostars. We use the protostellar luminosity function (PLF) formalism of Offner & McKee to calculate the total, FUV, and ionizing cluster luminosity for various protostellar accretion histories and cluster sizes. We2 compare the model predictions with surveys of Gould Belt star-forming regions and find that the tapered turbulent core model matches best the mean luminosities and the spread in the data. We combine the cluster model with the photodissociation region astrochemistry code, 3D-PDR, to compute the impact of the FUV luminosity from embedded protostars on the CO-to-H2 conversion factor, X CO, as a function of cluster size, gas mass, and star formation efficiency. We find that X CO has a weak dependence on the FUV radiation from embedded sources for large clusters owing to high cloud optical depths. In smaller and more efficient clusters the embedded FUV increases X CO to levels consistent with the average Milky Way values. The internal physical and chemical structures of the cloud are significantly altered, and X CO depends strongly on the protostellar cluster mass for small efficient clouds.

Great Optically Luminous Dropout Research Using Subaru HSC (GOLDRUSH). I. UV luminosity functions at z ˜ 4-7 derived with the half-million dropouts on the 100 deg2 sky

NASA Astrophysics Data System (ADS)

Ono, Yoshiaki; Ouchi, Masami; Harikane, Yuichi; Toshikawa, Jun; Rauch, Michael; Yuma, Suraphong; Sawicki, Marcin; Shibuya, Takatoshi; Shimasaku, Kazuhiro; Oguri, Masamune; Willott, Chris; Akhlaghi, Mohammad; Akiyama, Masayuki; Coupon, Jean; Kashikawa, Nobunari; Komiyama, Yutaka; Konno, Akira; Lin, Lihwai; Matsuoka, Yoshiki; Miyazaki, Satoshi; Nagao, Tohru; Nakajima, Kimihiko; Silverman, John; Tanaka, Masayuki; Taniguchi, Yoshiaki; Wang, Shiang-Yu

2018-01-01

We study the UV luminosity functions (LFs) at z ˜ 4, 5, 6, and 7 based on the deep large-area optical images taken by the Hyper Suprime-Cam (HSC) Subaru Strategic Program (SSP). On the 100 deg2 sky of the HSC SSP data available to date, we take enormous samples consisting of a total of 579565 dropout candidates at z ˜ 4-7 by the standard color selection technique, 358 out of which are spectroscopically confirmed by our follow-up spectroscopy and other studies. We obtain UV LFs at z ˜ 4-7 that span a very wide UV luminosity range of ˜0.002-100 L_UV^\\ast (-26 < MUV < -14 mag) by combining LFs from our program and the ultra-deep Hubble Space Telescope legacy surveys. We derive three parameters of the best-fit Schechter function, ϕ*, M_UV^{ \\ast}, and α, of the UV LFs in the magnitude range where the active galactic nucleus (AGN) contribution is negligible, and find that α and ϕ* decrease from z ˜ 4 to 7 with no significant evolution of M_UV^{ \\ast}. Because our HSC SSP data bridge the LFs of galaxies and AGNs with great statistical accuracy, we carefully investigate the bright end of the galaxy UV LFs that are estimated by the subtraction of the AGN contribution either aided by spectroscopy or the best-fit AGN UV LFs. We find that the bright end of the galaxy UV LFs cannot be explained by the Schechter function fits at >2 σ significance, and require either double power-law functions or modified Schechter functions that consider a magnification bias due to gravitational lensing.

A catalogue of faint local radio AGN and the properties of their host galaxies

NASA Astrophysics Data System (ADS)

Lofthouse, E. K.; Kaviraj, S.; Smith, D. JB; Hardcastle, M. J.

2018-05-01

We present a catalogue of local (z < 0.1) galaxies that contain faint AGN. We select these objects by identifying galaxies that exhibit a significant excess in their radio luminosities, compared to what is expected from the observed levels of star-formation activity in these systems. This is achieved by comparing the optical (spectroscopic) star formation rate (SFR) to the 1.4 GHz luminosity measured from the FIRST survey. The majority of the AGN identified in this study are fainter than those in previous work, such as in the Best and Heckman (2012) catalogue. We show that these faint AGN make a non-negligible contribution to the radio luminosity function at low luminosities (below 1022.5 W Hz-1), and host ˜13 per cent of the local radio luminosity budget. Their host galaxies are predominantly high stellar-mass systems (with a median stellar mass of 1011M⊙), are found across a range of environments (but typically in denser environments than star-forming galaxies) and have early-type morphologies. This study demonstrates a general technique to identify AGN in galaxy populations where reliable optical SFRs can be extracted using spectro-photometry and where radio data are also available so that a radio excess can be measured. Our results also demonstrate that it is unsafe to infer SFRs from radio emission alone, even if bright AGN have been excluded from a sample, since there is a significant population of faint radio AGN which may contaminate the radio-derived SFRs.

The Faint End of the z = 5 Quasar Luminosity Function from the CFHTLS

NASA Astrophysics Data System (ADS)

McGreer, Ian D.; Fan, Xiaohui; Jiang, Linhua; Cai, Zheng

2018-03-01

We present results from a spectroscopic survey of z ∼ 5 quasars in the CFHT Legacy Survey. Using both optical color selection and a likelihood method, we select 97 candidates over an area of 105 deg2 to a limit of i AB < 23.2, and 7 candidates in the range 23.2 < i AB < 23.7 over an area of 18.5 deg2. Spectroscopic observations for 43 candidates were obtained with Gemini, MMT, and Large Binocular Telescope, of which 37 are z > 4 quasars. This sample extends measurements of the quasar luminosity function ∼1.5 mag fainter than our previous work in Sloan Digital Sky Survey Stripe 82. The resulting luminosity function is in good agreement with our previous results, and suggests that the faint end slope is not steep. We perform a detailed examination of our survey completeness, particularly the impact of the Lyα emission assumed in our quasar spectral models, and find hints that the observed Lyα emission from faint z ∼ 5 quasars is weaker than for z ∼ 3 quasars at a similar luminosity. Our results strongly disfavor a significant contribution of faint quasars to the hydrogen-ionizing background at z = 5.

White Dwarfs in the GALEX Survey

NASA Technical Reports Server (NTRS)

Kawka, Adela; Vennes, Stephane

2007-01-01

We have cross-correlated the 2dF QSO Redshift Survey (2QZ) white dwarf catalog with the GALEX 2nd Data Release and the Sloan Digital Sky Survey (SDSS) data release 5 to obtain ultraviolet photometry (FUV, NUV) for approximately 700 objects and optical photometry (ugriz) for approximately 800 objects. We have compared the optical-ultraviolet colors to synthetic white dwarf colors to obtain temperature estimates for approximately 250 of these objects. These white dwarfs have effective temperatures ranging from 10 000 K (cooling age of about 1Gyr) up to about 40000 K (cooling age of about 3 Myrs), with a few that have even higher temperatures. We found that to distinguish white dwarfs from other stellar luminosity classes both optical and ultraviolet colors are necessary, in particular for the hotter objects where there is contamination from B and 0 main-sequence stars. Using this sample we build a luminosity function for the DA white dwarfs with Mv < 12 mag.

THE OBSCURED FRACTION OF ACTIVE GALACTIC NUCLEI IN THE XMM-COSMOS SURVEY: A SPECTRAL ENERGY DISTRIBUTION PERSPECTIVE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lusso, E.; Hennawi, J. F.; Richards, G. T.

2013-11-10

The fraction of active galactic nucleus (AGN) luminosity obscured by dust and re-emitted in the mid-IR is critical for understanding AGN evolution, unification, and parsec-scale AGN physics. For unobscured (Type 1) AGNs, where we have a direct view of the accretion disk, the dust covering factor can be measured by computing the ratio of re-processed mid-IR emission to intrinsic nuclear bolometric luminosity. We use this technique to estimate the obscured AGN fraction as a function of luminosity and redshift for 513 Type 1 AGNs from the XMM-COSMOS survey. The re-processed and intrinsic luminosities are computed by fitting the 18 bandmore » COSMOS photometry with a custom spectral energy distribution fitting code, which jointly models emission from hot dust in the AGN torus, from the accretion disk, and from the host galaxy. We find a relatively shallow decrease of the luminosity ratio as a function of L{sub bol}, which we interpret as a corresponding decrease in the obscured fraction. In the context of the receding torus model, where dust sublimation reduces the covering factor of more luminous AGNs, our measurements require a torus height that increases with luminosity as h ∝ L{sub bol}{sup 0.3-0.4}. Our obscured-fraction-luminosity relation agrees with determinations from Sloan Digital Sky Survey censuses of Type 1 and Type 2 quasars and favors a torus optically thin to mid-IR radiation. We find a much weaker dependence of the obscured fraction on 2-10 keV luminosity than previous determinations from X-ray surveys and argue that X-ray surveys miss a significant population of highly obscured Compton-thick AGNs. Our analysis shows no clear evidence for evolution of the obscured fraction with redshift.« less

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Willott, Chris J.; Crampton, David; Hutchings, John B.

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 deepmore » XMM-Newton survey showing that optical selection is still a very efficient tool for finding high-redshift quasars.« less

Eddington limit for a gaseous stratus with finite optical depth

NASA Astrophysics Data System (ADS)

Fukue, Jun

2015-06-01

The Eddington luminosity of a spherical source is usually defined for a uniformly extending normal plasma. We usually suppose that the gas can accrete to the central object at the sub-Eddington luminosity, while it would be blown off from the central luminous source in the super-Eddington case. We reconsider this central dogma of the Eddington limit under the radiative transfer effect for the purely scattering case, using analytical and numerical methods. For the translucent isolated gas cloud (stratus) with finite optical depth, the concept of the Eddington luminosity is drastically changed. In an heuristic way, we find that the critical condition is approximately expressed as Γ = (1 + μ* + τc)/2, where Γ (=L/LE) is the central luminosity L normalized by the Eddington luminosity LE, τc is the optical depth of the stratus, and μ* (=√{1-R_*^2/R^2}) is the direction cosine of the central object, R* being the radius of the central object, and R the distance from the central object. When the optical depth of the stratus is around unity, the classical Eddington limit roughly holds for the stratus; Γ ˜ 1. However, when the optical depth is greater than unity, the critical condition becomes roughly Γ ˜ τc/2, and the stratus would infall on to the central source even at the highly super-Eddington luminosity. When the optical depth is less than unity, on the other hand, the critical condition reduces to Γ ≳ (1 + μ*)/2, and the stratus could be blown off in some limited ranges, depending on μ*. This new concept of the Eddington limit for the isolated stratus could drastically change the accretion and outflow physics of highly inhomegeneous plasmas, with relevance for astrophysical jets and winds and supermassive black hole formation.

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.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bonne, Nicolas J.; Brown, Michael J. I.; Jones, Heath

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 thatmore » 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.« less

Spectroscopy of luminous infrared galaxies at 2 microns: 1. The ultraluminous galaxies (L(sub IR) approximately greater than 10 (exp 12) solar luminosity)

NASA Technical Reports Server (NTRS)

Goldader, Jeffrey D.; Joseph, R. D.; Doyon, Rene; Sanders, D. B.

1995-01-01

We present high-quality spectra covering the K window at a resolving power of 340 for a sample of 13 ultraluminous (L(sub IR) approximately greater than 10(exp 12) solar luminosity) infrared-selected galaxies, and line fluxes for a comparison sample of 24 lower luminosity galaxies. The 2 micrometers spectra of 10 of the ultraluminous galaxies are characterized by emission and absorption features commonly associated with stars and star formation; two others have the red power-law spectra and Br gamma line widths of Seyfert 1 galaxies; the final galaxy has strong emission from hot dust. We have found no broad-line active nuclei not already known from optical observations, despite the fact that the extinction at 2 micrometers is 1/10 that at optical wavelengths; any putative Seyfert 1 nuclei must be deeply buried. Powerful continua and emission lines from H2 and Br gamma are detected in all the ultraluminous galaxies. Comparing the H2 1-0 S(1), Br gamma, and 2 micrometers and far-infrared luminosities to those of the lower luminosity galaxies yields several major results. First, the dereddened Br gamma emission, relative to the far-infrared luminosity is significantly depressed in the ultraluminous sample, when compared to the lower luminosity galaxies. Five of the ultraluminous galaxies have L(sub Br gamma)L(sub IR) ratios lower than for any of the comparison objects. Second, the H2 1-0 S(1) luminosity is also responsible, directly or indirectly, for producing the excited H2, and that the H2 apparently comes from optically thin regions in both classes of objects. Third, eight of the 13 ultraluminous systems have lower 2 micrometers/far-infrared luminosity ratios than any of the lower luminosity galaxies, and five of these are the galaxies also deficient in Br gamma. These three findings may be understood if the the H2, Br gamma, and 2 mircometers continua in the ultraluminous galaxies arise from spatially distinct regions, with the continuum and Br gamma largely coming from volumes optically thick even at 2 micrometers, and obscured in such a fashion that the extinctions measured using optical spectroscopy do not properly measure the true optical depths. If this is the case, then even near-infrared spectroscopy may be unable to exclude the presence of undetected powerful active galactive nuclei in the ultraluminous galaxies.

Narrow vs. Broad line Seyfert 1 galaxies: X-ray, optical and mid-infrared AGN characteristics

NASA Astrophysics Data System (ADS)

Lakićević, Maša; Popović, Luka Č.; Kovačević-Dojčinović, Jelena

2018-05-01

We investigated narrow line Seyfert 1 galaxies (NLS1s) at optical, mid-infrared (MIR) and X-ray wavelengths, comparing them to the broad line active galactic nuclei (BLAGNs). We found that black hole mass, coronal line luminosities, X-ray hardness ratio and X-ray, optical and MIR luminosities are higher for the BLAGNs than for NLS1s, while policyclic aromatic hydrocarbon (PAH) contribution and the accretion rates are higher for the NLS1s. Furthermore, we found some trends among spectral parameters that NLS1s have and BLAGNs do not have. The evolution of FWHM(Hβ) with the luminosities of MIR and coronal lines, continuum luminosities, PAH contribution, Hβ broad line luminosity, FWHM[O III] and EW(HβNLR), are important trends found for NLS1s. That may contribute to the insight that NLS1s are developing AGNs, growing their black holes, while their luminosities and FWHM(Hβ) consequently grow, and that BLAGNs are mature, larger objects of slower and/or different evolution. Black hole mass is related to PAH contribution only for NLS1s, which may suggest that PAHs are more efficiently destroyed in NLS1s.

On the Scatter in the Radius-Luminosity Relationship for Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Kilerci Eser, E.; Vestergaard, M.; Peterson, B. M.; Denney, K. D.; Bentz, M. C.

2015-03-01

We investigate and quantify the observed scatter in the empirical relationship between the broad line region size R and the luminosity of the active galactic nucleus, in order to better understand its origin. This study is motivated by the indispensable role of this relationship in the mass estimation of cosmologically distant black holes, but may also be relevant to the recently proposed application of this relationship for measuring cosmic distances. We study six nearby reverberation-mapped active galactic nuclei (AGNs) for which simultaneous UV and optical monitoring data exist. We also examine the long-term optical luminosity variations of the Seyfert 1 galaxy NGC 5548 and employ Monte Carlo simulations to study the effects of the intrinsic variability of individual objects on the scatter in the global relationship for a sample of ~40 AGNs. We find the scatter in this relationship has a correctable dependence on color. For individual AGNs, the size of the Hβ emitting region has a steeper dependence on the nuclear optical luminosity than on the UV luminosity, which can introduce a scatter of ~0.08 dex into the global relationship, due the nonlinear relationship between the variations in the ionizing continuum and those in the optical continuum. Also, our analysis highlights the importance of understanding and minimizing the scatter in the relationship traced by the intrinsic variability of individual AGNs since it propagates directly into the global relationship. We find that using the UV luminosity as a substitute for the ionizing luminosity can reduce a sizable fraction of the current observed scatter of ~0.13 dex.

Gamma-ray burster recurrence timescales

NASA Technical Reports Server (NTRS)

Schaefer, B. E.; Cline, T. L.

1984-01-01

Three optical transients have been found which are associated with gamma-ray bursters (GRBs). The deduced recurrence timescale for these optical transients (tau sub opt) will depend on the minimum brightness for which a flash would be detected. A detailed analysis using all available data of tau sub opt as a function of E(gamma)/E(opt) is given. For flashes similar to those found in the Harvard archives, the best estimate of tau sub opt is 0.74 years, with a 99% confidence interval from 0.23 years to 4.7 years. It is currently unclear whether the optical transients from GRBs also give rise to gamma-ray events. One way to test this association is to measure the recurrence timescale of gamma-ray events tau sub gamma. A total of 210 gamma-ray error boxes were examined and it was found that the number of observed overlaps is not significantly different from the number expected from chance coincidence. This observation can be used to place limits on tau sub gamma for an assumed luminosity function. It was found that tau sub gamma is approx. 10 yr if bursts are monoenergetic. However, if GRBs have a power law luminosity function with a wide dynamic range, then the limit is tau sub gamma 0.5 yr. Hence, the gamma-ray data do not require tau sub gamma and tau sub opt to be different.

The Rest-Frame Optical Luminosity Functions of Galaxies at 2<=z<=3.5

NASA Astrophysics Data System (ADS)

Marchesini, D.; van Dokkum, P.; Quadri, R.; Rudnick, G.; Franx, M.; Lira, P.; Wuyts, S.; Gawiser, E.; Christlein, D.; Toft, S.

2007-02-01

We present the rest-frame optical (B, V, and R band) luminosity functions (LFs) of galaxies at 2<=z<=3.5, measured from a K-selected sample constructed from the deep NIR MUSYC, the ultradeep FIRES, and the GOODS-CDFS. This sample is unique for its combination of area and range of luminosities. The faint-end slopes of the LFs at z>2 are consistent with those at z~0. The characteristic magnitudes are significantly brighter than the local values (e.g., ~1.2 mag in the R band), while the measured values for Φ* are typically ~5 times smaller. The B-band luminosity density at z~2.3 is similar to the local value, and in the R band it is ~2 times smaller than the local value. We present the LF of distant red galaxies (DRGs), which we compare to that of non-DRGs. While DRGs and non-DRGs are characterized by similar LFs at the bright end, the faint-end slope of the non-DRG LF is much steeper than that of DRGs. The contribution of DRGs to the global densities down to the faintest probed luminosities is 14%-25% in number and 22%-33% in luminosity. From the derived rest-frame U-V colors and stellar population synthesis models, we estimate the mass-to-light ratios (M/L) of the different subsamples. The M/L ratios of DRGs are ~5 times higher (in the R and V bands) than those of non-DRGs. The global stellar mass density at 2<=z<=3.5 appears to be dominated by DRGs, whose contribution is of order ~60%-80% of the global value. Qualitatively similar results are obtained when the population is split by rest-frame U-V color instead of observed J-K color. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS5-26555. Also based on observations collected at the European Southern Observatories on Paranal, Chile as part of the ESO program 164.O-0612.

Gamma-ray luminosity and photon index evolution of FSRQ blazars and contribution to the gamma-ray background

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singal, J.; Ko, A.; Petrosian, V., E-mail: jsingal@richmond.edu

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 accountedmore » 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.« less

Coronal Activity in the R CrA T Association

NASA Technical Reports Server (NTRS)

Patten, Brian M.; Oliversen, Ronald J. (Technical Monitor)

2005-01-01

Brian Patten is the Principal Investigator of the NASA ROSS-ADP project Coronal Activity in the R CrA T Association. For this project we have extracted net counts and variability information for all of the X-ray sources found in 23 archival ROSAT PSPC and HRI images in the region of the R CrA T association. These data have been merged with an extensive database of optical and near-infrared photometry, optical spectroscopy, and parallax data. These data have been used to (1) identify new association members and clarify the membership status of a number of previously suspected members of the association, and (2) derive, for the first time, an accurate coronal luminosity function for the T Tauri members of this T association and make direct comparisons between the coronal luminosity functions for other T associations and those of large clusters. We have used our survey data to assess (a) the importance of the star-formation environment in initial coronal activity levels, (b) the effects of PMS evolution on dynamo activity as a function of mass and age, and (c) the level of contamination by field post-T Tauri stars on association membership surveys.

Deep CFHT Y-band Imaging of VVDS-F22 Field. II. Quasar Selection and Quasar Luminosity Function

NASA Astrophysics Data System (ADS)

Yang, Jinyi; Wu, Xue-Bing; Liu, Dezi; Fan, Xiaohui; Yang, Qian; Wang, Feige; McGreer, Ian D.; Fan, Zuhui; Yuan, Shuo; Shan, Huanyuan

2018-03-01

We report the results of a faint quasar survey in a one-square-degree field. The aim is to test the Y-K/g-z and J-K/i-Y color selection criteria for quasars at faint magnitudes to obtain a complete sample of quasars based on deep optical and near-infrared color–color selection and to measure the faint end of the quasar luminosity function (QLF) over a wide redshift range. We carried out a quasar survey based on the Y-K/g-z and J-K/i-Y quasar selection criteria, using the deep Y-band data obtained from our CFHT/WIRCam Y-band images in a two-degree field within the F22 field of the VIMOS VLT deep survey, optical co-added data from Sloan Digital Sky Survey Stripe 82 and deep near-infrared data from the UKIDSS Deep Extragalactic Survey in the same field. We discovered 25 new quasars at 0.5< z< 4.5 and i< 22.5 mag within one-square-degree field. The survey significantly increases the number of faint quasars in this field, especially at z∼ 2{--}3. It confirms that our color selections are highly complete in a wide redshift range (z< 4.5), especially over the quasar number density peak at z∼ 2{--}3, even for faint quasars. Combining all previous known quasars and new discoveries, we construct a sample with 109 quasars and measure the binned QLF and parametric QLF. Although the sample is small, our results agree with a pure luminosity evolution at lower redshift and luminosity evolution and density evolution model at redshift z> 2.5.

Reaching record-low β* at the CERN Large Hadron Collider using a novel scheme of collimator settings and optics

NASA Astrophysics Data System (ADS)

Bruce, R.; Bracco, C.; De Maria, R.; Giovannozzi, M.; Mereghetti, A.; Mirarchi, D.; Redaelli, S.; Quaranta, E.; Salvachua, B.

2017-03-01

The Large Hadron Collider (LHC) at CERN is built to collide intense proton beams with an unprecedented energy of 7 TeV. The design stored energy per beam of 362 MJ makes the LHC beams highly destructive, so that any beam losses risk to cause quenches of superconducting magnets or damage to accelerator components. Collimators are installed to protect the machine and they define a minimum normalized aperture, below which no other element is allowed. This imposes a limit on the achievable luminosity, since when squeezing β* (the β-function at the collision point) to smaller values for increased luminosity, the β-function in the final focusing system increases. This leads to a smaller normalized aperture that risks to go below the allowed collimation aperture. In the first run of the LHC, this was the main limitation on β*, which was constrained to values above the design specification. In this article, we show through theoretical and experimental studies how tighter collimator openings and a new optics with specific phase-advance constraints allows a β* as small as 40 cm, a factor 2 smaller than β*=80 cm used in 2015 and significantly below the design value β*=55 cm, in spite of a lower beam energy. The proposed configuration with β*=40 cm has been successfully put into operation and has been used throughout 2016 as the LHC baseline. The decrease in β* compared to 2015 has been an essential contribution to reaching and surpassing, in 2016, the LHC design luminosity for the first time, and to accumulating a record-high integrated luminosity of around 40 fb-1 in one year, in spite of using less bunches than in the design.

Full-data Results of Hubble Frontier Fields: UV Luminosity Functions at z ∼ 6–10 and a Consistent Picture of Cosmic Reionization

NASA Astrophysics Data System (ADS)

Ishigaki, Masafumi; Kawamata, Ryota; Ouchi, Masami; Oguri, Masamune; Shimasaku, Kazuhiro; Ono, Yoshiaki

2018-02-01

We present UV luminosity functions of dropout galaxies at z∼ 6{--}10 with the complete Hubble Frontier Fields data. We obtain a catalog of ∼450 dropout-galaxy candidates (350, 66, and 40 at z∼ 6{--}7, 8, and 9, respectively), with UV absolute magnitudes that reach ∼ -14 mag, ∼2 mag deeper than the Hubble Ultra Deep Field detection limits. We carefully evaluate number densities of the dropout galaxies by Monte Carlo simulations, including all lensing effects such as magnification, distortion, and multiplication of images as well as detection completeness and contamination effects in a self-consistent manner. We find that UV luminosity functions at z∼ 6{--}8 have steep faint-end slopes, α ∼ -2, and likely steeper slopes, α ≲ -2 at z∼ 9{--}10. We also find that the evolution of UV luminosity densities shows a non-accelerated decline beyond z∼ 8 in the case of {M}trunc}=-15, but an accelerated one in the case of {M}trunc}=-17. We examine whether our results are consistent with the Thomson scattering optical depth from the Planck satellite and the ionized hydrogen fraction Q H II at z≲ 7 based on the standard analytic reionization model. We find that reionization scenarios exist that consistently explain all of the observational measurements with the allowed parameters of {f}esc}={0.17}-0.03+0.07 and {M}trunc}> -14.0 for {log}{ξ }ion}/[{erg}}-1 {Hz}]=25.34, where {f}esc} is the escape fraction, M trunc is the faint limit of the UV luminosity function, and {ξ }ion} is the conversion factor of the UV luminosity to the ionizing photon emission rate. The length of the reionization period is estimated to be {{Δ }}z={3.9}-1.6+2.0 (for 0.1< {Q}{{H}{{II}}}< 0.99), consistent with the recent estimate from Planck.

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.

2017-01-01

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 then 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.

ON A NEW THEORETICAL FRAMEWORK FOR RR LYRAE STARS. I. THE METALLICITY DEPENDENCE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marconi, M.; Coppola, G.; Musella, I.

2015-07-20

We present new nonlinear, time-dependent convective hydrodynamical models of RR Lyrae stars computed assuming a constant helium-to-metal enrichment ratio and a broad range in metal abundances (Z = 0.0001–0.02). The stellar masses and luminosities adopted to construct the pulsation models were fixed according to detailed central He-burning horizontal-branch evolutionary models. The pulsation models cover a broad range in stellar luminosity and effective temperatures and the modal stability is investigated for both fundamental (FU) and first overtone polsators (FOs). We predict the topology of the instability strip (IS) as a function of the metal content and new analytical relations for themore » edges of the IS in the observational plane. Moreover, a new analytical relation to constrain the pulsation mass of double pulsators as a function of the period ratio and the metal content is provided. We derive new Period–Radius–Metallicity relations for FU and FO pulsators. They agree quite well with similar empirical and theoretical relations in the literature. From the predicted bolometric light curves, transformed into optical (UBVRI) and near-infrared (NIR; JHK) bands, we compute the intensity-averaged mean magnitudes along the entire pulsation cycle and in turn new and homogenous metal-dependent (RIJHK) Period–Luminosity relations. Moreover, we compute new dual and triple-band optical, optical–NIR, and NIR Period–Wesenheit–Metallicity relations. Interestingly, we find that the optical Period-W(V, B–V) is independent of the metal content and that the accuracy of individual distances is a balance between the adopted diagnostics and the precision of photometric and spectroscopic data sets.« less

A Bridge from Optical to Infrared Galaxies: Explaining Local Properties, Predicting Galaxy Counts and the Cosmic Background Radiation

NASA Astrophysics Data System (ADS)

Totani, T.; Takeuchi, T. T.

2001-12-01

A new model of infrared galaxy counts and the cosmic background radiation (CBR) is developed by extending a model for optical/near-infrared galaxies. Important new characteristics of this model are that mass scale dependence of dust extinction is introduced based on the size-luminosity relation of optical galaxies, and that the big grain dust temperature T dust is calculated based on a physical consideration for energy balance, rather than using the empirical relation between T dust and total infrared luminosity L IR found in local galaxies, which has been employed in most of previous works. Consequently, the local properties of infrared galaxies, i.e., optical/infrared luminosity ratios, L IR-T dust correlation, and infrared luminosity function are outputs predicted by the model, while these have been inputs in a number of previous models. Our model indeed reproduces these local properties reasonably well. Then we make predictions for faint infrared counts (in 15, 60, 90, 170, 450, and 850 μ m) and CBR by this model. We found considerably different results from most of previous works based on the empirical L IR-T dust relation; especially, it is shown that the dust temperature of starbursting primordial elliptical galaxies is expected to be very high (40--80K). This indicates that intense starbursts of forming elliptical galaxies should have occurred at z ~ 2--3, in contrast to the previous results that significant starbursts beyond z ~ 1 tend to overproduce the far-infrared (FIR) CBR detected by COBE/FIRAS. On the other hand, our model predicts that the mid-infrared (MIR) flux from warm/nonequilibrium dust is relatively weak in such galaxies making FIR CBR, and this effect reconciles the prima facie conflict between the upper limit on MIR CBR from TeV gamma-ray observations and the COBE\\ detections of FIR CBR. The authors thank the financial support by the Japan Society for Promotion of Science.

AGN are cooler than you think: the intrinsic far-IR emission from QSOs

NASA Astrophysics Data System (ADS)

Symeonidis, M.; Giblin, B. M.; Page, M. J.; Pearson, C.; Bendo, G.; Seymour, N.; Oliver, S. J.

2016-06-01

We present an intrinsic AGN spectral energy distribution (SED) extending from the optical to the submm, derived with a sample of unobscured, optically luminous (νLν,5100 > 1043.5 erg s-1) QSOs at z < 0.18 from the Palomar Green survey. The intrinsic AGN SED was computed by removing the contribution from stars using the 11.3 μm polycyclic aromatic hydrocarbon (PAH) feature in the QSOs' mid-IR spectra; the 1σ uncertainty on the SED ranges between 12 and 45 per cent as a function of wavelength and is a combination of PAH flux measurement errors and the uncertainties related to the conversion between PAH luminosity and star-forming luminosity. Longwards of 20 μm, the shape of the intrinsic AGN SED is independent of the AGN power indicating that our template should be applicable to all systems hosting luminous AGN (νLν, 5100 or L_X(2-10 keV) ≳ 1043.5 erg s-1). We note that for our sample of luminous QSOs, the average AGN emission is at least as high as, and mostly higher than, the total stellar powered emission at all wavelengths from the optical to the submm. This implies that in many galaxies hosting powerful AGN, there is no `safe' broad-band photometric observation (at λ < 1000 μm) which can be used in calculating star formation rates without subtracting the AGN contribution. Roughly, the AGN contribution may be ignored only if the intrinsic AGN luminosity at 5100 AA is at least a factor of 4 smaller than the total infrared luminosity (LIR, 8-1000 μm) of the galaxy. Finally, we examine the implication of our work in statistical studies of star formation in AGN host galaxies.

INJECTION OPTICS FOR THE JLEIC ION COLLIDER RING

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morozov, Vasiliy; Derbenev, Yaroslav; Lin, Fanglei

2016-05-01

The Jefferson Lab Electron-Ion Collider (JLEIC) will accelerate protons and ions from 8 GeV to 100 GeV. A very low beta function at the Interaction Point (IP) is needed to achieve the required luminosity. One consequence of the low beta optics is that the beta function in the final focusing (FF) quadrupoles is extremely high. This leads to a large beam size in these magnets as well as strong sensitivity to errors which limits the dynamic aperture. These effects are stronger at injection energy where the beam size is maximum, and therefore very large aperture FF magnets are required tomore » allow a large dynamic aperture. A standard solution is a relaxed injection optics with IP beta function large enough to provide a reasonable FF aperture. This also reduces the effects of FF errors resulting in a larger dynamic aperture at injection. We describe the ion ring injection optics design as well as a beta-squeeze transition from the injection to collision optics.« less

VizieR Online Data Catalog: RX J105453.3+552102 cluster SDSS photometry (Aguerri+, 2011)

NASA Astrophysics Data System (ADS)

Aguerri, J. A. L.; Girardi, M.; Boschin, W.; Barrena, R.; Mendez-Abreu, J.; Sanchez-Janssen, R.; Borgani, S.; Castro-Rodriguez, N.; Corsini, E. M.; Del Burgo, C.; D'Onghia, E.; Iglesias-Paramo, J.; Napolitano, N.; Vilchez, J. M.

2011-08-01

Optical imaging of RX J105453.3+552102 was carried out at the 2.5m NOT telescope in March 2008. Optical deep images were used for studying the properties of the brightest group galaxy and for computing the photometric luminosity function of the group. We have also performed a detail dynamical analysis of the system based on redshift data for 116 galaxies. Combining galaxy velocities and positions we selected 78 group members. (1 data file).

Soft X-ray observations of pre-main sequence stars in the chamaeleon dark cloud

NASA Technical Reports Server (NTRS)

Feigelson, Eric D.; Kriss, Gerard A.

1987-01-01

Einstein IPC observations of the nearby Chamaeleon I star forming cloud show 22 well-resolved soft X-ray sources in a 1x2 deg region. Twelve are associated with H-alpha emission line pre-main sequence (PMS) stars, and four with optically selected PMS stars. Several X-ray sources have two or more PMS stars in their error circles. Optical spectra were obtained at CTIO of possible stellar counterparts of the remaining X-ray sources. They reveal 5 probable new cloud members, K7-MO stars with weak or absent emission lines. These naked X-ray selected PMS stars are similar to those found in the Taurus-Auriga cloud. The spatial distributions and H-R diagrams of the X-ray and optically selected PMS stars in the cloud are very similar. Luminosity functions indicate the Chamaeleon stars are on average approximately 5 times more X-ray luminous than Pleiad dwarfs. A significant correlation between L sub x and optical magnitude suggests this trend may continue within the PMS phase of stellar evolution. The relation of increasing X-ray luminosity with decreasing stellar ages is thus extended to stellar ages as young as 1 million years.

ON THE SCATTER IN THE RADIUS-LUMINOSITY RELATIONSHIP FOR ACTIVE GALACTIC NUCLEI

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kilerci Eser, E.; Vestergaard, M.; Peterson, B. M.

2015-03-01

We investigate and quantify the observed scatter in the empirical relationship between the broad line region size R and the luminosity of the active galactic nucleus, in order to better understand its origin. This study is motivated by the indispensable role of this relationship in the mass estimation of cosmologically distant black holes, but may also be relevant to the recently proposed application of this relationship for measuring cosmic distances. We study six nearby reverberation-mapped active galactic nuclei (AGNs) for which simultaneous UV and optical monitoring data exist. We also examine the long-term optical luminosity variations of the Seyfert 1more » galaxy NGC 5548 and employ Monte Carlo simulations to study the effects of the intrinsic variability of individual objects on the scatter in the global relationship for a sample of ∼40 AGNs. We find the scatter in this relationship has a correctable dependence on color. For individual AGNs, the size of the Hβ emitting region has a steeper dependence on the nuclear optical luminosity than on the UV luminosity, which can introduce a scatter of ∼0.08 dex into the global relationship, due the nonlinear relationship between the variations in the ionizing continuum and those in the optical continuum. Also, our analysis highlights the importance of understanding and minimizing the scatter in the relationship traced by the intrinsic variability of individual AGNs since it propagates directly into the global relationship. We find that using the UV luminosity as a substitute for the ionizing luminosity can reduce a sizable fraction of the current observed scatter of ∼0.13 dex.« less

A Bridge from Optical to Infrared Galaxies: Explaining Local Properties and Predicting Galaxy Counts and the Cosmic Background Radiation

NASA Astrophysics Data System (ADS)

Totani, Tomonori; Takeuchi, Tsutomu T.

2002-05-01

We give an explanation for the origin of various properties observed in local infrared galaxies and make predictions for galaxy counts and cosmic background radiation (CBR) using a new model extended from that for optical/near-infrared galaxies. Important new characteristics of this study are that (1) mass scale dependence of dust extinction is introduced based on the size-luminosity relation of optical galaxies and that (2) the large-grain dust temperature Tdust is calculated based on a physical consideration for energy balance rather than by using the empirical relation between Tdust and total infrared luminosity LIR found in local galaxies, which has been employed in most previous works. Consequently, the local properties of infrared galaxies, i.e., optical/infrared luminosity ratios, LIR-Tdust correlation, and infrared luminosity function are outputs predicted by the model, while these have been inputs in a number of previous models. Our model indeed reproduces these local properties reasonably well. Then we make predictions for faint infrared counts (in 15, 60, 90, 170, 450, and 850 μm) and CBR using this model. We found results considerably different from those of most previous works based on the empirical LIR-Tdust relation; especially, it is shown that the dust temperature of starbursting primordial elliptical galaxies is expected to be very high (40-80 K), as often seen in starburst galaxies or ultraluminous infrared galaxies in the local and high-z universe. This indicates that intense starbursts of forming elliptical galaxies should have occurred at z~2-3, in contrast to the previous results that significant starbursts beyond z~1 tend to overproduce the far-infrared (FIR) CBR detected by COBE/FIRAS. On the other hand, our model predicts that the mid-infrared (MIR) flux from warm/nonequilibrium dust is relatively weak in such galaxies making FIR CBR, and this effect reconciles the prima facie conflict between the upper limit on MIR CBR from TeV gamma-ray observations and the COBE detections of FIR CBR. The intergalactic optical depth of TeV gamma rays based on our model is also presented.

Ultra-faint ultraviolet galaxies at z ∼ 2 behind the lensing cluster A1689: The luminosity function, dust extinction, and star formation rate density

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alavi, Anahita; Siana, Brian; Freeman, William R.

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 themore » 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 extinction correction of 4.2 over all luminosities and a Kroupa initial mass function) of 0.148{sub −0.020}{sup +0.023} M {sub ☉} yr{sup –1} Mpc{sup –3}, significantly higher than previous determinations because of the additional population of fainter galaxies and the larger dust correction factors.« less

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.

Measuring the X-ray luminosities of SDSS DR7 clusters from ROSAT All Sky Survey

NASA Astrophysics Data System (ADS)

Wang, Lei; Yang, Xiaohu; Shen, Shiyin; Mo, H. J.; van den Bosch, Frank C.; Luo, Wentao; Wang, Yu; Lau, Erwin T.; Wang, Q. D.; Kang, Xi; Li, Ran

2014-03-01

We use ROSAT All Sky Survey broad-band X-ray images and the optical clusters identified from Sloan Digital Sky Survey Data Release 7 to estimate the X-ray luminosities around ˜65 000 candidate clusters with masses ≳ 1013 h- 1 M⊙ based on an optical to X-ray (OTX) code we develop. We obtain a catalogue with X-ray luminosity for each cluster. This catalogue contains 817 clusters (473 at redshift z ≤ 0.12) with signal-to-noise ratio >3 in X-ray detection. We find about 65 per cent of these X-ray clusters have their most massive member located near the X-ray flux peak; for the rest 35 per cent, the most massive galaxy is separated from the X-ray peak, with the separation following a distribution expected from a Navarro-Frenk-White profile. We investigate a number of correlations between the optical and X-ray properties of these X-ray clusters, and find that the cluster X-ray luminosity is correlated with the stellar mass (luminosity) of the clusters, as well as with the stellar mass (luminosity) of the central galaxy and the mass of the halo, but the scatter in these correlations is large. Comparing the properties of X-ray clusters of similar halo masses but having different X-ray luminosities, we find that massive haloes with masses ≳ 1014 h- 1 M⊙ contain a larger fraction of red satellite galaxies when they are brighter in X-ray. An opposite trend is found in central galaxies in relative low-mass haloes with masses ≲ 1014 h- 1 M⊙ where X-ray brighter clusters have smaller fraction of red central galaxies. Clusters with masses ≳ 1014 h- 1 M⊙ that are strong X-ray emitters contain many more low-mass satellite galaxies than weak X-ray emitters. These results are also confirmed by checking X-ray clusters of similar X-ray luminosities but having different characteristic stellar masses. A cluster catalogue containing the optical properties of member galaxies and the X-ray luminosity is available at http://gax.shao.ac.cn/data/Group.html.

Rest-frame Optical Spectra and Black Hole Masses of 3 < z < 6 Quasars

NASA Astrophysics Data System (ADS)

Jun, Hyunsung David; Im, Myungshin; Lee, Hyung Mok; Ohyama, Youichi; Woo, Jong-Hak; Fan, Xiaohui; Goto, Tomotsugu; Kim, Dohyeong; Kim, Ji Hoon; Kim, Minjin; Lee, Myung Gyoon; Nakagawa, Takao; Pearson, Chris; Serjeant, Stephen

2015-06-01

We present the rest-frame optical spectral properties of 155 luminous quasars at 3.3 < z < 6.4 taken with the AKARI space telescope, including the first detection of the Hα emission line as far out as z ∼ 6. We extend the scaling relation between the rest-frame optical continuum and the line luminosity of active galactic nuclei (AGNs) to the high-luminosity, high-redshift regime that has rarely been probed before. Remarkably, we find that a single log-linear relation can be applied to the 5100 Å and Hα AGN luminosities over a wide range of luminosity (1042 < L5100 < 1047 ergs s-1) or redshift (0 < z < 6), suggesting that the physical mechanism governing this relation is unchanged from z = 0 to 6, over five decades in luminosity. Similar scaling relations are found between the optical and the UV continuum luminosities or line widths. Applying the scaling relations to the Hβ black hole (BH) mass (MBH) estimator of local AGNs, we derive the MBH estimators based on the Hα, Mg ii, and C iv lines, finding that the UV-line-based masses are overall consistent with the Balmer-line-based, but with a large intrinsic scatter of 0.40 dex for the C iv estimates. Our 43 MBH estimates from Hα confirm the existence of BHs as massive as ∼ 1010 M⊙ out to z ∼ 5 and provide a secure footing for previous results from Mg ii-line-based studies that a rapid MBH growth has occurred in the early universe.

VizieR Online Data Catalog: Warm IRAS sources. II. (de Grijp+, 1992)

NASA Astrophysics Data System (ADS)

de Grijp, M. H. K.; Keel, W. C.; Miley, G. K.; Goudfrooij, P.; Lub, J.

2011-01-01

We present optical spectra for a sample of 563 high-latitude IRAS sources selected from the Point Source Catalog to have relatively warm 25 to 60 micron colours. We have shown this selection criterion to be an efficient indicator for finding Seyfert galaxies. Plots of the optical spectra are shown and the fluxes of the strongest emission lines in these spectra are tabulated. After excluding 128 sources which are clearly galactic foreground objects, we obtained spectroscopic information for 358 extragalactic objects. Emission-line ratios have been used to classify these objects, resulting in 80 Seyfert 1, 141 Seyfert 2 and 133 HII-type objects. In comparison with samples of active nuclei selected in other ways, about 50% of known Seyfert nuclei are included by our colour criteria. This fraction is larger for high luminosities, reaching 80% for quasar luminosities. For lower-luminosity objects, contamination by the host galaxies becomes important and the sample becomes seriously incomplete. It should be moderately complete and representative for core luminosities greater than 1023.5W/Hz at 12m. Finally, the infrared luminosity function for each type of object is derived; the shapes for Seyfert 1 and 2 nuclei are identical, with a type 2/type 1 space-density ratio of 3.0. Our census is consistent with an obscuration scheme for producing both types of object from a single parent population, though the origin of excess cool IR radiation Irom many Seyferts is still unclear. We note the appearance of an apparent type II supernova in IRAS 0225-103 observed in 1985 September. Its spectrum suggests that it was observed between 1 and 2 months after maximum, perhaps in a "plateau" phase. (2 data files).

Space Density of Optically Selected Type 2 Quasars

NASA Astrophysics Data System (ADS)

Reyes, Reinabelle; Zakamska, Nadia L.; Strauss, Michael A.; Green, Joshua; Krolik, Julian H.; Shen, Yue; Richards, Gordon T.; Anderson, Scott F.; Schneider, Donald P.

2008-12-01

Type 2 quasars are luminous active galactic nuclei whose central regions are obscured by large amounts of gas and dust. In this paper, we present a catalog of type 2 quasars from the Sloan Digital Sky Survey, selected based on their optical emission lines. The catalog contains 887 objects with redshifts z < 0.83; this is 6 times larger than the previous version and is by far the largest sample of type 2 quasars in the literature. We derive the [O III]5007 luminosity function (LF) for 108.3 L sun < L [O III] < 1010 L sun (corresponding to intrinsic luminosities up to M[2500 Å] ~= -28 mag or bolometric luminosities up to 4 × 1047 erg s-1). This LF provides robust lower limits to the actual space density of obscured quasars due to our selection criteria, the details of the spectroscopic target selection, and other effects. We derive the equivalent LF for the complete sample of type 1 (unobscured) quasars and determine the ratio of type 2 to type 1 quasar number densities. Our data constrain this ratio to be at least ~1.5:1 for 108.3 L sun < L [O III] < 109.5 L sun at z < 0.3, and at least ~1.2:1 for L [O III] ~ 1010 L sun at 0.3 < z < 0.83. Type 2 quasars are at least as abundant as type 1 quasars in the relatively nearby universe (z <~ 0.8) for the highest luminosities.

Emission Line Properties of Seyfert Galaxies in the 12 μm Sample

NASA Astrophysics Data System (ADS)

Malkan, Matthew A.; Jensen, Lisbeth D.; Rodriguez, David R.; Spinoglio, Luigi; Rush, Brian

2017-09-01

We present optical and ultraviolet spectroscopic measurements of the emission lines of 81 Seyfert 1 and 104 Seyfert 2 galaxies that comprise nearly all of the IRAS 12 μm AGN sample. We have analyzed the emission-line luminosity functions, reddening, and other diagnostics. For example, the narrow-line regions (NLR) of Seyfert 1 and 2 galaxies do not significantly differ from each other in most of these diagnostics. Combining the Hα/Hβ ratio with a new reddening indicator—the [S II]6720/[O II]3727 ratio—we find the average E(B-V) is 0.49 ± 0.35 for type 1 and 0.52 ± 0.26 for type 2 Seyferts. The NLR of Sy 1s has an ionization level insignificantly higher than that of Sy 2s. For the broad-line region (BLR), we find that the C IV equivalent width correlates more strongly with [O III]/Hβ than with UV luminosity. Our bright sample of local active galaxies includes 22 Seyfert nuclei with extremely weak broad wings in Hα, known as Seyfert 1.9s and 1.8s, depending on whether or not broad Hβ wings are detected. Aside from these weak broad lines, our low-luminosity Seyferts are more similar to the Sy 2s than to Sy 1s. In a BPT diagram, we find that Sy 1.8s and 1.9s overlap the region occupied by Sy 2s. We compare our results on optical emission lines with those obtained by previous investigators, using AGN subsamples from the Sloan Digital Sky Survey. The luminosity functions of forbidden emission lines [O II]λ3727 Å, [O III]λ5007 Å, and [S II]λ6720 Å in Sy 1s and Sy 2s are indistinguishable. They all show strong downward curvature. Unlike the LFs of Seyfert galaxies measured by the Sloan Digital Sky Survey, ours are nearly flat at low luminosities. The larger number of faint Sloan “AGN” is attributable to their inclusion of weakly emitting LINERs and H II+AGN “composite” nuclei, which do not meet our spectral classification criteria for Seyferts. In an Appendix, we have investigated which emission line luminosities can provide the most reliable measures of the total non-stellar luminosity, estimated from our extensive multi-wavelength database. The hard X-ray or near-ultraviolet continuum luminosity can be crudely predicted from either the [O III]λ5007 Å luminosity or the combinations of [O III]+Hβ or [N II]+Hα lines, with a scatter of +/- 4 times for Sy 1s and +/- 10 times for Sy 2s. Although these uncertainties are large, the latter two hybrid (NLR+BLR) indicators have the advantage of predicting the same HX luminosity independent of Seyfert type.

Optical–Mid-infrared Period–Luminosity Relations for W UMa-type Contact Binaries Based on Gaia DR 1: 8% Distance Accuracy

NASA Astrophysics Data System (ADS)

Chen, Xiaodian; Deng, Licai; de Grijs, Richard; Wang, Shu; Feng, Yuting

2018-06-01

W Ursa Majoris (W UMa)-type contact binary systems (CBs) are useful statistical distance indicators because of their large numbers. Here, we establish (orbital) period–luminosity relations (PLRs) in 12 optical to mid-infrared bands (GBVRIJHK s W1W2W3W4) based on 183 nearby W UMa-type CBs with accurate Tycho–Gaia parallaxes. The 1σ dispersion of the PLRs decreases from optical to near- and mid-infrared wavelengths. The minimum scatter, 0.16 mag, implies that W UMa-type CBs can be used to recover distances to 7% precision. Applying our newly determined PLRs to 19 open clusters containing W UMa-type CBs demonstrates that the PLR and open cluster CB distance scales are mutually consistent to within 1%. Adopting our PLRs as secondary distance indicators, we compiled a catalog of 55,603 CB candidates, of which 80% have distance estimates based on a combination of optical, near-infrared, and mid-infrared photometry. Using Fourier decomposition, 27,318 high-probability W UMa-type CBs were selected. The resulting 8% distance accuracy implies that our sample encompasses the largest number of objects with accurate distances within a local volume with a radius of 3 kpc available to date. The distribution of W UMa-type CBs in the Galaxy suggests that in different environments, the CB luminosity function may be different: larger numbers of brighter (longer-period) W UMa-type CBs are found in younger environments.

A coordinated X-ray, optical, and microwave study of the flare star Proxima Centauri

NASA Technical Reports Server (NTRS)

Haisch, B. M.; Linsky, J. L.; Slee, O. B.; Hearn, D. R.; Walker, A. R.; Rydgren, A. E.; Nicolson, G. D.

1978-01-01

Results are reported for a three-day coordinated observing program to monitor the flare star Proxima Centauri in the X-ray, optical, and radio spectrum. During this interval 30 optical flares and 12 possible radio bursts were observed. The SAS 3 X-ray satellite made no X-ray detections. An upper limit of 0.08 on the X-ray/optical luminosity ratio is derived for the brightest optical flare. The most sensitive of the radio telescopes failed to detect 6-cm emission during one major and three minor optical flares, and on this basis an upper limit on the flare radio emission (1 hundred-thousandth of the optimal luminosity) is derived.

A Magnified View of the Epoch of Reionization with the Hubble Frontier Fields

NASA Astrophysics Data System (ADS)

Livermore, Rachael C.; Finkelstein, Steven L.; Lotz, Jennifer M.

2017-06-01

The Hubble Frontier Fields program has obtained deep optical and near-infrared Hubble Space Telescope imaging of six galaxy clusters and associated parallel fields. The depth of the imaging (m_AB ~ 29) means we can identify faint galaxies at z >6, and those in the cluster fields also benefit from magnification due to strong gravitational lensing. Using wavelet decomposition to subtract the foreground cluster galaxies, we can reach intrinsic absolute magnitudes of M_UV ~ -12.5 at z ~ 6. Here, we present the UV luminosity functions at 6

Distant Cluster Hunting. II; A Comparison of X-Ray and Optical Cluster Detection Techniques and Catalogs from the ROSAT Optical X-Ray Survey

NASA Technical Reports Server (NTRS)

Donahue, Megan; Scharf, Caleb A.; Mack, Jennifer; Lee, Y. Paul; Postman, Marc; Rosait, Piero; Dickinson, Mark; Voit, G. Mark; Stocke, John T.

2002-01-01

We present and analyze the optical and X-ray catalogs of moderate-redshift cluster candidates from the ROSA TOptical X-Ray Survey, or ROXS. The survey covers the sky area contained in the fields of view of 23 deep archival ROSA T PSPC pointings, 4.8 square degrees. The cross-correlated cluster catalogs were con- structed by comparing two independent catalogs extracted from the optical and X-ray bandpasses, using a matched-filter technique for the optical data and a wavelet technique for the X-ray data. We cross-identified cluster candidates in each catalog. As reported in Paper 1, the matched-filter technique found optical counter- parts for at least 60% (26 out of 43) of the X-ray cluster candidates; the estimated redshifts from the matched filter algorithm agree with at least 7 of 1 1 spectroscopic confirmations (Az 5 0.10). The matched filter technique. with an imaging sensitivity of ml N 23, identified approximately 3 times the number of candidates (155 candidates, 142 with a detection confidence >3 u) found in the X-ray survey of nearly the same area. There are 57 X-ray candidates, 43 of which are unobscured by scattered light or bright stars in the optical images. Twenty-six of these have fairly secure optical counterparts. We find that the matched filter algorithm, when applied to images with galaxy flux sensitivities of mI N 23, is fairly well-matched to discovering z 5 1 clusters detected by wavelets in ROSAT PSPC exposures of 8000-60,000 s. The difference in the spurious fractions between the optical and X-ray (30%) and IO%, respectively) cannot account for the difference in source number. In Paper I, we compared the optical and X-ray cluster luminosity functions and we found that the luminosity functions are consistent if the relationship between X-ray and optical luminosities is steep (Lx o( L&f). Here, in Paper 11, we present the cluster catalogs and a numerical simulation of the ROXS. We also present color-magnitude plots for several of the cluster candidates, and examine the prominence of the red sequence in each. We find that the X-ray clusters in our survey do not all have a prominent red sequence. We conclude that while the red sequence may be a distinct feature in the color-magnitude plots for virialized massive clusters, it may be less distinct in lower mass clusters of galaxies at even moderate redshifts. Multiple, complementary methods of selecting and defining clusters may be essential, particularly at high redshift where all methods start to run into completeness limits, incomplete understanding of physical evolution, and projection effects.

Achieving BLISS: Challenges for Building Fast, Ultra-Sensitive Transition-Edge Sensors

NASA Technical Reports Server (NTRS)

Beyer, Andrew D.; Runyan, M. C.; Kenyon, M.; Echternach, P. M .; Chui, T.; Bumble, B.; Bradford, C. M.; Holmes, W. A.; Bock, J. J.

2012-01-01

Topics: 1.Motivation and Intro to TESs. 2. BLISS Specifications-tolerance to dark power. 3.Measuring stray (dark) power-Tc (alpha) and G measurements. a) Overview two methods: JTD vs. TES. b) TES arrays: measurement and complications for Pd, Tc, and alpha. 4. Results: Pd compare, NEP, tau, 1/f issues. LIRGs and ULIRGs: Excellent example of distinct optical/UV and IR luminosity. Interaction long known, but huge luminosity is not predicted based on optical studies. (greater than 90% of the energy is emitted at in the far-IR). Large luminosity has both starburst and accretion components.

Stellar Populations in the Central 0.5 pc of the Galaxy. I. A New Method for Constructing Luminosity Functions and Surface-density Profiles

NASA Astrophysics Data System (ADS)

Do, T.; Lu, J. R.; Ghez, A. M.; Morris, M. R.; Yelda, S.; Martinez, G. D.; Wright, S. A.; Matthews, K.

2013-02-01

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 ~10 M ⊙ 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, Σ(R)vpropR -Γ, for the young stars and late-type giants are consistent with earlier results (Γearly = 0.93 ± 0.09, Γlate = 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.

Calibration and Limitations of the Mg II Line-based Black Hole Masses

NASA Astrophysics Data System (ADS)

Woo, Jong-Hak; Le, Huynh Anh N.; Karouzos, Marios; Park, Dawoo; Park, Daeseong; Malkan, Matthew A.; Treu, Tommaso; Bennert, Vardha N.

2018-06-01

We present single-epoch black hole mass ({M}BH}) calibrations based on the rest-frame ultraviolet (UV) and optical measurements of Mg II 2798 Å and Hβ 4861 Å lines and the active galactic nucleus (AGN) continuum, using a sample of 52 moderate-luminosity AGNs at z ∼ 0.4 and z ∼ 0.6 with high-quality Keck spectra. We combine this sample with a large number of luminous AGNs from the Sloan Digital Sky Survey to increase the dynamic range for a better comparison of UV and optical velocity and luminosity measurements. With respect to the reference {M}BH} based on the line dispersion of Hβ and continuum luminosity at 5100 Å, we calibrate the UV and optical mass estimators by determining the best-fit values of the coefficients in the mass equation. By investigating whether the UV estimators show a systematic trend with Eddington ratio, FWHM of Hβ, Fe II strength, or UV/optical slope, we find no significant bias except for the slope. By fitting the systematic difference of Mg II-based and Hβ-based masses with the L 3000/L 5100 ratio, we provide a correction term as a function of the spectral index as ΔC = 0.24 (1 + α λ ) + 0.17, which can be added to the Mg II-based mass estimators if the spectral slope can be well determined. The derived UV mass estimators typically show >∼0.2 dex intrinsic scatter with respect to the Hβ-based {M}BH}, suggesting that the UV-based mass has an additional uncertainty of ∼0.2 dex, even if high-quality rest-frame UV spectra are available.

Optical Follow-up of Gravitational-wave Events with Las Cumbres Observatory

NASA Astrophysics Data System (ADS)

Arcavi, Iair; McCully, Curtis; Hosseinzadeh, Griffin; Howell, D. Andrew; Vasylyev, Sergiy; Poznanski, Dovi; Zaltzman, Michael; Maoz, Dan; Singer, Leo; Valenti, Stefano; Kasen, Daniel; Barnes, Jennifer; Piran, Tsvi; Fong, Wen-fai

2017-10-01

We present an implementation of the Gehrels et al. galaxy-targeted strategy for gravitational-wave (GW) follow-up using the Las Cumbres Observatory global network of telescopes. We use the Galaxy List for the Advanced Detector Era (GLADE) galaxy catalog, which we show is complete (with respect to a Schechter function) out to ˜300 Mpc for galaxies brighter than the median Schechter function galaxy luminosity. We use a prioritization algorithm to select the galaxies with the highest chance of containing the counterpart given their luminosity, their position, and their distance relative to a GW localization, and in which we are most likely to detect a counterpart given its expected brightness compared to the limiting magnitude of our telescopes. This algorithm can be easily adapted to any expected transient parameters and telescopes. We implemented this strategy during the second Advanced Detector Observing Run (O2) and followed the black hole merger GW170814 and the neutron star merger GW170817. For the latter, we identified an optical kilonova/macronova counterpart thanks to our algorithm selecting the correct host galaxy fifth in its ranked list among the 182 galaxies we identified in the Laser Interferometer Gravitational-wave Observatory (LIGO)/Virgo localization. This also allowed us to obtain some of the earliest observations of the first optical transient ever triggered by a GW detection (as presented in a companion paper).

Optical Follow-up of Gravitational-wave Events with Las Cumbres Observatory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arcavi, Iair; McCully, Curtis; Hosseinzadeh, Griffin

We present an implementation of the Gehrels et al. galaxy-targeted strategy for gravitational-wave (GW) follow-up using the Las Cumbres Observatory global network of telescopes. We use the Galaxy List for the Advanced Detector Era (GLADE) galaxy catalog, which we show is complete (with respect to a Schechter function) out to ∼300 Mpc for galaxies brighter than the median Schechter function galaxy luminosity. We use a prioritization algorithm to select the galaxies with the highest chance of containing the counterpart given their luminosity, their position, and their distance relative to a GW localization, and in which we are most likely tomore » detect a counterpart given its expected brightness compared to the limiting magnitude of our telescopes. This algorithm can be easily adapted to any expected transient parameters and telescopes. We implemented this strategy during the second Advanced Detector Observing Run (O2) and followed the black hole merger GW170814 and the neutron star merger GW170817. For the latter, we identified an optical kilonova/macronova counterpart thanks to our algorithm selecting the correct host galaxy fifth in its ranked list among the 182 galaxies we identified in the Laser Interferometer Gravitational-wave Observatory (LIGO)/Virgo localization. This also allowed us to obtain some of the earliest observations of the first optical transient ever triggered by a GW detection (as presented in a companion paper).« less

Mini-Survey Of SDSS of [OIII] AGN With Swift

NASA Technical Reports Server (NTRS)

Angelini, L.; George, I. M.; Hill, J.; Padgett, C. A.; Mushotzky, R. F.

2008-01-01

The number of AGN and their luminosity distribution are crucial parameters for our understanding of the AGN phenomenon. Recent work (e.g. Ferrarese and Merritt 2000) strongly suggests every massive galaxy has a central black hole. However, most of these objects either are not radiating or have been very difficult to detect. We are now in the era of large surveys, and the luminosity function (LF) of AGN has been estimated in various ways. In the X-ray band, Chandra and XMM surveys (e.g., Barger et al. 2005; Hasinger, et al. 2005) have revealed that the LF of Hard X-ray selected AGN shows a strong luminosity-dependent evolution with a dramatic break towards low L(x) (at al z). This is seen for all types of AGN, but is stronger for the broad-line objects (e.g., Steffen et al. 2004). In sharp contrast, the local LF of optically-selected samples shows no such break and no differences between narrow and broad-line objects (Hao et al. 2005). If, as been suggested, hard X-ray and optical emission line can both be fair indicators of AGN activity, it is important to first understand how reliable these characteristics are if we hope to understand the apparent discrepancy in the LFs.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prentice, S. J.; Mazzali, P. A.; Pian, E.

The optical and optical/near-infrared pseudo-bolometric light curves of 85 stripped-envelope supernovae (SNe) are constructed using a consistent method and a standard cosmology. The light curves are analysed to derive temporal characteristics and peak luminosity L p , enabling the construction of a luminosity function. Subsequently, the mass of 56 Ni synthesized in the explosion, along with the ratio of ejecta mass to ejecta kinetic energy, are found. Analysis shows that host-galaxy extinction is an important factor in accurately determining luminosity values as it is significantly greater than Galactic extinction in most cases. It is found that broad-lined SNe Ic (SNemore » Ic-BL) and gamma-ray burst SNe are the most luminous subtypes with a combined median L p , in erg s -1 , of log(L p) = 43.00 compared to 42.51 for SNe Ic, 42.50 for SNe Ib, and 42.36 for SNe IIb. It is also found that SNe Ic-BL synthesize approximately twice the amount of 56Ni compared with SNe Ic, Ib, and IIb, with median M Ni = 0.34, 0.16, 0.14, and 0.11 M ⊙ , respectively. SNe Ic-BL, and to a lesser extent SNe Ic, typically rise from L p /2 to L p more quickly than SNe Ib/IIb; consequently, their light curves are not as broad.« less

Heavily Obscured AGN with SIMBOL-X

NASA Astrophysics Data System (ADS)

Della Ceca, R.; Caccianiga, A.; Severgnini, P.

2009-05-01

By comparing an optically selected sample of narrow lines AGN with an X-ray selected sample of AGN we have recently derived an estimate of the intrinsic (i.e. before absorption) 2-10 keV luminosity function (XLF) of Compton Thick AGNs. We will use this XLF to derive the number of Compton Thick AGN that will be found in the SIMBOL-X survey(s).

THE LOCAL [C ii] 158 μ m EMISSION LINE LUMINOSITY FUNCTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hemmati, Shoubaneh; Yan, Lin; Capak, Peter

We present, for the first time, the local [C ii] 158 μ m emission line luminosity function measured using a sample of more than 500 galaxies from the Revised Bright Galaxy Sample. [C ii] luminosities are measured from the Herschel PACS observations of the Luminous Infrared Galaxies (LIRGs) in the Great Observatories All-sky LIRG Survey and estimated for the rest of the sample based on the far-infrared (far-IR) luminosity and color. The sample covers 91.3% of the sky and is complete at S{sub 60μm} > 5.24 Jy. We calculate the completeness as a function of [C ii] line luminosity and distance, basedmore » on the far-IR color and flux densities. The [C ii] luminosity function is constrained in the range ∼10{sup 7–9} L{sub ⊙} from both the 1/ V{sub max} and a maximum likelihood methods. The shape of our derived [C ii] emission line luminosity function agrees well with the IR luminosity function. For the CO(1-0) and [C ii] luminosity functions to agree, we propose a varying ratio of [C ii]/CO(1-0) as a function of CO luminosity, with larger ratios for fainter CO luminosities. Limited [C ii] high-redshift observations as well as estimates based on the IR and UV luminosity functions are suggestive of an evolution in the [C ii] luminosity function similar to the evolution trend of the cosmic star formation rate density. Deep surveys using the Atacama Large Millimeter Array with full capability will be able to confirm this prediction.« less

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kryukova, E.; Megeath, S. T.; Allen, T. S.

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). Usingmore » 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 functions to those predicted by models and find that our observed luminosity functions are best matched by models that invoke competitive accretion, although we do not find strong agreement between the high-mass SF clouds and any of the models.« less

The evolution of the disc variability along the hard state of the black hole transient GX 339-4

NASA Astrophysics Data System (ADS)

De Marco, B.; Ponti, G.; Muñoz-Darias, T.; Nandra, K.

2015-12-01

We report on the analysis of hard-state power spectral density function (PSD) of GX 339-4 down to the soft X-ray band, where the disc significantly contributes to the total emission. At any luminosity probed, the disc in the hard state is intrinsically more variable than in the soft state. However, the fast decrease of disc variability as a function of luminosity, combined with the increase of disc intensity, causes a net drop of fractional variability at high luminosities and low energies, which reminds the well-known behaviour of disc-dominated energy bands in the soft state. The peak frequency of the high-frequency Lorentzian (likely corresponding to the high-frequency break seen in active galactic nuclei, AGN) scales with luminosity, but we do not find evidence for a linear scaling. In addition, we observe that this characteristic frequency is energy dependent. We find that the normalization of the PSD at the peak of the high-frequency Lorentzian decreases with luminosity at all energies, though in the soft band this trend is steeper. Together with the frequency shift, this yields quasi-constant high-frequency (5-20 Hz) fractional rms at high energies, with less than 10 per cent scatter. This reinforces previous claims suggesting that the high-frequency PSD solely scales with black hole mass. On the other hand, this constancy breaks down in the soft band (where the scatter increases to ˜30 per cent). This is a consequence of the additional contribution from the disc component, and resembles the behaviour of optical variability in AGN.

Near-infrared Variability of Obscured and Unobscured X-Ray-selected AGNs in the COSMOS Field

NASA Astrophysics Data System (ADS)

Sánchez, P.; Lira, P.; Cartier, R.; Pérez, V.; Miranda, N.; Yovaniniz, C.; Arévalo, P.; Milvang-Jensen, B.; Fynbo, J.; Dunlop, J.; Coppi, P.; Marchesi, S.

2017-11-01

We present our statistical study of near-infrared (NIR) variability of X-ray-selected active galactic nuclei (AGNs) in the COSMOS field, using UltraVISTA data. This is the largest sample of AGN light curves in YJHKs bands, making it possible to have a global description of the nature of AGNs for a large range of redshifts and for different levels of obscuration. To characterize the variability properties of the sources, we computed the structure function. Our results show that there is an anticorrelation between the structure function A parameter (variability amplitude) and the wavelength of emission and a weak anticorrelation between A and the bolometric luminosity. We find that broad-line (BL) AGNs have a considerably larger fraction of variable sources than narrow-line (NL) AGNs and that they have different distributions of the A parameter. We find evidence that suggests that most of the low-luminosity variable NL sources correspond to BL AGNs, where the host galaxy could be damping the variability signal. For high-luminosity variable NL sources, we propose that they can be examples of “true type II” AGNs or BL AGNs with limited spectral coverage, which results in missing the BL emission. We also find that the fraction of variable sources classified as unobscured in the X-ray is smaller than the fraction of variable sources unobscured in the optical range. We present evidence that this is related to the differences in the origin of the obscuration in the optical and X-ray regimes.

Wavelength Dependent Luminosity Functions for Super Star Clusters

NASA Astrophysics Data System (ADS)

Garmany, Catharine

1997-07-01

Starburst galaxies, considered to exhibit enhanced star formation on a galaxy-wide scale, have now been found with HST to contain very intense knots of star formation, referred to as ``super star clusters'', or SSCs. A steepening of the luminosity function with increasing wavelength for young burst populations, such as SSCs, has recently been predicted by Hogg & Phinney {1997}. This prediction, not previously addressed in the literature, is straightforward to test with multi- wavelength photometry. Using the colors of the SSCs in a galaxy in combination with the difference in slopes of the luminosity functions derived from different wavelength bands and applying population synthesis models, we can also constrain the high mass stellar initial mass function {IMF}. Recent work has suggested that the slope of the IMF is roughly constant in a variety of local environments, from galactic OB associations to the closest analog of a super star cluster, R136 in the LMC. This investigation will allow us to compare the IMFs in the extreme environments of SSCs in starburst galaxies to IMFs found locally in the Galaxy, LMC, and SMC. Archival imaging data in both the UV and optical bands is available for about 10 young starburst systems. These data will allow us to test the predictions of Hogg & Phinney, as well as constrain the IMF for environments not found in the nearby universe.

On the evidence for axionlike particles from active galactic nuclei

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pettinari, Guido Walter; Crittenden, Robert

2010-10-15

Burrage, Davis, and Shaw recently suggested exploiting the correlations between high and low energy luminosities of astrophysical objects to probe possible mixing between photons and axionlike particles (ALP) in magnetic field regions. They also presented evidence for the existence of ALP's by analyzing the optical/UV and x-ray monochromatic luminosities of active galactic nuclei. We extend their work by using the monochromatic luminosities of 320 unobscured active galactic nuclei from the Sloan Digital Sky Survey/Xmm-Newton Quasar Survey which allows the exploration of 18 different combinations of optical/UV and x-ray monochromatic luminosities. However, we do not find compelling evidence for the existencemore » of ALPs. Moreover, it appears that the signal reported by Burrage et al. is more likely due to x-ray absorption rather than to photon-ALP oscillation.« less

Minor Contribution of Quasars to Ionizing Photon Budget at z ˜ 6: Update on Quasar Luminosity Function at the Faint End with Subaru/Suprime-Cam

NASA Astrophysics Data System (ADS)

Onoue, Masafusa; Kashikawa, Nobunari; Willott, Chris J.; Hibon, Pascale; Im, Myungshin; Furusawa, Hisanori; Harikane, Yuichi; Imanishi, Masatoshi; Ishikawa, Shogo; Kikuta, Satoshi; Matsuoka, Yoshiki; Nagao, Tohru; Niino, Yuu; Ono, Yoshiaki; Ouchi, Masami; Tanaka, Masayuki; Tang, Ji-Jia; Toshikawa, Jun; Uchiyama, Hisakazu

2017-10-01

We constrain the quasar contribution to the cosmic reionization based on our deep optical survey of z ˜ 6 quasars down to z R = 24.15 using Subaru/Suprime-Cam in three UKIDSS-DXS fields covering 6.5 deg2. In Kashikawa et al. (2015), we select 17 quasar candidates and report our initial discovery of two low-luminosity quasars ({M}1450˜ -23) from seven targets, one of which might be a Lyα-emitting galaxy. From an additional optical spectroscopy, none of the four candidates out of the remaining 10 turn out to be genuine quasars. Moreover, the deeper optical photometry provided by the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) shows that, unlike the two already-known quasars, the I - z and z - y colors of the last six candidates are consistent with M- or L-type brown dwarfs. Therefore, the quasar luminosity function (QLF) measurement in the previous paper is confirmed. Compiling the QLF measurements from the literature over a wide magnitude range, including an extremely faint AGN candidate from Parsa et al. (2017), to fit them with a double power law, we find that the best-fit faint-end slope is α =-{2.04}-0.18+0.33 (-{1.98}-0.21+0.48) and characteristic magnitude is {M}1450* =-{25.8}-1.9+1.1 (-{25.7}-1.8+1.0) in the case of two (one) quasar detection. Our result suggests that, if the QLF is integrated down to {M}1450=-18, quasars produce ˜1%-12% of the ionizing photons required to fully ionize the universe at z ˜ 6 with a 2σ confidence level, assuming that the escape fraction is {f}{esc}=1 and the intergalactic medium clumpy factor is C = 3. Even when the systematic uncertainties are taken into account, our result supports the scenario that quasars are the minor contributors of the reionization.

X-ray emission at low-mass end of the MS - Results from an extensive Einstein Observatory survey

NASA Technical Reports Server (NTRS)

Barbera, M.; Micela, G.; Sciortino, S.; Vaiana, G. S.; Harnden, F. R., Jr.; Rosner, R.

1992-01-01

The 0.16-4.0 keV X-ray emission from K and M stars of luminosity classes IV, V, and VI within 25 parsec of the sun was measured using all available Einstein Observatory IPC data and a critical compilation of catalogued optical data. Fifty four of 88 stars were detected, 70 of 138 M stars with Mv less than 13.4 (corresponding to M6) and 15 or 31 fainter M stars. The surveyed stars were grouped, on the basis of U, V, W space velocity components, into old-disk, young-disk, and halo population stars. Then, a subsample was selected which is statistically representative of the population of K and M stars in the solar neighborhood, on the basis of which unbiased Maximum Likelihood X-ray luminosity functions were constructed for K, early M, and late M stars. The investigation revealed a decrease of X-ray luminosity with increasing stellar age in the range of ages of disk population stars.

The role of environment in the observed Fundamental Plane of radio Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Shabala, Stanislav S.

2018-05-01

The optical Fundamental Plane of black hole activity relates radio continuum luminosity of Active Galactic Nuclei to [O III] luminosity and black hole mass. We examine the environments of low redshift (z < 0.2) radio-selected AGN, quantified through galaxy clustering, and find that halo mass provides similar mass scalings to black hole mass in the Fundamental Plane relations. AGN properties are strongly environment-dependent: massive haloes are more likely to host radiatively inefficient (low-excitation) radio AGN, as well as a higher fraction of radio luminous, extended sources. These AGN populations have different radio - optical luminosity scaling relations, and the observed mass scalings in the parent AGN sample are built up by combining populations preferentially residing in different environments. Accounting for environment-driven selection effects, the optical Fundamental Plane of supermassive black holes is likely to be mass-independent, as predicted by models.

The structure and appearance of winds from supercritical accretion disks. II - Dynamical theory of supercritical winds

NASA Technical Reports Server (NTRS)

Meier, D. L.

1982-01-01

A general analytic theory is presented of winds driven by super-Eddington luminosities. The relevant parameters are the mass of the central object, the radius at which the luminosity and matter are injected, the ratio of the free-fall time to the heating time at this radius, and the total luminosity injected at the radius. Several different regimes of dynamical wind structure are identified, and the analytic expressions are shown to agree with the numerical results in Meier (1979) in the appropriate case. It is noted that, in its general form, the theory is the optically thick (to electron scattering) counterpart to optically thin radiation pressure-driven stellar winds.

Extended X-Ray Emission around Quasars at Intermediate Redshift

NASA Technical Reports Server (NTRS)

Fiore, Fabrizio

1998-01-01

We compare the optical to soft X-ray spectral energy distribution (SED) of a sample of bright low-redshift (0.048 less than z less than 0.155), radio-quiet quasars, with a range of thermal models which have been proposed to explain the optical/UV/soft X-ray quasar emission: (a) optically thin emission from an ionized plasma, (b) optically thick emission from the innermost regions of an accretion disk in Schwarzschild and Kerr geometries. We presented ROSAT PSPC observations of these quasars in an earlier paper. Here our goals are to search for the signature of thermal emission in the quasar SED, and to investigate whether a single component is dominating at different frequencies. We find that isothermal optically thin plasma models can explain the observed soft X-ray color and the mean OUV color. However, they predict an ultraviolet (1325 Angstrom) luminosity a factor of 3 to 10 times lower than observed. Pure disk models, even in a Kerr geometry, do not have the necessary flexibility to account for the observed OUV and soft X-ray luminosities. Additional components are needed both in the optical and in the soft X-rays (e.g. a hot corona can explain the soft X-ray color). The most constrained modification of pure disk models, is the assumption of an underlying power law component extending from the infrared (3 micrometers) to the X-ray. This can explain both the OUV and soft X-ray colors and luminosities and does not exceed the 3 micrometers luminosity, where a contribution from hot dust is likely to be important. We also discuss the possibility that the observed soft X-ray color and luminosity are dominated by reflection from the ionized surface of the accretion disk. While modifications of both optically thin plasma models and pure disk models might account for the observed SED, we do not find any strong evidence that the OUV bump and soft X-ray emission are one and the same component. Likewise, we do not find any strong argument which definitely argues in favor of thermal models.

The bolometric light curves and physical parameters of stripped-envelope supernovae

DOE PAGES

Prentice, S. J.; Mazzali, P. A.; Pian, E.; ...

2016-02-08

The optical and optical/near-infrared pseudo-bolometric light curves of 85 stripped-envelope supernovae (SNe) are constructed using a consistent method and a standard cosmology. The light curves are analysed to derive temporal characteristics and peak luminosity L p , enabling the construction of a luminosity function. Subsequently, the mass of 56 Ni synthesized in the explosion, along with the ratio of ejecta mass to ejecta kinetic energy, are found. Analysis shows that host-galaxy extinction is an important factor in accurately determining luminosity values as it is significantly greater than Galactic extinction in most cases. It is found that broad-lined SNe Ic (SNemore » Ic-BL) and gamma-ray burst SNe are the most luminous subtypes with a combined median L p , in erg s -1 , of log(L p) = 43.00 compared to 42.51 for SNe Ic, 42.50 for SNe Ib, and 42.36 for SNe IIb. It is also found that SNe Ic-BL synthesize approximately twice the amount of 56Ni compared with SNe Ic, Ib, and IIb, with median M Ni = 0.34, 0.16, 0.14, and 0.11 M ⊙ , respectively. SNe Ic-BL, and to a lesser extent SNe Ic, typically rise from L p /2 to L p more quickly than SNe Ib/IIb; consequently, their light curves are not as broad.« less

Toward An Understanding of Cluster Evolution: A Deep X-Ray Selected Cluster Catalog from ROSAT

NASA Technical Reports Server (NTRS)

Jones, Christine; Oliversen, Ronald (Technical Monitor)

2002-01-01

In the past year, we have focussed on studying individual clusters found in this sample with Chandra, as well as using Chandra to measure the luminosity-temperature relation for a sample of distant clusters identified through the ROSAT study, and finally we are continuing our study of fossil groups. For the luminosity-temperature study, we compared a sample of nearby clusters with a sample of distant clusters and, for the first time, measured a significant change in the relation as a function of redshift (Vikhlinin et al. in final preparation for submission to Cape). We also used our ROSAT analysis to select and propose for Chandra observations of individual clusters. We are now analyzing the Chandra observations of the distant cluster A520, which appears to have undergone a recent merger. Finally, we have completed the analysis of the fossil groups identified in ROM observations. In the past few months, we have derived X-ray fluxes and luminosities as well as X-ray extents for an initial sample of 89 objects. Based on the X-ray extents and the lack of bright galaxies, we have identified 16 fossil groups. We are comparing their X-ray and optical properties with those of optically rich groups. A paper is being readied for submission (Jones, Forman, and Vikhlinin in preparation).

High levels of absorption in orientation-unbiased, radio-selected 3CR Active Galaxies

NASA Astrophysics Data System (ADS)

Wilkes, Belinda J.; Haas, Martin; Barthel, Peter; Leipski, Christian; Kuraszkiewicz, Joanna; Worrall, Diana; Birkinshaw, Mark; Willner, Steven P.

2014-08-01

A critical problem in understanding active galaxies (AGN) is the separation of intrinsic physical differences from observed differences that are due to orientation. Obscuration of the active nucleus is anisotropic and strongly frequency dependent leading to complex selection effects for observations in most wavebands. These can only be quantified using a sample that is sufficiently unbiased to test orientation effects. Low-frequency radio emission is one way to select a close-to orientation-unbiased sample, albeit limited to the minority of AGN with strong radio emission.Recent Chandra, Spitzer and Herschel observations combined with multi-wavelength data for a complete sample of high-redshift (1 24.2) = 2.5:1.4:1 in these high-luminosity (log L(0.3-8keV) ~ 44-46) sources. These ratios are consistent with current expectations based on modelingthe Cosmic X-ray Background. A strong correlation with radio orientation constrains the geometry of the obscuring disk/torus to have a ~60 degree opening angle and ~12 degree Compton-thick cross-section. The deduced ~50% obscured fraction of the population contrasts with typical estimates of ~20% obscured in optically- and X-ray-selected high-luminosity samples. Once the primary nuclear emission is obscured, AGN X-ray spectra are frequently dominated by unobscured non-nuclear or scattered nuclear emission which cannot be distinguished from direct nuclear emission with a lower obscuration level unless high quality data is available. As a result, both the level of obscuration and the estimated instrinsic luminosities of highly-obscured AGN are likely to be significantly (*10-1000) underestimated for 25-50% of the population. This may explain the lower obscured fractions reported for optical and X-ray samples which have no independent measure of the AGN luminosity. Correcting AGN samples for these underestimated luminosities would result in flatter derived luminosity functions and potentially change their evolution.

X-ray-selected galaxy groups in Boötes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vajgel, Bruna; Lopes, Paulo A. A.; Jones, Christine

2014-10-10

We present the X-ray and optical properties of the galaxy groups selected in the Chandra X-Boötes survey. We used follow-up Chandra observations to better define the group sample and their X-ray properties. Group redshifts were measured from the AGN and Galaxy Evolution Survey spectroscopic data. We used photometric data from the NOAO Deep Wide Field Survey to estimate the group richness (N {sub gals}) and the optical luminosity (L {sub opt}). Our final sample comprises 32 systems at z < 1.75 with 14 below z = 0.35. For these 14 systems, we estimate velocity dispersions (σ {sub gr}) and performmore » a virial analysis to obtain the radii (R {sub 200} and R {sub 500}) and total masses (M {sub 200} and M {sub 500}) for groups with at least 5 galaxy members. We use the Chandra X-ray observations to derive the X-ray luminosity (L{sub X} ). We examine the performance of the group properties σ{sub gr}, L {sub opt}, and L{sub X} , as proxies for the group mass. Understanding how well these observables measure the total mass is important to estimate how precisely the cluster/group mass function is determined. Exploring the scaling relations built with the X-Boötes sample and comparing these with samples from the literature, we find a break in the L{sub X} -M {sub 500} relation at approximately M {sub 500} = 5 × 10{sup 13} M {sub ☉} (for M {sub 500} > 5 × 10{sup 13} M {sub ☉}, M{sub 500}∝L{sub X}{sup 0.61±0.02}, while for M {sub 500} ≤ 5 × 10{sup 13} M {sub ☉}, M{sub 500}∝L{sub X}{sup 0.44±0.05}). Thus, the mass-luminosity relation for galaxy groups cannot be described by the same power law as galaxy clusters. A possible explanation for this break is the dynamical friction, tidal interactions, and projection effects that reduce the velocity dispersion values of the galaxy groups. By extending the cluster luminosity function to the group regime, we predict the number of groups that new X-ray surveys, particularly eROSITA, will detect. Based on our cluster/group luminosity function estimates, eROSITA will identify ∼1800 groups (L{sub X} = 10{sup 41}-10{sup 43} erg s{sup –1}) within a distance of 200 Mpc. Since groups lie in large-scale filaments, this group sample will map the large-scale structure of the local universe.« less

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.

VizieR Online Data Catalog: The CLASS BL Lac sample (Marcha+, 2013)

NASA Astrophysics Data System (ADS)

Marcha, M. J. M.; Caccianiga, A.

2014-04-01

This paper presents a new sample of BL Lac objects selected from a deep (30mJy) radio survey of flat spectrum radio sources (the CLASS blazar survey). The sample is one of the largest well-defined samples in the low-power regime with a total of 130 sources of which 55 satisfy the 'classical' optical BL Lac selection criteria, and the rest have indistinguishable radio properties. The primary goal of this study is to establish the radio luminosity function (RLF) on firm statistical ground at low radio luminosities where previous samples have not been able to investigate. The gain of taking a peek at lower powers is the possibility to search for the flattening of the luminosity function which is a feature predicted by the beaming model but which has remained elusive to observational confirmation. In this study, we extend for the first time the BL Lac RLF down to very low radio powers ~1022W/Hz, i.e. two orders of magnitude below the RLF currently available in the literature. In the process, we confirm the importance of adopting a broader, and more physically meaningful set of classification criteria to avoid the systematic missing of low-luminosity BL Lacs. Thanks to the good statistics we confirm the existence of weak but significant positive cosmological evolution for the BL Lac population, and we detect, for the first time the flattening of the RLF at L~1025W/Hz in agreement with the predictions of the beaming model. (1 data file).

X-ray emission at the low-mass end - Results from an extensive Einstein Observatory survey

NASA Technical Reports Server (NTRS)

Barbera, M.; Micela, G.; Sciortino, S.; Harnden, F. R., Jr.; Rosner, R.

1993-01-01

We have used available IPC data and a critical compilation of cataloged optical data to measure the 0.16-3.5 keV X-ray emission from 88 K and 169 M stars of luminosity classes IV, V, and VI within 25 pc from the Sun. The IPC detected 54 out of the 88 K stars, 70 out of the 138 M stars with M(v) less than 13.4, and 15 out of the 31 fainter M stars. We have identified a subsample of surveyed stars that is statistically representative of the population of K and M stars in the solar neighborhood. On the basis of this subsample (1) we have shown the occurrence of a drop in the level of X-ray emission for M stars later than approximately M5; (2) we have built unbiased maximum likelihood X-ray luminosity functions for the K, early M, and late M stars; (3) we have confirmed, both for K and M stars, the decrease of X-ray luminosity with increasing stellar age in the range of ages of disk population stars: and (4) we have shown that no obvious correlation is present between X-ray and bolometric luminosities in the entire representative samples of K and M stars, but only within flare stars which also seem to mark a saturation in X-ray luminosity level.

Long term dynamics of the high luminosity Large Hadron Collider with crab cavities

NASA Astrophysics Data System (ADS)

Barranco García, J.; De Maria, R.; Grudiev, A.; Tomás García, R.; Appleby, R. B.; Brett, D. R.

2016-10-01

The High Luminosity upgrade of the Large Hadron Collider (HL-LHC) aims to achieve an integrated luminosity of 200 - 300 fb-1 per year, including the contribution from the upgrade of the injector chain. For the HL-LHC the larger crossing angle together with a smaller beta function at the collision point would result in more than 70% luminosity loss due to the incomplete geometric overlap of colliding bunches. To recover head-on collisions at the high-luminosity particle-physics detectors ATLAS and CMS and benefit from the very low β* provided by the Achromatic Telescopic Squeezing (ATS) optics, a local crab cavity scheme provides transverse kicks to the proton bunches. The tight space constraints at the location of these cavities leads to designs which are axially non-symmetric, giving rise to high order multipoles components of the main deflecting mode and, since these kicks are harmonic in time, we expand them in a series of multipoles in a similar fashion as is done for static field magnets. In this work we calculate, for the first time, the higher order multipoles and their impact on beam dynamics for three different crab cavity prototypes. Different approaches to calculate the multipoles are presented. Furthermore, we perform the first calculation of their impact on the long term stability of the machine using the concept of dynamic aperture.

A limit to the X-ray luminosity of nearby normal galaxies

NASA Technical Reports Server (NTRS)

Worrall, D. M.; Marshall, F. E.; Boldt, E. A.

1979-01-01

Emission is studied at luminosities lower than those for which individual discrete sources can be studied. It is shown that normal galaxies do not appear to provide the numerous low luminosity X-ray sources which could make up the 2-60 keV diffuse background. Indeed, upper limits suggest luminosities comparable with, or a little less than, that of the galaxy. This is consistent with the fact that the average optical luminosity of the sample galaxies within approximately 20 Mpc is slightly lower than that of the galaxy. An upper limit of approximately 1% of the diffuse background from such sources is derived.

NGST: Exploring the Fossil Record of Galaxy Formation

NASA Technical Reports Server (NTRS)

Rich, R. Michael

1998-01-01

During this grant period the investigator has accomplished the following: developed and researched the science case for high resolution optical imaging with NGST (Next Generation Space Telescope); presented to the ASWG (Ad-Hoc Science Working Group) on the use of NGST to image and measure the proper motions of white dwarf stars that could account for the MACHO events toward the LMC (Large Magellanic Cloud); wrote proposals for the Design Reference Mission. Three proposals have been written on the following topics: Measuring the faint end of the white dwarf luminosity function to get an independent measure of the age of the oldest stars, measurement of the stellar luminosity function over the full range of age, abundance, and population type, and deep imaging of Local Group halos to measure the relative ages of the oldest stars in the Milky Way and other galaxies; he has introduced simulations of crowded field stellar photometry on a hypothetical population in the M31 halo. Using a physically correct luminosity function and a surface brightness of 24.5 mag/sq. arcsec, NGST imaging in 10 hours easily measures the turnoff and reaches 3 mags down the main sequence in the halo of M31; and has delivered talks at the NGST workshop in Liege, and at the meeting in Paris entitled "Connecting the Distant Universe with the Local Fossil Record".

The near-infrared radius-luminosity relationship for active galactic nuclei

NASA Astrophysics Data System (ADS)

Landt, Hermine; Bentz, Misty C.; Peterson, Bradley M.; Elvis, Martin; Ward, Martin J.; Korista, Kirk T.; Karovska, Margarita

2011-05-01

Black hole masses for samples of active galactic nuclei (AGNs) are currently estimated from single-epoch optical spectra. In particular, the size of the broad-line emitting region needed to compute the black hole mass is derived from the optical or ultraviolet continuum luminosity. Here we consider the relationship between the broad-line region size, R, and the near-infrared (near-IR) AGN continuum luminosity, L, as the near-IR continuum suffers less dust extinction than at shorter wavelengths and the prospects for separating the AGN continuum from host-galaxy starlight are better in the near-IR than in the optical. For a relationship of the form R∝Lα, we obtain for a sample of 14 reverberation-mapped AGN a best-fitting slope of α= 0.5 ± 0.1, which is consistent with the slope of the relationship in the optical band and with the value of 0.5 naïvely expected from photoionization theory. Black hole masses can then be estimated from the near-IR virial product, which is calculated using the strong and unblended Paschen broad emission lines (Paα or Paβ).

Black Holes in Bulgeless Galaxies: An XMM-Newton Investigation of NGC 3367 AND NGC 4536

NASA Technical Reports Server (NTRS)

McAlpine, W.; Satyapal, S.; Gliozzi, M.; Cheung, C. C.; Sambruna, R. M.; Eracleous, Michael

2012-01-01

The vast majority of optically identified active galactic nuclei (AGNs) in the local Universe reside in host galaxies with prominent bulges, supporting the hypothesis that black hole formation and growth is fundamentally connected to the build-up of galaxy bulges. However, recent mid-infrared spectroscopic studies with Spitzer of a sample of optically "normal" late-type galaxies reveal remarkably the presence of high-ionization [NeV] lines in several sources, providing strong evidence for AGNs in these galaxies. We present follow-up X-ray observations recently obtained with XMM-Newton of two such sources, the late-type optically normal galaxies NGC 3367 and NGC 4536. Both sources are detected in our observations. Detailed spectral analysis reveals that for both galaxies, the 2-10 keV emission is dominated by a power law with an X-ray luminosity in the L(sub 2- 10 keV) approximates 10(exp 39) - 10(exp 40) ergs/s range, consistent with low luminosity AGNs. While there is a possibility that X-ray binaries account for some fraction of the observed X-ray luminosity, we argue that this fraction is negligible. These observations therefore add to the growing evidence that the fraction of late-type galaxies hosting AGNs is significantly underestimated using optical observations alone. A comparison of the midinfrared [NeV] luminosity and the X-ray luminosities suggests the presence of an additional highly absorbed X-ray source in both galaxies, and that the black hole masses are in the range of 10(exp 5) - 10(exp 7) solar M for NGC 3367 and 10(exp 4) - (exp 10) solar M for NGC 4536

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.

The COSMIC-DANCE project: Unravelling the origin of the mass function

NASA Astrophysics Data System (ADS)

Bouy, H.; Bertin, E.; Sarro, L. M.; Barrado, D.; Berihuete, A.; Olivares, J.; Moraux, E.; Bouvier, J.; Tamura, M.; Cuillandre, J.-C.; Beletsky, Y.; Wright, N.; Huelamo, N.; Allen, L.; Solano, E.; Brandner, B.

2017-03-01

The COSMIC-DANCE project is an observational program aiming at understanding the origin and evolution of ultracool objects by measuring the mass function and internal dynamics of young nearby associations down to the fragmentation limit. The least massive members of young nearby associations are identified using modern statistical methods in a multi-dimensional space made of optical and infrared luminosities and colors and proper motions. The photometry and astrometry are obtained by combining ground and in some case space based archival observations with new observations, covering between one and two decades.

Rapidly Rising Optical Transients from the Birth of Binary Neutron Stars

NASA Astrophysics Data System (ADS)

Hotokezaka, Kenta; Kashiyama, Kazumi; Murase, Kohta

2017-11-01

We study optical counterparts of a new-born pulsar in a double neutron star system like PSR J0737-3039A/B. This system is believed to have ejected a small amount of mass of { O }(0.1 {M}⊙ ) at the second core-collapse supernova. We argue that the initial spin of the new-born pulsar can be determined by the orbital period at the time when the second supernova occurs. The spin angular momentum of the progenitor is expected to be similar to that of the He-burning core, which is tidally synchronized with the orbital motion, and then the second remnant may be born as a millisecond pulsar. If the dipole magnetic field strength of the nascent pulsar is comparable with that inferred from the current spin-down rate of PSR J0737-3039B, the initial spin-down luminosity is comparable to the luminosity of super-luminous supernovae. We consider thermal emission arising from the supernova ejecta driven by the relativistic wind from such a new-born pulsar. The resulting optical light curves have a rise time of ˜10 days and a peak luminosity of ˜1044 erg s-1. The optical emission may last for a month to several months, due to the reprocessing of X-rays and UV photons via photoelectric absorption. These features are broadly consistent with those of the rapidly rising optical transients. The high spin-down luminosity and small ejecta mass are favorable for the progenitor of the repeating fast radio burst, FRB 121102. We discuss a possible connection between new-born double pulsars and fast radio bursts.

Relationship between optical and X-ray properties of O-type stars surveyed with the Einstein Observatory

NASA Technical Reports Server (NTRS)

Sciortino, S.; Vaiana, G. S.; Harnden, F. R., Jr.; Ramella, M.; Morossi, C.

1990-01-01

An X-ray luminosity function is derived for a representative volume-limited sample of O-type stars selected from the catalog of Galactic O stars surveyed with the Einstein Observatory. It was found that, for the stars of this sample which is ten times larger than any previously analyzed, the level of X-ray emission is strongly correlated with bolometric luminosity, confirming previous findings of an Lx-L(bol) relationship (e.g., Harnden et al., 1979; Pallavicini et al., 1981). Correlations between the Lx and the mass loss rate with the wind terminal velocity or with the rotation rate were weak. However, there was a strong correlation with wind momentum flux as well as with the wind kinetic energy flux.

Ultraviolet spectrophotometry and optical and infrared photometry of the old nova GK Persei

NASA Technical Reports Server (NTRS)

Wu, Chi-Chao; Holm, Albert V.; Panek, Robert J.; Raymond, John C.; Hartmann, Lee W.; Swank, Jean H.

1989-01-01

IUE observations in the 1150-3250-A region were obtained of GK Per during the rise, at the maximum, and during the decline of the 2.5-mag optical outburst in 1981. The results support previous predictions for the interaction of an accretion disk with the magnetic field of an accretion star. The luminosity at minimum is found to be 2.3 solar luminosities, with 1/3 of this being attributed to the cool secondary star.

Dark-ages reionization and galaxy formation simulation - X. The small contribution of quasars to reionization

NASA Astrophysics Data System (ADS)

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

2017-12-01

Motivated by recent measurements of the number density of faint AGN at high redshift, we investigate the contribution of quasars to reionization by tracking the growth of central supermassive black holes in an update of the MERAXES semi-analytic model. The model is calibrated against the observed stellar mass function at z ∼ 0.6-7, the black hole mass function at z ≲ 0.5, the global ionizing emissivity at z ∼ 2-5 and the Thomson scattering optical depth. The model reproduces a Magorrian relation in agreement with observations at z < 0.5 and predicts a decreasing black hole mass towards higher redshifts at fixed total stellar mass. With the implementation of an opening angle of 80 deg for quasar radiation, corresponding to an observable fraction of ∼23.4 per cent due to obscuration by dust, the model is able to reproduce the observed quasar luminosity function at z ∼ 0.6-6. The stellar light from galaxies hosting faint active galactic nucleus (AGN) contributes a significant or dominant fraction of the UV flux. At high redshift, the model is consistent with the bright end quasar luminosity function and suggests that the recent faint z ∼ 4 AGN sample compiled by Giallongo et al. (2015) includes a significant fraction of stellar light. Direct application of this luminosity function to the calculation of AGN ionizing emissivity consequently overestimates the number of ionizing photons produced by quasars by a factor of 3 at z ∼ 6. We conclude that quasars are unlikely to make a significant contribution to reionization.

Dust-obscured star formation and the contribution of galaxies escaping UV/optical color selections at z ~ 2

NASA Astrophysics Data System (ADS)

Riguccini, L.; Le Floc'h, E.; Ilbert, O.; Aussel, H.; Salvato, M.; Capak, P.; McCracken, H.; Kartaltepe, J.; Sanders, D.; Scoville, N.

2011-10-01

Context. A substantial amount of the stellar mass growth across cosmic time occurred within dust-enshrouded environments. So far, identification of complete samples of distant star-forming galaxies from the short wavelength range has been strongly biased by the effect of dust extinction. Nevertheless, the exact amount of star-forming activity that took place in high-redshift dusty galaxies but that has currently been missed by optical surveys has barely been explored. Aims: Our goal is to determine the number of luminous star-forming galaxies at 1.5 ≲ z ≲ 3 that are potentially missed by the traditional color selection techniques because of dust extinction. We also aim at quantifying the contribution of these sources to the IR luminosity and cosmic star formation density at high redshift. Methods: We based our work on a sample of 24 μm sources brighter than 80 μJy and taken from the Spitzer survey of the COSMOS field. Almost all of these sources have accurate photometric redshifts. We applied to this mid-IR selected sample the BzK and BM/BX criteria, as well as the selections of the IRAC peakers and the Optically-Faint IR-bright (OFIR) galaxies. We analyzed the fraction of sources identified with these techniques. We also computed 8 μm rest-frame luminosity from the 24 μm fluxes of our sources, and considering the relationships between L8 μm and LPaα and between L8 μm and LIR, we derived ρIR and then ρSFR for our MIPS sources. Results: The BzK criterion offers an almost complete (~90%) identification of the 24 μm sources at 1.4 < z < 2.5. In contrast, the BM/BX criterion misses 50% of the MIPS sources. We attribute this bias to the effect of extinction, which reddens the typical colors of galaxies. The contribution of these two selections to the IR luminosity density produced by all the sources brighter than 80 μJy are on the same order. Moreover the criterion based on the presence of a stellar bump in their spectra (IRAC peakers) misses up to 40% of the IR luminosity density, while only 25% of the IR luminosity density at z ~ 2 is produced by OFIR galaxies characterized by extreme mid-IR to optical flux ratios. Conclusions: Color selections of distant star-forming galaxies must be used with care given the substantial bias they can suffer. In particular, the effect of dust extinction strongly affects the completeness of identifications at the bright end of the bolometric luminosity function, which implies large and uncertain extrapolations to account for the contribution of dusty galaxies missed by these selections. In the context of forthcoming facilities that will operate at long wavelengths (e.g., JWST, ALMA, SAFARI, EVLA, SKA), this emphasizes the importance of minimizing the extinction biases when probing the activity of star formation in the early Universe.

X-Ray Luminosity Functions of Normal Galaxies in the Great Observatories Origins Deep Survey

NASA Astrophysics Data System (ADS)

Ptak, Andrew; Mobasher, Bahram; Hornschemeier, Ann; Bauer, Franz; Norman, Colin

2007-10-01

We present soft (0.5-2 keV) X-ray luminosity functions (XLFs) in the Great Observatories Origins Deep Survey (GOODS) fields derived for galaxies at z~0.25 and 0.75. SED fitting was used to estimate photometric redshifts and separate galaxy types, resulting in a sample of 40 early-type galaxies and 46 late-type galaxies. We estimate k-corrections for both the X-ray/optical and X-ray/NIR flux ratios, which facilitates the separation of AGNs from the normal/starburst galaxies. We fit the XLFs with a power-law model using both traditional and Markov-Chain Monte Carlo (MCMC) procedures. A key advantage of the MCMC approach is that it explicitly takes into account upper limits and allows errors on ``derived'' quantities, such as luminosity densities, to be computed directly (i.e., without potentially questionable assumptions concerning the propagation of errors). The slopes of the early-type galaxy XLFs tend to be slightly flatter than the late-type galaxy XLFs, although the effect is significant at only the 90% and 97% levels for z~0.25 and 0.75. The XLFs differ between z<0.5 and z>0.5 at >99% significance levels for early-type, late-type, and all (early- and late-type) galaxies. We also fit Schechter and lognormal models to the XLFs, fitting the low- and high-redshift XLFs for a given sample simultaneously assuming only pure luminosity evolution. In the case of lognormal fits, the results of MCMC fitting of the local FIR luminosity function were used as priors for the faint- and bright-end slopes (similar to ``fixing'' these parameters at the FIR values, except here the FIR uncertainty is included). The best-fit values of the change in logL* with redshift were ΔlogL*=0.23+/-0.16 dex (for early-type galaxies) and 0.34+/-0.12 dex (for late-type galaxies), corresponding to (1+z)1.6 and (1+z)2.3. These results were insensitive to whether the Schechter or lognormal function was adopted.

NLC Luminosity as a Function of Beam Parameters

NASA Astrophysics Data System (ADS)

Nosochkov, Y.

2002-06-01

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.

Warm Dark Matter and Cosmic Reionization

DOE PAGES

Villanueva-Domingo, Pablo; Gnedin, Nickolay Y.; Mena, Olga

2018-01-10

In models with dark matter made of particles with keV masses, such as a sterile neutrino, small-scale density perturbations are suppressed, delaying the period at which the lowest mass galaxies are formed and therefore shifting the reionization processes to later epochs. In this study, focusing on Warm Dark Matter (WDM) with masses close to its present lower bound, i.e., around the 3 keV region, we derive constraints from galaxy luminosity functions, the ionization history and the Gunn–Peterson effect. We show that even if star formation efficiency in the simulations is adjusted to match the observed UV galaxy luminosity functions in bothmore » CDM and WDM models, the full distribution of Gunn–Peterson optical depth retains the strong signature of delayed reionization in the WDM model. Furthermore, until the star formation and stellar feedback model used in modern galaxy formation simulations is constrained better, any conclusions on the nature of dark matter derived from reionization observables remain model-dependent.« less

Warm Dark Matter and Cosmic Reionization

NASA Astrophysics Data System (ADS)

Villanueva-Domingo, Pablo; Gnedin, Nickolay Y.; Mena, Olga

2018-01-01

In models with dark matter made of particles with keV masses, such as a sterile neutrino, small-scale density perturbations are suppressed, delaying the period at which the lowest mass galaxies are formed and therefore shifting the reionization processes to later epochs. In this study, focusing on Warm Dark Matter (WDM) with masses close to its present lower bound, i.e., around the 3 keV region, we derive constraints from galaxy luminosity functions, the ionization history and the Gunn–Peterson effect. We show that even if star formation efficiency in the simulations is adjusted to match the observed UV galaxy luminosity functions in both CDM and WDM models, the full distribution of Gunn–Peterson optical depth retains the strong signature of delayed reionization in the WDM model. However, until the star formation and stellar feedback model used in modern galaxy formation simulations is constrained better, any conclusions on the nature of dark matter derived from reionization observables remain model-dependent.

Warm Dark Matter and Cosmic Reionization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Villanueva-Domingo, Pablo; Gnedin, Nickolay Y.; Mena, Olga

In models with dark matter made of particles with keV masses, such as a sterile neutrino, small-scale density perturbations are suppressed, delaying the period at which the lowest mass galaxies are formed and therefore shifting the reionization processes to later epochs. In this study, focusing on Warm Dark Matter (WDM) with masses close to its present lower bound, i.e., around the 3 keV region, we derive constraints from galaxy luminosity functions, the ionization history and the Gunn–Peterson effect. We show that even if star formation efficiency in the simulations is adjusted to match the observed UV galaxy luminosity functions in bothmore » CDM and WDM models, the full distribution of Gunn–Peterson optical depth retains the strong signature of delayed reionization in the WDM model. Furthermore, until the star formation and stellar feedback model used in modern galaxy formation simulations is constrained better, any conclusions on the nature of dark matter derived from reionization observables remain model-dependent.« less

The luminosity function for the CfA redshift survey slices

NASA Technical Reports Server (NTRS)

De Lapparent, Valerie; Geller, Margaret J.; Huchra, John P.

1989-01-01

The luminosity function for two complete slices of the extension of the CfA redshift survey is calculated. The nonparametric technique of Lynden-Bell (1971) and Turner (1979) is used to determine the shape for the luminosity function of the 12 deg slice of the redshift survey. The amplitude of the luminosity function is determined, taking large-scale inhomogeneities into account. The effects of the Malmquist bias on a magnitude-limited redshift survey are examined, showing that the random errors in the magnitudes for the 12 deg slice affect both the determination of the luminosity function and the spatial density constrast of large scale structures.

Extremely Luminous Far-infrared Sources (ELFS)

NASA Technical Reports Server (NTRS)

Harwit, Martin; Houck, James R.; Soifer, B. Thomas; Palumbo, Giorgio G. C.

1987-01-01

The Infrared Astronomical Satellite (IRAS) survey uncovered a class of Extremely Luminous Far Infrared Sources (ELFS), exhibiting luminosities up to and occasionally exceeding 10 to the 12th power L sub 0. Arguments are presented to show that sources with luminosities L equal to or greater than 3 x 10 to the 10th power L sub 0 may represent gas rich galaxies in collision. The more conventional explanation of these sources as sites of extremely active star formation fails to explain the observed low optical luminosities of ELFS as well as their high infrared excess. In contrast, a collisional model heats gas to a temperature of approx. 10 to the 6th power K where cooling takes place in the extreme ultraviolet. The UV is absorbed by dust and converted into far infrared radiation (FIR) without generation of appreciable optical luminosity. Gas recombination as it cools generates a Lyman alpha photon only once for every two extreme ultraviolet approx. 50eV photons emitted by the 10 to the 6th power gas. That accounts for the high infrared excess. Finally, the model also is able to explain the observed luminosity distribution of ELFS as well as many other traits.

The K-Band Quasar Luminosity Function from an SDSS and UKIDSS Matched Catalog

NASA Astrophysics Data System (ADS)

Peth, Michael; Ross, N. P.; Schneider, D. P.

2010-01-01

We match the 1,015,082 quasars from the Sloan Digital Sky Survey (SDSS) DR6 Photometric Quasar catalog to the UKIRT Infrared Digital Sky Survey (UKIDSS) Large Area Survey (LAS) DR3 to produce a catalog of 130,827 objects with optical (ugriz) and infrared (YJHK) measurements over an area of 1,200 sq. deg. A matching radius of 1'’ is used; the positional standard deviations of SDSS DR6 quasars and UKIDSS LAS is δRA = 0.137'’ and δDec = 0.131''. The catalog contains 74,351 K-band detections and 42,133 objects have coverage in all four NIR bands. In addition to the catalog, we present optical and NIR color-redshift and color-color plots. The photometric vs. spectroscopic redshift plots demonstrate how unreliable high reported photometric redshifts can be. This forces us to focus on z4.6 quasars are compared to our highest redshift objects. The giK color-color plot demonstrates that stellar contamination only affects a small sample of the objects. Distributions for Y,J,H,K and i-bands reveal insights into the flux limits in each magnitude. We investigate the distribution of redshifts from different data sets and investigate the legitimacy of certain measured photometric redshift regions. For in-depth analysis, we focus on the 300 sq. deg area equatorial SDSS region designated as Stripe 82. We measure the observed K-band quasar luminosity function (QLF) for a subset of 9,872, z<2.2 objects. We find the shape of the K-band QLF is very similar to that of the optical QLF, over the considered redshift ranges. Our calculated K-Band QLFs broadly match previous optical QLFs calculated from the SDSS and 2SLAQ QSO surveys and should provide important constraints linking unobscured optical quasars to Mid-Infrared detected, dusty and obscured AGNs at high-redshift.

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 luminosity function is due to beamed, non-BALQSOs.

The origin of the infrared luminosity in Centaurus A

NASA Technical Reports Server (NTRS)

Joy, Marshall; Lester, Daniel F.; Harvey, Paul M.; Ellis, H. Benton

1988-01-01

The origin of the infrared luminosity in Centaurus A is studied using new tracking and data acquisition techniques which yield diffraction-limited profiles at both 50 and 100 microns. Ninety percent of the 100 micron flux is found to originate in a source which extends 5 kpc along the optical dust lane that bisects the galaxy; the remaining 10 percent comes from an unresolved source coincident with the active radio nucleus. The extended 100 micron emission profile is fully consistent with a uniform disk of thermally radiating particles; when combined with results of previous studies at shorter wavelengths, these measurements indicate that nearly all of the infrared luminosity is produced by thermally emitting grains which are heated by massive young stars distributed throughout the optically thick dust lane.

Equilibrium configuration of a stratus floating above accretion disks: Full-disk calculation

NASA Astrophysics Data System (ADS)

Itanishi, Yusuke; Fukue, Jun

2017-06-01

We examine floating strati above a luminous accretion disk, supported by the radiative force from the entire disk, and calculate the equilibrium locus, which depends on the disk luminosity and the optical depth of the stratus. Due to the radiative transfer effect (albedo effect), the floating height of the stratus with a finite optical depth generally becomes high, compared with the particle case. In contrast to the case of the near-disk approximation, moreover, the floating height becomes yet higher in the present full-disk calculation, since the intense radiation from the inner disk is taken into account. As a result, when the disk luminosity normalized by the Eddington luminosity is ˜0.3 and the stratus optical depth is around unity, the stable configuration disappears at around r ˜ 50 rg, rg being the Schwarzschild radius, and the stratus would be blown off as a cloudy wind consisting of many strati with appropriate conditions. This luminosity is sufficiently smaller than the Eddington one, and the present results suggest that the radiation-driven cloudy wind can be easily blown off from the sub-Eddington disk, and this can explain various outflows observed in ultra-fast outflow objects as well as in broad-absorption-line quasars.

Multi-wavelength seds of Herschel-selected galaxies in the cosmos field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Nicholas; Sanders, D. B.; Casey, Caitlin M.

2013-12-01

We combine Herschel Photodetector Array Camera and Spectrometer and Spectral and Photometric Imaging Receiver maps of the full 2 deg{sup 2} Cosmic Evolution Survey (COSMOS) field with existing multi-wavelength data to obtain template and model-independent optical-to-far-infrared spectral energy distributions (SEDs) for 4218 Herschel-selected sources with log(L {sub IR}/L {sub ☉}) = 9.4-13.6 and z = 0.02-3.54. Median SEDs are created by binning the optical to far-infrared (FIR) bands available in COSMOS as a function of infrared luminosity. Herschel probes rest-frame wavelengths where the bulk of the infrared radiation is emitted, allowing us to more accurately determine fundamental dust properties ofmore » our sample of infrared luminous galaxies. We find that the SED peak wavelength (λ{sub peak}) decreases and the dust mass (M {sub dust}) increases with increasing total infrared luminosity (L {sub IR}). In the lowest infrared luminosity galaxies (log(L {sub IR}/L {sub ☉}) = 10.0-11.5), we see evidence of polycyclic aromatic hydrocarbon (PAH) features (λ ∼ 7-9 μm), while in the highest infrared luminosity galaxies (L {sub IR} > 10{sup 12} L {sub ☉}) we see an increasing contribution of hot dust and/or power-law emission, consistent with the presence of heating from an active galactic nucleus (AGN). We study the relationship between stellar mass and star formation rate of our sample of infrared luminous galaxies and find no evidence that Herschel-selected galaxies follow the SFR/M {sub *} 'main sequence' as previously determined from studies of optically selected, star-forming galaxies. Finally, we compare the mid-infrared to FIR properties of our infrared luminous galaxies using the previously defined diagnostic, IR8 ≡ L {sub IR}/L {sub 8}, and find that galaxies with L {sub IR} ≳ 10{sup 11.3} L {sub ☉} tend to systematically lie above (× 3-5) the IR8 'infrared main sequence', suggesting either suppressed PAH emission or an increasing contribution from AGN heating.« less

GRB Diversity vs. Utility as Cosmological Probes

NASA Technical Reports Server (NTRS)

Norris, J. P.; Scargle, J. D.; Bonnell, J. T.; Nemiroff, R. J.; Young, Richard E. (Technical Monitor)

1997-01-01

Recent detections of apparent gamma-ray burst (GRB) counterparts in optical and radio wavebands strongly favor the cosmological distance scale, at least for some GRBs, opening the possibility of GRBs serving as cosmological probes. But GRBs exhibit great diversity: in total duration; in number, width and pulse configuration; and in pulse and overall spectral evolution. However, it is possible that a portion of this behavior reflects a luminosity distribution, and possible that evolution of with cosmic time introduces dispersion into the average GRB characteristics -- issues analogous to those encountered with quasars. The temporal domain offers a rich avenue to investigate this problem. When corrected for assumed spectral redshift, time dilation of event durations, pulse widths, and intervals between pulses must yield the same time-dilation factor as a function of peak flux, or else a luminosity distribution may be the cause of observed time dilation effects. We describe results of burst analysis using an automated, Bayesian-based algorithm to determine burst temporal characteristics for different peak flux groups, and derived constraints on any physical process that would introduce a luminosity distribution.

A multiparametric analysis of the Einstein sample of early-type galaxies. 1: Luminosity and ISM parameters

NASA Technical Reports Server (NTRS)

Eskridge, Paul B.; Fabbiano, Giuseppina; Kim, Dong-Woo

1995-01-01

We have conducted bivariate and multivariate statistical analysis of data measuring the luminosity and interstellar medium of the Einstein sample of early-type galaxies (presented by Fabbiano, Kim, & Trinchieri 1992). We find a strong nonlinear correlation between L(sub B) and L(sub X), with a power-law slope of 1.8 +/- 0.1, steepening to 2.0 +/- if we do not consider the Local Group dwarf galaxies M32 and NGC 205. Considering only galaxies with log L(sub X) less than or equal to 40.5, we instead find a slope of 1.0 +/- 0.2 (with or without the Local Group dwarfs). Although E and S0 galaxies have consistent slopes for their L(sub B)-L(sub X) relationships, the mean values of the distribution functions of both L(sub X) and L(sub X)/L(sub B) for the S0 galaxies are lower than those for the E galaxies at the 2.8 sigma and 3.5 sigma levels, respectively. We find clear evidence for a correlation between L(sub X) and the X-ray color C(sub 21), defined by Kim, Fabbiano, & Trinchieri (1992b), which indicates that X-ray luminosity is correlated with the spectral shape below 1 keV in the sense that low-L(sub X) systems have relatively large contributions from a soft component compared with high-L(sub X) systems. We find evidence from our analysis of the 12 micron IRAS data for our sample that our S0 sample has excess 12 micron emission compared with the E sample, scaled by their optical luminosities. This may be due to emission from dust heated in star-forming regions in S0 disks. This interpretation is reinforced by the existence of a strong L(sub 12)-L(sub 100) correlation for our S0 sample that is not found for the E galaxies, and by an analysis of optical-IR colors. We find steep slopes for power-law relationships between radio luminosity and optical, X-ray, and far-IR (FIR) properties. This last point argues that the presence of an FIR-emitting interstellar medium (ISM) in early-type galaxies is coupled to their ability to generate nonthermal radio continuum, as previously argued by, e.g., Walsh et al. (1989). We also find that, for a given L(sub 100), galaxies with larger L(sub X)/L(sub B) tend to be stronger nonthermal radio sources, as originally suggested by Kim & Fabbiano (1990). We note that, while L(sub B) is most strongly correlated with L(sub 6), the total radio luminosity, both L(sub X) and L(sub X)/L(sub B) are more strongly correlated with L(sub 6 CO), the core radio luminosity. These points support the argument (proposed by Fabbiano, Gioia, & Trinchieri 1989) that radio cores in early-type galaxies are fueled by the hot ISM.

The infrared luminosity function of AKARI 90 μm galaxies in the local Universe

NASA Astrophysics Data System (ADS)

Kilerci Eser, Ece; Goto, Tomotsugu

2018-03-01

Local infrared (IR) luminosity functions (LFs) are necessary benchmarks for high-redshift IR galaxy evolution studies. Any accurate IR LF evolution studies require accordingly accurate local IR LFs. We present IR galaxy LFs at redshifts of z ≤ 0.3 from AKARI space telescope, which performed an all-sky survey in six IR bands (9, 18, 65, 90, 140, and 160 μm) with 10 times better sensitivity than its precursor Infrared Astronomical Satellite. Availability of 160 μm filter is critically important in accurately measuring total IR luminosity of galaxies, covering across the peak of the dust emission. By combining data from Wide-field Infrared Survey Explorer (WISE), Sloan Digital Sky Survey (SDSS) Data Release 13 (DR 13), six-degree Field Galaxy Survey and the 2MASS Redshift Survey, we created a sample of 15 638 local IR galaxies with spectroscopic redshifts, factor of 7 larger compared to previously studied AKARI-SDSS sample. After carefully correcting for volume effects in both IR and optical, the obtained IR LFs agree well with previous studies, but comes with much smaller errors. Measured local IR luminosity density is ΩIR = 1.19 ± 0.05 × 108L⊙ Mpc-3. The contributions from luminous IR galaxies and ultraluminous IR galaxies to ΩIR are very small, 9.3 per cent and 0.9 per cent, respectively. There exists no future all-sky survey in far-IR wavelengths in the foreseeable future. The IR LFs obtained in this work will therefore remain an important benchmark for high-redshift studies for decades.

Luminosity and redshift dependence of the covering factor of active galactic nuclei viewed with WISE and Sloan digital sky survey

DOE Office of Scientific and Technical Information (OSTI.GOV)

Toba, Y.; Matsuhara, H.; Oyabu, S.

2014-06-10

In this work, we investigate the dependence of the covering factor (CF) of active galactic nuclei (AGNs) on the mid-infrared (MIR) luminosity and the redshift. We constructed 12 and 22 μm luminosity functions (LFs) at 0.006 ≤z ≤ 0.3 using Wide-field Infrared Survey Explorer (WISE) data. Combining the WISE catalog with Sloan Digital Sky Survey (SDSS) spectroscopic data, we selected 223,982 galaxies at 12 μm and 25,721 galaxies at 22 μm for spectroscopic classification. We then identified 16,355 AGNs at 12 μm and 4683 AGNs at 22 μm by their optical emission lines and cataloged classifications in the SDSS. Followingmore » that, we estimated the CF as the fraction of Type 2 AGN in all AGNs whose MIR emissions are dominated by the active nucleus (not their host galaxies) based on their MIR colors. We found that the CF decreased with increasing MIR luminosity, regardless of the choice of Type 2 AGN classification criteria, and the CF did not change significantly with redshift for z ≤ 0.2. Furthermore, we carried out various tests to determine the influence of selection bias and confirmed that similar dependences exist, even when taking these uncertainties into account. The luminosity dependence of the CF can be explained by the receding torus model, but the 'modified' receding torus model gives a slightly better fit, as suggested by Simpson.« less

Evolution of the luminosity function of quasar accretion disks

NASA Technical Reports Server (NTRS)

Caditz, David M.; Petrosian, Vahe; Wandel, Amri

1991-01-01

Using an accretion-disk model, accretion disk luminosities are calculated for a grid of black hole masses and accretion rates. It is shown that, as the black-hole mass increases with time, the monochromatic luminosity at a given frequency first increases and then decreases rapidly as this frequency is crossed by the Wien cutoff. The upper limit on the monochromatic luminosity, which is characteristic for a given epoch, constrains the evolution of quasar luminosities and determines the evolultion of the quasar luminosity function.

Big Data in the SHELA Field: Investigating Galaxy Quenching at High Redshifts

NASA Astrophysics Data System (ADS)

Stevans, Matthew L.; Finkelstein, Steven L.; Wold, Isak; Kawinwanichakij, Lalitwadee; Sherman, Sydney; Gebhardt, Karl; Jogee, Shardha; Papovich, Casey J.; Ciardullo, Robin; Gronwall, Caryl; Gawiser, Eric J.; Acquaviva, Viviana; Casey, Caitlin; Florez, Jonathan; HETDEX Team

2017-06-01

We present a measurement of the z ~ 4 Lyman break galaxy (LBG) rest-frame UV luminosity function to investigate the onset of quenching in the early universe. The bright-end of the galaxy luminosity function typically shows an exponential decline far steeper than that of the underlying halo mass function. This is typically attributed to negative feedback from past active galactic nuclei (AGN) activity as well as dust attenuation. Constraining the abundance of bright galaxies at early times (z > 3) can provide a key insight into the mechanisms regulating star formation in galaxies. However, existing studies suffer from low number statistics and/or the inability to robustly remove stellar and AGN contaminants. In this study we take advantage of the unprecedentedly large (24 deg^2) Spitzer/HETDEX Exploratory Large Area (SHELA) field and its deep multi-wavelength photometry, which includes DECam ugriz, NEWFIRM K-band, Spitzer/IRAC, Herschel/SPIRE, and X-ray from XMM-Newton and Chandra. With SHELA’s deep imaging over a large area we are uniquely positioned to study statistically significant samples of massive galaxies at high redshifts (z > 3) when the first massive galaxies began quenching. We select our sample using photometric redshifts from the EAZY software package (Brammer et al. 2008) based on the optical and far-infrared imaging. We directly identify and remove stellar contaminants and AGN with IRAC colors and X-ray detections, respectively. By pinning down the exact shape of the bright-end of the z ~ 4 LBG luminosity function, we provide the deepest probe yet into the baryonic physics dominating star formation and quenching in the early universe.

XMM-Newton Proposal 03001001

NASA Astrophysics Data System (ADS)

Barrado Y Navascues, David

2004-10-01

We propose observations with XMM-EPIC/MOS in five distinct sibling associations belonging to the Lambda Orionis Star Forming Region (2-5 Myr, 340 pc). We have already optical and IR photometry and spectroscopy for objects down to 0.015 M(sun). The goals are: i) Assess the membership of our candidates and detect new members. ii) Derive accurate IMFs for each association, checking the universality of the IMF. iii) Study the properties and evolution of the X-ray Luminosity Functions.

An unbiased X-ray sampling of stars within 25 parsecs of the Sun

NASA Technical Reports Server (NTRS)

Johnson, H. M.

1985-01-01

A search of all of the Einstein Observatory IPC and HRI fields for untargeted stars in the Woolley, et al., Catalogue of the nearby stars is reported. Optical data and IPC coordinates, flux density F sub x, and luminosity L sub x, or upper limits, are tabulated for 126 single or blended systems, and HRI results for a few of them. IPC luminosity functions are derived for the systems, for 193 individual stars in the systems (with L sub x shared equally among blended components), and for 63 individual M dwarfs. These stars have relatively large X-ray flux densities that are free of interstellar extinction, because they are nearby, but they are otherwise unbiased with respect to the X-ray properties that are found in a defined small space around the Sun.

High resolution radio and optical observations of the central starburst in the low-metallicity dwarf galaxy II Zw 40

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kepley, Amanda A.; Reines, Amy E.; Johnson, Kelsey E.

2014-02-01

The extent to which star formation varies in galaxies with low masses, low metallicities, and high star formation rate surface densities is not well constrained. To gain insight into star formation under these physical conditions, this paper estimates the ionizing photon fluxes, masses, and ages for young massive clusters in the central region of II Zw 40—the prototypical low-metallicity dwarf starburst galaxy—from radio continuum and optical observations. Discrete, cluster-sized sources only account for half the total radio continuum emission; the remainder is diffuse. The young (≲ 5 Myr) central burst has a star formation rate surface density that significantly exceedsmore » that of the Milky Way. Three of the 13 sources have ionizing photon fluxes (and thus masses) greater than R136 in 30 Doradus. Although isolating the effects of galaxy mass and metallicity is difficult, the H II region luminosity function and the internal extinction in the center of II Zw 40 appear to be primarily driven by a merger-related starburst. The relatively flat H II region luminosity function may be the result of an increase in interstellar medium pressure during the merger and the internal extinction is similar to that generated by the clumpy and porous dust in other starburst galaxies.« less

The quasar luminosity function at redshift 4 with the Hyper Suprime-Cam Wide Survey

NASA Astrophysics Data System (ADS)

Akiyama, Masayuki; He, Wanqiu; Ikeda, Hiroyuki; Niida, Mana; Nagao, Tohru; Bosch, James; Coupon, Jean; Enoki, Motohiro; Imanishi, Masatoshi; Kashikawa, Nobunari; Kawaguchi, Toshihiro; Komiyama, Yutaka; Lee, Chien-Hsiu; Matsuoka, Yoshiki; Miyazaki, Satoshi; Nishizawa, Atsushi J.; Oguri, Masamune; Ono, Yoshiaki; Onoue, Masafusa; Ouchi, Masami; Schulze, Andreas; Silverman, John D.; Tanaka, Manobu M.; Tanaka, Masayuki; Terashima, Yuichi; Toba, Yoshiki; Ueda, Yoshihiro

2018-01-01

We present the luminosity function of z ˜ 4 quasars based on the Hyper Suprime-Cam Subaru Strategic Program Wide layer imaging data in the g, r, i, z, and y bands covering 339.8 deg2. From stellar objects, 1666 z ˜ 4 quasar candidates are selected via the g-dropout selection down to i = 24.0 mag. Their photometric redshifts cover the redshift range between 3.6 and 4.3, with an average of 3.9. In combination with the quasar sample from the Sloan Digital Sky Survey in the same redshift range, a quasar luminosity function covering the wide luminosity range of M1450 = -22 to -29 mag is constructed. The quasar luminosity function is well described by a double power-law model with a knee at M1450 = -25.36 ± 0.13 mag and a flat faint-end slope with a power-law index of -1.30 ± 0.05. The knee and faint-end slope show no clear evidence of redshift evolution from those seen at z ˜ 2. The flat slope implies that the UV luminosity density of the quasar population is dominated by the quasars around the knee, and does not support the steeper faint-end slope at higher redshifts reported at z > 5. If we convert the M1450 luminosity function to the hard X-ray 2-10 keV luminosity function using the relation between the UV and X-ray luminosity of quasars and its scatter, the number density of UV-selected quasars matches well with that of the X-ray-selected active galactic nuclei (AGNs) above the knee of the luminosity function. Below the knee, the UV-selected quasars show a deficiency compared to the hard X-ray luminosity function. The deficiency can be explained by the lack of obscured AGNs among the UV-selected quasars.

A STUDY OF RO-VIBRATIONAL OH EMISSION FROM HERBIG Ae/Be STARS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brittain, Sean D.; Reynolds, Nickalas; Najita, Joan R.

2016-10-20

We present a study of ro-vibrational OH and CO emission from 21 disks around Herbig Ae/Be stars. We find that the OH and CO luminosities are proportional over a wide range of stellar ultraviolet luminosities. The OH and CO line profiles are also similar, indicating that they arise from roughly the same radial region of the disk. The CO and OH emission are both correlated with the far-ultraviolet luminosity of the stars, while the polycyclic aromatic hydrocarbon (PAH) luminosity is correlated with the longer wavelength ultraviolet luminosity of the stars. Although disk flaring affects the PAH luminosity, it is notmore » a factor in the luminosity of the OH and CO emission. These properties are consistent with models of UV-irradiated disk atmospheres. We also find that the transition disks in our sample, which have large optically thin inner regions, have lower OH and CO luminosities than non-transition disk sources with similar ultraviolet luminosities. This result, while tentative given the small sample size, is consistent with the interpretation that transition disks lack a gaseous disk close to the star.« less

Probing black hole accretion in quasar pairs at high redshift

NASA Astrophysics Data System (ADS)

Vignali, C.; Piconcelli, E.; Perna, M.; Hennawi, J.; Gilli, R.; Comastri, A.; Zamorani, G.; Dotti, M.; Mathur, S.

2018-06-01

Models and observations suggest that luminous quasar activity is triggered by mergers, so it should preferentially occur in the most massive primordial dark matter haloes, where the frequency of mergers is expected to be the highest. Since the importance of galaxy mergers increases with redshift, we identify the high-redshift Universe as the ideal laboratory for studying dual AGN. Here, we present the X-ray properties of two systems of dual quasars at z = 3.0-3.3 selected from the SDSS DR6 at separations of 6-8 arcsec (43-65 kpc) and observed by Chandra for ≈65 ks each. Both members of each pair are detected with good photon statistics to allow us to constrain the column density, spectral slope and intrinsic X-ray luminosity. We also include a recently discovered dual quasar at z = 5 (separation of 21 arcsec, 136 kpc) for which XMM-Newton archival data allow us to detect the two components separately. Using optical spectra we derived bolometric luminosities, BH masses and Eddington ratios that were compared to those of luminous SDSS quasars in the same redshift ranges. We find that the brighter component of both quasar pairs at z ≈ 3.0-3.3 has high luminosities compared to the distribution of SDSS quasars at similar redshift, with J1622A having an order magnitude higher luminosity than the median. This source lies at the luminous end of the z ≈ 3.3 quasar luminosity function. While we cannot conclusively state that the unusually high luminosities of our sources are related to their having a close companion, for J1622A there is only a 3 per cent probability that it is by chance.

EDDINGTON RATIO DISTRIBUTION OF X-RAY-SELECTED BROAD-LINE AGNs AT 1.0 < z < 2.2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suh, Hyewon; Hasinger, Günther; Steinhardt, Charles

2015-12-20

We investigate the Eddington ratio distribution of X-ray-selected broad-line active galactic nuclei (AGNs) in the redshift range 1.0 < z < 2.2, where the number density of AGNs peaks. Combining the optical and Subaru/Fiber Multi Object Spectrograph near-infrared spectroscopy, we estimate black hole masses for broad-line AGNs in the Chandra Deep Field South (CDF-S), Extended Chandra Deep Field South (E-CDF-S), and the XMM-Newton Lockman Hole (XMM-LH) surveys. AGNs with similar black hole masses show a broad range of AGN bolometric luminosities, which are calculated from X-ray luminosities, indicating that the accretion rate of black holes is widely distributed. We find a substantial fraction ofmore » massive black holes accreting significantly below the Eddington limit at z ≲ 2, in contrast to what is generally found for luminous AGNs at high redshift. Our analysis of observational selection biases indicates that the “AGN cosmic downsizing” phenomenon can be simply explained by the strong evolution of the comoving number density at the bright end of the AGN luminosity function, together with the corresponding selection effects. However, one might need to consider a correlation between the AGN luminosity and the accretion rate of black holes, in which luminous AGNs have higher Eddington ratios than low-luminosity AGNs, in order to understand the relatively small fraction of low-luminosity AGNs with high accretion rates in this epoch. Therefore, the observed downsizing trend could be interpreted as massive black holes with low accretion rates, which are relatively fainter than less-massive black holes with efficient accretion.« less

A reevaluation of the infrared-radio correlation for spiral galaxies

NASA Technical Reports Server (NTRS)

Devereux, Nicholas A.; Eales, Stephen A.

1989-01-01

The infrared radio correlation has been reexamined for a sample of 237 optically bright spiral galaxies which range from 10 to the 8th to 10 to the 11th solar luminosities in far-infrared luminosity. The slope of the correlation is not unity. A simple model in which dust heating by both star formation and the interstellar radiation field contribute to the far-infrared luminosity can account for the nonunity slope. The model differs from previous two component models, however, in that the relative contribution of the two components is independent of far-infrared color temperature, but is dependent on the far-infrared luminosity.

Hard X-Ray Emission and the Ionizing Source in LINERs

NASA Technical Reports Server (NTRS)

Terashima, Yuichi; Ho, Luis C.; Ptak, Andrew F.

2000-01-01

We report X-ray fluxes in the 2-10 keV band from LINERs (low-ionization nuclear emission-line regions) and low-luminosity Seyfert galaxies obtained with the ASCA satellite. Observed X-ray luminosities are in the range between 4 x 10(exp 39) and 5 x 10(exp 41) ergs/s, which are significantly smaller than that of the "classical" low-luminosity Seyfert 1 galaxy NGC 4051. We found that X-ray luminosities in 2-10 keV of LINERs with broad H.alpha emission in their optical spectra (LINER 1s) are proportional to their Ha luminosities. This correlation strongly supports the hypothesis that the dominant ionizing source in LINER 1s is photoionization by hard photons from low-luminosity AGNs. On the other hand, the X-ray luminosities of most LINERs without broad H.alpha emission (LINER 2s) in our sample are lower than LINER 1s at a given H.alpha luminosity. The observed X-ray luminosities in these objects are insufficient to power their H.alpha luminosities, suggesting that their primary ionizing source is other than an AGN, or that an AGN, if present, is obscured even at energies above 2 keV.

Fossil group origins. III. The relation between optical and X-ray luminosities

NASA Astrophysics Data System (ADS)

Girardi, M.; Aguerri, J. A. L.; De Grandi, S.; D'Onghia, E.; Barrena, R.; Boschin, W.; Méndez-Abreu, J.; Sánchez-Janssen, R.; Zarattini, S.; Biviano, A.; Castro-Rodriguez, N.; Corsini, E. M.; del Burgo, C.; Iglesias-Páramo, J.; Vilchez, J. M.

2014-05-01

Aims: This study is part of the Fossil group origins (FOGO) project which aims to carry out a systematic and multiwavelength study of a large sample of fossil systems. Here we focus on the relation between the optical luminosity (Lopt) and X-ray luminosity (LX). Methods: Out of a total sample of 28 candidate fossil systems, we consider a sample of 12 systems whose fossil classification has been confirmed by a companion study. They are compared with the complementary sample of 16 systems whose fossil nature has not been confirmed and with a subsample of 102 galaxy systems from the RASS-SDSS galaxy cluster survey. Fossil and normal systems span the same redshift range 0

The Swift Burst and Transient Telescope (BAT)

NASA Technical Reports Server (NTRS)

Mushotzky, Richard

2008-01-01

The Swift Burst and Transient telescope (BAT) has surveyed the entire sky for the last 3.5 years obtaining the first sensitive all sky survey of the 14-195 kev sky. At high galactic latitudes the vast majority of the detected sources are AGN. Since hard x-rays penetrate all but Compton thick obscuring material (Column densities of 1.6324 atms/sq cm) this survey is unbiased with respect to obscuration, host galaxy type, optical , radio or IR properties. We will present results on the broad band x-ray properties, the nature of the host galaxies, the luminosity function and will discuss a few of the optical, IR and x-ray results in detail.

Optical study of the DAFT/FADA galaxy cluster survey

NASA Astrophysics Data System (ADS)

Martinet, N.; Durret, F.; Clowe, D.; Adami, C.

2013-11-01

DAFT/FADA (Dark energy American French Team) is a large survey of ˜90 high redshift (0.42×10^{14} M_{⊙}) clusters with HST weak lensing oriented data, plus BVRIZJ 4m ground based follow up to compute photometric redshifts. The main goals of this survey are to constrain dark energy parameters using weak lensing tomography and to study a large homogeneous sample of high redshift massive clusters. We will briefly review the latest results of this optical survey, focusing on two ongoing works: the calculation of galaxy luminosity functions from photometric redshift catalogs and the weak lensing analysis of ground based data.

The Tully-Fisher relation of the IRAS minisurvey galaxies

NASA Technical Reports Server (NTRS)

Van Driel, W.; Van Den Broek, A. C.; Baan, W. A.

1995-01-01

We investigated the possible influence on the Tully-Fisher relation of active massive star formation in IRAS galaxies, in order to estimate the contribution of star formation to their near-infrared luminosity. We observed 60 galaxies from the infrared complete so-called IRAS Minisurvey sample in the 21 cm H1 line at Arecibo, determined the near-infrared (H-band) Tully-Fisher relation for the 36 objects in the sample we judged to be usable for this purpose, and compared this relation with that of optically selected normal galaxies. The results show no significant enhancement of the near-infrared luminosities of the IRAS Minisurvey galaxies compared to those of the optically selected normal glaxies. From these results we inferred that in the minisurvey galaxies the average contribution of the active massive star formation to the total near-infrared luminosity is less and that exponential decay times for the starbursts occurring in the Minisurvey galaxies are of the order of 10 Myr. The Tully-Fisher relation shows one exceptional galaxy (IRAS 03565+2139) with an about 25 times higher luminosity than average for its rotational velocity.

Introductory Overview of Intermediate-luminosity X-ray Objects

NASA Astrophysics Data System (ADS)

Colbert, E. J. M.

2001-05-01

Intermediate-luminosity X-ray Objects (IXOs) are defined as compact objects having X-ray luminosities between those of X-ray binaries and low-luminosity AGNs (i.e., 1039.0 erg s-1 < ~ LX [IXOs] < ~ 1041.0 erg s-1). It is not currently known if these objects are intermediate-mass (M ~ 102-104 Msun) black holes accreting near the Eddington limit, near-solar-mass black holes in a super-Eddington state, or are, in some cases, just supermassive black holes accreting at very low rates. However, the first idea has been popularized by recent press coverage. IXOs are quite common (present in about half of spiral galaxies) and are typically found displaced from the optical nucleus, reducing the likelihood that they are low-luminosity AGN. Nearly all of our knowledge of these objects comes from X-ray observations, as observations of optical, NIR and radio counterparts are not widely known. In this session, we will address (1) the phenomenology of the objects, (2) possible geometry and accretion mechanisms for these objects (i.e., are they more similar to black hole X-ray binaries or AGNs), (3) the central black hole masses, and (4) the formation mechanism for these black holes, if they are of intermediate mass. In this talk, I will focus primarily on giving background information of these fascinating objects.

Probing the accretion flow and emission-line regions of M81, the nearest broad-lined low-luminosity AGN

NASA Astrophysics Data System (ADS)

Barth, Aaron

2017-08-01

The nucleus of M81 is an object of singular importance as a template for low-luminosity accretion flows onto supermassive black holes. We propose to obtain a complete, small-aperture, high S/N STIS UV/optical spectrum of the M81 nucleus and multi-filter WFC3 imaging covering the UV through near-IR. Such data have never previously been obtained with HST; the only prior archival UV/optical spectra of M81 have low S/N, incomplete wavelength coverage, and are strongly contaminated by starlight. Combined with new Chandra X-ray data, our proposed observations will comprise the definitive reference dataset on the spectral energy distribution of this benchmark low-luminosity AGN. These data will provide unique new constraints on the possible contribution of a truncated thin accretion disk to the AGN emission spectrum, clarifying a fundamental property of low-luminosity accretion flows. The data will additionally provide new insights into broad-line region structure and black hole mass scaling relationships at the lowest AGN luminosities, and spatially resolved diagnostics of narrow-line region excitation conditions at unprecedented spatial resolution to assess the impact of the AGN on the ionization state of the gas in the host galaxy bulge.

Accretion Disks in Supersoft X-ray Sources

NASA Technical Reports Server (NTRS)

Popham, Robert; DiStefano, Rosanne

1996-01-01

We examine the role of the accretion disk in the steady-burning white dwarf model for supersoft sources. The accretion luminosity of the disk is quite small compared to the nuclear burning luminosity of the central source. Thus, in contrast to standard accretion disks, the main role of the disk is to reprocess the radiation from the white dwarf. We calculate models of accretion disks around luminous white dwarfs and compare the resulting disk fluxes to optical and UV observations of the LMC supersoft sources CAL 83, CAL 87, and RX J0513.9-6951. We find that if the white dwarf luminosity is near the upper end of the steady-burning region, and the flaring of the disk is included, then reprocessing by the disk can account for the UV fluxes and a substantial fraction of the optical fluxes of these systems. Reprocessing by the companion star can provide additional optical flux, and here too the disk plays an important role: since the disk is fairly thick, it shadows a significant fraction of the companion's surface.

X-raying the most luminous quasars at cosmic noon

NASA Astrophysics Data System (ADS)

Piconcelli, E.; Martocchia, S.; Zappacosta, L.

2017-10-01

The WISE/SDSS hyper-luminous (log L_Bol > 47) quasar (WISSH) survey is performing a multi-band systematic exploration of the most luminous AGN shining at the golden epoch of AGN activity (i.e. z ˜ 2-4). This gives the opportunity of overcoming the luminosity bias in the exploration of the accretion phenomenon and the impact of AGN radiative output on the host. In this talk, I present the results of our study of the X-ray spectra of 40 WISSH quasars. I report on the correlations between the X-ray and Optical, UV and MIR properties, and the behavior of the X-ray bolometric correction at the brightest end of the luminosity function. I discuss the relative X-ray weakness of these very powerful quasars compared to less luminous AGN. This X-ray weakness can be a key ingredient for accelerating powerful ionized outflows (ubiquitously revealed in the UV/optical spectra of WISSH quasars) and, furthermore, radiation-driven winds can be effective in destroying the X-ray corona and quenching the X-ray emission. The potential offered by Athena in studying this extreme class of AGN is also discussed.

ETHOS - an effective theory of structure formation: predictions for the high-redshift Universe - abundance of galaxies and reionization

NASA Astrophysics Data System (ADS)

Lovell, Mark R.; Zavala, Jesús; Vogelsberger, Mark; Shen, Xuejian; Cyr-Racine, Francis-Yan; Pfrommer, Christoph; Sigurdson, Kris; Boylan-Kolchin, Michael; Pillepich, Annalisa

2018-07-01

We contrast predictions for the high-redshift galaxy population and reionization history between cold dark matter (CDM) and an alternative self-interacting dark matter model based on the recently developed ETHOS framework that alleviates the small-scale CDM challenges within the Local Group. We perform the highest resolution hydrodynamical cosmological simulations (a 36 Mpc3 volume with gas cell mass of ˜ 105 M_{⊙} and minimum gas softening of ˜180 pc) within ETHOS to date - plus a CDM counterpart - to quantify the abundance of galaxies at high redshift and their impact on reionization. We find that ETHOS predicts galaxies with higher ultraviolet (UV) luminosities than their CDM counterparts and a faster build-up of the faint end of the UV luminosity function. These effects, however, make the optical depth to reionization less sensitive to the power spectrum cut-off: the ETHOS model differs from the CDM τ value by only 10 per cent and is consistent with Planck limits if the effective escape fraction of UV photons is 0.1-0.5. We conclude that current observations of high-redshift luminosity functions cannot differentiate between ETHOS and CDM models, but deep James Webb Space Telescope surveys of strongly lensed, inherently faint galaxies have the potential to test non-CDM models that offer attractive solutions to CDM's Local Group problems.

THE CHANDRA COSMOS LEGACY SURVEY: OPTICAL/IR IDENTIFICATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marchesi, S.; Civano, F.; Urry, C. M.

2016-01-20

We present the catalog of optical and infrared counterparts of the Chandra  COSMOS-Legacy  Survey, a 4.6 Ms Chandra  program on the 2.2 deg{sup 2} of the COSMOS field, combination of 56 new overlapping observations obtained in Cycle 14 with the previous C-COSMOS survey. In this Paper we report the i, K, and 3.6 μm identifications of the 2273 X-ray point sources detected in the new Cycle 14 observations. We use the likelihood ratio technique to derive the association of optical/infrared (IR) counterparts for 97% of the X-ray sources. We also update the information for the 1743 sources detected in C-COSMOS,more » using new K and 3.6 μm information not available when the C-COSMOS analysis was performed. The final catalog contains 4016 X-ray sources, 97% of which have an optical/IR counterpart and a photometric redshift, while ≃54% of the sources have a spectroscopic redshift. The full catalog, including spectroscopic and photometric redshifts and optical and X-ray properties described here in detail, is available online. We study several X-ray to optical (X/O) properties: with our large statistics we put better constraints on the X/O flux ratio locus, finding a shift toward faint optical magnitudes in both soft and hard X-ray band. We confirm the existence of a correlation between X/O and the the 2–10 keV luminosity for Type 2 sources. We extend to low luminosities the analysis of the correlation between the fraction of obscured AGNs and the hard band luminosity, finding a different behavior between the optically and X-ray classified obscured fraction.« less

A Study of Low-mass X-Ray Binaries in the Low-luminosity Regime

NASA Astrophysics Data System (ADS)

Sonbas, E.; Dhuga, K. S.; Göğüş, E.

2018-02-01

A recent study of a small sample of X-ray binaries (XRBs) suggests a significant softening of spectra of neutron star (NS) binaries as compared to black hole (BH) binaries in the luminosity range 1034–1037 erg s‑1. This softening is quantified as an anticorrelation between the spectral index and the 0.5–10 keV X-ray luminosity. We extend the study to significantly lower luminosities (i.e., ∼a few × 1030 erg s‑1) for a larger sample of XRBs. We find evidence for a significant anticorrelation between the spectral index and the luminosity for a group of NS binaries in the luminosity range 1032–1033 erg s‑1. Our analysis suggests a steep slope for the correlation i.e., ‑2.12 ± 0.63. In contrast, BH binaries do not exhibit the same behavior. We examine the possible dichotomy between NS and BH binaries in terms of a Comptonization model that assumes a feedback mechanism between an optically thin hot corona and an optically thick cool source of soft photons. We gauge the NS–BH dichotomy by comparing the extracted corona temperatures, Compton-y parameters, and the Comptonization amplification factors: the mean temperature of the NS group is found to be significantly lower than the equivalent temperature for the BH group. The extracted Compton-y parameters and the amplification factors follow the theoretically predicted relation with the spectral index.

Measurement of the total cross section from elastic scattering in pp collisions at s = 8   TeV with the ATLAS detector

DOE PAGES

Aaboud, M.

2016-08-16

A measurement of the total pp cross section at the LHC at √s = 8 TeV is presented. An integrated luminosity of 500 μb –1 was accumulated in a special run with high-β* beam optics to measure the differential elastic cross section as a function of the Mandelstam momentum transfer variable t. Here, the measurement is performed with the ALFA sub-detector of ATLAS.

Measurement of the total cross section from elastic scattering in pp collisions at s = 8   TeV with the ATLAS detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aaboud, M.

A measurement of the total pp cross section at the LHC at √s = 8 TeV is presented. An integrated luminosity of 500 μb –1 was accumulated in a special run with high-β* beam optics to measure the differential elastic cross section as a function of the Mandelstam momentum transfer variable t. Here, the measurement is performed with the ALFA sub-detector of ATLAS.

Measuring the stellar luminosity function and spatial density profile of the inner 0.5 pc of the Milky Way nuclear star cluster

NASA Astrophysics Data System (ADS)

Do, Tuan; Ghez, Andrea; Lu, Jessica R.; Morris, Mark R.; Yelda, Sylvana; Martinez, Gregory D.; Peter, Annika H. G.; Wright, Shelley; Bullock, James; Kaplinghat, Manoj; Matthews, K.

2012-07-01

We report on measurements of the luminosity function of early (young) and late-type (old) stars in the central 0.5 pc of the Milky Way nuclear star cluster as well as the density profiles of both components. The young (~ 6 Myr) and old stars (> 1 Gyr) in this region provide different physical probes of the environment around a supermassive black hole; the luminosity function of the young stars offers us a way to measure the initial mass function from star formation in an extreme environment, while the density profile of the old stars offers us a probe of the dynamical interaction of a star cluster with a massive black hole. The two stellar populations are separated through a near-infrared spectroscopic survey using the integral-field spectrograph OSIRIS on Keck II behind the laser guide star adaptive optics system. This spectroscopic survey is able to separate early-type (young) and late-type (old) stars with a completeness of 50% at K' = 15.5. We describe our method of completeness correction using a combination of star planting simulations and Bayesian inference. The completeness corrected luminosity function of the early-type stars contains significantly more young stars at faint magnitudes compared to previous surveys with similar depth. In addition, by using proper motion and radial velocity measurements along with anisotropic spherical Jeans modeling of the cluster, it is possible to measure the spatial density profile of the old stars, which has been difficult to constrain with number counts alone. The most probable model shows that the spatial density profile, n(r) propto r-γ, to be shallow with γ = 0.4 ± 0.2, which is much flatter than the dynamically relaxed case of γ = 3/2 to 7/4, but does rule out a 'hole' in the distribution of old stars. We show, for the first time, that the spatial density profile, the black hole mass, and velocity anisotropy can be fit simultaneously to obtain a black hole mass that is consistent with that derived from individual orbits of stars at distances < 1000 AU from the Galactic center.

Luminosity-velocity diagrams for Virgo Cluster spirals. I - Inner rotation curves

NASA Technical Reports Server (NTRS)

Woods, David; Fahlman, Gregory G.; Madore, Barry F.

1990-01-01

Optical rotation curves are presented for the innermost portions of nine spiral galaxies in the Virgo Cluster. The emission-line (H-alpha and forbidden N II) velocity data are to be used in combination with new CCD photometry to construct luminosity-velocity diagrams, in a continuing investigation of an apparent initial linear branch and its potential as a distance indicator. Compared to recent H I data, the present optical rotation curves generally show systematically steeper inner gradients. This effect is ascribed to the poorer resolution of the H I data and/or to holes in the gas distribution.

Extragalactic SETI: The Tully-Fisher Relation as a Probe of Dysonian Astroengineering in Disk Galaxies

NASA Astrophysics Data System (ADS)

Zackrisson, Erik; Calissendorff, Per; Asadi, Saghar; Nyholm, Anders

2015-09-01

If advanced extraterrestrial civilizations choose to construct vast numbers of Dyson spheres to harvest radiation energy, this could affect the characteristics of their host galaxies. Potential signatures of such astroengineering projects include reduced optical luminosity, boosted infrared luminosity, and morphological anomalies. Here, we apply a technique pioneered by Annis to search for Kardashev type III civilizations in disk galaxies, based on the predicted offset of these galaxies from the optical Tully-Fisher (TF) relation. By analyzing a sample of 1359 disk galaxies, we are able to set a conservative upper limit of ≲ 3% on the fraction of local disks subject to Dysonian astroengineering on galaxy-wide scales. However, the available data suggests that a small subset of disk galaxies actually may be underluminous with respect to the TF relation in the way expected for Kardashev type III objects. Based on the optical morphologies and infrared-to-optical luminosity ratios of such galaxies in our sample, we conclude that none of them stand out as strong Kardashev type III candidates and that their inferred properties likely have mundane explanations. This allows us to set a tentative upper limit at ≲ 0.3% on the fraction of Karashev type III disk galaxies in the local universe.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cattaneo, Andrea; Salucci, Paolo; Papastergis, Emmanouil, E-mail: andrea.cattaneo@oamp.fr, E-mail: salucci@sissa.it, E-mail: papastergis@astro.cornell.edu

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 fullymore » 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.« less

A Search for Low-Luminosity BL Lacertae Objects

NASA Astrophysics Data System (ADS)

Rector, Travis A.; Stocke, John T.; Perlman, Eric S.

1999-05-01

Many properties of BL Lacs have become explicable in terms of the ``relativistic beaming'' hypothesis, whereby BL Lacs are FR 1 radio galaxies viewed nearly along the jet axis. However, a possible problem with this model is that a transition population between beamed BL Lacs and unbeamed FR 1 galaxies has not been detected. A transition population of ``low-luminosity BL Lacs'' was predicted to exist in abundance in X-ray-selected samples such as the Einstein Extended Medium Sensitivity Survey (EMSS) by Browne & Marcha. However, these BL Lacs may have been misidentified as clusters of galaxies. We have conducted a search for such objects in the EMSS with the ROSAT High-Resolution Imager (HRI) here we present ROSAT HRI images, optical spectra, and VLA radio maps for a small number of BL Lacs that were previously misidentified in the EMSS catalog as clusters of galaxies. While these objects are slightly lower in luminosity than other EMSS BL Lacs, their properties are too similar to the other BL Lacs in the EMSS sample to ``bridge the gap'' between BL Lacs and FR 1 radio galaxies. Also, the number of new BL Lacs found is too low to alter significantly the X-ray luminosity function or value for the X-ray-selected EMSS BL Lac sample. Thus, these observations do not explain fully the discrepancy between the X-ray- and radio-selected BL Lac samples.

The dependence of the soft X ray spectral slope with radio property, luminosity, and redshift, for a large sample of AGN from the Einstein IPC data base

NASA Technical Reports Server (NTRS)

Brunner, H.; Worrall, D. M.; Wilkes, Belinda J.; Elvis, Martin

1989-01-01

The dependence of the soft X-ray spectral slope on radio, optical and X-ray properties, and on redshift are reported for a large sample of Active Galactic Nuclei (AGN). The sample includes 317 optically and radio-selected AGN from a preliminary version of the Einstein Imaging Proportional Counter (IPC) quasar and AGN data base. The main results are: the difference in X-ray slope between radio-loud and radio-quiet AGN were confirmed for an independent and much larger sample of sources; a difference in X-ray slope between flat and steep radio spectrum AGN is observed only in high luminosity sub-sample; in flat radio spectrum AGNs there is an indication for a dependence of the X-ray spectral index on X-ray luminosity redshift and alpha sub 0x.

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.;

An XMM-Newton spectral survey of 12 μm selected galaxies - II. Implications for AGN selection and unification

NASA Astrophysics Data System (ADS)

Brightman, Murray; Nandra, Kirpal

2011-07-01

We present a multi-waveband analysis of a 126-galaxy sub-sample of the 12 μm galaxy sample (12MGS), for which we have carried out a detailed X-ray spectral analysis in a previous paper. We determine the activity class of the galaxies by way of optical-line ratio diagnostics and characterize the optical classes by their X-ray, 12 μm and [O III] luminosities and X-ray spectral properties. Our most interesting results from this investigation are as follows. (i) Seyfert (Sy) 1s and Sy2s show a significantly different X-ray luminosity distributions from each other. (ii) Sy2 galaxies with a detection of a hidden broad-line region show a significantly higher X-ray luminosity than those without a detection, supporting the findings of Tran. (iii) Sy1s also present a significantly different 12 μm luminosity distribution from both intermediate Sy types and Sy2s. (iv) The Sy2 fraction decreases towards high X-ray luminosities. (v) X-ray indications of active galactic nuclei (AGN) power agree well with the optical classifications. (vi) There is X-ray evidence for the presence of an AGN in 17 per cent of H II/AGN composite galaxies and 40 per cent of LINERs. (vii) We advocate the use of a 2-10 keV X-ray luminosity of 1041 erg s-1 in the X-ray selection of AGN, rather than 1042 erg s-1, which we find gives a contamination rate of only 3 per cent from star-forming galaxies. (viii) From an analysis of the X-ray power-law index, Γ, we find that Sy1s and Sy2 have the same intrinsic distributions, implying that the central engines are the same, in support of AGN unification schemes. (ix) In 24 per cent of cases the absorption measured in the X-ray spectra does not correspond directly to that implied in the optical band from the visibility of the broad-line regions (BLRs), which is in conflict with AGN unification schemes. (x) We confirm the previous work showing that the obscured fraction in AGN declines at high X-ray luminosity, but also find a decrease at low luminosity having peaked at LX˜ 1042 erg s-1, suggesting that source luminosity has a large effect on the obscuring material, therefore also calling for a modification to unified schemes. (xi) The average obscured and Compton-thick fractions for this sample are 62 ± 5 per cent and 20 ± 4 per cent, respectively, which are higher than hard X-ray and optically selected samples, therefore supporting mid-infrared (MIR) selection as a relatively unbiased method of selecting AGN. (xii) We assess the use of the 'T' ratio (?) for selecting Compton-thick candidates. We conclude here that this quantity can often be unreliable due to uncertainties in the extinction corrections to the [O III] flux. These results have important impacts on AGN selection and unification, and the results from the 12MGS are particularly useful as a local analogue to Spitzer/MIPS 24 μm samples selected at z= 1, as observed 24 μm emission originates at rest-frame 12 μm in sources at this redshift.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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 increasemore » 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.« less

Size–Luminosity Relations and UV Luminosity Functions at z = 6–9 Simultaneously Derived from the Complete Hubble Frontier Fields Data

NASA Astrophysics Data System (ADS)

Kawamata, Ryota; Ishigaki, Masafumi; Shimasaku, Kazuhiro; Oguri, Masamune; Ouchi, Masami; Tanigawa, Shingo

2018-03-01

We construct z ∼ 6–7, 8, and 9 faint Lyman break galaxy samples (334, 61, and 37 galaxies, respectively) with accurate size measurements with the software glafic from the complete Hubble Frontier Fields (HFF) cluster and parallel fields data. These are the largest samples hitherto and reach down to the faint ends of recently obtained deep luminosity functions. At faint magnitudes, however, these samples are highly incomplete for galaxies with large sizes, implying that derivation of the luminosity function sensitively depends on the intrinsic size–luminosity relation. We thus conduct simultaneous maximum-likelihood estimation of luminosity function and size–luminosity relation parameters from the observed distribution of galaxies on the size–luminosity plane with the help of a completeness map as a function of size and luminosity. At z ∼ 6–7, we find that the intrinsic size–luminosity relation expressed as r e ∝ L β has a notably steeper slope of β ={0.46}-0.09+0.08 than those at lower redshifts, which in turn implies that the luminosity function has a relatively shallow faint-end slope of α =-{1.86}-0.18+0.17. This steep β can be reproduced by a simple analytical model in which smaller galaxies have lower specific angular momenta. The β and α values for the z ∼ 8 and 9 samples are consistent with those for z ∼ 6–7 but with larger errors. For all three samples, there is a large, positive covariance between β and α, implying that the simultaneous determination of these two parameters is important. We also provide new strong lens mass models of Abell S1063 and Abell 370, as well as updated mass models of Abell 2744 and MACS J0416.1‑2403.

An X-ray halo around Cassiopeia A

NASA Astrophysics Data System (ADS)

Stewart, G. C.; Fabian, A. C.; Seward, F. D.

The large-scale X-ray emission of Cas A is characterized, and mechanisms are proposed to explain it. The Einstein HRI image of Murray et al. (1979) is binned into 16-arcsec pixels, a point-spread function based on the 2.04-keV monochromatic Zr source is applied, and the data are modeled as a series of circularly symmetric rings of emission. A significant excess extending to a radius of 6 arcmin (roughly the size of the optical H II region) is found to have a total 0.5-3-keV luminosity of about 5 x 10 to the 34th erg/s, or about 2 percent of the total luminosity of Cas A, which is assumed to lie at a distance of 3 kpc. Thermal bremsstrahlung, synchrotron radiation, and dust scattering of the main-shell emission are examined and found to be plausible emission mechanisms; further observations are required to identify the one active in Cas A.

THE VLA SURVEY OF CHANDRA DEEP FIELD SOUTH. V. EVOLUTION AND LUMINOSITY FUNCTIONS OF SUB-MILLIJANSKY RADIO SOURCES AND THE ISSUE OF RADIO EMISSION IN RADIO-QUIET ACTIVE GALACTIC NUCLEI

DOE Office of Scientific and Technical Information (OSTI.GOV)

Padovani, P.; Mainieri, V.; Rosati, P.

2011-10-10

We present the evolutionary properties and luminosity functions of the radio sources belonging to the Chandra Deep Field South Very Large Array survey, which reaches a flux density limit at 1.4 GHz of 43 {mu}Jy at the field center and redshift {approx}5 and which includes the first radio-selected complete sample of radio-quiet active galactic nuclei (AGNs). We use a new, comprehensive classification scheme based on radio, far- and near-IR, optical, and X-ray data to disentangle star-forming galaxies (SFGs) from AGNs and radio-quiet from radio-loud AGNs. We confirm our previous result that SFGs become dominant only below 0.1 mJy. The sub-millijanskymore » radio sky turns out to be a complex mix of SFGs and radio-quiet AGNs evolving at a similar, strong rate; non-evolving low-luminosity radio galaxies; and declining radio powerful (P {approx}> 3 x 10{sup 24} W Hz{sup -1}) AGNs. Our results suggest that radio emission from radio-quiet AGNs is closely related to star formation. The detection of compact, high brightness temperature cores in several nearby radio-quiet AGNs can be explained by the coexistence of two components, one non-evolving and AGN related and one evolving and star formation related. Radio-quiet AGNs are an important class of sub-millijansky sources, accounting for {approx}30% of the sample and {approx}60% of all AGNs, and outnumbering radio-loud AGNs at {approx}< 0.1 mJy. This implies that future, large area sub-millijansky surveys, given the appropriate ancillary multiwavelength data, have the potential of being able to assemble vast samples of radio-quiet AGNs, bypassing the problems of obscuration that plague the optical and soft X-ray bands.« less

Compensation of the long-range beam-beam interactions as a path towards new configurations for the high luminosity LHC

DOE PAGES

Fartoukh, Stéphane; Valishev, Alexander; Papaphilippou, Yannis; ...

2015-12-01

Colliding bunch trains in a circular collider demands a certain crossing angle in order to separate the two beams transversely after the collision. The magnitude of this crossing angle is a complicated function of the bunch charge, the number of long-range beam-beam interactions, of β* and type of optics (flat or round), and possible compensation or additive effects between several low-β insertions in the ring depending on the orientation of the crossing plane at each interaction point. About 15 years ago, the use of current bearing wires was proposed at CERN in order to mitigate the long-range beam-beam effects [J.P. Koutchouk,more » CERN Report No. LHC-Project-Note 223, 2000], therefore offering the possibility to minimize the crossing angle with all the beneficial effects this might have: on the luminosity performance by reducing the need for crab-cavities or lowering their voltage, on the required aperture of the final focus magnets, on the strength of the orbit corrector involved in the crossing bumps, and finally on the heat load and radiation dose deposited in the final focus quadrupoles. In this paper, a semianalytical approach is developed for the compensation of the long-range beam-beam interactions with current wires. This reveals the possibility of achieving optimal correction through a careful adjustment of the aspect ratio of the β functions at the wire position. We consider the baseline luminosity upgrade plan of the Large Hadron Collider (HL-LHC project), and compare it to alternative scenarios, or so-called ''configurations,'' where modifications are applied to optics, crossing angle, or orientation of the crossing plane in the two low-β insertions of the ring. Furthermore, for all these configurations, the beneficial impact of beam-beam compensation devices is then demonstrated on the tune footprint, the dynamical aperture, and/or the frequency map analysis of the nonlinear beam dynamics as the main figures of merit.« less

The Swift/UVOT catalogue of NGC 4321 star-forming sources: a case against density wave theory

NASA Astrophysics Data System (ADS)

Ferreras, Ignacio; Cropper, Mark; Kawata, Daisuke; Page, Mat; Hoversten, Erik A.

2012-08-01

We study the star-forming regions in the spiral galaxy NGC 4321 (M100). We take advantage of the spatial resolution (2.5 arcsec full width at half-maximum) of the Swift/Ultraviolet/Optical Telescope camera and the availability of three ultraviolet (UV) passbands in the region 1600 < λ < 3000 Å, in combination with optical and infrared (IR) imaging from Sloan Digital Sky Survey, KPNO/Hα and Spitzer/IRAC, to obtain a catalogue of 787 star-forming regions out to three disc scalelengths. We use a large volume of star formation histories, combined with stellar population synthesis, to determine the properties of the young stellar component and its relationship with the spiral arms. The Hα luminosities of the sources have a strong decreasing radial trend, suggesting more massive star-forming regions in the central part of the galaxy. When segregated with respect to near-UV (NUV)-optical colour, blue sources have a significant excess of flux in the IR at 8 μm, revealing the contribution from polycyclic aromatic hydrocarbons, although the overall reddening of these sources stays below E(B - V) = 0.2 mag. The distribution of distances to the spiral arms is compared for subsamples selected according to Hα luminosity, NUV-optical colour or ages derived from a population synthesis model. An offset would be expected between these subsamples as a function of radius if the pattern speed of the spiral arm were constant - as predicted by classic density wave theory. No significant offsets are found, favouring instead a mechanism where the pattern speed has a radial dependence.

Space Telescope and Optical Reverberation Mapping Project. III. Optical Continuum Emission and Broadband Time Delays in NGC 5548

NASA Technical Reports Server (NTRS)

Fausnaugh, M. M.; Denney, K. D.; Barth, A.J.; Bentz, M.C.; Bottorff, M.C.; Carini, M.T.; Croxall, K. V.; Rosa, G. De; Goad, M.R.; Gehrels, Cornelis;

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.

X-ray properties of quasars

NASA Technical Reports Server (NTRS)

Ku, W. H.-M.; Helfand, D. J.; Lucy, L. B.

1980-01-01

The X-ray properties of 111 catalogued quasars have been examined with the imaging proportional counter on board the Einstein Observatory. Thirty-five of the objects, of redshift between 0.064 and 3.53, were detected as X-ray sources. The 0.5-4.5-keV X-ray properties of these quasars are correlated with their optical and radio continuum properties and with their redshifts and variability characteristics. The X-ray luminosity of quasars tends to be highest for those objects which are bright in the optical and radio regimes and which exhibit optically violent variability. These observations suggest that quasars should be divided into two classes on the basis of radio luminosities, spectra, evolution and underlying morphology and that quasars can make up a significant portion of the diffuse soft X-ray background only if the slope of the optical quasar log N-log S relation is steeper than 2 to m sub b of about 21.5.

A Database of Young Star Clusters for Five Hundred Galaxies

NASA Astrophysics Data System (ADS)

Whitmore, Brad

2009-07-01

We propose to use the source lists developed as part of the Hubble Legacy Archive {HLA: Data Release 1 - February 8, 2008} to obtain a large {N 50 galaxies for multi-wavelength, N 500 galaxies for ACS F814W}, uniform {ACS + WFPC2 + NICMOS: DAOphot used for object detection} database of super star clusters in nearby star-forming galaxies in order to address two fundamental astronomical questions: 1} To what degree is the cluster luminosity {and mass} function of star clusters universal ? 2} What fraction of super star clusters are "missing" in optical studies {i.e., are hidden by dust}? This database will also support comparisons with new Monte-Carlo simulations that have independently been developed in the past few years by co-I Larsen and PI Whitmore, and will be used to test the Whitmore, Chandar, Fall {2007} framework designed to understand the demographics of star clusters in all star forming galaxies. The catalogs will increase the number of galaxies with measured mass and luminosity functions by an order of magnitude, and will provide a powerful new tool for comparative studies, both ours and the community's.

Radio and infrared properties of young stars

NASA Technical Reports Server (NTRS)

Panagia, Nino

1987-01-01

Observing young stars, or more appropriately, pre-main-sequence (PMS) stars, in the infrared and at radio frequencies has the advantage over optical observation in that the heavy extinction associated with a star forming region is only a minor problem, so that the whole region can be studied thoroughly. Therefore, it means being able to: (1) search for stars and do statistical studies on the rate of star formation; (2) determine their luminosity, hence, to study luminosity functions and initial mass functions down to low masses; and (3) to study their spectra and, thus, to determine the prevailing conditions at and near the surface of a newly born star and its relations with the surrounding environment. The third point is of principal interest. The report limits itself to a consideration of the observations concerning the processes of outflows from, and accretion onto, PMS stars and the theory necessary to interpret them. Section 2 discusses the radiative processes relevant in stellar outflows. The main observational results are presented in Section 3. A discussion of the statistical properties of stellar winds from PMS stars are given in Section 4.

Evolution of the observed Lyα luminosity function from z = 6.5 to z = 7.7: evidence for the epoch of reionization?

NASA Astrophysics Data System (ADS)

Clément, B.; Cuby, J.-G.; Courbin, F.; Fontana, A.; Freudling, W.; Fynbo, J.; Gallego, J.; Hibon, P.; Kneib, J.-P.; Le Fèvre, O.; Lidman, C.; McMahon, R.; Milvang-Jensen, B.; Moller, P.; Moorwood, A.; Nilsson, K. K.; Pentericci, L.; Venemans, B.; Villar, V.; Willis, J.

2012-02-01

Aims: Lyα emitters (LAEs) can be detected out to very high redshifts during the epoch of reionization. The evolution of the LAE luminosity function with redshift is a direct probe of the Lyα transmission of the intergalactic medium (IGM), and therefore of the IGM neutral-hydrogen fraction. Measuring the Lyα luminosity function (LF) of Lyα emitters at redshift z = 7.7 therefore allows us to constrain the ionizing state of the Universe at this redshift. Methods: We observed three 7'.5 × 7'.5 fields with the HAWK-I instrument at the VLT with a narrow band filter centred at 1.06 μm and targeting Lyα emitters at redshift z ~ 7.7. The fields were chosen for the availability of multiwavelength data. One field is a galaxy cluster, the Bullet Cluster, which allowed us to use gravitational amplification to probe luminosities that are fainter than in the field. The two other fields are subareas of the GOODS Chandra Deep Field South and CFHTLS-D4 deep field. We selected z = 7.7 LAE candidates from a variety of colour criteria, in particular from the absence of detection in the optical bands. Results: We do not find any LAE candidates at z = 7.7 in ~2.4 × 104 Mpc3 down to a narrow band AB magnitude of ~26, which allows us to infer robust constraints on the Lyα LAE luminosity function at this redshift. Conclusions: The predicted mean number of objects at z = 6.5, derived from somewhat different luminosity functions of Hu et al. (2010, ApJ, 725, 394), Ouchi et al. (2010, ApJ, 723, 869), and Kashikawa et al. (2011, ApJ, 734, 119) are 2.5, 13.7, and 11.6, respectively. Depending on which of these luminosity functions we refer to, we exclude a scenario with no evolution from z = 6.5 to z = 7.7 at 85% confidence without requiring a strong change in the IGM Lyα transmission, or at 99% confidence with a significant quenching of the IGM Lyα transmission, possibly from a strong increase in the high neutral-hydrogen fraction between these two redshifts. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere (ESO), Chile, Prog-Id 181.A-0485, 181.A-0717, 60.A-9284, 084.A-0749. Based on observations obtained at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France (CNRS), and the University of Hawaii. This work is based in part on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA and in part on data products produced at TERAPIX and the Canadian Astronomy Data Centre as part of the Canada-France-Hawaii Telescope Legacy Survey, a collaborative project of NRC and CNRS. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

On the surface density of X-ray selected BL Lacertae objects

NASA Technical Reports Server (NTRS)

Maccacaro, T.; Gioia, I. M.; Maccagni, D.; Stocke, J. T.

1984-01-01

Only a handful of BL Lac objects have been found as a result of systematic optical identification of serendipitous Einstein X-ray sources. By combining the data from two flux-limited complete X-ray surveys (the HEAO 1 A-2 and the Einstein Observatory Medium Sensitivity Survey) the surface density of X-ray emitting BL Lac objects is evaluated as a function of their X-ray flux. It is found that a single power law is not an acceptable representation of the BL Lac objects' X-ray log N-log S. The number-flux relationship is consistent with the Euclidean slope at 'high' flux levels but shows a drastic flattnring below fluxes of the order of 10 to the -12th ergs per sq cm/s. The implications of this result are briefly discussed with respect to the luminosity function, the cosmological evolution, and the X-ray to optical flux ratio in BL Lac objects.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gutiérrez, Carlos M.; Moon, Dae-Sik, E-mail: cgc@iac.es

We present the identification and characterization of the optical counterpart to 2XMM J011942.7+032421, one of the most luminous and distant ultra-luminous X-ray sources (ULXs). The counterpart is located near a star-forming region in a spiral arm of the galaxy NGC 470 with u, g, and r magnitudes of 21.53, 21.69, and 21.71 mag, respectively. The luminosity of the counterpart is much larger than that of a single O-type star, indicating that it may be a stellar cluster. Our optical spectroscopic observations confirm the association of the X-ray source and the optical counterpart with its host galaxy NGC 470, which validates the high,more » ≳10{sup 41} erg s{sup -1}, X-ray luminosity of the source. Its optical spectrum is embedded with numerous emission lines, including H recombination lines, metallic forbidden lines, and more notably the high-ionization He II (λ4686) line. That line shows a large velocity dispersion of ≅410 km s{sup -1}, consistent with the existence of a compact (<5 AU) highly ionized accretion disk rotating around the central X-ray source. The ∼1.4 × 10{sup 37} erg s{sup -1} luminosity of the He II line emission makes the source one of the most luminous ULXs in that emission. This, together with the high X-ray luminosity and the large velocity dispersion of the He II emission, suggests that the source is an ideal candidate for more extensive follow-up observations for understanding the nature of hyper-luminous X-ray sources, a more luminous subgroup of ULXs, and more likely candidates for intermediate-mass black holes.« less

The joint fit of the BHMF and ERDF for the BAT AGN Sample

NASA Astrophysics Data System (ADS)

Weigel, Anna K.; Koss, Michael; Ricci, Claudio; Trakhtenbrot, Benny; Oh, Kyuseok; Schawinski, Kevin; Lamperti, Isabella

2018-01-01

A natural product of an AGN survey is the AGN luminosity function. This statistical measure describes the distribution of directly measurable AGN luminosities. Intrinsically, the shape of the luminosity function depends on the distribution of black hole masses and Eddington ratios. To constrain these fundamental AGN properties, the luminosity function thus has to be disentangled into the black hole mass and Eddington ratio distribution function. The BASS survey is unique as it allows such a joint fit for a large number of local AGN, is unbiased in terms of obscuration in the X-rays and provides black hole masses for type-1 and type-2 AGN. The black hole mass function at z ~ 0 represents an essential baseline for simulations and black hole growth models. The normalization of the Eddington ratio distribution function directly constrains the AGN fraction. Together, the BASS AGN luminosity, black hole mass and Eddington ratio distribution functions thus provide a complete picture of the local black hole population.

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.

A New Compton-Thick AGN in Our Cosmic Backyard: Unveiling the Buried Nucleus in NGC 1448 with NuSTAR

NASA Technical Reports Server (NTRS)

Annuar, A.; Alexander, D. M.; Ghandi, P.; Lansbury, G. B.; Asmus, D.; Ballantyne, D. R.; Bauer, F. E.; Boggs, S. E.; Boorman, P. G.; Brandt, W. N.;

Accounting for the dispersion in the x ray properties of early-type galaxies

NASA Technical Reports Server (NTRS)

White, Raymond E., III; Sarazin, Craig L.

1990-01-01

The x ray luminosities of early-type galaxies are correlated with their optical (e.g., blue) luminosities (L sub X approx. L sub B exp 1.6), but the x ray luminosities exhibit considerable scatter for a given optical luminosity L sub B. This dispersion in x ray luminosity is much greater than the dispersion of other properties of early-type galaxies (for a given L sub B), such as luminosity scale-length, velocity dispersion, color, and metallicity. Here, researchers consider several possible sources for the dispersion in x ray luminosity. Some of the scatter in x ray luminosity may result from stellar population variations between galaxies with similar L sub B. Since the x ray emitting gas is from accumulated stellar mass loss, the L sub X dispersion may be due to variations in integrated stellar mass loss rates. Another possible cause of the L sub X dispersion may be variations in the amount of cool material in the galaxies; cool gas may act as an energy sink for the hot gas. Infrared emission may be used to trace such cool material, so researchers look for a correlation between the infrared emission and the x ray emission of early-type galaxies at fixed L sub B. Velocity dispersion variations between galaxies of similar L sub B may also contribute to the L sub X dispersion. The most likely a priori source of the dispersion in L sub X is probably the varying amount of ram-pressure stripping in a range of galaxy environments. The hot gaseous halos of early-type galaxies can be stripped in encounters with other galaxies or with ambient cluster gas if the intracluster gas is sufficiently dense. Researchers find that the most likely cause of dispersion in the x ray properties of early type galaxies is probably the ram-pressure stripping of gaseous halos from galaxies. For a sample of 81 early-type galaxies with x ray luminosities or upper limits derived from Einstein Observatory observations (CFT) researchers calculated the cumulative distribution of angular distances between the x ray sample members and bright galaxies from the Revised Shapley - Ames catalog. Collectively, galaxies with low x ray luminosities (for a given L sub B) tend to be in denser environments than galaxies with higher x ray luminosities.

The Evolution of Globular Cluster Systems In Early-Type Galaxies

NASA Astrophysics Data System (ADS)

Grillmair, Carl

1999-07-01

We will measure structural parameters {core radii and concentrations} of globular clusters in three early-type galaxies using deep, four-point dithered observations. We have chosen globular cluster systems which have young, medium-age and old cluster populations, as indicated by cluster colors and luminosities. Our primary goal is to test the hypothesis that globular cluster luminosity functions evolve towards a ``universal'' form. Previous observations have shown that young cluster systems have exponential luminosity functions rather than the characteristic log-normal luminosity function of old cluster systems. We will test to see whether such young system exhibits a wider range of structural parameters than an old systems, and whether and at what rate plausible disruption mechanisms will cause the luminosity function to evolve towards a log-normal form. A simple observational comparison of structural parameters between different age cluster populations and between diff er ent sub-populations within the same galaxy will also provide clues concerning both the formation and destruction mechanisms of star clusters, the distinction between open and globular clusters, and the advisability of using globular cluster luminosity functions as distance indicators.

Global dust attenuation in disc galaxies: strong variation with specific star formation and stellar mass, and the importance of sample selection

NASA Astrophysics Data System (ADS)

Devour, Brian M.; Bell, Eric F.

2016-06-01

We study the relative dust attenuation-inclination relation in 78 721 nearby galaxies using the axis ratio dependence of optical-near-IR colour, as measured by the Sloan Digital Sky Survey, the Two Micron All Sky Survey, and the Wide-field Infrared Survey Explorer. In order to avoid to the greatest extent possible attenuation-driven biases, we carefully select galaxies using dust attenuation-independent near- and mid-IR luminosities and colours. Relative u-band attenuation between face-on and edge-on disc galaxies along the star-forming main sequence varies from ˜0.55 mag up to ˜1.55 mag. The strength of the relative attenuation varies strongly with both specific star formation rate and galaxy luminosity (or stellar mass). The dependence of relative attenuation on luminosity is not monotonic, but rather peaks at M3.4 μm ≈ -21.5, corresponding to M* ≈ 3 × 1010 M⊙. This behaviour stands seemingly in contrast to some older studies; we show that older works failed to reliably probe to higher luminosities, and were insensitive to the decrease in attenuation with increasing luminosity for the brightest star-forming discs. Back-of-the-envelope scaling relations predict the strong variation of dust optical depth with specific star formation rate and stellar mass. More in-depth comparisons using the scaling relations to model the relative attenuation require the inclusion of star-dust geometry to reproduce the details of these variations (especially at high luminosities), highlighting the importance of these geometrical effects.

The Swift BAT Hard X-ray Survey - A New Window on the Local AGN Universe

NASA Technical Reports Server (NTRS)

Mushotzky, Richard

2009-01-01

The Swift Burst and Transient telescope (BAT) has surveyed the entire sky for the last 3.5 years obtaining the first sensitive all sky survey of the 14-195 keV sky. At high galactic latitudes the vast majority of the detected sources are AGN. Since hard x-rays penetrate all but Compton thick obscuring material (Column densities of 1.6E24 atms/cm2) this survey is unbiased with respect to obscuration, host galaxy type, optical , radio or IR properties. We will present results on the broad band x-ray properties, the nature of the host galaxies, the luminosity function and will discuss a few of the optical, IR and x-ray results in detail.

A near-infrared relationship for estimating black hole masses in active galactic nuclei

NASA Astrophysics Data System (ADS)

Landt, Hermine; Ward, Martin J.; Peterson, Bradley M.; Bentz, Misty C.; Elvis, Martin; Korista, Kirk T.; Karovska, Margarita

2013-06-01

Black hole masses for samples of active galactic nuclei (AGN) are currently estimated from single-epoch optical spectra using scaling relations anchored in reverberation mapping results. In particular, the two quantities needed for calculating black hole masses, namely the velocity and the radial distance of the orbiting gas are derived from the widths of the Balmer hydrogen broad emission lines and the optical continuum luminosity, respectively. We have recently presented a near-infrared (near-IR) relationship for estimating AGN black hole masses based on the widths of the Paschen hydrogen broad emission lines and the total 1 μm continuum luminosity. The near-IR offers several advantages over the optical: it suffers less from dust extinction, the AGN continuum is observed only weakly contaminated by the host galaxy and the strongest Paschen broad emission lines Paα and Paβ are unblended. Here, we improve the calibration of the near-IR black hole mass relationship by increasing the sample from 14 to 23 reverberation-mapped AGN using additional spectroscopy obtained with the Gemini Near-Infrared Spectrograph. The additional sample improves the number statistics in particular at the high-luminosity end.

The WISSH quasars project. III. X-ray properties of hyper-luminous quasars

NASA Astrophysics Data System (ADS)

Martocchia, S.; Piconcelli, E.; Zappacosta, L.; Duras, F.; Vietri, G.; Vignali, C.; Bianchi, S.; Bischetti, M.; Bongiorno, A.; Brusa, M.; Lanzuisi, G.; Marconi, A.; Mathur, S.; Miniutti, G.; Nicastro, F.; Bruni, G.; Fiore, F.

2017-12-01

We performed a survey of the X-ray properties of 41 objects from the WISE/SDSS selected hyper-luminous (WISSH) quasars sample, which includes 86 broad-line quasars with bolometric luminosity LBol ≳ 2 × 1047 erg s-1 shining at z 2-4. We used both proprietary and archival Chandra and XMM-Newton observations. Twenty-one quasars have sufficient quality data to perform a spectroscopic analysis, while for the remaining sources, X-ray properties are derived through hardness-ratio analysis (apart for six sources that result to be undetected). The bulk ( 70%) of the detected WISSH quasars exhibit NH <5 × 1022 cm-2, in agreement with their optical Type 1 AGN classification. All but three quasars show unabsorbed 2-10 keV luminosities L2-10≥ 1045 erg s-1. Thanks to their extreme radiative output across the mid-IR-to-X-ray range, WISSH quasars therefore offer the opportunity to significantly extend and validate the existing relations involving L2-10. Specifically, we studied the X-ray luminosity as a function of (i) X-ray-to-optical (X/O) flux ratio; (ii) mid-IR luminosity (LMIR); (iii) LBol, and (iv) αOX versus 2500 Å luminosity. We find that the WISSH quasars show (i) unreported very low X/O ( <0.1) compared to typical AGN values; (ii) L2-10/LMIR ratios that are significantly smaller than those derived for AGN with lower luminosity; (iii) a large X-ray bolometric correction, kBol,X ≈ 100-1000; and (iv) steep -2≳αOX≳-1.7. These results lead to a scenario in which the X-ray emission of hyper-luminous quasars is relatively weaker compared to lower luminosity AGN. Models predict that such an X-ray weakness can be relevant for the acceleration of powerful high-ionization, emission-line-driven winds, which are commonly detected in the UV spectra of WISSH quasars and can, in turn, perturb the X-ray corona and weaken its emission. Accordingly, hyper-luminous quasars represent the ideal laboratory to study the link between the AGN energy output and wind acceleration. Additionally, WISSH quasars exhibit very large SMBH masses (log [MBH/M⊙]≳ 9.5). This enables a more robust modeling of the Γ-MBH relation by increasing the statistics at high masses. We derive a flatter Γ dependence than previously found over the broad range 5 ≲log (MBH/M⊙)≲ 11. Finally, we estimate that only 300 ks observations of X-IFU on board Athena will offer a detailed view of the properties of absorption features associated with powerful X-ray SMBH winds for a representative sample of WISSH quasars.

What powers Hyperluminous infrared galaxies at z˜1-2?

NASA Astrophysics Data System (ADS)

Symeonidis, M.; Page, M. J.

2018-06-01

We investigate what powers hyperluminous infrared galaxies (HyLIRGs; LIR, 8-1000μm > 1013 L⊙) at z˜1-2, by examining the behaviour of the infrared AGN luminosity function in relation to the infrared galaxy luminosity function. The former corresponds to emission from AGN-heated dust only, whereas the latter includes emission from dust heated by stars and AGN. Our results show that the two luminosity functions are substantially different below 1013 L⊙ but converge in the HyLIRG regime. We find that the fraction of AGN dominated sources increases with total infrared luminosity and at L_IR>10^{13.5} L_{⊙} AGN can account for the entire infrared emission. We conclude that the bright end of the 1 < z < 2 infrared galaxy luminosity function is shaped by AGN rather than star-forming galaxies.

Axions and the luminosity function of white dwarfs. The thin and thick disks, and the halo

NASA Astrophysics Data System (ADS)

Isern, J.; García-Berro, E.; Torres, S.; Cojocaru, R.; Catalán, S.

2018-05-01

The evolution of white dwarfs is a simple gravothermal process of cooling. Since the shape of their luminosity function is sensitive to the characteristic cooling time, it is possible to use its slope to test the existence of additional sources or sinks of energy, such as those predicted by alternative physical theories. The aim of this paper is to study if the changes in the slope of the white dwarf luminosity function around bolometric magnitudes ranging from 8 to 10 and previously attributed to axion emission are, effectively, a consequence of the existence of axions and not an artifact introduced by the star formation rate. We compute theoretical luminosity functions of the thin and thick disk, and of the stellar halo including axion emission and we compare them with the existing observed luminosity functions. Since these stellar populations have different star formation histories, the slope change should be present in all of them at the same place if it is due to axions or any other intrinsic cooling mechanism. The signature of an unexpected cooling seems to be present in the luminosity functions of the thin and thick disks, as well as in the halo luminosity function. This additional cooling is compatible with axion emission, thus supporting to the idea that DFSZ axions, with a mass in the range of 4 to 10 meV, could exist. If this were the case, these axions could be detected by the future solar axioscope IAXO.

The Intermediate Luminosity Optical Transient SN 2010da: The Progenitor, Eruption, and Aftermath of a Peculiar Supergiant High-mass X-Ray Binary

NASA Astrophysics Data System (ADS)

Villar, V. A.; Berger, E.; Chornock, R.; Margutti, R.; Laskar, T.; Brown, P. J.; Blanchard, P. K.; Czekala, I.; Lunnan, R.; Reynolds, M. T.

2016-10-01

We present optical spectroscopy, ultraviolet-to-infrared imaging, and X-ray observations of the intermediate luminosity optical transient (ILOT) SN 2010da in NGC 300 (d = 1.86 Mpc) spanning from -6 to +6 years relative to the time of outburst in 2010. Based on the light-curve and multi-epoch spectral energy distributions of SN 2010da, we conclude that the progenitor of SN 2010da is a ≈10-12 M ⊙ yellow supergiant possibly transitioning into a blue-loop phase. During outburst, SN 2010da had a peak absolute magnitude of M bol ≲ -10.4 mag, dimmer than other ILOTs and supernova impostors. We detect multi-component hydrogen Balmer, Paschen, and Ca II emission lines in our high-resolution spectra, which indicate a dusty and complex circumstellar environment. Since the 2010 eruption, the star has brightened by a factor of ≈5 and remains highly variable in the optical. Furthermore, we detect SN 2010da in archival Swift and Chandra observations as an ultraluminous X-ray source (L X ≈ 6 × 1039 erg s-1). We additionally attribute He II 4686 Å and coronal Fe emission lines in addition to a steady X-ray luminosity of ≈1037 erg s-1 to the presence of a compact companion.

First results from the BOXING (Birmingham-OCIW XMM and IMACS Nearby Groups) project.

NASA Astrophysics Data System (ADS)

Miles, T. A.; Raychaudhury, S.; Mulchaey, J. S.

2004-12-01

We present the first results from the BOXING (Birmingham-OCIW XMM and IMACS Nearby Groups) project, a collaboration between the Observatories of the Carnegie Institute of Washington (OCIW) and the University of Birmingham U.K. to study a sample of 25 galaxy groups (z ˜ 0.06) by means of optical photometry and spectroscopy (du Pont 2.5m; IMACS/Magellan) combined with x-ray observations (XMM). The combination of x-ray with optical data allows us to study the nature of the relationship between the properties of the groups and the galaxies that they contain. In this preliminary study, we present optical luminosity functions, which shows bimodal behavior in the poorer systems, interpreted as result of rapid merging. We also examine the dependence of galaxy morphology on local environment. Once spectroscopic observations are completed, we will be able to study velocity dispersions, star formation and nuclear activity in individual galaxies.

Star Formation Rate Distribution in the Galaxy NGC 1232

NASA Astrophysics Data System (ADS)

Araújo de Souza, Alexandre; Martins, Lucimara P.; Rodríguez-Ardila, Alberto; Fraga, Luciano

2018-06-01

NGC 1232 is a face-on spiral galaxy and a great laboratory for the study of star formation due to its proximity. We obtained high spatial resolution Hα images of this galaxy, with adaptive optics, using the SAM instrument at the SOAR telescope, and used these images to study its H II regions. These observations allowed us to produce the most complete H II region catalog for it to date, with a total of 976 sources. This doubles the number of H II regions previously found for this object. We used these data to construct the H II luminosity function, and obtained a power-law index lower than the typical values found for Sc galaxies. This shallower slope is related to the presence of a significant number of high-luminosity H II regions (log L > 39 dex). We also constructed the size distribution function, verifying that, as for most galaxies, NGC 1232 follows an exponential law. We also used the Hα luminosity to calculate the star formation rate. An extremely interesting fact about this galaxy is that X-ray diffuse observations suggest that NGC 1232 recently suffered a collision with a dwarf galaxy. We found an absence of star formation around the region where the X-ray emission is more intense, which we interpret as a star formation quenching due to the collision. Along with that, we found an excess of star-forming regions in the northeast part of the galaxy, where the X-ray emission is less intense.

OPTICAL PHOTOMETRIC AND POLARIMETRIC INVESTIGATION OF NGC 1931

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pandey, A. K.; Eswaraiah, C.; Sharma, Saurabh

We present optical photometric and polarimetric observations of stars toward NGC 1931 with the aim of deriving cluster parameters such as distance, reddening, age, and luminosity/mass function as well as understanding dust properties and star formation in the region. The distance to the cluster is found to be 2.3 {+-} 0.3 kpc and the reddening E(B - V) in the region is found to be variable. The stellar density contours reveal two clusters in the region. The observations suggest a differing reddening law within the cluster region. Polarization efficiency of the dust grains toward the direction of the cluster ismore » found to be less than that for the general diffuse interstellar medium (ISM). The slope of the mass function (-0.98 {+-} 0.22) in the southern region in the mass range of 0.8 < M/M {sub Sun} < 9.8 is found to be shallower in comparison to that in the northern region (-1.26 {+-} 0.23), which is comparable to the Salpeter value (-1.35). The K-band luminosity function (KLF) of the region is found to be comparable to the average value of the slope ({approx}0.4) for young clusters obtained by Lada and Lada; however, the slope of the KLF is steeper in the northern region as compared to the southern region. The region is probably ionized by two B2 main-sequence-type stars. The mean age of the young stellar objects (YSOs) is found to be 2 {+-} 1 Myr, which suggests that the identified YSOs could be younger than the ionizing sources of the region. The morphology of the region, the distribution and ages of the YSOs, and ionizing sources indicate a triggered star formation in the region.« less

The Cambridge-Cambridge X-ray Serendipity Survey: I X-ray luminous galaxies

NASA Technical Reports Server (NTRS)

Boyle, B. J.; Mcmahon, R. G.; Wilkes, B. J.; Elvis, M.

1994-01-01

We report on the first results obtained from a new optical identification program of 123 faint X-ray sources with S(0.5-2 keV) greater than 2 x 10(exp -14) erg/s/sq cm serendipitously detected in ROSAT PSPC pointed observations. We have spectroscopically identified the optical counterparts to more than 100 sources in this survey. Although the majority of the sample (68 objects) are QSO's, we have also identified 12 narrow emission line galaxies which have extreme X-ray luminosities (10(exp 42) less than L(sub X) less than 10(exp 43.5) erg/s). Subsequent spectroscopy reveals them to be a mixture of star-burst galaxies and Seyfert 2 galaxies in approximately equal numbers. Combined with potentially similar objects identified in the Einstein Extended Medium Sensitivity Survey, these X-ray luminous galaxies exhibit a rate of cosmological evolution, L(sub X) varies as (1 + z)(exp 2.5 +/- 1.0), consistent with that derived for X-ray QSO's. This evolution, coupled with the steep slope determined for the faint end of the X-ray luminosity function (Phi(L(sub X)) varies as L(sub X)(exp -1.9)), implies that such objects could comprise 15-35% of the soft (1-2 keV) X-ray background.

AN OPTICAL AND X-RAY STUDY OF THE FOSSIL GROUP RX J1340.6+4018

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mendes de Oliveira, Claudia L.; Cypriano, Eduardo S.; Sodre, Laerte

2009-08-15

Fossil groups are systems with one single central elliptical galaxy and an unusual lack of luminous galaxies in the inner regions. The standard explanation for the formation of these systems suggests that the lack of bright galaxies is due to galactic cannibalism. In this study, we show the results of an optical and X-ray analysis of RX J1340.6+4018, the prototype fossil group. The data indicate that RX J1340.6+4018 is similar to clusters in almost every sense (dynamical mass, X-ray luminosity, M/L, and luminosity function) except for the lack of L* galaxies. There are claims in the literature that fossil systemsmore » have a lack of small mass halos, compared to predictions based on the lambda cold dark matter scenario. The observational data gathered on this and other fossil groups so far offer no support for this idea. Analysis of the SN Ia/SN II ejecta ratio in the inner and outer regions shows a marginally significant central dominance of SN Ia material. This suggests that either the merger which originated in the central galaxy was dry or the group has been formed at early epochs, although better data are needed to confirm this result.« less

The Lambda Orionis Star Forming Region: a Test for the Universality of the IMF

NASA Astrophysics Data System (ADS)

Barrado Y Navascues, David

2005-10-01

We propose observations with XMM-EPIC/MOS in five distinct sibling associations belonging to the Lambda Orionis Star Forming Region (2--5 Myr, 340 pc). We have already optical, near-IR, and Spitzer photometry, and spectroscopy for objects down to 0.015 M(sun). The goals are: i) Assess the membership of our candidates and detect new members. ii) Derive accurate IMFs for each association, checking the universality of the IMF. iii) Study the properties and evolution of the X-ray Luminosity Functions.

Clustering, Cosmology and a New Era of Black Hole Demographics: The Conditional Luminosity Function of AGNs

NASA Astrophysics Data System (ADS)

Ballantyne, David R.

2016-04-01

Deep X-ray surveys have provided a comprehensive and largely unbiased view of 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, we present 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 demonstrated at z ≈0 and 0.9, and clear luminosity dependence in the AGN bias and mean halo mass is predicted at both z. The results support the idea that there are at least two different modes of AGN triggering: one, at high luminosity, that only occurs in high mass, highly biased haloes, and one that can occur over a wide range of halo masses and leads to luminosities that are correlated with halo mass. This latter mode dominates at z<0.9. The CLFs for Type 2 and Type 1 AGNs are also constrained at z ≈0, and we find evidence that unobscured quasars are more likely to be found in higher mass halos than obscured quasars. Thus, the AGN unification model seems to fail at quasar luminosities.

Half of the Most Luminous Quasars May Be Obscured: Investigating the Nature of WISE-Selected Hot Dust-Obscured Galaxies

NASA Astrophysics Data System (ADS)

Assef, R. J.; Eisenhardt, P. R. M.; Stern, D.; Tsai, C.-W.; Wu, J.; Wylezalek, D.; Blain, A. W.; Bridge, C. R.; Donoso, E.; Gonzales, A.; Griffith, R. L.; Jarrett, T. H.

2015-05-01

The Wide-field Infrared Survey Explorer mission has unveiled a rare population of high-redshift (z = 1-4.6), dusty, hyper-luminous galaxies, with infrared luminosities {{L}IR}\\gt {{10}13} {{L}⊙ }, and sometimes exceeding {{10}14} {{L}⊙ }. Previous work has shown that their dust temperatures and overall far-infrared spectral energy distributions (SEDs) are significantly hotter than expected to be powered by star formation. We present here an analysis of the rest-frame optical through mid-infrared SEDs for a large sample of these so-called “hot, dust-obscured galaxies” (Hot DOGs). We find that the SEDs of Hot DOGs are generally well modeled by the combination of a luminous, yet obscured active galactic nuclei (AGNs) that dominates the rest-frame emission at λ \\gt 1 μ m and the bolometric luminosity output, and a less luminous host galaxy that is responsible for the bulk of the rest optical/UV emission. Even though the stellar mass of the host galaxies may be as large as 1011-1012 M⊙, the AGN emission, with a range of luminosities comparable to those of the most luminous QSOs known, require that either Hot DOGs have black hole masses significantly in excess of the local relations, or that they radiate significantly above the Eddington limit, at a level at least 10 times more efficiently than z ˜ 2 QSOs. We show that, while rare, the number density of Hot DOGs is comparable to that of equally luminous but unobscured (i.e., Type 1) QSOs. This may be at odds with the trend suggested at lower luminosities for the fraction of obscured AGNs to decrease with increasing luminosity. That trend may, instead, reverse at higher luminosities. Alternatively, Hot DOGs may not be the torus-obscured counterparts of the known optically selected, largely unobscured, hyper-luminous QSOs, and may represent a new component of the galaxy evolution paradigm. Finally, we discuss the environments of Hot DOGs and statistically show that these objects are in regions as dense as those of known high-redshift proto-clusters.

Coronal Activity in Low-Mass Pre-Main Sequence Stars: NGC 2264

NASA Technical Reports Server (NTRS)

Tebbe, H. J.; Patten, B. M.

2000-01-01

We present the preliminary results of an analysis of ROSAT images in the region of the populous young (age approx. 3 Myr) star-forming region NGC 2264. The cluster was imaged with the ROSAT HRI in two sets of pointings -- one set near the central region of the cluster, centered on the star LW Mon, and the other set in the southern part of the cluster, centered near the star V428 Mon, just south of the Cone Nebula. In total 113 unique X-ray sources have been identified in the ROSAT images with signal-to-noise ratios greater than 3. The limiting luminosities (log Lx(ergs/sec)) for 3-sigma detections are estimated to be 30.18, 30.23, and 30.08 for the northern field, southern field, and overlap region between the two fields respectively. Extensive optical photometry, classification spectroscopy, and proper motions, obtained from recent ground-based surveys of this region, were used to identify the most likely optical counterpart to each X-ray source. Although most of our X-ray selected sample appears to be associated with NGC 2264 members, we find that the vast majority of the cluster membership was undetected in the ROSAT HRI survey. The X-ray cumulative luminosity function for solar-mass stars in NGC 2264 shows that most of the low-mass members probably have X-ray luminosities similar to those seen for the X-ray brightest members of older clusters such as IC 2391/IC 2602 (age approx. 50 Myr) and the Pleiades (age approx. 100 Myr). This research was funded in part by the SAO Summer Intern Program and NASA grant NAG5-8120.

Medium-resolution near-infrared spectroscopy of massive young stellar objects

NASA Astrophysics Data System (ADS)

Pomohaci, R.; Oudmaijer, R. D.; Lumsden, S. L.; Hoare, M. G.; Mendigutía, I.

2017-12-01

We present medium-resolution (R ∼ 7000) near-infrared echelle spectroscopic data for 36 massive young stellar objects (MYSOs) drawn from the Red MSX Source survey. This is the largest sample observed at this resolution at these wavelengths of MYSOs to date. The spectra are characterized mostly by emission from hydrogen recombination lines and accretion diagnostic lines. One MYSO shows photospheric H I absorption, a comparison with spectral standards indicates that the star is an A-type star with a low surface gravity, implying that the MYSOs are probably swollen, as also suggested by evolutionary calculations. An investigation of the Brγ line profiles shows that most are in pure emission, while 13 ± 5 per cent display P Cygni profiles, indicative of outflow, while less than 8 ± 4 per cent have inverse P Cygni profiles, indicative of infall. These values are comparable with investigations into the optically bright Herbig Be stars, but not with those of Herbig Ae and T Tauri stars, consistent with the notion that the more massive stars undergo accretion in a different fashion than lower mass objects that are undergoing magnetospheric accretion. Accretion luminosities and rates as derived from the Br γ line luminosities agree with results for lower mass sources, providing tentative evidence for massive star formation theories based on scaling of low-mass scenarios. We present Br γ/Br12 line profile ratios exploiting the fact that optical depth effects can be traced as a function of Doppler shift across the lines. These show that the winds of MYSOs in this sample are nearly equally split between constant, accelerating and decelerating velocity structures. There are no trends between the types of features we see and bolometric luminosities or near-infrared colours.

Hyper-luminous dust-obscured galaxies discovered by the Hyper Suprime-Cam on Subaru and WISE

NASA Astrophysics Data System (ADS)

Toba, Yoshiki; Nagao, Tohru; Strauss, Michael A.; Aoki, Kentaro; Goto, Tomotsugu; Imanishi, Masatoshi; Kawaguchi, Toshihiro; Terashima, Yuichi; Ueda, Yoshihiro; Bosch, James; Bundy, Kevin; Doi, Yoshiyuki; Inami, Hanae; Komiyama, Yutaka; Lupton, Robert H.; Matsuhara, Hideo; Matsuoka, Yoshiki; Miyazaki, Satoshi; Morokuma, Tomoki; Nakata, Fumiaki; Oi, Nagisa; Onoue, Masafusa; Oyabu, Shinki; Price, Paul; Tait, Philip J.; Takata, Tadafumi; Tanaka, Manobu M.; Terai, Tsuyoshi; Turner, Edwin L.; Uchida, Tomohisa; Usuda, Tomonori; Utsumi, Yousuke; Yamada, Yoshihiko; Wang, Shiang-Yu

2015-10-01

We present the photometric properties of a sample of infrared (IR) bright dust-obscured galaxies (DOGs). Combining wide and deep optical images obtained with the Hyper Suprime-Cam on the Subaru Telescope and all-sky mid-IR (MIR) images taken with Wide-Field Infrared Survey Explorer, we discovered 48 DOGs with i - Ks > 1.2 and i - [22] > 7.0, where i, Ks, and [22] represent AB magnitude in the i-band, Ks-band, and 22 μm, respectively, in the GAMA 14 hr field (˜ 9 deg2). Among these objects, 31 (˜ 65%) show power-law spectral energy distributions (SEDs) in the near-IR (NIR) and MIR regime, while the remainder show an NIR bump in their SEDs. Assuming that the redshift distribution for our DOGs sample is Gaussian, with mean and sigma z = 1.99 ± 0.45, we calculated their total IR luminosity using an empirical relation between 22 μm luminosity and total IR luminosity. The average value of the total IR luminosity is (3.5 ± 1.1) × 1013 L⊙, which classifies them as hyper-luminous infrared galaxies. We also derived the total IR luminosity function (LF) and IR luminosity density (LD) for a flux-limited subsample of 18 DOGs with 22 μm flux greater than 3.0 mJy and with i-band magnitude brighter than 24 AB magnitude. The derived space density for this subsample is log φ = -6.59 ± 0.11 [Mpc-3]. The IR LF for DOGs including data obtained from the literature is fitted well by a double-power law. The derived lower limit for the IR LD for our sample is ρIR ˜ 3.8 × 107 [L⊙ Mpc-3] and its contributions to the total IR LD, IR LD of all ultra-luminous infrared galaxies, and that of all DOGs are > 3%, > 9%, and > 15%, respectively.

iPTF16fnl: A Faint and Fast Tidal Disruption Event in an E+A Galaxy

DOE PAGES

Blagorodnova, N.; Gezari, S.; Hung, T.; ...

2017-07-20

Here, we present ground-based and Swift observations of iPTF16fnl, a likely tidal disruption event (TDE) discovered by the intermediate Palomar Transient Factory (iPTF) survey at 66.6 Mpc. The light curve of the object peaked at an absolute magmore » $${M}_{g}=-17.2$$. The maximum bolometric luminosity (from optical and UV) was $${L}_{p}\\simeq (1.0\\pm 0.15)\\times {10}^{43}$$ erg s -1, an order of magnitude fainter than any other optical TDE discovered so far. The luminosity in the first 60 days is consistent with an exponential decay, with $$L\\propto {e}^{-(t-{t}_{0})/\\tau }$$, where t 0 = 57631.0 (MJD) and $$\\tau \\simeq 15$$ days. The X-ray shows a marginal detection at $${L}_{X}={2.4}_{-1.1}^{1.9}\\times {10}^{39}$$ erg s -1 (Swift X-ray Telescope). No radio counterpart was detected down to 3σ, providing upper limits for monochromatic radio luminosities of $${\

iPTF16fnl: A Faint and Fast Tidal Disruption Event in an E+A Galaxy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blagorodnova, N.; Gezari, S.; Hung, T.

Here, we present ground-based and Swift observations of iPTF16fnl, a likely tidal disruption event (TDE) discovered by the intermediate Palomar Transient Factory (iPTF) survey at 66.6 Mpc. The light curve of the object peaked at an absolute magmore » $${M}_{g}=-17.2$$. The maximum bolometric luminosity (from optical and UV) was $${L}_{p}\\simeq (1.0\\pm 0.15)\\times {10}^{43}$$ erg s -1, an order of magnitude fainter than any other optical TDE discovered so far. The luminosity in the first 60 days is consistent with an exponential decay, with $$L\\propto {e}^{-(t-{t}_{0})/\\tau }$$, where t 0 = 57631.0 (MJD) and $$\\tau \\simeq 15$$ days. The X-ray shows a marginal detection at $${L}_{X}={2.4}_{-1.1}^{1.9}\\times {10}^{39}$$ erg s -1 (Swift X-ray Telescope). No radio counterpart was detected down to 3σ, providing upper limits for monochromatic radio luminosities of $${\

Consistency between the luminosity function of resolved millisecond pulsars and the galactic center excess

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ploeg, Harrison; Gordon, Chris; Crocker, Roland

Fermi Large Area Telescope data reveal an excess of GeV gamma rays from the direction of the Galactic Center and bulge. Several explanations have been proposed for this excess including an unresolved population of millisecond pulsars (MSPs) and self-annihilating dark matter. It has been claimed that a key discriminant for or against the MSP explanation can be extracted from the properties of the luminosity function describing this source population. Specifically, is the luminosity function of the putative MSPs in the Galactic Center consistent with that characterizing the resolved MSPs in the Galactic disk? To investigate this we have used amore » Bayesian Markov Chain Monte Carlo to evaluate the posterior distribution of the parameters of the MSP luminosity function describing both resolved MSPs and the Galactic Center excess. At variance with some other claims, our analysis reveals that, within current uncertainties, both data sets can be well fit with the same luminosity function.« less

Optical Variability Properties of High Luminosity AGN Classes

NASA Astrophysics Data System (ADS)

Stalin, C. S.; Gopal Krishna; Sagar, Ram; Wiita, Paul J.

2004-03-01

We present the results of a comparative study of the intranight optical variability (INOV) characteristics of radio-loud and radioquiet quasars, which involves a systematic intra-night optical monitoring of seven sets of high luminosity AGNs covering the redshift range z ' 0:2 to z ' 2:2. The sample, matched in the optical luminosity - redshift .MB?z/ plane, consists of seven radio-quiet quasars (RQQs), eight radio lobedominated quasars (LDQs), five radio core-dominated quasars (CDQs) and six BL Lac objects (BLs). Systematic CCD observations, aided by a careful data analysis procedure, have allowed us to detect INOV with amplitudes as low as about 1%. Present observations cover a total of 113 nights (720 hours) with only a single quasar monitored as continuously as possible on a given night. Considering the cases of only unambiguous detections of INOV we have estimated duty cycles (DCs) of 17%, 12%, 20% and 61% for RQQs, LDQs, CDQs, and BLs, respectively. The much lower amplitude and DC of INOV shown by RQQs compared to BLs may be understood in terms of their having optical synchrotron jets which are modestly misdirected from us. From our fairly extensive dataset, no general trend of a correlation between the INOVamplitude and the apparent optical brightness of the quasar is noticed. This suggests that the physical mechanisms of INOV and long term optical variability (LTOV) do not have a one-to-one relationship and different factors are involved. Also, the absence of a clear negative correlation between the INOV and LTOV characteristics of blazars of our sample points toward an inconspicuous contribution of accretion disk fluctuations to the observed INOV. The INOVduty cycle of theAGNs observed in this program suggests that INOV is associated predominantly with the highly polarized optical emission components. We also report new VLA imaging of two RQQs .1029C329&1252C020/ in our sample which has yielded a 5 GHz detection in one of them .1252 C 020I S5 GHz ' 1 mJy/.

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. Our sample does not show evidence of a rapid decline of the AGN luminosity function up to redshift four.

A volume-limited ROSAT survey of extreme ultraviolet emission from all nondegenerate stars within 10 parsecs

NASA Technical Reports Server (NTRS)

Wood, Brian E.; Brown, Alexander; Linsky, Jeffrey L.; Kellett, Barry J.; Bromage, Gordon E.; Hodgkin, Simon T.; Pye, John P.

1994-01-01

We report the results of a volume-limited ROSAT Wide Field Camera (WFC) survey of all nondegenerate stars within 10 pc. Of the 220 known star systems within 10 pc, we find that 41 are positive detections in at least one of the two WFC filter bandpasses (S1 and S2), while we consider another 14 to be marginal detections. We compute X-ray luminosities for the WFC detections using Einstein Imaging Proportional Counter (IPC) data, and these IPC luminosities are discussed along with the WFC luminosities throughout the paper for purposes of comparison. Extreme ultraviolet (EUV) luminosity functions are computed for single stars of different spectral types using both S1 and S2 luminosities, and these luminosity functions are compared with X-ray luminosity functions derived by previous authors using IPC data. We also analyze the S1 and S2 luminosity functions of the binary stars within 10 pc. We find that most stars in binary systems do not emit EUV radiation at levels different from those of single stars, but there may be a few EUV-luminous multiple-star systems which emit excess EUV radiation due to some effect of binarity. In general, the ratio of X-ray luminosity to EUV luminosity increases with increasing coronal emission, suggesting that coronally active stars have higher coronal temperatures. We find that our S1, S2, and IPC luminosities are well correlated with rotational velocity, and we compare activity-rotation relations determined using these different luminosities. Late M stars are found to be significantly less luminous in the EUV than other late-type stars. The most natural explanation for this results is the concept of coronal saturation -- the idea that late-type stars can emit only a limited fraction of their total luminosity in X-ray and EUV radiation, which means stars with very low bolometric luminosities must have relatively low X-ray and EUV luminosities as well. The maximum level of coronal emission from stars with earlier spectral types is studied also. To understand the saturation levels for these stars, we have compiled a large number of IPC luminosities for stars with a wide variety of spectral types and luminosity classes. We show quantitatively that if the Sun were completely covered with X-ray-emitting coronal loops, it would be near the saturation limit implied by this compilation, supporting the idea that stars near upper limits in coronal activity are completely covered with active regions.

DUSTY EXPLOSIONS FROM DUSTY PROGENITORS: THE PHYSICS OF SN 2008S AND THE 2008 NGC 300-OT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kochanek, C. S.

2011-11-01

SN 2008S and the 2008 NGC 300-OT were explosive transients of stars self-obscured by very dense, dusty stellar winds. An explosive transient with an unobserved shock breakout luminosity of order 10{sup 10} L{sub sun} is required to render the transients little obscured and visible in the optical at their peaks. Such a large breakout luminosity then implies that the progenitor stars were cool, red supergiants, most probably {approx}9 M{sub sun} extreme asymptotic giant branch stars. As the shocks generated by the explosions propagate outward through the dense wind, they produce a shock luminosity in soft X-rays that powers the long-livedmore » luminosity of the transients. Unlike typical cases of transients exploding into a surrounding circumstellar medium, the progenitor winds in these systems are optically thick to soft X-rays, easily absorb radio emission, and rapidly reform dust destroyed by the peak luminosity of the transients. As a result, X-rays are absorbed by the gas and the energy is ultimately radiated by the reformed dust. Three years post-peak, both systems are still significantly more luminous than their progenitor stars, but they are again fully shrouded by the reformed dust and only visible in the mid-IR. The high luminosity and heavy obscuration may make it difficult to determine the survival of the progenitor stars for {approx}10 years. However, our model indicates that SN 2008S, but not the NGC 300-OT, should now be a detectable X-ray source. SN 2008S has a higher estimated shock velocity and a lower density wind, so the X-rays begin to escape at a much earlier phase.« less

LOFAR/H-ATLAS: the low-frequency radio luminosity-star formation rate relation

NASA Astrophysics Data System (ADS)

Gürkan, G.; Hardcastle, M. J.; Smith, D. J. B.; Best, P. N.; Bourne, N.; Calistro-Rivera, G.; Heald, G.; Jarvis, M. J.; Prandoni, I.; Röttgering, H. J. A.; Sabater, J.; Shimwell, T.; Tasse, C.; Williams, W. L.

2018-04-01

Radio emission is a key indicator of star formation activity in galaxies, but the radio luminosity-star formation relation has to date been studied almost exclusively at frequencies of 1.4 GHz or above. At lower radio frequencies, the effects of thermal radio emission are greatly reduced, and so we would expect the radio emission observed to be completely dominated by synchrotron radiation from supernova-generated cosmic rays. As part of the LOFAR Surveys Key Science project, the Herschel-ATLAS NGP field has been surveyed with LOFAR at an effective frequency of 150 MHz. We select a sample from the MPA-JHU catalogue of Sloan Digital Sky Survey galaxies in this area: the combination of Herschel, optical and mid-infrared data enable us to derive star formation rates (SFRs) for our sources using spectral energy distribution fitting, allowing a detailed study of the low-frequency radio luminosity-star formation relation in the nearby Universe. For those objects selected as star-forming galaxies (SFGs) using optical emission line diagnostics, we find a tight relationship between the 150 MHz radio luminosity (L150) and SFR. Interestingly, we find that a single power-law relationship between L150 and SFR is not a good description of all SFGs: a broken power-law model provides a better fit. This may indicate an additional mechanism for the generation of radio-emitting cosmic rays. Also, at given SFR, the radio luminosity depends on the stellar mass of the galaxy. Objects that were not classified as SFGs have higher 150-MHz radio luminosity than would be expected given their SFR, implying an important role for low-level active galactic nucleus activity.

Super-Eddington stellar winds: unifying radiative-enthalpy versus flux-driven models

NASA Astrophysics Data System (ADS)

Owocki, Stanley P.; Townsend, Richard H. D.; Quataert, Eliot

2017-12-01

We derive semi-analytic solutions for optically thick, super-Eddington stellar winds, induced by an assumed steady energy addition Δ {\\dot{E}} concentrated around a near-surface heating radius R in a massive star of central luminosity L*. We show that obtaining steady wind solutions requires both that the resulting total luminosity L_o = L_\\ast + Δ {\\dot{E}} exceed the Eddington luminosity, Γo ≡ Lo/LEdd > 1, and that the induced mass-loss rate be such that the 'photon-tiring' parameter, m ≡ {\\dot{M}} GM/R L_o ≤ 1-1/Γ _o, ensuring the luminosity is sufficient to overcome the gravitational potential GM/R. Our analysis unifies previous super-Eddington wind models that either: (1) assumed a direct radiative flux-driving without accounting for the advection of radiative enthalpy that can become important in such an optically thick flow; or (2) assumed that such super-Eddington outflows are adiabatic, neglecting the effects of the diffusive radiative flux. We show that these distinct models become applicable in the asymptotic limits of small versus large values of mΓo, respectively. By solving the coupled differential equations for radiative diffusion and wind momentum, we obtain general solutions that effectively bridge the behaviours of these limiting models. Two key scaling results are for the terminal wind speed to escape speed, which is found to vary as v_∞^2/v_esc^2 = Γ _o/(1+m Γ _o) -1, and for the final observed luminosity Lobs, which for all allowed steady-solutions with m < 1 - 1/Γo exceeds the Eddington luminosity, Lobs > LEdd. Our super-Eddington wind solutions have potential applicability for modelling phases of eruptive mass-loss from massive stars, classical novae, and the remnants of stellar mergers.

The red and blue galaxy populations in the GOODS field: evidence for an excess of red dwarfs

NASA Astrophysics Data System (ADS)

Salimbeni, S.; Giallongo, E.; Menci, N.; Castellano, M.; Fontana, A.; Grazian, A.; Pentericci, L.; Trevese, D.; Cristiani, S.; Nonino, M.; Vanzella, E.

2008-01-01

Aims: We study the evolution of the galaxy population up to z˜ 3 as a function of its colour properties. In particular, luminosity functions and luminosity densities were derived as a function of redshift for the blue/late and red/early populations. Methods: We use data from the GOODS-MUSIC catalogue, which have typical magnitude limits z850≤ 26 and K_s≤ 23.5 for most of the sample. About 8% of the galaxies have spectroscopic redshifts; the remaining have well calibrated photometric redshifts derived from the extremely wide multi-wavelength coverage in 14 bands (from the U band to the Spitzer 8~ μm band). We have derived a catalogue of galaxies complete in the rest-frame B-band, which has been divided into two subsamples according to their rest-frame U-V colour (or derived specific star formation rate) properties. Results: We confirm a bimodality in the U-V colour and specific star formation rate of the galaxy sample up to z˜ 3. This bimodality is used to compute the luminosity functions of the blue/late and red/early subsamples. The luminosity functions of the blue/late and total samples are well represented by steep Schechter functions evolving in luminosity with increasing redshifts. The volume density of the luminosity functions of the red/early populations decreases with increasing redshift. The shape of the red/early luminosity functions shows an excess of faint red dwarfs with respect to the extrapolation of a flat Schechter function and can be represented by the sum of two Schechter functions. Our model for galaxy formation in the hierarchical clustering scenario, which also includes external feedback due to a diffuse UV background, shows a general broad agreement with the luminosity functions of both populations, the larger discrepancies being present at the faint end for the red population. Hints on the nature of the red dwarf population are given on the basis of their stellar mass and spatial distributions.

Powerful radiative jets in supercritical accretion discs around non-spinning black holes

NASA Astrophysics Data System (ADS)

Sądowski, Aleksander; Narayan, Ramesh

2015-11-01

We describe a set of simulations of supercritical accretion on to a non-rotating supermassive black hole (BH). The accretion flow takes the form of a geometrically thick disc with twin low-density funnels around the rotation axis. For accretion rates {gtrsim } 10 dot{M}_Edd, there is sufficient gas in the funnel to make this region optically thick. Radiation from the disc first flows into the funnel, after which it accelerates the optically thick funnel gas along the axis. The resulting jet is baryon loaded and has a terminal density-weighted velocity ≈0.3c. Much of the radiative luminosity is converted into kinetic energy by the time the escaping gas becomes optically thin. These jets are not powered by BHrotation or magnetic driving, but purely by radiation. Their characteristic beaming angle is ˜0.2 rad. For an observer viewing down the axis, the isotropic equivalent luminosity of total energy is as much as 1048 erg s- 1 for a 107 M⊙ BH accreting at 103 Eddington. Therefore, energetically, the simulated jets are consistent with observations of the most powerful tidal disruption events, e.g. Swift J1644. The jet velocity is, however, too low to match the Lorentz factor γ > 2 inferred in J1644. There is no such conflict in the case of other tidal disruption events. Since favourably oriented observers see isotropic equivalent luminosities that are highly super-Eddington, the simulated models can explain observations of ultraluminous X-ray sources, at least in terms of luminosity and energetics, without requiring intermediate-mass BHs.

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.

Obscured Black Hole Growth at High Redshift and High Luminosity

NASA Astrophysics Data System (ADS)

Urry, C. Megan

We propose to complete the census of cosmic black hole growth by measuring luminous and/or distant quasars using Spitzer, Herschel, Chandra and XMM-Newton imaging in Stripe 82 the deepest Sloan Digital Sky Survey field, and now the premier legacy field among 100 deg2 survey areas. These extensive ancillary data offer unsurpassed sensitivity to accreting supermassive black holes in luminous quasars out to z 6, including obscured objects missed by optical/UV surveys. We address six science goals centered on the growth of supermassive black holes: 1) We will constrain the mass accreted in luminous quasars by determining the evolving luminosity function of high-luminosity X-ray-selected AGN, including obscured quasars, especially at high redshift, where previous surveys have limited statistics. 2) We will build a comprehensive multi-wavelength population synthesis model that describes cosmic black hole accretion across most of the history of the Universe, constrained by the wealth of data now available. This will be the first population synthesis model that is constrained at high luminosity and high redshift (courtesy of Stripe 82X). 3) We will characterize the spectral energy distributions (SEDs) of luminous X-ray selected quasars, including obscured ones. We will assess the dust content in the host galaxies and diagnose the relative contributions of black hole fueling and star formation, using Herschel data to probe the cold molecular gas from which stars form and comparing X-rays from accretion onto the central black hole. We will also use high-quality optical imaging to disentangle nuclear from host galaxy emission in a representative sub-sample of quasars. 4) Using Spitzer, Herschel, Chandra, XMM-Newton, and optical data, we will identify candidates for the most heavily obscured black holes, which we will follow up with ground-based IR spectroscopy using Keck and Palomar (to which Yale has guaranteed access). In this way we will recover obscured AGN missed by optical surveys, mitigating optical biases in quasar demography. 5) We will investigate the large-scale environments of quasars, in which black holes appear to acquire at least half of their mass, by studying the clustering of AGN in Stripe 82. Specifically, we will measure the halo occupation distribution, which is the probability of a dark matter halo of a given mass to host central and satellite AGN above a given luminosity. We will assess whether rapid black hole growth depends on halo mass, and how the average halo mass in which AGN occur might depend on AGN or galaxy properties. For this analysis, the hundreds of luminous quasars at z>2 in Stripe 82X and its high redshift completeness (92%) are particularly important. 6) We will investigate early black hole growth at z>6 by analyzing fluctuations in the infrared and X-ray backgrounds (i.e., below source detection levels). Specifically, we will directly correlate the Spitzer-measured cosmic infrared background (CIB) and the cosmic X-ray background (CXB) measured with XMM-Newton, on roughly 20 times larger scales than previous studies. This offers the best probe of early BH growth until high-sensitivity X-ray observatories like Athena and Lynx. These studies will determine how much mass is accreted in the most luminous and/or obscured quasars, and how the energy released into galaxies depends on key variables such as redshift, AGN luminosity, Eddington ratio and wavelength. This accurate, data validated estimate of the radiation deposited into host galaxies is essential for incorporating feedback into models of galaxy evolution. The Stripe 82X survey, as the richest multiwavelength survey covering >30 deg2 of the sky, deep enough in X-rays to see luminous quasars out to z 10, will yield many important discoveries, ideally including unexpected ones found by others in the community.

The detonation of a sub-Chandrasekhar-mass white dwarf at the origin of the low-luminosity Type Ia supernova 1999by

NASA Astrophysics Data System (ADS)

Blondin, Stéphane; Dessart, Luc; Hillier, D. John

2018-03-01

While Chandrasekhar-mass (MCh) models with a low 56Ni yield can match the peak luminosities of fast-declining, 91bg-like Type Ia supernovae (SNe Ia), they systematically fail to reproduce their faster light-curve evolution. Here, we illustrate the impact of a low ejecta mass on the radiative display of low-luminosity SNe Ia, by comparing a sub-MCh model resulting from the pure central detonation of a C-O white dwarf (WD) to an MCh delayed-detonation model with the same 56Ni yield of 0.12 M⊙. Our sub-MCh model from a 0.90 M⊙ WD progenitor has a ˜5 d shorter rise time in the integrated UV-optical-IR (uvoir) luminosity, as well as in the B band, and a ˜20 per cent higher peak uvoir luminosity (˜1 mag brighter peak MB). This sub-MCh model also displays bluer maximum-light colours due to the larger specific heating rate, and larger post-maximum uvoir and B-band decline rates. The luminosity decline at nebular times is also more pronounced, reflecting the enhanced escape of gamma rays resulting from the lower density of the progenitor WD. The deficit of stable nickel in the innermost ejecta leads to a notable absence of forbidden lines of [Ni II] in the nebular spectra. In contrast, the MCh model displays a strong line due to [Ni II] 1.939 μm, which could in principle serve to distinguish between different progenitor scenarios. Our sub-MCh model offers an unprecedented agreement with optical and near-infrared observations of the 91bg-like SN 1999by, making a strong case for a WD progenitor significantly below the Chandrasekhar-mass limit for this event and other low-luminosity SNe Ia.

Studying the accretion geometry of EXO 2030+375 at luminosities close to the propeller regime

NASA Astrophysics Data System (ADS)

Fürst, F.; Kretschmar, P.; Kajava, J. J. E.; Alfonso-Garzón, J.; Kühnel, M.; Sanchez-Fernandez, C.; Blay, P.; Wilson-Hodge, C. A.; Jenke, P.; Kreykenbohm, I.; Pottschmidt, K.; Wilms, J.; Rothschild, R. E.

2017-10-01

The Be X-ray binary EXO 2030+375was in an extended low-luminosity state during most of 2016. We observed this state with NuSTARand Swift, supported by INTEGRALobservations and optical spectroscopy with the Nordic Optical Telescope (NOT). We present a comprehensive spectral and timing analysis of these data here to study the accretion geometry and investigate a possible onset of the propeller effect. The Hα data show that the circumstellar disk of the Be-star is still present. We measure equivalent widths similar to values found during more active phases in the past, indicating that the low-luminosity state is not simply triggered by a smaller Be disk. The NuSTARdata, taken at a 3-78 keV luminosity of 6.8 × 1035 erg s-1 (for a distance of 7.1 kpc), are nicely described by standard accreting pulsar models such as an absorbed power law with a high-energy cutoff. We find that pulsations are still clearly visible at these luminosities, indicating that accretion is continuing despite the very low mass transfer rate. In phase-resolved spectroscopy we find a peculiar variation of the photon index from 1.5 to 2.5 over only about 3% of the rotational period. This variation is similar to that observed with XMM-Newtonat much higher luminosities. It may be connected to the accretion column passing through our line of sight. With Swift/XRT we observe luminosities as low as 1034 erg s-1 where the data quality did not allow us to search for pulsations, but the spectrum is much softer and well described by either a blackbody or soft power-law continuum. This softer spectrum might be due to the accretion being stopped by the propeller effect and we only observe the neutron star surface cooling.

SN 2009js AT THE CROSSROADS BETWEEN NORMAL AND SUBLUMINOUS TYPE IIP SUPERNOVAE: OPTICAL AND MID-INFRARED EVOLUTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gandhi, P.; Yamanaka, M.; Itoh, R.

2013-04-20

We present a study of SN 2009js in NGC 918. Multi-band Kanata optical photometry covering the first {approx}120 days shows the source to be a Type IIP SN. Reddening is dominated by that due to our Galaxy. One-year-post-explosion photometry with the New Technology Telescope and a Subaru optical spectrum 16 days post-discovery both imply a good match with the well-studied subluminous SN 2005cs. The plateau-phase luminosity of SN 2009js and its plateau duration are more similar to the intermediate luminosity IIP SN 2008in. Thus, SN 2009js shares characteristics with both subluminous and intermediate luminosity supernovae (SNe). Its radioactive tail luminositymore » lies between SN 2005cs and SN 2008in, whereas its quasi-bolometric luminosity decline from peak to plateau (quantified by a newly defined parameter {Delta}logL, which measures adiabatic cooling following shock breakout) is much smaller than both the others'. We estimate the ejected mass of {sup 56}Ni to be low ({approx}0.007 M{sub Sun }). The SN explosion energy appears to have been small, similar to that of SN 2005cs. SN 2009js is the first subluminous SN IIP to be studied in the mid-infrared. It was serendipitously caught by Spitzer at very early times. In addition, it was detected by WISE 105 days later with a significant 4.6 {mu}m flux excess above the photosphere. The infrared excess luminosity relative to the photosphere is clearly smaller than that of SN 2004dj, which has been extensively studied in the mid-infrared. The excess may be tentatively assigned to heated dust with mass {approx}3 Multiplication-Sign 10{sup -5} M{sub Sun }, or to CO fundamental emission as a precursor to dust formation.« less

[Results from the X-ray and Optical Follow-up Observations of the Swift BAT AGN Survey

NASA Technical Reports Server (NTRS)

Mushotzky, R.

2008-01-01

I will present results from the x-ray and optical follow-up observations of the Swift BAT ACN survey. I will discuss the nature of obscuration in these objects, the relationship to optical properties and the change of properties with luminosity and galaxy type and how they will influence the design of XO.

The HELLAS2XMM survey. IV. Optical identifications and the evolution of the accretion luminosity in the Universe

NASA Astrophysics Data System (ADS)

Fiore, F.; Brusa, M.; Cocchia, F.; Baldi, A.; Carangelo, N.; Ciliegi, P.; Comastri, A.; La Franca, F.; Maiolino, R.; Matt, G.; Molendi, S.; Mignoli, M.; Perola, G. C.; Severgnini, P.; Vignali, C.

2003-10-01

We present results from the photometric and spectroscopic identification of 122 X-ray sources recently discovered by XMM-Newton in the 2-10 keV band (the HELLAS2XMM 1dF sample). Their flux cover the range 8*E-15-4*E-13 erg cm-2 s-1 and the total area surveyed is 0.9 square degrees. One of the most interesting results (which is found also in deeper sourveys) is that about 20% of the hard X-ray selected sources have an X-ray to optical flux ratio (X/O) ten times or more higher than that of optically selected AGN. Unlike the faint sources found in the ultra-deep Chandra and XMM-Newton surveys, which reach X-ray (and optical) fluxes more than one order of magnitude lower than the HELLAS2XMM survey sources, many of the extreme X/O sources in our sample have Rprotect la25 and are therefore accessible to optical spectroscopy. We report the identification of 13 sources with X/Oprotect ga10 (to be compared with 9 sources known from the deeper, pencil-beam surveys). Eight of them are narrow line QSO (seemingly the extension to very high luminosity of the type 2 Seyfert galaxies), four are broad line QSO. The results from our survey are also used to make reliable predictions about the luminosity of the sources not yet spectroscopically identified, both in our sample and in deeper Chandra and XMM-Newton samples. We then use a combined sample of 317 hard X-ray selected sources (HELLAS2XMM 1dF, Chandra Deep Field North 1Msec, Chandra SSA13 and XMM-Newton Lockman Hole flux limited samples), 221 with measured redshifts, to evaluate the cosmological evolution of the hard X-ray source's number and luminosity densities. Looking backward in time, the low luminosity sources (log L2-10 keV=43-44 erg s-1) increase in number at a much slower rate than the very high luminosity sources (log L2-10 keV >44.5 erg s-1), reaching a maximum around z=1 and then levelling off beyond z=2. This translates into an accretion driven luminosity density which is dominated by sources with log L2-10 keV <44.5 erg s-1 up to at least z=1, while the contribution of the same sources and of those with log L2-10 keV >44.5 erg s-1 appear, with yet rather large uncertainties, to be comparable between z=2 and 4. Based on observations collected at the European Southern Observatory, La Silla and Paranal, Chile, and at the Telescopio Nazionale Galileo, Roque de Los Muchachos, La Palma, TF, Spain. Based also on observations made with XMM-Newton, an ESA science mission. Table 1 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/409/79

Padé Approximant and Minimax Rational Approximation in Standard Cosmology

NASA Astrophysics Data System (ADS)

Zaninetti, Lorenzo

2016-02-01

The luminosity distance in the standard cosmology as given by $\\Lambda$CDM and consequently the distance modulus for supernovae can be defined by the Pad\\'e approximant. A comparison with a known analytical solution shows that the Pad\\'e approximant for the luminosity distance has an error of $4\\%$ at redshift $= 10$. A similar procedure for the Taylor expansion of the luminosity distance gives an error of $4\\%$ at redshift $=0.7 $; this means that for the luminosity distance, the Pad\\'e approximation is superior to the Taylor series. The availability of an analytical expression for the distance modulus allows applying the Levenberg--Marquardt method to derive the fundamental parameters from the available compilations for supernovae. A new luminosity function for galaxies derived from the truncated gamma probability density function models the observed luminosity function for galaxies when the observed range in absolute magnitude is modeled by the Pad\\'e approximant. A comparison of $\\Lambda$CDM with other cosmologies is done adopting a statistical point of view.

Polycrystalline CdTe detectors: A luminosity monitor for the LHC

NASA Astrophysics Data System (ADS)

Gschwendtner, E.; Placidia, M.; Schmicklera, H.

2003-09-01

The luminosity at the four interaction points of the Large Hadron Collider must be continuously monitored in order to provide an adequate tool for the control and optimization of the collision parameters and the beam optics. At both sides of the interaction points absorbers are installed to protect the super-conducting accelerator elements from quenches caused by the deposited energy of collision products. The luminosity detectors will be installed in the copper core of these absorbers to measure the electromagnetic and hadronic showers caused by neutral particles that are produced at the proton-proton collision in the interaction points. The detectors have to withstand extreme radiation levels (108 Gy/yr at the design luminosity) and their long-term operation has to be assured without requiring human intervention. In addition the demand for bunch-by-bunch luminosity measurements, i.e. 40 MHz detection speed, puts severe constraints on the detectors. Polycrystalline CdTe detectors have a high potential to fulfill the requirements and are considered as LHC luminosity monitors. In this paper the interaction region is shown and the characteristics of the CdTe detectors are presented.

Exploring the Faint End of the Luminosity-Metallicity Relation with Hα Dots

NASA Astrophysics Data System (ADS)

Hirschauer, Alec S.; Salzer, John J.

2015-01-01

The well-known correlation between a galaxy's luminosity and its gas-phase oxygen abundance (the luminosity-metallicity (L-Z) relation) offers clues toward our understanding of chemical enrichment histories and evolution. Bright galaxies are comparatively better studied than faint ones, leaving a relative dearth of observational data points to constrain the L-Z relation in the low-luminosity regime. We present high S/N nebular spectroscopy of low-luminosity star-forming galaxies observed with the KPNO 4m using the new KOSMOS spectrograph to derive direct-method metallicities. Our targets are strong point-like emission-line sources discovered serendipitously in continuum-subtracted narrowband images from the ALFALFA Hα survey. Follow-up spectroscopy of these "Hα dots" shows that these objects represent some of the lowest luminosity star-forming systems in the local Universe. Our KOSMOS spectra cover the full optical region and include detection of [O III] λ4363 in roughly a dozen objects. This paper presents some of the first scientific results obtained using this new spectrograph, and demonstrates its capabilities and effectiveness in deriving direct-method metallicities of faint objects.

Spectroscopic follow-up of variability-selected active galactic nuclei in the Chandra Deep Field South

NASA Astrophysics Data System (ADS)

Boutsia, K.; Leibundgut, B.; Trevese, D.; Vagnetti, F.

2009-04-01

Context: Supermassive black holes with masses of 10^5-109 M⊙ are believed to inhabit most, if not all, nuclear regions of galaxies, and both observational evidence and theoretical models suggest a scenario where galaxy and black hole evolution are tightly related. Luminous AGNs are usually selected by their non-stellar colours or their X-ray emission. Colour selection cannot be used to select low-luminosity AGNs, since their emission is dominated by the host galaxy. Objects with low X-ray to optical ratio escape even the deepest X-ray surveys performed so far. In a previous study we presented a sample of candidates selected through optical variability in the Chandra Deep Field South, where repeated optical observations were performed in the framework of the STRESS supernova survey. Aims: The analysis is devoted to breaking down the sample in AGNs, starburst galaxies, and low-ionisation narrow-emission line objects, to providing new information about the possible dependence of the emission mechanisms on nuclear luminosity and black-hole mass, and eventually studying the evolution in cosmic time of the different populations. Methods: We obtained new optical spectroscopy for a sample of variability selected candidates with the ESO NTT telescope. We analysed the new spectra, together with those existing in the literature and studied the distribution of the objects in U-B and B-V colours, optical and X-ray luminosity, and variability amplitude. Results: A large fraction (17/27) of the observed candidates are broad-line luminous AGNs, confirming the efficiency of variability in detecting quasars. We detect: i) extended objects which would have escaped the colour selection and ii) objects of very low X-ray to optical ratio, in a few cases without any X-ray detection at all. Several objects resulted to be narrow-emission line galaxies where variability indicates nuclear activity, while no emission lines were detected in others. Some of these galaxies have variability and X-ray to optical ratio close to active galactic nuclei, while others have much lower variability and X-ray to optical ratio. This result can be explained by the dilution of the nuclear light due to the host galaxy. Conclusions: Our results demonstrate the effectiveness of supernova search programmes to detect large samples of low-luminosity AGNs. A sizable fraction of the AGN in our variability sample had escaped X-ray detection (5/47) and/or colour selection (9/48). Spectroscopic follow-up to fainter flux limits is strongly encouraged. Based on observations collected at the European Southern Observatory, Chile, 080.B-0187(A).

Different Characteristics of the Bright Branches of the Globular Clusters M15 and M92

NASA Astrophysics Data System (ADS)

Cho, Dong-Hwan; Lee, Sang-Gak

2007-05-01

We carried out relatively wide-field BVI CCD photometric observations of the globular clusters M15 (NGC 7078) and M92 (NGC 6341) using the 1.8 m telescope of the Bohyun Optical Astronomy Observatory. We present color-magnitude diagrams (V vs. B-V, V vs. V-I, and V vs. B-I) of M15 and M92. We found asymptotic giant branch (AGB) bumps at VbumpAGB=15.20+/-0.05 mag and VbumpAGB=14.50+/-0.05 mag for M15 and M92, respectively. We identified the red giant branch (RGB) bumps of the two clusters. We have estimated the population ratios R and R2 for M15 and M92 in two cases: when only normal horizontal-branch (HB) stars are used and when all the HB stars are used. We have compared the observed RGB luminosity functions of M15 and M92 with the theoretical RGB luminosity functions of Bergbusch & VandenBerg and found no significant ``extra stars'' in the comparisons. This implies that the HB morphology difference between M15 and M92 is not certain due to the results of deep mixing in the RGB sequence.

New cataclysmic variables and other exotic binaries in the globular cluster 47 Tucanae*

NASA Astrophysics Data System (ADS)

Rivera Sandoval, L. E.; van den Berg, M.; Heinke, C. O.; Cohn, H. N.; Lugger, P. M.; Anderson, J.; Cool, A. M.; Edmonds, P. D.; Wijnands, R.; Ivanova, N.; Grindlay, J. E.

2018-04-01

We present 22 new (+3 confirmed) cataclysmic variables (CVs) in the non-core-collapsed globular cluster 47 Tucanae (47 Tuc). The total number of CVs in the cluster is now 43, the largest sample in any globular cluster so far. For the identifications we used near-ultraviolet (NUV) and optical images from the Hubble Space Telescope, in combination with X-ray results from the Chandra X-ray Observatory. This allowed us to build the deepest NUV CV luminosity function of the cluster to date. We found that the CVs in 47 Tuc are more concentrated towards the cluster centre than the main-sequence turn-off stars. We compared our results to the CV populations of the core-collapsed globular clusters NGC 6397 and NGC 6752. We found that 47 Tuc has fewer bright CVs per unit mass than those two other clusters. That suggests that dynamical interactions in core-collapsed clusters play a major role creating new CVs. In 47 Tuc, the CV population is probably dominated by primordial and old dynamically formed systems. We estimated that the CVs in 47 Tuc have total masses of ˜1.4 M⊙. We also found that the X-ray luminosity function of the CVs in the three clusters is bimodal. Additionally, we discuss a possible double degenerate system and an intriguing/unclassified object. Finally, we present four systems that could be millisecond pulsar companions given their X-ray and NUV/optical colours. For one of them we present very strong evidence for being an ablated companion. The other three could be CO or He white dwarfs.

MUSE deep-fields: the Ly α luminosity function in the Hubble Deep Field-South at 2.91 < z < 6.64

NASA Astrophysics Data System (ADS)

Drake, Alyssa B.; Guiderdoni, Bruno; Blaizot, Jérémy; Wisotzki, Lutz; Herenz, Edmund Christian; Garel, Thibault; Richard, Johan; Bacon, Roland; Bina, David; Cantalupo, Sebastiano; Contini, Thierry; den Brok, Mark; Hashimoto, Takuya; Marino, Raffaella Anna; Pelló, Roser; Schaye, Joop; Schmidt, Kasper B.

2017-10-01

We present the first estimate of the Ly α luminosity function using blind spectroscopy from the Multi Unit Spectroscopic Explorer, MUSE, in the Hubble Deep Field-South. Using automatic source-detection software, we assemble a homogeneously detected sample of 59 Ly α emitters covering a flux range of -18.0 < log10 (F) < -16.3 (erg s-1 cm-2), corresponding to luminosities of 41.4 < log10 (L) < 42.8 (erg s-1). As recent studies have shown, Ly α fluxes can be underestimated by a factor of 2 or more via traditional methods, and so we undertake a careful assessment of each object's Ly α flux using a curve-of-growth analysis to account for extended emission. We describe our self-consistent method for determining the completeness of the sample, and present an estimate of the global Ly α luminosity function between redshifts 2.91 < z < 6.64 using the 1/Vmax estimator. We find that the luminosity function is higher than many number densities reported in the literature by a factor of 2-3, although our result is consistent at the 1σ level with most of these studies. Our observed luminosity function is also in good agreement with predictions from semi-analytic models, and shows no evidence for strong evolution between the high- and low-redshift halves of the data. We demonstrate that one's approach to Ly α flux estimation does alter the observed luminosity function, and caution that accurate flux assessments will be crucial in measurements of the faint-end slope. This is a pilot study for the Ly α luminosity function in the MUSE deep-fields, to be built on with data from the Hubble Ultra Deep Field that will increase the size of our sample by almost a factor of 10.

Stellar mass buildup in galaxies in the first 1.5 Gyr of the universe

NASA Astrophysics Data System (ADS)

Gonzalez, Valentino

In this thesis we have made extensive use of the deepest optical and infrared images currently available from the Hubble Space Telescope (HST) and the Spitzer Space Telescope to study the properties of the stellar populations and the stellar mass buildup in galaxies in the first 1.5 Gyr after the Big Bang. The star formation Rates (SFRs) estimated for LBGs at z ≳ 4 are generally in the range 1 -- 100 M⊙ yr--1. The stellar mass estimates are most robust for sources with good Spitzer/IRAC detections, corresponding to galaxies with stellar masses ≳ 108.5 M⊙ at z ˜ 4 ( ≳ 109.5 M⊙ at z ˜ 7). For sources with lower rest-frame optical luminosities, that, as a result, are individually undetected in IRAC, their average stellar masses have been studied in a stacking analysis of a large number of sources. This enables us to reach stellar masses ˜ 10 7.8 M⊙ at z ˜ 4. The stellar masses show a fairly tight correlation with UV luminosity or SFR, and the zeropoint of the relation does not seem to evolve strongly with redshift. We have taken advantage of the UV luminosity vs. stellar mass relation observed in LBGs at z ≳ 4 -- 7 to derive the stellar mass function (SMF) of galaxies at these redshifts. The method uses a combination of the UV LF and the mean UV vs. stellar mass relation (including the scatter, estimated to be ˜ 0.5 dex at bright luminosities at z ˜ 4). This method allows an analytic estimate of the low mass slope of the SMF. This slope (the power-law exponent of the SMF at low masses), is estimated to be in the --1.44 -- --1.55, range which is flatter than the UV LF faint end slope at these redshifts ( ≲ --1.74). This means that low mass systems contribute less to the total stellar mass density (SMD) of the Universe than would have been estimated assuming a constant mass-to-UV-light ratio. We show that this is also much flatter than the theoretical predictions from simulations, which generally over-predict the number density of low mass systems at these redshifts. The UV luminosity vs. stellar mass relation indicates only a small variation of the mass-to-light ratio as a function of UV luminosity. This is confirmed in a stacking analysis of a large number of sources from the HUDF and the Early Release Science fields (˜ 400 z ˜ 4, ˜ 120 z ˜ 5, ˜ 60 z ˜ 6, 36 at z ˜ 7). Interestingly, the stacked SEDs at z ≳ 5 in the rest-frame optical shows a color [3.6] -- [4.5] ˜ 0.3 mag. This color is hard to reproduce by synthetic stellar population models that only include stellar continua, and it probably indicates the presence of moderately strong emission lines (Halpha EWrest ˜ 300 A). The contribution from such emission lines in the IRAC fluxes indicates that the stellar masses and ages could both be over-estimated by a factor ˜ 2. One of the most interesting results presented in this thesis is the apparent plateau of the specific SFR (sSFR = SFR / stellar mass). In early results, the similarity in the SEDs of galaxies at a given UV luminosity in the z ˜ 4 -- 7 redshift range resulted in very similar estimates of the SFR and stellar masses of these galaxies. Furthermore, we find that the reported sSFR estimates at z ˜ 2 are also very similar to the ones in the z ˜ 4 -- 7 redshift range (˜ 2 Gyr--1 for ˜ 5 x 109 M⊙ galaxies). A puzzle arises from the fact that the dark matter accretion rate onto halos is predicted to decrease monotonically and rather fast as a function of cosmic time (approximately ∝ (1 + z) 2.5). If gas and star formation follow the inflow of dark matter, the sSFR at a constant mass should also decrease monotonically with time, which is contrary to the indication from these observations. When we include the possible effects of emission lines, the stellar masses decrease by a factor ˜ 2x at z ≳ 5. The revised stellar masses may favor a slowly rising sSFR at z ≳ 2, but the rise as a function of redshift is still much slower (sSFR(z) ∝ (1 + z)0.7) than that of specific dark matter accretion rate. This suggests that the stellar mass buildup is somehow decoupled from the dark matter buildup at early times. (Abstract shortened by UMI.)

THE INTERMEDIATE LUMINOSITY OPTICAL TRANSIENT SN 2010DA: THE PROGENITOR, ERUPTION, AND AFTERMATH OF A PECULIAR SUPERGIANT HIGH-MASS X-RAY BINARY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Villar, V. A.; Berger, E.; Blanchard, P. K.

We present optical spectroscopy, ultraviolet-to-infrared imaging, and X-ray observations of the intermediate luminosity optical transient (ILOT) SN 2010da in NGC 300 ( d = 1.86 Mpc) spanning from −6 to +6 years relative to the time of outburst in 2010. Based on the light-curve and multi-epoch spectral energy distributions of SN 2010da, we conclude that the progenitor of SN 2010da is a ≈10–12 M {sub ⊙} yellow supergiant possibly transitioning into a blue-loop phase. During outburst, SN 2010da had a peak absolute magnitude of M {sub bol} ≲ −10.4 mag, dimmer than other ILOTs and supernova impostors. We detect multi-componentmore » hydrogen Balmer, Paschen, and Ca ii emission lines in our high-resolution spectra, which indicate a dusty and complex circumstellar environment. Since the 2010 eruption, the star has brightened by a factor of ≈5 and remains highly variable in the optical. Furthermore, we detect SN 2010da in archival Swift and Chandra observations as an ultraluminous X-ray source ( L {sub X} ≈ 6 × 10{sup 39} erg s{sup −1}). We additionally attribute He ii 4686 Å and coronal Fe emission lines in addition to a steady X-ray luminosity of ≈10{sup 37} erg s{sup −1} to the presence of a compact companion.« less

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

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gnedin, Nickolay Y.

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

Does the evolution of the radio luminosity function of star-forming galaxies match that of the star formation rate function?

NASA Astrophysics Data System (ADS)

Bonato, Matteo; Negrello, Mattia; Mancuso, Claudia; De Zotti, Gianfranco; Ciliegi, Paolo; Cai, Zhen-Yi; Lapi, Andrea; Massardi, Marcella; Bonaldi, Anna; Sajina, Anna; Smolčić, Vernesa; Schinnerer, Eva

2017-08-01

The assessment of the relationship between radio continuum luminosity and star formation rate (SFR) is of crucial importance to make reliable predictions for the forthcoming ultra-deep radio surveys and to allow a full exploitation of their results to measure the cosmic star formation history. We have addressed this issue by matching recent accurate determinations of the SFR function up to high redshifts with literature estimates of the 1.4 GHz luminosity functions of star-forming galaxies (SFGs). This was done considering two options, proposed in the literature, for the relationship between the synchrotron emission (Lsynch), that dominates at 1.4 GHz, and the SFR: a linear relation with a decline of the Lsynch/SFR ratio at low luminosities or a mildly non-linear relation at all luminosities. In both cases, we get good agreement with the observed radio luminosity functions but, in the non-linear case, the deviation from linearity must be small. The luminosity function data are consistent with a moderate increase of the Lsynch/SFR ratio with increasing redshift, indicated by other data sets, although a constant ratio cannot be ruled out. A stronger indication of such increase is provided by recent deep 1.4-GHz counts, down to μJy levels. This is in contradiction with models predicting a decrease of that ratio due to inverse Compton cooling of relativistic electrons at high redshifts. Synchrotron losses appear to dominate up to z ≃ 5. We have also updated the Massardi et al. evolutionary model for radio loud AGNs.

Obscured Active Galactic Nuclei in Luminous Infrared Galaxies

NASA Astrophysics Data System (ADS)

Shier, L. M.; Rieke, M. J.; Rieke, G. H.

1996-10-01

We examine the nature of the central power source in very luminous infrared galaxies. The infrared properties of the galaxies, including their far-infrared and 2.2 micron fluxes, CO indices, and Brackett line fluxes are compared to models of starburst stellar populations. Among seven galaxies we found two dominated by emission from young stars, two dominated by emission from an AGN, and three transition cases. Our results are consistent with evidence for active nuclei in the same galaxies at other wavelengths. Nuclear mass measurements obtained for the galaxies indicate an initial mass function biased toward high-mass stars in two galaxies. After demonstrating our methods in well-studied galaxies, we define complete samples of high luminosity and ultraluminous galaxies. We find that the space density of embedded and unembedded quasars in the local universe is similar for objects of similar luminosity. If quasars evolve from embedded sources to optically prominent objects, it appears that the lifetime of a quasar is no more than about 108 yr.

The Short Bursts in SGR 1806-20, 1E 1048-5937, and SGR 0501+4516

NASA Astrophysics Data System (ADS)

Qu, Zhijie; Li, Zhaosheng; Chen, Yupeng; Dai, Shi; Ji, Long; Xu, Renxin; Zhang, Shu

2015-03-01

We analyzed temporal and spectral properties, focusing on the short bursts, for three anomalous X-ray pulsars (AXPs) and soft gamma repeaters (SGRs), including SGR 1806-20, 1E 1048-5937 and SGR 0501+4516. Using the data from XMM-Newton, we located the short bursts by Bayesian blocks algorithm. The short bursts' duration distributions for three sources were fitted by two lognormal functions. The spectra of shorter bursts ($< 0.2~\\rm s$) and longer bursts ($\\geq 0.2~\\rm s$) can be well fitted in two blackbody components model or optically thin thermal bremsstrahlung model for SGR 0501+4516. We also found that there is a positive correlation between the burst luminosity and the persistent luminosity with a power law index $\\gamma = 1.23 \\pm 0.18 $. The energy ratio of this persistent emission to the time averaged short bursts is in the range of $10 - 10^3$, being comparable to the case in Type I X-ray burst.

The X-ray cluster Abell 744

NASA Technical Reports Server (NTRS)

Kurtz, M. J.; Huchra, J. P.; Beers, T. C.; Geller, M. J.; Gioia, I. M.

1985-01-01

X-ray and optical observations of the cluster of galaxies Abell 744 are presented. The X-ray flux (assuming H(0) = 100 km/s per Mpc) is about 9 x 10 to the 42nd erg/s. The X-ray source is extended, but shows no other structure. Photographic photometry (in Kron-Cousins R), calibrated by deep CCD frames, is presented for all galaxies brighter than 19th magnitude within 0.75 Mpc of the cluster center. The luminosity function is normal, and the isopleths show little evidence of substructure near the cluster center. The cluster has a dominant central galaxy, which is classified as a normal brightest-cluster elliptical on the basis of its luminosity profile. New redshifts were obtained for 26 galaxies in the vicinity of the cluster center; 20 appear to be cluster members. The spatial distribution of redshifts is peculiar; the dispersion within the 150 kpc core radius is much greater than outside. Abell 744 is similar to the nearby cluster Abell 1060.

The formation of bulges and black holes: lessons from a census of active galaxies in the SDSS.

PubMed

Kauffmann, Guinevere; Heckman, Timothy M

2005-03-15

We examine the relationship between galaxies, supermassive black holes and AGN using a sample of 23,000 narrow-emission-line ('type 2') active galactic nuclei (AGN) drawn from a sample of 123,000 galaxies from the Sloan Digital Sky Survey. We have studied how AGN host properties compare with those of normal galaxies and how they depend on the luminosity of the active nucleus. We find that AGN reside in massive galaxies and have distributions of sizes and concentrations that are similar to those of the early-type galaxies in our sample. The host galaxies of low-luminosity AGN have stellar populations similar to normal early types. The hosts of high- luminosity AGN have much younger mean stellar ages, and a significant fraction have experienced recent starbursts. High-luminosity AGN are also found in lower-density environments. We then use the stellar velocity dispersions of the AGN hosts to estimate black hole masses and their [OIII]lambda5007 emission-line luminosities to estimate black hole accretion rates. We find that the volume averaged ratio of star formation to black hole accretion is approximately 1000 for the bulge-dominated galaxies in our sample. This is remarkably similar to the observed ratio of stellar mass to black hole mass in nearby bulges. Most of the present-day black hole growth is occurring in black holes with masses less than 3 x 10(7)M(3). Our estimated accretion rates imply that low-mass black holes are growing on a time-scale that is comparable with the age of the Universe. Around 50% this growth takes place in AGN that are radiating within a factor of five of the Eddington luminosity. Such systems are rare, making up only 0.2% of the low-mass black hole population at the present day. The remaining growth occurs in lower luminosity AGN. The growth time-scale increases by more than an order of magnitude for the most massive black holes in our sample. We conclude that the evolution of the AGN luminosity function documented in recent optical and X-ray surveys is driven by a decrease in the characteristic mass scale of actively accreting black holes.

LEO P: AN UNQUENCHED VERY LOW-MASS GALAXY

DOE Office of Scientific and Technical Information (OSTI.GOV)

McQuinn, Kristen B. W.; Skillman, Evan D.; Berg, Danielle

Leo P is a low-luminosity dwarf galaxy discovered through the blind H i Arecibo Legacy Fast ALFA survey. The H i and follow-up optical observations have shown that Leo P is a gas-rich dwarf galaxy with active star formation, an underlying older population, and an extremely low oxygen abundance. We have obtained optical imaging with the Hubble Space Telescope to two magnitudes below the red clump in order to study the evolution of Leo P. We refine the distance measurement to Leo P to be 1.62 ± 0.15 Mpc, based on the luminosity of the horizontal branch stars and 10more » newly identified RR Lyrae candidates. This places the galaxy at the edge of the Local Group, ∼0.4 Mpc from Sextans B, the nearest galaxy in the NGC 3109 association of dwarf galaxies of which Leo P is clearly a member. The star responsible for ionizing the H ii region is most likely an O7V or O8V spectral type, with a stellar mass ≳25 M{sub ⊙}. The presence of this star provides observational evidence that massive stars at the upper end of the initial mass function are capable of being formed at star formation rates as low as ∼10{sup −5} M{sub ⊙} yr{sup −1}. The best-fitting star formation history (SFH) derived from the resolved stellar populations of Leo P using the latest PARSEC models shows a relatively constant star formation rate over the lifetime of the galaxy. The modeled luminosity characteristics of Leo P at early times are consistent with low-luminosity dSph Milky Way satellites, suggesting that Leo P is what a low-mass dSph would look like if it evolved in isolation and retained its gas. Despite the very low mass of Leo P, the imprint of reionization on its SFH is subtle at best, and consistent with being totally negligible. The isolation of Leo P, and the total quenching of star formation of Milky Way satellites of similar mass, implies that the local environment dominates the quenching of the Milky Way satellites.« less

Local Luminosity Function at 15 micro m and Galaxy Evolution Seen by ISOCAM 15 micro m Surveys

NASA Technical Reports Server (NTRS)

Xu, C.

2000-01-01

A local luminosity function at 15 micro m is derived using the bivariate (15 micro m vs. 60 micro m luminosities) method, based on the newly published ISOCAM LW3-band (15 micro m) survey of the very deep IRAS 60 micro m sample in the north ecliptic pole region (NEPR).

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.

RX J1548.9+0851, a fossil cluster?

NASA Astrophysics Data System (ADS)

Eigenthaler, P.; Zeilinger, W. W.

2012-04-01

Context. Fossil galaxy groups are spatially extended X-ray sources with X-ray luminosities above L{X, bol ≥ 1042 h50-2} erg s-1 and a central elliptical galaxy dominating the optical, the second-brightest galaxy being at least 2 mag fainter in the R band. Whether these systems are a distinct class of objects resulting from exceptional formation and evolution histories is still unclear, mainly due to the small number of objects studied so far, mostly lacking spectroscopy of group members for group membership confirmation and a detailed kinematical analysis. Aims: To complement the scarce sample of spectroscopically studied fossils down to their faint galaxy populations, the fossil candidate RX J1548.9+0851 (z = 0.072) is studied in this work. Our results are compared with existing data from fossils in the literature. Methods: We use ESO VLT VIMOS multi-object spectroscopy to determine redshifts of the faint galaxy population and study the luminosity-weighted dynamics and luminosity function of the system. The full-spectrum fitting package ULySS is used to determine ages and metallicities of group members. VIMOS imaging data are used to study the morphology of the central elliptical. Results: We identify 40 group members spectroscopically within the central 300 kpc of the system and find 31 additional redshifts from the literature, resulting in a total number of 54 spectroscopically confirmed group members within 1 Mpc. RX J1548.9+0851 is made up of two bright ellipticals in the central region with a magnitude gap of Δm1,2 = 1.34 in the SDSS r' band leaving the definition of RX J1548.9+0851 being a fossil to the assumption of the virial radius. We find a luminosity-weighted velocity dispersion of 568 km s-1 and a mass of 2.5 × 1014 M⊙ for the system confirming previous studies that revealed fossils to be massive. An average mass-to-light ratio of M/L 400 M⊙/L⊙ is derived from the SDSS g', r', and i' bands. The central elliptical is well-fitted by a pure deVaucouleurs r1/4 law without a cD envelope. Symmetric shells are revealed along the major axis of the galaxy indicating a recent minor merger. RX J1548.9+0851 shows a steep, increasing luminosity function with a faint-end slope of α = -1.4 ± 0.1. Satellite galaxies show a clear spatial segregation with respect to their stellar populations - objects with old stars are confined to an elongated, central distribution aligned with the major axis of the central elliptical. Conclusions: Although RX J1548.9+0851 shows similar properties compared to other fossils studied recently, it might not be a fossil at all, being dominated by 2 bright central ellipticals. Comparing RX J1548.9+0851 with scaling relations from ordinary poor groups and clusters confirm the idea that fossils might simply be normal clusters with the richness and optical luminosity of poor groups.

The Extremely Luminous Quasar Survey (ELQS) in SDSS and the high-z bright-end Quasar Luminosity Function

NASA Astrophysics Data System (ADS)

Schindler, Jan-Torge; Fan, Xiaohui; McGreer, Ian

2018-01-01

Studies of the most luminous quasars at high redshift directly probe the evolution of the most massive black holes in the early Universe and their connection to massive galaxy formation. Unfortunately, extremely luminous quasars at high redshift are very rare objects. Only wide area surveys have a chance to constrain their population. The Sloan Digital Sky Survey (SDSS) nd the Baryon Oscillation Spectroscopic Survey (BOSS) have so far provided the most widely adopted measurements of the type I quasar luminosity function (QLF) at z>3. However, a careful re-examination of the SDSS quasar sample revealed that the SDSS quasar selection is in fact missing a significant fraction of $z~3$ quasars at the brightest end.We have identified the purely optical color selection of SDSS, where quasars at these redshifts are strongly contaminated by late-type dwarfs, and the spectroscopic incompleteness of the SDSS footprint as the main reasons. Therefore we have designed the Extremely Luminous Quasar Survey (ELQS), based on a novel near-infrared JKW2 color cut using WISE AllWISE and 2MASS all-sky photometry, to yield high completeness for very bright (i < 18.0) quasars in the redshift range of 2.8<= z<=5.0. It effectively uses Random Forest machine-learning algorithms on SDSS and WISE photometry for quasar-star classification and photometric redshift estimation.The ELQS is spectroscopically following up ~230 new quasar candidates in an area of ~12000 deg2 in the SDSS footprint, to obtain a well-defined and complete quasar sample for an accurate measurement of the bright-end quasar luminosity function (QLF) at 2.8<= z<=5.0. So far the ELQS has identified 75 bright new quasars in this redshift range and observations of the fall sky will continue until the end of the year. At the AAS winter meeting we will present the full spectroscopic results of the survey, including a re-estimation and extension of the high-z QLF toward higher luminosities.

THE XMM-NEWTON WIDE-FIELD SURVEY IN THE COSMOS FIELD (XMM-COSMOS): DEMOGRAPHY AND MULTIWAVELENGTH PROPERTIES OF OBSCURED AND UNOBSCURED LUMINOUS ACTIVE GALACTIC NUCLEI

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brusa, M.; Cappelluti, N.; Merloni, A.

2010-06-10

We report the final optical identifications of the medium-depth ({approx}60 ks), contiguous (2 deg{sup 2}) XMM-Newton survey of the COSMOS field. XMM-Newton has detected {approx}1800 X-ray sources down to limiting fluxes of {approx}5 x 10{sup -16}, {approx}3 x 10{sup -15}, and {approx}7 x 10{sup -15} erg cm{sup -2} s{sup -1} in the 0.5-2 keV, 2-10 keV, and 5-10 keV bands, respectively ({approx}1 x 10{sup -15}, {approx}6 x 10{sup -15}, and {approx}1 x 10{sup -14} erg cm{sup -2} s{sup -1}, in the three bands, respectively, over 50% of the area). The work is complemented by an extensive collection of multiwavelength datamore » from 24 {mu}m to UV, available from the COSMOS survey, for each of the X-ray sources, including spectroscopic redshifts for {approx}>50% of the sample, and high-quality photometric redshifts for the rest. The XMM and multiwavelength flux limits are well matched: 1760 (98%) of the X-ray sources have optical counterparts, 1711 ({approx}95%) have IRAC counterparts, and 1394 ({approx}78%) have MIPS 24 {mu}m detections. Thanks to the redshift completeness (almost 100%) we were able to constrain the high-luminosity tail of the X-ray luminosity function confirming that the peak of the number density of log L{sub X} > 44.5 active galactic nuclei (AGNs) is at z {approx} 2. Spectroscopically identified obscured and unobscured AGNs, as well as normal and star-forming galaxies, present well-defined optical and infrared properties. We devised a robust method to identify a sample of {approx}150 high-redshift (z > 1), obscured AGN candidates for which optical spectroscopy is not available. We were able to determine that the fraction of the obscured AGN population at the highest (L{sub X} > 10{sup 44} erg s{sup -1}) X-ray luminosity is {approx}15%-30% when selection effects are taken into account, providing an important observational constraint for X-ray background synthesis. We studied in detail the optical spectrum and the overall spectral energy distribution of a prototypical Type 2 QSO, caught in a stage transitioning from being starburst dominated to AGN dominated, which was possible to isolate only thanks to the combination of X-ray and infrared observations.« less

An order statistics approach to the halo model for galaxies

NASA Astrophysics Data System (ADS)

Paul, Niladri; Paranjape, Aseem; Sheth, Ravi K.

2017-04-01

We use the halo model to explore the implications of assuming that galaxy luminosities in groups are randomly drawn from an underlying luminosity function. We show that even the simplest of such order statistics models - one in which this luminosity function p(L) is universal - naturally produces a number of features associated with previous analyses based on the 'central plus Poisson satellites' hypothesis. These include the monotonic relation of mean central luminosity with halo mass, the lognormal distribution around this mean and the tight relation between the central and satellite mass scales. In stark contrast to observations of galaxy clustering; however, this model predicts no luminosity dependence of large-scale clustering. We then show that an extended version of this model, based on the order statistics of a halo mass dependent luminosity function p(L|m), is in much better agreement with the clustering data as well as satellite luminosities, but systematically underpredicts central luminosities. This brings into focus the idea that central galaxies constitute a distinct population that is affected by different physical processes than are the satellites. We model this physical difference as a statistical brightening of the central luminosities, over and above the order statistics prediction. The magnitude gap between the brightest and second brightest group galaxy is predicted as a by-product, and is also in good agreement with observations. We propose that this order statistics framework provides a useful language in which to compare the halo model for galaxies with more physically motivated galaxy formation models.

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

NASA Technical Reports Server (NTRS)

Chokshi, Arati; Lonsdale, Carol J.; Mazzei, Paola; De Zotti, Gianfranco

1994-01-01

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

A possible width-luminosity correlation of the Ca II K1 and Mg II k1 features. [of stellar atmospheres

NASA Technical Reports Server (NTRS)

Ayres, T. R.; Shine, R. A.; Linsky, J. L.

1975-01-01

Existing high resolution stellar profiles of the Ca II and Mg II resonance lines suggest a possible width-luminosity correlation of the K1 minimum features. It is shown that such a correlation can be simply understood if the continuum optical depth of the stellar temperature minimum is relatively independent of surface gravity as suggested by three stars studied in detail.

Constraints on submicrojansky radio number counts based on evolving VLA-COSMOS luminosity functions

NASA Astrophysics Data System (ADS)

Novak, M.; Smolčić, V.; Schinnerer, E.; Zamorani, G.; Delvecchio, I.; Bondi, M.; Delhaize, J.

2018-06-01

We present an investigation of radio luminosity functions (LFs) and number counts based on the Karl G. Jansky Very Large Array-COSMOS 3 GHz Large Project. The radio-selected sample of 7826 galaxies with robust optical/near-infrared counterparts with excellent photometric coverage allows us to construct the total radio LF since z 5.7. Using the Markov chain Monte Carlo algorithm, we fit the redshift dependent pure luminosity evolution model to the data and compare it with previously published VLA-COSMOS LFs obtained on individual populations of radio-selected star-forming galaxies and galaxies hosting active galactic nuclei classified on the basis of presence or absence of a radio excess with respect to the star-formation rates derived from the infrared emission. We find they are in excellent agreement, thus showing the reliability of the radio excess method in selecting these two galaxy populations at radio wavelengths. We study radio number counts down to submicrojansky levels drawn from different models of evolving LFs. We show that our evolving LFs are able to reproduce the observed radio sky brightness, even though we rely on extrapolations toward the faint end. Our results also imply that no new radio-emitting galaxy population is present below 1 μJy. Our work suggests that selecting galaxies with radio flux densities between 0.1 and 10 μJy will yield a star-forming galaxy in 90-95% of the cases with a high percentage of these galaxies existing around a redshift of z 2, thus providing useful constraints for planned surveys with the Square Kilometer Array and its precursors.

Particle content, radio-galaxy morphology, and jet power: all radio-loud AGN are not equal

NASA Astrophysics Data System (ADS)

Croston, J. H.; Ineson, J.; Hardcastle, M. J.

2018-05-01

Ongoing and future radio surveys aim to trace the evolution of black hole growth and feedback from active galactic nuclei (AGNs) throughout cosmic time; however, there remain major uncertainties in translating radio luminosity functions into a reliable assessment of the energy input as a function of galaxy and/or dark matter halo mass. A crucial and long-standing problem is the composition of the radio-lobe plasma that traces AGN jet activity. In this paper, we carry out a systematic comparison of the plasma conditions in Fanaroff & Riley class I and II radio galaxies to demonstrate conclusively that their internal composition is systematically different. This difference is best explained by the presence of an energetically dominant proton population in the FRI, but not the FRII radio galaxies. We show that, as expected from this systematic difference in particle content, radio morphology also affects the jet-power/radio-luminosity relationship, with FRII radio galaxies having a significantly lower ratio of jet power to radio luminosity than the FRI cluster radio sources used to derive jet-power scaling relations via X-ray cavity measurements. Finally, we also demonstrate conclusively that lobe composition is unconnected to accretion mode (optical excitation class): the internal conditions of low- and high-excitation FRII radio lobes are indistinguishable. We conclude that inferences of population-wide AGN impact require careful assessment of the contribution of different jet subclasses, particularly given the increased diversity of jet evolutionary states expected to be present in deep, low-frequency radio surveys such as the LOFAR Two-Metre Sky Survey.

Theoretical Models of Optical Transients. I. A Broad Exploration of the Duration-Luminosity Phase Space

NASA Astrophysics Data System (ADS)

Villar, V. Ashley; Berger, Edo; Metzger, Brian D.; Guillochon, James

2017-11-01

The duration-luminosity phase space (DLPS) of optical transients is used, mostly heuristically, to compare various classes of transient events, to explore the origin of new transients, and to influence optical survey observing strategies. For example, several observational searches have been guided by intriguing voids and gaps in this phase space. However, we should ask, do we expect to find transients in these voids given our understanding of the various heating sources operating in astrophysical transients? In this work, we explore a broad range of theoretical models and empirical relations to generate optical light curves and to populate the DLPS. We explore transients powered by adiabatic expansion, radioactive decay, magnetar spin-down, and circumstellar interaction. For each heating source, we provide a concise summary of the basic physical processes, a physically motivated choice of model parameter ranges, an overall summary of the resulting light curves and their occupied range in the DLPS, and how the various model input parameters affect the light curves. We specifically explore the key voids discussed in the literature: the intermediate-luminosity gap between classical novae and supernovae, and short-duration transients (≲ 10 days). We find that few physical models lead to transients that occupy these voids. Moreover, we find that only relativistic expansion can produce fast and luminous transients, while for all other heating sources events with durations ≲ 10 days are dim ({M}{{R}}≳ -15 mag). Finally, we explore the detection potential of optical surveys (e.g., Large Synoptic Survey Telescope) in the DLPS and quantify the notion that short-duration and dim transients are exponentially more difficult to discover in untargeted surveys.

Composite Spectral Energy Distributions and Infrared-Optical Colors of Type 1 and Type 2 Quasars

NASA Astrophysics Data System (ADS)

Hickox, Ryan C.; Myers, Adam D.; Greene, Jenny E.; Hainline, Kevin N.; Zakamska, Nadia L.; DiPompeo, Michael A.

2017-11-01

We present observed mid-infrared and optical colors and composite spectral energy distributions (SEDs) of type 1 (broad-line) and 2 (narrow-line) quasars selected from Sloan Digital Sky Survey (SDSS) spectroscopy. A significant fraction of powerful quasars are obscured by dust and are difficult to detect in optical photometric or spectroscopic surveys. However, these may be more easily identified on the basis of mid-infrared (MIR) colors and SEDs. Using samples of SDSS type 1 and 2 matched in redshift and [O III] luminosity, we produce composite rest-frame 0.2-15 μm SEDs based on SDSS, UKIDSS, and Wide-field Infrared Survey Explorer photometry and perform model fits using simple galaxy and quasar SED templates. The SEDs of type 1 and 2 quasars are remarkably similar, with the differences explained primarily by the extinction of the quasar component in the type 2 systems. For both types of quasar, the flux of the active galactic nucleus (AGN) relative to the host galaxy increases with AGN luminosity ({L}[{{O}{{III}}]}) and redder observed MIR color, but we find only weak dependencies of the composite SEDs on mechanical jet power as determined through radio luminosity. We conclude that luminous quasars can be effectively selected using simple MIR color criteria similar to those identified previously ({{W}}1{--}{{W}}2> 0.7; Vega), although these criteria miss many heavily obscured objects. Obscured quasars can be further identified based on optical-IR colors (for example, (u{--}{{W}}3 [{AB}])> 1.4({{W}}1{--}{{W}}2 [{Vega}])+3.2). These results illustrate the power of large statistical studies of obscured quasars selected on the basis of MIR and optical photometry.

"A Richness Study of 14 Distant X-Ray Clusters from the 160 Square Degree Survey"

NASA Technical Reports Server (NTRS)

Jones, Christine; West, Donald (Technical Monitor)

2001-01-01

We have measured the surface density of galaxies toward 14 X-ray-selected cluster candidates at redshifts z(sub i) 0.46, and we show that they are associated with rich galaxy concentrations. These clusters, having X-ray luminosities of Lx(0.5-2 keV) approx. (0.5 - 2.6) x 10(exp 44) ergs/ sec are among the most distant and luminous in our 160 deg(exp 2) ROSAT Position Sensitive Proportional Counter cluster survey. We find that the clusters range between Abell richness classes 0 and 2 and have a most probable richness class of 1. We compare the richness distribution of our distant clusters to those for three samples of nearby clusters with similar X-ray luminosities. We find that the nearby and distant samples have similar richness distributions, which shows that clusters have apparently not evolved substantially in richness since redshift z=0.5. There is, however, a marginal tendency for the distant clusters to be slightly poorer than nearby clusters, although deeper multicolor data for a large sample would be required to confirm this trend. We compare the distribution of distant X-ray clusters in the L(sub X)-richness plane to the distribution of optically selected clusters from the Palomar Distant Cluster Survey. The optically selected clusters appear overly rich for their X-ray luminosities, when compared to X-ray-selected clusters. Apparently, X-ray and optical surveys do not necessarily sample identical mass concentrations at large redshifts. This may indicate the existence of a population of optically rich clusters with anomalously low X-ray emission, More likely, however, it reflects the tendency for optical surveys to select unvirialized mass concentrations, as might be expected when peering along large-scale filaments.

Internal kinematics of disk galaxies in the local universe

NASA Astrophysics Data System (ADS)

Catinella, Barbara

2005-11-01

This dissertation makes use of a homogeneous sample of several thousand normal, non-interacting, spiral galaxies, for which I-band photometry and optical and/ or radio spectroscopy are available, to investigate the average kinematic properties of disk systems at low redshifts ( z [Special characters omitted.] 0.1). New long-slit Ha rotation curves (RCs) for 402 galaxies, which were incorporated into the larger sample, are presented in this work. The main goals of this thesis are: (a) The definition of a set of average, or template , RCs in bins covering a wide range of galaxy luminosity. The template relations represent an accurate description of the average circular velocity field of local spiral galaxies, and are intended to be a standard reference for more distant samples and to constrain theoretical models of galactic disks. (b) The characterization of the systematics associated with different velocity width measurement techniques, and the derivation of a robust measure of rotational velocity to be used for applications of the Tully-Fisher (TF) distance method. A direct cross-calibration of the optical and radio widths has been obtained. (c) The assessment of the impact of the limitations on optical line widths extracted from fixed apertures, such as those being collected for ~10 6 galaxies by the on-going Sloan Digital Sky Survey (SDSS). Since the SDSS fiber technique generally does not sample the full extent of a galaxy RC, the observed line widths yield rotational width measurements that depend on the redshifts of the objects, on the physical sizes of their line-emitting regions, and on the intrinsic shapes of their RCs. Numerical simulations of these biases have been carried out for galaxies with realistic circular velocity fields (described by the template RCs) in the redshift range covered by the SDSS spectroscopic sample. Statistical corrections to be applied to the aperture line widths as a function of galaxy redshift and luminosity have been derived, and their impact on the TF relation examined. The use of the SDSS line widths, corrected for aperture effects, has the potential to solve the debated issue of luminosity evolution of galaxies at intermediate redshifts.

A Multi-color Optical Survey of the Orion Nebula Cluster. II. The H-R Diagram

NASA Astrophysics Data System (ADS)

Da Rio, N.; Robberto, M.; Soderblom, D. R.; Panagia, N.; Hillenbrand, L. A.; Palla, F.; Stassun, K. G.

2010-10-01

We present a new analysis of the stellar population of the Orion Nebula Cluster (ONC) based on multi-band optical photometry and spectroscopy. We study the color-color diagrams in BVI, plus a narrowband filter centered at 6200 Å, finding evidence that intrinsic color scales valid for main-sequence dwarfs are incompatible with the ONC in the M spectral-type range, while a better agreement is found employing intrinsic colors derived from synthetic photometry, constraining the surface gravity value as predicted by a pre-main-sequence isochrone. We refine these model colors even further, empirically, by comparison with a selected sample of ONC stars with no accretion and no extinction. We consider the stars with known spectral types from the literature, and extend this sample with the addition of 65 newly classified stars from slit spectroscopy and 182 M-type from narrowband photometry; in this way, we isolate a sample of about 1000 stars with known spectral type. We introduce a new method to self-consistently derive the stellar reddening and the optical excess due to accretion from the location of each star in the BVI color-color diagram. This enables us to accurately determine the extinction of the ONC members, together with an estimate of their accretion luminosities. We adopt a lower distance for the Orion Nebula than previously assumed, based on recent parallax measurements. With a careful choice of also the spectral-type-temperature transformation, we produce the new Hertzsprung-Russell diagram of the ONC population, more populated than previous works. With respect to previous works, we find higher luminosity for late-type stars and a slightly lower luminosity for early types. We determine the age distribution of the population, peaking from ~2 to ~3 Myr depending on the model. We study the distribution of the members in the mass-age plane and find that taking into account selection effects due to incompleteness, removes an apparent correlation between mass and age. We derive the initial mass function for low- and intermediate-mass members of the ONC, which turns out to be model dependent and shows a turnover at M <~ 0.2 M sun.

Thermal winds in stellar mass black hole and neutron star binary systems

NASA Astrophysics Data System (ADS)

Done, Chris; Tomaru, Ryota; Takahashi, Tadayuki

2018-01-01

Black hole binaries show equatorial disc winds at high luminosities, which apparently disappear during the spectral transition to the low/hard state. This is also where the radio jet appears, motivating speculation that both wind and jet are driven by different configurations of the same magnetic field. However, these systems must also have thermal winds, as the outer disc is clearly irradiated. We develop a predictive model of the absorption features from thermal winds, based on pioneering work of Begelman, McKee & Shields. We couple this to a realistic model of the irradiating spectrum as a function of luminosity to predict the entire wind evolution during outbursts. We show that the column density of the thermal wind scales roughly with luminosity, and does not shut off at the spectral transition, though its visibility will be affected by the abrupt change in ionizing spectrum. We re-analyse the data from H1743-322, which most constrains the difference in wind across the spectral transition, and show that these are consistent with the thermal wind models. We include simple corrections for radiation pressure, which allows stronger winds to be launched from smaller radii. These winds become optically thick around Eddington, which may even explain the exceptional wind seen in one observation of GRO J1655-40. These data can instead be fit by magnetic wind models, but similar winds are not seen in this or other systems at similar luminosities. Hence, we conclude that the majority (perhaps all) of current data can be explained by thermal or thermal-radiative winds.

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.

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.

SN 2012fr: Ultraviolet, Optical, and Near-infrared Light Curves of a Type Ia Supernova Observed within a Day of Explosion

DOE PAGES

Contreras, Carlos; Phillips, M. M.; Burns, Christopher R.; ...

2018-05-18

We present detailed ultraviolet, optical, and near-infrared light curves of the Type Ia supernova (SN) 2012fr, which exploded in the Fornax cluster member NGC 1365. These precise high-cadence light curves provide a dense coverage of the flux evolution from -12 to +140 days with respect to the epoch of B-band maximum (more » $${t}_{{B}_{\\max }}$$). Supplementary imaging at the earliest epochs reveals an initial slow and nearly linear rise in luminosity with a duration of ~2.5 days, followed by a faster rising phase that is well reproduced by an explosion model with a moderate amount of 56 Ni mixing in the ejecta. From our analysis of the light curves, we conclude that: (i) the explosion occurred < 22 hr before the first detection of the supernova, (ii) the rise time to peak bolometric (λ >1800) luminosity was 16.5 ± 0.6 days, (iii) the supernova suffered little or no host-galaxy dust reddening, (iv) the peak luminosity in both the optical and near-infrared was consistent with the bright end of normal Type Ia diversity, and (v) 0.60 ± 0.15 M ⊙ of 56Ni was synthesized in the explosion. Despite its normal luminosity, SN 2012fr displayed unusually prevalent high-velocity Ca ii and Si ii absorption features, and a nearly constant photospheric velocity of the Si ii λ6355 line at ~12,000 km s -1 that began ~5 days before $${t}_{{B}_{\\max }}$$. We also highlight some of the other peculiarities in the early phase photometry and the spectral evolution. SN 2012fr also adds to a growing number of Type Ia supernovae that are hosted by galaxies with direct Cepheid distance measurements.« less

Late Time Multi-wavelength Observations of Swift J1644+5734: A Luminous Optical/IR Bump and Quiescent X-Ray Emission

NASA Astrophysics Data System (ADS)

Levan, A. J.; Tanvir, N. R.; Brown, G. C.; Metzger, B. D.; Page, K. L.; Cenko, S. B.; O'Brien, P. T.; Lyman, J. D.; Wiersema, K.; Stanway, E. R.; Fruchter, A. S.; Perley, D. A.; Bloom, J. S.

2016-03-01

We present late time multi-wavelength observations of Swift J1644+57, suggested to be a relativistic tidal disruption flare (TDF). Our observations extend to >4 years from discovery and show that 1.4 years after outburst the relativistic jet switched off on a timescale less than tens of days, corresponding to a power-law decay faster than t-70. Beyond this point weak X-rays continue to be detected at an approximately constant luminosity of LX ˜ 5 × 1042 erg s-1 and are marginally inconsistent with a continuing decay of t-5/3, similar to that seen prior to the switch-off. Host photometry enables us to infer a black hole mass of MBH = 3 × 106 M⊙, consistent with the late time X-ray luminosity arising from sub-Eddington accretion onto the black hole in the form of either an unusually optically faint active galactic nucleus or a slowly varying phase of the transient. Optical/IR observations show a clear bump in the light curve at timescales of 30-50 days, with a peak magnitude (corrected for host galaxy extinction) of MR ˜ -22 to -23. The luminosity of the bump is significantly higher than seen in other, non-relativistic TDFs and does not match any re-brightening seen at X-ray or radio wavelengths. Its luminosity, light curve shape, and spectrum are broadly similar to those seen in superluminous supervnovae, although subject to large uncertainties in the correction of the significant host extinction. We discuss these observations in the context of both TDF and massive star origins for Swift J1644+5734 and other candidate relativistic tidal flares.

SN 2012fr: Ultraviolet, Optical, and Near-infrared Light Curves of a Type Ia Supernova Observed within a Day of Explosion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Contreras, Carlos; Phillips, M. M.; Burns, Christopher R.

We present detailed ultraviolet, optical, and near-infrared light curves of the Type Ia supernova (SN) 2012fr, which exploded in the Fornax cluster member NGC 1365. These precise high-cadence light curves provide a dense coverage of the flux evolution from -12 to +140 days with respect to the epoch of B-band maximum (more » $${t}_{{B}_{\\max }}$$). Supplementary imaging at the earliest epochs reveals an initial slow and nearly linear rise in luminosity with a duration of ~2.5 days, followed by a faster rising phase that is well reproduced by an explosion model with a moderate amount of 56 Ni mixing in the ejecta. From our analysis of the light curves, we conclude that: (i) the explosion occurred < 22 hr before the first detection of the supernova, (ii) the rise time to peak bolometric (λ >1800) luminosity was 16.5 ± 0.6 days, (iii) the supernova suffered little or no host-galaxy dust reddening, (iv) the peak luminosity in both the optical and near-infrared was consistent with the bright end of normal Type Ia diversity, and (v) 0.60 ± 0.15 M ⊙ of 56Ni was synthesized in the explosion. Despite its normal luminosity, SN 2012fr displayed unusually prevalent high-velocity Ca ii and Si ii absorption features, and a nearly constant photospheric velocity of the Si ii λ6355 line at ~12,000 km s -1 that began ~5 days before $${t}_{{B}_{\\max }}$$. We also highlight some of the other peculiarities in the early phase photometry and the spectral evolution. SN 2012fr also adds to a growing number of Type Ia supernovae that are hosted by galaxies with direct Cepheid distance measurements.« less

Six months of multiwavelength follow-up of the tidal disruption candidate ASASSN-14li and implied TDE rates from ASAS-SN

NASA Astrophysics Data System (ADS)

Holoien, T. W.-S.; Kochanek, C. S.; Prieto, J. L.; Stanek, K. Z.; Dong, Subo; Shappee, B. J.; Grupe, D.; Brown, J. S.; Basu, U.; Beacom, J. F.; Bersier, D.; Brimacombe, J.; Danilet, A. B.; Falco, E.; Guo, Z.; Jose, J.; Herczeg, G. J.; Long, F.; Pojmanski, G.; Simonian, G. V.; Szczygieł, D. M.; Thompson, T. A.; Thorstensen, J. R.; Wagner, R. M.; Woźniak, P. R.

2016-01-01

We present ground-based and Swift photometric and spectroscopic observations of the candidate tidal disruption event (TDE) ASASSN-14li, found at the centre of PGC 043234 (d ≃ 90 Mpc) by the All-Sky Automated Survey for SuperNovae (ASAS-SN). The source had a peak bolometric luminosity of L ≃ 1044 erg s-1 and a total integrated energy of E ≃ 7 × 1050 erg radiated over the ˜6 months of observations presented. The UV/optical emission of the source is well fitted by a blackbody with roughly constant temperature of T ˜ 35 000 K, while the luminosity declines by roughly a factor of 16 over this time. The optical/UV luminosity decline is broadly consistent with an exponential decline, L∝ e^{-t/t_0}, with t0 ≃ 60 d. ASASSN-14li also exhibits soft X-ray emission comparable in luminosity to the optical and UV emission but declining at a slower rate, and the X-ray emission now dominates. Spectra of the source show broad Balmer and helium lines in emission as well as strong blue continuum emission at all epochs. We use the discoveries of ASASSN-14li and ASASSN-14ae to estimate the TDE rate implied by ASAS-SN, finding an average rate of r ≃ 4.1 × 10-5 yr-1 per galaxy with a 90 per cent confidence interval of (2.2-17.0) × 10-5 yr-1 per galaxy. ASAS-SN found roughly 1 TDE for every 70 Type Ia supernovae in 2014, a rate that is much higher than that of other surveys.

Scuss u-Band Emission as a Star-Formation-Rate Indicator

NASA Astrophysics Data System (ADS)

Zhou, Zhimin; Zhou, Xu; Wu, Hong; Fan, Xiao-Hui; Fan, Zhou; Jiang, Zhao-Ji; Jing, Yi-Peng; Li, Cheng; Lesser, Michael; Jiang, Lin-Hua; Ma, Jun; Nie, Jun-Dan; Shen, Shi-Yin; Wang, Jia-Li; Wu, Zhen-Yu; Zhang, Tian-Meng; Zou, Hu

2017-01-01

We present and analyze the possibility of using optical u-band luminosities to estimate star-formation rates (SFRs) of galaxies based on the data from the South Galactic Cap u band Sky Survey (SCUSS), which provides a deep u-band photometric survey covering about 5000 deg2 of the South Galactic Cap. Based on two samples of normal star-forming galaxies selected by the BPT diagram, we explore the correlations between u-band, Hα, and IR luminosities by combing SCUSS data with the Sloan Digital Sky Survey and Wide-field Infrared Survey Explorer (WISE). The attenuation-corrected u-band luminosities are tightly correlated with the Balmer decrement-corrected Hα luminosities with an rms scatter of ˜0.17 dex. The IR-corrected u luminosities are derived based on the correlations between the attenuation of u-band luminosities and WISE 12 (or 22) μm luminosities, and then calibrated with the Balmer-corrected Hα luminosities. The systematic residuals of these calibrations are tested against the physical properties over the ranges covered by our sample objects. We find that the best-fitting nonlinear relations are better than the linear ones and recommended to be applied in the measurement of SFRs. The systematic deviations mainly come from the pollution of old stellar population and the effect of dust extinction; therefore, a more detailed analysis is needed in future work.

Muon collider interaction region design

DOE PAGES

Alexahin, Y. I.; Gianfelice-Wendt, E.; Kashikhin, V. V.; ...

2011-06-02

Design of a muon collider interaction region (IR) presents a number of challenges arising from low β* < 1 cm, correspondingly large beta-function values and beam sizes at IR magnets, as well as the necessity to protect superconducting magnets and collider detectors from muon decay products. As a consequence, the designs of the IR optics, magnets and machine-detector interface are strongly interlaced and iterative. A consistent solution for the 1.5 TeV center-of-mass muon collider IR is presented. It can too provide an average luminosity of 10 34 cm -2s -1 with an adequate protection of magnet and detector components.

The Swift AGN and Cluster Survey

NASA Astrophysics Data System (ADS)

Dai, Xinyu

A key question in astrophysics is to constrain the evolution of the largest gravitationally bound structures in the universe. The serendipitous observations of Swift-XRT form an excellent medium-deep and wide soft X-ray survey, with a sky area of 160 square degrees at the flux limit of 5e-15 erg/s/cm^2. This survey is about an order of magnitude deeper than previous surveys of similar areas, and an order of magnitude wider than previous surveys of similar depth. It is comparable to the planned eROSITA deep survey, but already with the data several years ahead. The unique combination of the survey area and depth enables it to fill in the gap between the deep, pencil beam surveys (such as the Chandra Deep Fields) and the shallow, wide area surveys measured with ROSAT. With it, we will place independent and complementary measurements on the number counts and luminosity functions of X-ray sources. It has been proved that this survey is excellent for X-ray selected galaxy cluster surveys, based on our initial analysis of 1/4 of the fields and other independent studies. The highest priority goal is to produce the largest, uniformly selected catalog of X-ray selected clusters and increase the sample of intermediate to high redshift clusters (z > 0.5) by an order of magnitude. From this catalog, we will study the evolution of cluster number counts, luminosity function, scaling relations, and eventually the mass function. For example, various smaller scale surveys concluded divergently on the evolution of a key scaling relation, between temperature and luminosity of clusters. With the statistical power from this large sample, we will resolve the debate whether clusters evolve self-similarly. This is a crucial step in mapping cluster evolution and constraining cosmological models. First, we propose to extract the complete serendipitous extended source list for all Swift-XRT data to 2015. Second, we will use optical/IR observations to further identify galaxy clusters. These optical/IR observations include data from the SDSS, WISE, and deep optical follow-up observations from the APO, MDM, Magellan, and NOAO telescopes. WISE will confirm all z0.5 clusters. We will use ground-based observations to measure redshifts for z>0.5 clusters, with a focus of measuring 1/10 of the spectroscopic redshifts of z>0.5 clusters within the budget period. Third, we will analyze our deep Suzaku Xray follow-up observations of a sample of medium redshift clusters, and the 1/10 bright Swift clusters suitable for spectral analysis. We will also perform stacking analysis using the Swift data for clusters in different redshift bins to constrain the evolution of cluster properties.

Luminosity Function of Faint Globular Clusters in M87

NASA Astrophysics Data System (ADS)

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

2006-10-01

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.

Clustering, Cosmology and a New Era of Black Hole Demographics: The Conditional Luminosity Function of AGNs

NASA Astrophysics Data System (ADS)

Ballantyne, David R.

2017-01-01

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, we present 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, 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.

NGC 2024: Multi-wavelength Infrared and Radio Observations

NASA Technical Reports Server (NTRS)

Smith, H. A.; Fischer, J.; Geballe, T. R.; Thronson, H. A., Jr.; Johnston, K. J.; Schwartz, P. R.; Wilson, T. L.; Crutcher, R. M.; Henkel, C.; Bieging, J.

1984-01-01

A series of far-infrared maps obtained on the KAO find the total IR luminosity of NGC 2024 is to the 4th power L, and show a peak in flux density and optical depth about 1' south of IRS 2. High resolution spectra of IRS 2 in Brackett alfa and Pfund gamma indicate the presence of an optically thick wind with M approx. 7 x 10 to the minus 7 power M sub yr to minus 1 power, from which we infer that IRS 2 is unable to supply the luminosity observed. A six centimeter continuum map peaks near the location of the far-infrared peak and confirms it as a likely site for a source to provide this luminosity. Maps in HCN, CS, and H2CO show the gas is dense in the direction of the far IR peak. Velocity analysis shows the H2 region created by the far IR source and IRS 2 forms an expanding bubble in front of which the H2CO is seen in absorption, and which is bounded in the south and behind by dense material.

The luminosity function for different morphological types in the CfA Redshift Survey

NASA Technical Reports Server (NTRS)

Marzke, Ronald O.; Geller, Margaret J.; Huchra, John P.; Corwin, Harold G., Jr.

1994-01-01

We derive the luminosity function for different morphological types in the original CfA Redshift Survey (CfA1) and in the first two slices of the CfA Redshift Survey Extension (CfA2). CfA1 is a complete sample containing 2397 galaxies distributed over 2.7 steradians with m(sub z) less than or equal 14.5. The first two complete slices of CfA2 contain 1862 galaxies distributed over 0.42 steradians with m(sub z)=15.5. The shapes of the E-S0 and spiral luminosity functions (LF) are indistinguishable. We do not confirm the steeply decreasing faint end in the E-S0 luminosity function found by Loveday et al. for an independent sample in the southern hemisphere. We demonstrate that incomplete classification in deep redshift surveys can lead to underestimates of the faint end of the elliptical luminosity function and could be partially responsible for the difference between the CfA survey and other local field surveys. The faint end of the LF for the Magellanic spirals and irregulars is very steep. The Sm-Im luminosity function is well fit by a Schechter function with M*=-18.79, alpha=-1.87, and phi*=0.6x10(exp -3) for M(sub z) less than or equal to -13. These galaxies are largely responsible for the excess at the faint end of the general CfA luminosity function. The abundance of intrinsically faint, blue galaxies nearby affects the interpretation of deep number counts. The dwarf population increases the expected counts at B=25 in a no-evolution, q(sub 0)=0.05 model by a factor of two over standard no-evolution estimates. These dwarfs change the expected median redshift in deep redshift surveys by less than 10 percent . Thus the steep Sm-Im LF may contribute to the reconciliation of deep number counts with deep redshift surveys.

A deeper look at the X-ray point source population of NGC 4472

NASA Astrophysics Data System (ADS)

Joseph, T. D.; Maccarone, T. J.; Kraft, R. P.; Sivakoff, G. R.

2017-10-01

In this paper we discuss the X-ray point source population of NGC 4472, an elliptical galaxy in the Virgo cluster. We used recent deep Chandra data combined with archival Chandra data to obtain a 380 ks exposure time. We find 238 X-ray point sources within 3.7 arcmin of the galaxy centre, with a completeness flux, FX, 0.5-2 keV = 6.3 × 10-16 erg s-1 cm-2. Most of these sources are expected to be low-mass X-ray binaries. We finding that, using data from a single galaxy which is both complete and has a large number of objects (˜100) below 1038 erg s-1, the X-ray luminosity function is well fitted with a single power-law model. By cross matching our X-ray data with both space based and ground based optical data for NGC 4472, we find that 80 of the 238 sources are in globular clusters. We compare the red and blue globular cluster subpopulations and find red clusters are nearly six times more likely to host an X-ray source than blue clusters. We show that there is evidence that these two subpopulations have significantly different X-ray luminosity distributions. Source catalogues for all X-ray point sources, as well as any corresponding optical data for globular cluster sources, are also presented here.

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.

Investigation of the feasibility of temperature profiling optical diagnostics in the SSME fuel pre-burner

NASA Technical Reports Server (NTRS)

Shirley, J. A.

1983-01-01

Results of an analytical investigation to determine the feasibility of temperature profiling in the space shuttle main engine (SSME) fuel preburner are presented. In this application it is desirable to measure temperature in the preburner combustor with a remote, nonintrusive optical technique. Several techniques using laser excitation were examined with a consideration of the constraints imposed by optical access in the fuel preburner and the problems associated with operation near the functioning space shuttle engine. The potential performance of practical diagnostic systems based on spontaneous Raman backscattering, laser induced fluorescence, and coherent anti-Stokes Raman spectroscopy were compared analytically. A system using collection of spontaneous Raman backscattering excited by a remotely located 5 to 10 watt laser propagated to the SSME through a small diameter optical fiber was selected as the best approach. Difficulties normally associated with Raman scattering: weak signal strength and interference due to background radiation are not expected to be problematic due to the very high density in this application, and the low flame luminosity expected in the fuel rich hydrogen oxygen flame.

Outbursts in Symbiotic Binaries

NASA Technical Reports Server (NTRS)

Mushotzky, Richard (Technical Monitor); Kenyon, Scott J.

2003-01-01

Two models have been proposed for the outbursts of symbiotic stars. In the thermonuclear model, outbursts begin when the hydrogen burning shell of a hot white dwarf reaches a critical mass. After a rapid increase in the luminosity and effective temperature, the white dwarf evolves at constant luminosity to lower effective temperatures, remains at optical maximum for several years, and then returns to quiescence along a white dwarf cooling curve. In disk instability models, the brightness rises when the accretion rate from the disk onto the central white dwarf abruptly increases by factors of 5-20. After a few month to several year period at maximum, both the luminosity and the effective temperature of the disk decline as the system returns to quiescence.

Multi-wavelength properties of two supersoft X-ray sources CAL83 and RXJ0513.9-6951

NASA Astrophysics Data System (ADS)

Rajoelimanana, A.; Meintjes, P.; Charles, P.

2017-10-01

Supersoft X-ray sources (SSS) are highly luminous (˜10^{38} erg s^{-1}), yet low temperature 10^{6} K sources, interpreted as a white dwarf (WD) accreting matter at a very high rate from its (heavy) companion, leading to Eddington-limited, steady hydrogen burning on the WD surface at T˜15-80 eV. A large fraction of this energy irradiates the surface of the disc, which gives rise to a reprocessed flux much larger than the intrinsic disc luminosity, accounting for the large optical and UV fluxes detected in SSS. We present the multi-wavelength properties of two prototypical LMC SSS, CAL83 and RXJ0513.9-6951, with particular emphasis on the anti-correlation between their X-ray and optical behaviour. Our SALT spectra show variable high excitation OVI emission as a function of optical brightness state, and which we link to the cyclic changes in the temperature and size of the WD, and hence the mass accretion rate.

Einstein X-ray observations of M101

NASA Technical Reports Server (NTRS)

Trinchieri, G.; Fabbiano, G.; Romaine, S.

1990-01-01

The Einstein X-ray observations of the face-on spiral galaxy M101 are presented. The global X-ray luminosity L(x) of M101 is about 1.2 x 10 to the 40th ergs/s for D = 7.2 Mpc, consistent with the expected X-ray luminosity of normal spiral galaxies of its optical magnitude. The X-ray emission is mostly due to very luminous individual sources, with L(x) greater than 10 to the 38th ergs/s each, most likely very massive accreting binary systems. The data suggest a deficiency of sources in the luminosity range of L(x) from about 10 to the 37th to about 10 to the 38th ergs/s, which would indicate that the luminosity distribution of the X-ray sources in M101 might be different from that of M31 or M33.

Joint NuSTAR and Chandra analysis of the obscured quasar in IC 2497 - Hanny's Voorwerp system

NASA Astrophysics Data System (ADS)

Sartori, Lia F.; Schawinski, Kevin; Koss, Michael J.; Ricci, Claudio; Treister, Ezequiel; Stern, Daniel; Lansbury, George; Maksym, W. Peter; Baloković, Mislav; Gandhi, Poshak; Keel, William C.; Ballantyne, David R.

2018-02-01

We present new Nuclear Spectroscopic Telescope Array (NuSTAR) observations of the core of IC 2497, the galaxy associated with Hanny's Voorwerp. The combined fits of the Chandra (0.5-8 keV) and NuSTAR (3-24 keV) X-ray spectra, together with WISE mid-IR photometry, optical longslit spectroscopy and optical narrow-band imaging, suggest that the galaxy hosts a Compton-thick active galactic nucleus (AGN) (NH ˜ 2 × 1024 cm-2, current intrinsic luminosity Lbol ˜ 2-5 × 1044 erg s-1) whose luminosity dropped by a factor of ˜50 within the last ˜100 kyr. This corresponds to a change in Eddington ratio (ER) from λEdd ˜ 0.35 to λEdd ˜ 0.007. We argue that the AGN in IC 2497 should not be classified as a changing-look AGN, but rather we favour the interpretation where the AGN is undergoing a change in accretion state (from radiatively efficient to radiatively inefficient). In this scenario, the observed drop in luminosity and ER corresponds to the final stage of an AGN accretion phase. Our results are consistent with previous studies in the optical, X-ray and radio although the magnitude of the drop is lower than previously suggested. In addition, we discuss a possible analogy between X-ray binaries and an AGN.

Biasing and High-Order Statistics from the Southern-Sky Redshift Survey

NASA Astrophysics Data System (ADS)

Benoist, C.; Cappi, A.; da Costa, L. N.; Maurogordato, S.; Bouchet, F. R.; Schaeffer, R.

1999-04-01

We analyze different volume-limited samples extracted from the Southern-Sky Redshift Survey (SSRS2), using counts-in-cells to compute the count probability distribution function (CPDF). From the CPDF we derive volume-averaged correlation functions to fourth order and the normalized skewness and kurtosis S3=ξ3¯/ξ¯22 and S4=ξ4¯/ξ¯32. We find that the data satisfies the hierarchical relations in the range 0.3<~ξ2¯<~10. In this range we find S3 to be scale independent, with a value of ~1.8, in good agreement with the values measured from other optical redshift surveys probing different volumes, but significantly smaller than that inferred from the Automatic Plate Measuring Facility (APM) angular catalog. In addition, the measured values of S3 do not show a significant dependence on the luminosity of the galaxies considered. This result is supported by several tests of systematic errors that could affect our measures and estimates of the cosmic variance determined from mock catalogs extracted from N-body simulations. This result is in marked contrast to what would be expected from the strong dependence of the two-point correlation function on luminosity in the framework of a linear biasing model. We discuss the implications of our results and compare them to some recent models of the galaxy distribution that address the problem of bias.

CATALOG AND STATISTICAL STUDY OF X-RAY SELECTED BL LACERTAE OBJECTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kapanadze, Bidzina Z., E-mail: bidzina_kapandaze@iliauni.edu.ge

2013-02-01

This paper presents a catalog of 312 X-ray selected BL Lacerate objects (XBLs), optically identified through the end of 2011. It contains the names from different surveys, equatorial coordinates, redshifts, multifrequency flux values, and luminosities for each source. In addition, the different characteristics of XBLs are statistically investigated (redshift, radio/optical/X-ray luminosities, central black hole (BH) mass, synchrotron peak frequency, broadband spectral indices, optical flux variability). Their values are collected through an extensive bibliographic and database search or calculated by us. The redshifts range from 0.031 to 0.702 with a maximum of the distribution at z = 0.223. The 1.4 GHzmore » luminosities of XBLs log {nu}L{sub {nu}} {approx} 39-42 erg s{sup -1} while optical V and X-ray 0.1-2.4 keV bands show log {nu}L{sub {nu}} {approx} 43-46 erg s{sup -1}. The XBL hosts are elliptical galaxies with effective radii r{sub eff} = 3.2625.40 kpc and ellipticities, in = 0.040.52. Their R-band absolute magnitudes M{sub R} range from -21.11 mag to -24.86 mag with a mean value of -22.83 mag. The V - R indices of the hosts span from 0.61 to 1.52 and reveal a fourth-degree polynomial relationship with z that enables us to evaluate the redshifts of five sources whose V - R indices were determined from the observations but whose irredshifts values are either not found or not confirmed. The XBL nuclei show a wider range of 7.31 mag for M{sub R} with the highest luminosity corresponding to M{sub R} = -27.24 mag. The masses of central BHs are found in the interval log M{sub BH} = 7.39-9.30 solar masses (with distribution maximum at log M{sub BH}/M{sub Sun} = 8.30). The synchrotron peak frequencies are spread over the range log {nu}{sub peak} = 14.56-19.18 Hz with a peak of the distribution at log {nu}{sub peak} = 16.60 Hz. The broadband radio-to-optical ({alpha}{sub ro}), optical-to-X-ray ({alpha}{sub ox}), and radio-to-X-ray ({alpha}{sub rx}) spectral indices are distributed in the intervals (0.17,0.59), (0.56,1.48), and (0.41,0.75), respectively. In the optical energy range, the overall flux variability increases, on average, towards shorter wavelengths: ({Delta}m) = 1.22, 1.50, and 1.82 mag through the R, V, B bands of Johnson-Cousins system, respectively. XBLs seem be optically less variable at the intranight timescales compared to the radio-selected BL Lacs (RBLs).« less

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.

2017-01-01

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 AGN inhabit. Exploring this connection will be crucial to understanding the triggering mechanisms of AGN 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 AGN 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 are 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 AGN of different luminosities in cosmological simulations.

Keck Deep Fields. II. The Ultraviolet Galaxy Luminosity Function at z ~ 4, 3, and 2

NASA Astrophysics Data System (ADS)

Sawicki, Marcin; Thompson, David

2006-05-01

We use very deep UnGRI multifield imaging obtained at the Keck telescope to study the evolution of the rest-frame 1700 Å galaxy luminosity function as the universe doubles its age from z~4 to ~2. We use exactly the same filters and color-color selection as those used by the Steidel team but probe significantly fainter limits, well below L*. The depth of our imaging allows us to constrain the faint end of the luminosity function, reaching M1700~-18.5 at z~3 (equivalent to ~1 Msolar yr-1), accounting for both N1/2 uncertainty in the number of galaxies and cosmic variance. We carefully examine many potential sources of systematic bias in our LF measurements before drawing the following conclusions. We find that the luminosity function of Lyman break galaxies evolves with time and that this evolution is differential with luminosity. The result is best constrained between the epochs at z~4 and ~3, where we find that the number density of sub-L* galaxies increases with time by at least a factor of 2.3 (11 σ statistical confidence); while the faint end of the LF evolves, the bright end appears to remain virtually unchanged, indicating that there may be differential, luminosity-dependent evolution (98.5% statistical probability). Potential systematic biases restrict our ability to draw strong conclusions about continued evolution of the luminosity function to lower redshifts, z~2.2 and ~1.7, but, nevertheless, it appears certain that the number density of z~2.2 galaxies at all luminosities we studied, -22>M1700>-18, is at least as high as that of their counterparts at z~3. While it is not yet clear what mechanism underlies the observed evolution, the fact that this evolution is differential with luminosity opens up new avenues of improving our understanding of how galaxies form and evolve at high redshift. Based on data 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 NASA and was made possible by the generous financial support of the W. M. Keck Foundation.

Erratum: "Space Density of Optically Selected Type 2 Quasars" (2008, AJ, 136, 2373)

NASA Astrophysics Data System (ADS)

Reyes, Reinabelle; Zakamska, Nadia L.; Strauss, Michael A.; Green, Joshua; Krolik, Julian H.; Shen, Yue; Richards, Gordon T.; Anderson, Scott F.; Schneider, Donald P.

2010-03-01

Figure 12 of the paper "Space Density of Optically Selected Type 2 Quasars" compares the obscured quasar fractions derived in our work with those of other studies. Unfortunately, some of the points from these other studies were shown incorrectly. Specifically, the results from X-ray data—Hasinger (2004; open circles) and Ueda et al. (2003; open squares)—which we had taken from Figure 16 of Hopkins et al. (2006), were affected by a luminosity conversion error, in the sense that the displayed luminosities for these data were too high by ~1 dex. With this erratum, we correct this problem and update the figure. The new version (Figure 12) shows more recent results from Hasinger (2008), in lieu of the Hasinger (2004) data points. These are based on data in the redshift range z = 0.2-3.2 (open circles) in that work. The best linear fit to these data (black dashed line) is consistent with that derived for the redshift slice z = 0.4-0.8, which overlaps with the highest redshift bin in our study, and is higher than that derived for redshifts smaller than 0.4 (corresponding to a shift of ~0.7 dex in luminosity). Figure 12 also shows estimates of the obscured quasar fraction derived from the ratio of IR to bolometric luminosities of an AGN sample at redshift z ~ 1 (Treister et al. 2008; filled triangles). Because the obscured quasar fractions derived from our analysis (colored arrows) are strict lower limits, there was already a hint in the previous version of Figure 12 that at high quasar luminosities, we find higher obscured quasar fractions than X-ray surveys. The correction and updates of Figure 12 strengthen this conclusion. At face value, our derived obscured quasar fractions are consistent with those from IR data (Treister et al. 2008; filled triangles). However, we find that they are significantly higher than those derived from X-ray surveys at L_[O\\,\\mathsc {iii]}\\gtrsim 10^{9.5}\\;L_{\\odot }, especially those from the recent analysis by Hasinger (2008). This comparison strongly suggests that optical selection successfully identifies a population of luminous obscured quasars that are missed by X-ray selection.

Correlation function of the luminosity distances

DOE Office of Scientific and Technical Information (OSTI.GOV)

Biern, Sang Gyu; Yoo, Jaiyul, E-mail: sgbiern@physik.uzh.ch, E-mail: jyoo@physik.uzh.ch

We present the correlation function of the luminosity distances in a flat ΛCDM universe. Decomposing the luminosity distance fluctuation into the velocity, the gravitational potential, and the lensing contributions in linear perturbation theory, we study their individual contributions to the correlation function. The lensing contribution is important at large redshift ( z ∼> 0.5) but only for small angular separation (θ ∼< 3°), while the velocity contribution dominates over the other contributions at low redshift or at larger separation. However, the gravitational potential contribution is always subdominant at all scale, if the correct gauge-invariant expression is used. The correlation functionmore » of the luminosity distances depends significantly on the matter content, especially for the lensing contribution, thus providing a novel tool of estimating cosmological parameters.« less

The clustering amplitude of X-ray-selected AGN at z ˜ 0.8: evidence for a negative dependence on accretion luminosity

NASA Astrophysics Data System (ADS)

Mountrichas, G.; Georgakakis, A.; Menzel, M.-L.; Fanidakis, N.; Merloni, A.; Liu, Z.; Salvato, M.; Nandra, K.

2016-04-01

The northern tile of the wide-area and shallow XMM-XXL X-ray survey field is used to estimate the average dark matter halo mass of relatively luminous X-ray-selected active galactic nucleus (AGN) [log {L}_X (2-10 keV)= 43.6^{+0.4}_{-0.4} erg s^{-1}] in the redshift interval z = 0.5-1.2. Spectroscopic follow-up observations of X-ray sources in the XMM-XXL field by the Sloan telescope are combined with the VIMOS Public Extragalactic Redshift Survey spectroscopic galaxy survey to determine the cross-correlation signal between X-ray-selected AGN (total of 318) and galaxies (about 20 000). We model the large scales (2-25 Mpc) of the correlation function to infer a mean dark matter halo mass of log M / (M_{{⊙}} h^{-1}) = 12.50 ^{+0.22} _{-0.30} for the X-ray-selected AGN sample. This measurement is about 0.5 dex lower compared to estimates in the literature of the mean dark matter halo masses of moderate-luminosity X-ray AGN [LX(2-10 keV) ≈ 1042-1043 erg s- 1] at similar redshifts. Our analysis also links the mean clustering properties of moderate-luminosity AGN with those of powerful ultraviolet/optically selected QSOs, which are typically found in haloes with masses few times 1012 M⊙. There is therefore evidence for a negative luminosity dependence of the AGN clustering. This is consistent with suggestions that AGN have a broad dark matter halo mass distribution with a high mass tail that becomes subdominant at high accretion luminosities. We further show that our results are in qualitative agreement with semi-analytic models of galaxy and AGN evolution, which attribute the wide range of dark matter halo masses among the AGN population to different triggering mechanisms and/or black hole fuelling modes.

Spitzer Observations of GRB Hosts: A Legacy Approach

NASA Astrophysics Data System (ADS)

Perley, Daniel; Tanvir, Nial; Hjorth, Jens; Berger, Edo; Laskar, Tanmoy; Michalowski, Michal; Chary, Ranga-Ram; Fynbo, Johan; Levan, Andrew

2012-09-01

The host galaxies of long-duration GRBs are drawn from uniquely broad range of luminosities and redshifts. Thus they offer the possibility of studying the evolution of star-forming galaxies without the limitations of other luminosity-selected samples, which typically are increasingly biased towards the most massive systems at higher redshift. However, reaping the full benefits of this potential requires careful attention to the selection biases affecting host identification. To this end, we propose observations of a Legacy sample of 70 GRB host galaxies (an additional 70 have already been observed by Spitzer), in order to constrain the mass and luminosity function in GRB-selected galaxies at high redshift, including its dependence on redshift and on properties of the afterglow. Crucially, and unlike previous Spitzer surveys, this sample is carefully designed to be uniform and free of optical selection biases that have caused previous surveys to systematically under-represent the role of luminous, massive hosts. We also propose to extend to larger, more powerfully constraining samples the study of two science areas where Spitzer observations have recently shown spectacular success: the hosts of dust-obscured GRBs (which promise to further our understanding of the connection between GRBs and star-formation in the most luminous galaxies), and the evolution of the mass-metallicity relation at z>2 (for which GRB host observations provide particularly powerful constraints on high-z chemical evolution).

Galaxy cluster luminosities and colours, and their dependence on cluster mass and merger state

NASA Astrophysics Data System (ADS)

Mulroy, Sarah L.; McGee, Sean L.; Gillman, Steven; Smith, Graham P.; Haines, Chris P.; Démoclès, Jessica; Okabe, Nobuhiro; Egami, Eiichi

2017-12-01

We study a sample of 19 galaxy clusters in the redshift range 0.15 < z < 0.30 with highly complete spectroscopic membership catalogues (to K < K*(z) + 1.5) from the Arizona Cluster Redshift Survey, individual weak-lensing masses and near-infrared data from the Local Cluster Substructure Survey, and optical photometry from the Sloan Digital Sky Survey. We fit the scaling relations between total cluster luminosity in each of six bandpasses (grizJK) and cluster mass, finding cluster luminosity to be a promising mass proxy with low intrinsic scatter σln L|M of only ∼10-20 per cent for all relations. At fixed overdensity radius, the intercept increases with wavelength, consistent with an old stellar population. The scatter and slope are consistent across all wavelengths, suggesting that cluster colour is not a function of mass. Comparing colour with indicators of the level of disturbance in the cluster, we find a narrower variety in the cluster colours of 'disturbed' clusters than of 'undisturbed' clusters. This trend is more pronounced with indicators sensitive to the initial stages of a cluster merger, e.g. the Dressler Schectman statistic. We interpret this as possible evidence that the total cluster star formation rate is 'standardized' in mergers, perhaps through a process such as a system-wide shock in the intracluster medium.

Mini-Survey on SDSS OIII AGN with Swift

NASA Technical Reports Server (NTRS)

Angelini, Lorella

2008-01-01

The number of AGN and their luminosity distribution are crucial parameters for our understanding of the AGN phenomenon. There is a common wisdom that every massive galaxy has a massive black hole. However, most of these objects either are not radiating or until recently have been very difficult to detect. The Sloan Digital Sky Survey (SDSS) data, based on the [OIII] line indicate that perhaps up to 20% of all galaxies may be classified as AGN a surprising result that must be checked with independent data. X-ray surveys have revealed that hard X-ray selected AGN show a strong luminosity dependent evolution and their luminosity function (LF) shows a dramatic break towards low $L_X$ (at all $z$). This is seen for all types of AGN, but is stronger for the broad-line objects. In sharp contrast, the local LF of {it optically-selected samples} shows no such break and no differences between narrow and broad-line objects. Assuming both hard X-ray and [O{\\sc iii}] emission are fair indicators of AGN activity, it is important to understand this discrepancy. We present here the results of a min-survey done with Swift on a selected sample of SDSS selected AGN. The objects have been sampled at different L([O{\\sc iii}]) to check the relation with the $L_X$ observed with Swift.

STELLAR X-RAY SOURCES IN THE CHANDRA COSMOS SURVEY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wright, N. J.; Drake, J. J.; Civano, F., E-mail: nwright@cfa.harvard.ed

2010-12-10

We present an analysis of the X-ray properties of a sample of solar- and late-type field stars identified in the Chandra Cosmic Evolution Survey (COSMOS), a deep (160 ks) and wide ({approx}0.9 deg{sup 2}) extragalactic survey. The sample of 60 sources was identified using both morphological and photometric star/galaxy separation methods. We determine X-ray count rates, extract spectra and light curves, and perform spectral fits to determine fluxes and plasma temperatures. Complementary optical and near-IR photometry is also presented and combined with spectroscopy for 48 of the sources to determine spectral types and distances for the sample. We find distancesmore » ranging from 30 pc to {approx}12 kpc, including a number of the most distant and highly active stellar X-ray sources ever detected. This stellar sample extends the known coverage of the L{sub X}-distance plane to greater distances and higher luminosities, but we do not detect as many intrinsically faint X-ray sources compared to previous surveys. Overall the sample is typically more luminous than the active Sun, representing the high-luminosity end of the disk and halo X-ray luminosity functions. The halo population appears to include both low-activity spectrally hard sources that may be emitting through thermal bremsstrahlung, as well as a number of highly active sources in close binaries.« less

Hybrid accretion disks in active galactic nuclei. I - Structure and spectra

NASA Technical Reports Server (NTRS)

Wandel, Amri; Liang, Edison P.

1991-01-01

A unified treatment is presented of the two distinct states of vertically thin AGN accretion disks: a cool (about 10 to the 6th K) optically thick solution, and a hot (about 10 to the 9th K) optically thin solution. A generalized formalism and a new radiative cooling equation valid in both regimes are introduced. A new luminosity limit is found at which the hot and cool alpha solutions merge into a single solution of intermediate optical depth. Analytic solutions for the disk structure are given, and output spectra are computed numerically. This is used to demonstrate the prospect of fitting AGN broadband spectra containing both the UV bump as well as the hard X-ray and gamma-ray tail, using a single accretion disk model. Such models are found to make definite predictions about the observed spectrum, such as the relation between the hard X-ray spectral index, the UV-to-X-ray luminosity ratio, and a feature of about 1 MeV.

Far-infrared observations of young clusters embedded in the R Coronae Australis and Rho Ophiuchi dark clouds

NASA Technical Reports Server (NTRS)

Wilking, B. A.; Harvey, P. M.; Joy, M.; Hyland, A. R.; Jones, T. J.

1985-01-01

Multicolor far-infrared maps in two nearby dark clouds, R Coronae Australis and Rho Ophiuchi, have been made in order to investigate the individual contribution of low-mass stars to the energetics and dynamics of the surrounding gas and dust. Emission from cool dust associated with five low-mass stars has been detected in CrA and four in Rho Oph; their far-infrared luminosities range from 2 solar luminosities to 40 solar luminosities. When an estimate of the bolometric luminosity was possible, it was found that typically more than 50 percent of the star's energy was radiated longward of 20 microns. Meaningful limits to the far-infrared luminosities of an additional 11 association members in CrA and two in Rho Oph were also obtained. The dust optical depth surrounding the star R CrA appears to be asymmetric and may control the dynamics of the surrounding molecular gas. The implications of these results for the cloud energetics and star formation efficiency in these two clouds are discussed.

VLA observations of unidentified Leiden-Berkeley Deep-Survey sources - Luminosity and redshift dependence of spectral properties

NASA Technical Reports Server (NTRS)

Kapahi, Vijay K.; Kulkarni, Vasant K.

1990-01-01

VLA observations of a complete subset of the Leiden-Berkeley Deep Survey sources that have S(1.4 GHz) greater than 10 mJy and are not optically identified down to F=22 mag are reported. By comparing the spectral and structural properties of the sources with samples from the literature, an attempt was made to disentangle the luminosity and redshift dependence of the spectral indices of extended emission in radio galaxies and of the incidence of compact steep-spectrum sources. It is found that the fraction of compact sources among those with a steep spectrum is related primarily to redshift, being much larger at high redshifts for sources of similar radio luminosity. Only a weak and marginally significant dependence of spectral indices of the extended sources on luminosity and redshift is found in samples selected at 1.4 and 2.7 GHz. It is pointed out that the much stronger correlation of spectral indices with luminosity may be arising partly from spectral curvature, and partly due to the preferential inclusion of very steep-spectrum sources from high redshift in low-frequency surveys.

Far-infrared observations of young clusters embedded in the R Coronae Austrinae and RHO Ophiuchi dark clouds

NASA Technical Reports Server (NTRS)

Wilking, B. A.; Harvey, P. M.; Joy, M.; Hyland, A. R.; Jones, T. J.

1985-01-01

Multicolor far infrared maps in two nearby dark clouds, R Coronae Austrinae and rho Ophiuchi, were made in order to investigate the individual contribution of low mass stars to the energetics and dynamics of the surrounding gas and dust. Emission from cool dust associated with five low mass stars in Cr A and four in rho Oph was detected; their far infrared luminosities range from 2 far infrared luminosities L. up to 40 far infrared luminosities. When an estimate of the bolometric luminosity was possible, it was found that typically more than 50% of the star's energy was radiated longward of 20 micrometers. meaningful limits to the far infrared luminosities of an additional eleven association members in Cr A and two in rho Oph were also obtained. The dust optical depth surrounding the star R Cr A appears to be asymmetric and may control the dynamics of the surrounding molecular gas. The implications of the results for the cloud energetics and star formation efficiency in these two clouds are discussed.

Tracing the Far-Infrared Roles of AGN in Dusty Star-Forming Galaxies

NASA Astrophysics Data System (ADS)

Brown, Arianna; Nayyeri, Hooshang; Cooray, Asantha R.; Mitchell-Wynne, Ketron

2017-01-01

Active galactic nuclei (AGNs) are suggested to play an important role in quenching their host galaxy’s star formation rate (SFR) by heating up and/or consuming the cool gas necessary to create stars. This mechanism is theorized as a critical step in AGN evolutionary models. The efforts to study this effect suffer in part from low-number statistics at high x-ray luminosities (LXR > 1044 ergs/s) for AGNs at z≈1-3, and a lack of separately estimated SFRs for AGN in dusty, star-forming galaxies (DSFGs). In this work, we extend our analysis to build a more complete picture using the variety of available multi-wavelength data in the XBoötes region. The Chandra XBoötes Survey is a 5-ks X-ray survey of the 9.3 square degree Boötes Field of the NOAO Deep Wide-Field Survey, a survey imaged from the optical to the near-IR. We estimate AGN spectral energy distributions and SFRs for ~400 x-ray sources using available data in all four Spitzer IRAC bands, the Spitzer MIPS 24µm band, all five Herschel SPIRE and PACS bands, along with NEWFIRM optical bands. Preliminary results show an exponential correlation between x-ray luminosity and star formation. As a comparison, we will use a stacking technique for the ~500 x-ray sources that were not detected at submillimeter wavelengths, where sources are binned by x-ray luminosity. We will compare these two samples and expect to see a difference in slope. Using these techniques, we hope to place tighter constraints on the mean SFRs of high-luminosity AGNs inside DSFGs, and determine if x-ray luminosities are independent of average SFRs for our sample in the Boötes field.

A new phenomenon?

NASA Astrophysics Data System (ADS)

Ganci, S.

2017-03-01

This letter describes an interesting optical phenomenon engaging the reflected images of a new tube LED lamp (an array of high luminosity LEDs substituting the old fluorescent lamps) on any convex glossy black surface.

The Taurus Spitzer Legacy Project

NASA Astrophysics Data System (ADS)

McCabe, Caer-Eve; Padgett, D. L.; Rebull, L.; Noriega-Crespo, A.; Carey, S.; Brooke, T.; Stapelfeldt, K. R.; Fukagawa, M.; Hines, D.; Terebey, S.; Huard, T.; Hillenbrand, L.; Guedel, M.; Audard, M.; Monin, J.; Guieu, S.; Knapp, G.; Evans, N. J., III; Menard, F.; Harvey, P.; Allen, L.; Wolf, S.; Skinner, S.; Strom, S.; Glauser, A.; Saavedra, C.; Koerner, D.; Myers, P.; Shupe, D.; Latter, W.; Grosso, N.; Heyer, M.; Dougados, C.; Bouvier, J.

2009-01-01

Without massive stars and dense stellar clusters, Taurus plays host to a distributed mode of low-mass star formation particularly amenable to observational and theoretical study. In 2005-2007, our team mapped the central 43 square degrees of the main Taurus clouds at wavelengths from 3.6 - 160 microns with the IRAC and MIPS cameras on the Spitzer Space Telescope. Together, these images form the largest contiguous Spitzer map of a single star-forming region (and any region outside the galactic plane). Our Legacy team has generated re-reduced mosaic images and source catalogs, available to the community via the Spitzer Science Center website http://ssc.spitzer.caltech.edu/legacy/all.html . This Spitzer survey is a central and crucial part of a multiwavelength study of the Taurus cloud complex that we have performed using XMM, CFHT, and the SDSS. The seven photometry data points from Spitzer allow us to characterize the circumstellar environment of each object, and, in conjunction with optical and NIR photometry, construct a complete luminosity function for the cloud members that will place constraints on the initial mass function. We present results drawing upon our catalog of several hundred thousand IRAC and thousands of MIPS sources. Initial results from our study of the Taurus clouds include new disks around brown dwarfs, new low luminosity YSO candidates, and new Herbig-Haro objects.

SCUSS u- BAND EMISSION AS A STAR-FORMATION-RATE INDICATOR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Zhimin; Zhou, Xu; Wu, Hong

2017-01-20

We present and analyze the possibility of using optical u- band luminosities to estimate star-formation rates (SFRs) of galaxies based on the data from the South Galactic Cap u band Sky Survey (SCUSS), which provides a deep u -band photometric survey covering about 5000 deg{sup 2} of the South Galactic Cap. Based on two samples of normal star-forming galaxies selected by the BPT diagram, we explore the correlations between u -band, H α , and IR luminosities by combing SCUSS data with the Sloan Digital Sky Survey and Wide-field Infrared Survey Explorer ( WISE ). The attenuation-corrected u -band luminositiesmore » are tightly correlated with the Balmer decrement-corrected H α luminosities with an rms scatter of ∼0.17 dex. The IR-corrected u luminosities are derived based on the correlations between the attenuation of u- band luminosities and WISE 12 (or 22) μ m luminosities, and then calibrated with the Balmer-corrected H α luminosities. The systematic residuals of these calibrations are tested against the physical properties over the ranges covered by our sample objects. We find that the best-fitting nonlinear relations are better than the linear ones and recommended to be applied in the measurement of SFRs. The systematic deviations mainly come from the pollution of old stellar population and the effect of dust extinction; therefore, a more detailed analysis is needed in future work.« less

A statistical analysis of the Einstein normal galaxy sample. III - Radio and X-ray properties of elliptical and S0 galaxies

NASA Technical Reports Server (NTRS)

Fabbiano, G.; Klein, U.; Trinchieri, G.; Wielebinski, R.

1987-01-01

Radioastronomy, optical and X-ray data were used to probe the cause of high X-ray luminosities of 28 radio-quiet elliptical galaxies (RQE) and S0 galaxies previously scanned by the Einstein Observatory. Comparisons were made with similar data on double-lobed 3CR galaxies. Radio luminosities were highly correlated with the X-ray luminosities, agreeing with models of radio nuclear sources in early-type galaxies as accreting compact objects. Additionally, 3CR galaxies seemed to be large-scale versions of normal RQE. The significance of interstellar medium/intracluster medium interactions for high correlations between the core and total radio power from X-ray emitting galaxies is discussed.

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.

THE TAIWAN ECDFS NEAR-INFRARED SURVEY: VERY BRIGHT END OF THE LUMINOSITY FUNCTION AT z > 7

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hsieh, Bau-Ching; Wang, Wei-Hao; Lin, Lihwai

2012-04-10

The primary goal of the Taiwan ECDFS Near-Infrared Survey (TENIS) is to find well-screened galaxy candidates at z > 7 (z' dropout) in the Extended Chandra Deep Field-South (ECDFS). To this end, TENIS provides relatively deep J and K{sub s} data ({approx}25.3 ABmag, 5{sigma}) for an area of 0.5 Multiplication-Sign 0.5 deg. Leveraged with existing data at mid-infrared to optical wavelengths, this allows us to screen for the most luminous high-z objects, which are rare and thus require a survey over a large field to be found. We introduce new color selection criteria to select a z > 7 samplemore » with minimal contaminations from low-z galaxies and Galactic cool stars; to reduce confusion in the relatively low angular resolution Infrared Array Camera (IRAC) images, we introduce a novel deconvolution method to measure the IRAC fluxes of individual sources. Illustrating perhaps the effectiveness at which we screen out interlopers, we find only one z > 7 candidate, TENIS-ZD1. The candidate has a weighted z{sub phot} of 7.8, and its colors and luminosity indicate a young (45M years old) starburst galaxy with a stellar mass of 3.2 Multiplication-Sign 10{sup 10} M{sub Sun }. The result matches with the observational luminosity function analysis and the semianalytic simulation result based on the Millennium Simulations, which may over predict the volume density for high-z massive galaxies. The existence of TENIS-ZD1, if confirmed spectroscopically to be at z > 7, therefore poses a challenge to current theoretical models for how so much mass can accumulate in a galaxy at such a high redshift.« less

LOFAR-Boötes: properties of high- and low-excitation radio galaxies at 0.5 < z < 2.0

NASA Astrophysics Data System (ADS)

Williams, W. L.; Calistro Rivera, G.; Best, P. N.; Hardcastle, M. J.; Röttgering, H. J. A.; Duncan, K. J.; de Gasperin, F.; Jarvis, M. J.; Miley, G. K.; Mahony, E. K.; Morabito, L. K.; Nisbet, D. M.; Prandoni, I.; Smith, D. J. B.; Tasse, C.; White, G. J.

2018-04-01

This paper presents a study of the redshift evolution of radio-loud active galactic nuclei (AGN) as a function of the properties of their galaxy hosts in the Boötes field. To achieve this we match low-frequency radio sources from deep 150-MHz LOFAR (LOw Frequency ARray) observations to an I-band-selected catalogue of galaxies, for which we have derived photometric redshifts, stellar masses, and rest-frame colours. We present spectral energy distribution (SED) fitting to determine the mid-infrared AGN contribution for the radio sources and use this information to classify them as high- versus low-excitation radio galaxies (HERGs and LERGs) or star-forming galaxies. Based on these classifications, we construct luminosity functions for the separate redshift ranges going out to z = 2. From the matched radio-optical catalogues, we select a sub-sample of 624 high power (P150 MHz > 1025 W Hz-1) radio sources between 0.5 ≤ z < 2. For this sample, we study the fraction of galaxies hosting HERGs and LERGs as a function of stellar mass and host galaxy colour. The fraction of HERGs increases with redshift, as does the fraction of sources in galaxies with lower stellar masses. We find that the fraction of galaxies that host LERGs is a strong function of stellar mass as it is in the local Universe. This, combined with the strong negative evolution of the LERG luminosity functions over this redshift range, is consistent with LERGs being fuelled by hot gas in quiescent galaxies.

Lyman-break Galaxies at z ˜ 3 in the Subaru Deep Field: Luminosity Function, Clustering, and [O III] Emission

NASA Astrophysics Data System (ADS)

Malkan, Matthew A.; Cohen, Daniel P.; Maruyama, Miyoko; Kashikawa, Nobunari; Ly, Chun; Ishikawa, Shogo; Shimasaku, Kazuhiro; Hayashi, Masao; Motohara, Kentaro

2017-11-01

We combined deep U-band and optical/near-infrared imaging, in order to select Lyman Break Galaxies (LBGs) at z˜ 3 using U - V and V-{R}c colors in the Subaru Deep Field. The resulting sample of 5161 LBGs gives a UV luminosity function (LF) down to {M}{UV}=-18, with a steep faint-end slope of α =-1.78+/- 0.05. We analyze UV-to-NIR energy distributions (SEDs) from optical photometry and photometry on IR median-stacked images. In the stacks, we find a systematic background depression centered on the LBGs. This results from the difficulty of finding faint galaxies in regions with higher-than-average surface densities of foreground galaxies, so we corrected for this deficit. Best-fit stellar population models for the LBG SEDs indicate stellar masses and star formation rates of {{log}}10({M}* /{M}⊙ )≃ 10 and ≃ 50 M ⊙ yr-1 at < {i}{AB}{\\prime }> =24, down to {{log}}10({M}* /{M}⊙ )≃ 8 and ≃ 3 {M}⊙ yr-1 at < {i}{AB}{\\prime }> =27. The faint LBGs show a ˜1 mag excess over the stellar continuum in K-band. We interpret this excess flux as redshifted [O III]λ λ {4959,5007} lines. The observed excesses imply equivalent widths that increase with decreasing mass, reaching {{EW}}0([{{O}} {{iii}}]4959,5007+{{H}}β )≳ 1500 Å (rest-frame). Such strong [O III] emission is seen only in a miniscule fraction of local emission-line galaxies, but is probably universal in the faint galaxies that reionized the universe. Our halo occupation distribution analysis of the angular correlation function gives a halo mass of {{log}}10(< {M}{{h}}> /{h}-1{M}⊙ )=11.29+/- 0.12 for the full sample of LBGs, and {{log}}10(< {M}{{h}}> /{h}-1{M}⊙ )=11.49+/- 0.1 for the brightest half of the sample.

The composite nature of Dust-Obscured Galaxies (DOGs) at z ˜ 2-3 in the COSMOS field - I. A far-infrared view

NASA Astrophysics Data System (ADS)

Riguccini, L.; Le Floc'h, E.; Mullaney, J. R.; Menéndez-Delmestre, K.; Aussel, H.; Berta, S.; Calanog, J.; Capak, P.; Cooray, A.; Ilbert, O.; Kartaltepe, J.; Koekemoer, A.; Lutz, D.; Magnelli, B.; McCracken, H.; Oliver, S.; Roseboom, I.; Salvato, M.; Sanders, D.; Scoville, N.; Taniguchi, Y.; Treister, E.

2015-09-01

Dust-Obscured Galaxies (DOGs) are bright 24 μm-selected sources with extreme obscuration at optical wavelengths. They are typically characterized by a rising power-law continuum of hot dust (TD ˜ 200-1000 K) in the near-IR indicating that their mid-IR luminosity is dominated by an active galactic nucleus (AGN). DOGs with a fainter 24 μm flux display a stellar bump in the near-IR and their mid-IR luminosity appears to be mainly powered by dusty star formation. Alternatively, it may be that the mid-IR emission arising from AGN activity is dominant but the torus is sufficiently opaque to make the near-IR emission from the AGN negligible with respect to the emission from the host component. In an effort to characterize the astrophysical nature of the processes responsible for the IR emission in DOGs, this paper exploits Herschel data (PACS + SPIRE) on a sample of 95 DOGs within the COSMOS field. We derive a wealth of far-IR properties (e.g. total IR luminosities; mid-to-far-IR colours; dust temperatures and masses) based on spectral energy distribution fitting. Of particular interest are the 24 μm-bright DOGs (F24 μm > 1 mJy). They present bluer far-IR/mid-IR colours than the rest of the sample, unveiling the potential presence of an AGN. The AGN contribution to the total 8-1000 μm flux increases as a function of the rest-frame 8 μm-luminosity irrespective of the redshift. This confirms that faint DOGs (L8 μm < 1012 L⊙) are dominated by star formation while brighter DOGs show a larger contribution from an AGN.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Juneau, Stéphanie; Bournaud, Frédéric; Daddi, Emanuele

Emission line diagnostic diagrams probing the ionization sources in galaxies, such as the Baldwin-Phillips-Terlevich (BPT) diagram, have been used extensively to distinguish active galactic nuclei (AGN) from purely star-forming galaxies. However, they remain poorly understood at higher redshifts. We shed light on this issue with an empirical approach based on a z ∼ 0 reference sample built from ∼300,000 Sloan Digital Sky Survey galaxies, from which we mimic selection effects due to typical emission line detection limits at higher redshift. We combine this low-redshift reference sample with a simple prescription for luminosity evolution of the global galaxy population to predictmore » the loci of high-redshift galaxies on the BPT and Mass-Excitation (MEx) diagnostic diagrams. The predicted bivariate distributions agree remarkably well with direct observations of galaxies out to z ∼ 1.5, including the observed stellar mass-metallicity (MZ) relation evolution. As a result, we infer that high-redshift star-forming galaxies are consistent with having normal interstellar medium (ISM) properties out to z ∼ 1.5, after accounting for selection effects and line luminosity evolution. Namely, their optical line ratios and gas-phase metallicities are comparable to that of low-redshift galaxies with equivalent emission-line luminosities. In contrast, AGN narrow-line regions may show a shift toward lower metallicities at higher redshift. While a physical evolution of the ISM conditions is not ruled out for purely star-forming galaxies and may be more important starting at z ≳ 2, we find that reliably quantifying this evolution is hindered by selections effects. The recipes provided here may serve as a basis for future studies toward this goal. Code to predict the loci of galaxies on the BPT and MEx diagnostic diagrams and the MZ relation as a function of emission line luminosity limits is made publicly available.« less

Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs). III. Star formation properties of the host galaxies at z ≳ 6 studied with ALMA

NASA Astrophysics Data System (ADS)

Izumi, Takuma; Onoue, Masafusa; Shirakata, Hikari; Nagao, Tohru; Kohno, Kotaro; Matsuoka, Yoshiki; Imanishi, Masatoshi; Strauss, Michael A.; Kashikawa, Nobunari; Schulze, Andreas; Silverman, John D.; Fujimoto, Seiji; Harikane, Yuichi; Toba, Yoshiki; Umehata, Hideki; Nakanishi, Kouichiro; Greene, Jenny E.; Tamura, Yoichi; Taniguchi, Akio; Yamaguchi, Yuki; Goto, Tomotsugu; Hashimoto, Yasuhiro; Ikarashi, Soh; Iono, Daisuke; Iwasawa, Kazushi; Lee, Chien-Hsiu; Makiya, Ryu; Minezaki, Takeo; Tang, Ji-Jia

2018-04-01

We present our ALMA Cycle 4 measurements of the [C II] emission line and the underlying far-infrared (FIR) continuum emission from four optically low-luminosity (M1450 > -25) quasars at z ≳ 6 discovered by the Subaru Hyper Suprime Cam (HSC) survey. The [C II] line and FIR continuum luminosities lie in the ranges L_[C II] = (3.8-10.2)× 108 L_{⊙} and LFIR = (1.2-2.0) × 1011 L_{⊙}, which are at least one order of magnitude smaller than those of optically-luminous quasars at z ≳ 6. We estimate the star formation rates (SFRs) of our targets as ≃ 23-40 M_{⊙} yr-1. Their line and continuum-emitting regions are marginally resolved, and found to be comparable in size to those of optically-luminous quasars, indicating that their SFR or likely gas mass surface densities (key controlling parameter of mass accretion) are accordingly different. The L_[C II]/L_FIR ratios of the hosts, ≃ (2.2-8.7) × 10-3, are fully consistent with local star-forming galaxies. Using the [C II] dynamics, we derived their dynamical masses within a radius of 1.5-2.5 kpc as ≃ (1.4-8.2) × 1010 M_{⊙}. By interpreting these masses as stellar ones, we suggest that these faint quasar hosts are on or even below the star-forming main sequence at z ˜ 6, i.e., they appear to be transforming into quiescent galaxies. This is in contrast to the optically-luminous quasars at those redshifts, which show starburst-like properties. Finally, we find that the ratios of black hole mass to host galaxy dynamical mass of most of the low-luminosity quasars, including the HSC ones, are consistent with the local value. The mass ratios of the HSC quasars can be reproduced by a semi-analytical model that assumes merger-induced black hole host galaxy evolution.

Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs). III. Star formation properties of the host galaxies at z ≳ 6 studied with ALMA

NASA Astrophysics Data System (ADS)

Izumi, Takuma; Onoue, Masafusa; Shirakata, Hikari; Nagao, Tohru; Kohno, Kotaro; Matsuoka, Yoshiki; Imanishi, Masatoshi; Strauss, Michael A.; Kashikawa, Nobunari; Schulze, Andreas; Silverman, John D.; Fujimoto, Seiji; Harikane, Yuichi; Toba, Yoshiki; Umehata, Hideki; Nakanishi, Kouichiro; Greene, Jenny E.; Tamura, Yoichi; Taniguchi, Akio; Yamaguchi, Yuki; Goto, Tomotsugu; Hashimoto, Yasuhiro; Ikarashi, Soh; Iono, Daisuke; Iwasawa, Kazushi; Lee, Chien-Hsiu; Makiya, Ryu; Minezaki, Takeo; Tang, Ji-Jia

2018-06-01

We present our ALMA Cycle 4 measurements of the [C II] emission line and the underlying far-infrared (FIR) continuum emission from four optically low-luminosity (M1450 > -25) quasars at z ≳ 6 discovered by the Subaru Hyper Suprime Cam (HSC) survey. The [C II] line and FIR continuum luminosities lie in the ranges L_[C II] = (3.8-10.2)× 108 L_{⊙} and LFIR = (1.2-2.0) × 1011 L_{⊙}, which are at least one order of magnitude smaller than those of optically-luminous quasars at z ≳ 6. We estimate the star formation rates (SFRs) of our targets as ≃ 23-40 M_{⊙} yr-1. Their line and continuum-emitting regions are marginally resolved, and found to be comparable in size to those of optically-luminous quasars, indicating that their SFR or likely gas mass surface densities (key controlling parameter of mass accretion) are accordingly different. The L_[C II}]}/L_FIR ratios of the hosts, ≃ (2.2-8.7) × 10-3, are fully consistent with local star-forming galaxies. Using the [C II] dynamics, we derived their dynamical masses within a radius of 1.5-2.5 kpc as ≃ (1.4-8.2) × 1010 M_{⊙}. By interpreting these masses as stellar ones, we suggest that these faint quasar hosts are on or even below the star-forming main sequence at z ˜ 6, i.e., they appear to be transforming into quiescent galaxies. This is in contrast to the optically-luminous quasars at those redshifts, which show starburst-like properties. Finally, we find that the ratios of black hole mass to host galaxy dynamical mass of most of the low-luminosity quasars, including the HSC ones, are consistent with the local value. The mass ratios of the HSC quasars can be reproduced by a semi-analytical model that assumes merger-induced black hole host galaxy evolution.

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 late-type M dwarfs are substellar. The luminosity function data together with an empirical derivation of the mass-luminosity relation (from Henry & McCarthy) are used to compute a mass function independent of theory. This mass function increases toward the end of the main sequence, but the observed density of M dwarfs is still insufficient to account for the missing mass. If the increases seen in the luminosity and mass functions are indicative of a large, unseen, substellar population, brown dwarfs may yet add significantly to the mass of the Galaxy.

Galaxy And Mass Assembly: evolution of the Hα luminosity function and star formation rate density up to z < 0.35

NASA Astrophysics Data System (ADS)

Gunawardhana, M. L. P.; Hopkins, A. M.; Bland-Hawthorn, J.; Brough, S.; Sharp, R.; Loveday, J.; Taylor, E.; Jones, D. H.; Lara-López, M. A.; Bauer, A. E.; Colless, M.; Owers, M.; Baldry, I. K.; López-Sánchez, A. R.; Foster, C.; Bamford, S.; Brown, M. J. I.; Driver, S. P.; Drinkwater, M. J.; Liske, J.; Meyer, M.; Norberg, P.; Robotham, A. S. G.; Ching, J. H. Y.; Cluver, M. E.; Croom, S.; Kelvin, L.; Prescott, M.; Steele, O.; Thomas, D.; Wang, L.

2013-08-01

Measurements of the low-z Hα luminosity function, Φ, have a large dispersion in the local number density of sources (˜0.5-1 Mpc-3 dex-1), and correspondingly in the star formation rate density (SFRD). The possible causes for these discrepancies include limited volume sampling, biases arising from survey sample selection, different methods of correcting for dust obscuration and active galactic nucleus contamination. The Galaxy And Mass Assembly (GAMA) survey and Sloan Digital Sky Survey (SDSS) provide deep spectroscopic observations over a wide sky area enabling detection of a large sample of star-forming galaxies spanning 0.001 < SFRHα (M⊙ yr- 1) < 100 with which to robustly measure the evolution of the SFRD in the low-z Universe. The large number of high-SFR galaxies present in our sample allow an improved measurement of the bright end of the luminosity function, indicating that the decrease in Φ at bright luminosities is best described by a Saunders functional form rather than the traditional Schechter function. This result is consistent with other published luminosity functions in the far-infrared and radio. For GAMA and SDSS, we find the r-band apparent magnitude limit, combined with the subsequent requirement for Hα detection leads to an incompleteness due to missing bright Hα sources with faint r-band magnitudes.

Mass functions for globular cluster main sequences based on CCD photometry and stellar models

NASA Astrophysics Data System (ADS)

McClure, Robert D.; Vandenberg, Don A.; Smith, Graeme H.; Fahlman, Gregory G.; Richer, Harvey B.; Hesser, James E.; Harris, William E.; Stetson, Peter B.; Bell, R. A.

1986-08-01

Main-sequence luminosity functions constructed from CCD observations of globular clusters reveal a strong trend in slope with metal abundance. Theoretical luminosity functions constructed from VandenBerg and Bell's (1985) isochrones have been fitted to the observations and reveal a trend between x, the power-law index of the mass function, and metal abundance. The most metal-poor clusters require an index of about x = 2.5, whereas the most metal-rich clusters exhibit an index of x of roughly -0.5. The luminosity functions for two sparse clusters, E3 and Pal 5, are distinct from those of the more massive clusters, in that they show a turndown which is possibly a result of mass loss or tidal disruption.

The TexOx-1000 redshift survey of radio sources I: the TOOT00 region

NASA Astrophysics Data System (ADS)

Vardoulaki, Eleni; Rawlings, Steve; Hill, Gary J.; Mauch, Tom; Inskip, Katherine J.; Riley, Julia; Brand, Kate; Croft, Steve; Willott, Chris J.

2010-01-01

We present optical spectroscopy, near-infrared (mostly K-band) and radio (151-MHz and 1.4-GHz) imaging of the first complete region (TOOT00) of the TexOx-1000 (TOOT) redshift survey of radio sources. The 0.0015-sr (~5 deg2) TOOT00 region is selected from pointed observations of the Cambridge Low-Frequency Survey Telescope at 151 MHz at a flux density limit of ~=100 mJy, approximately five times fainter than the 7C Redshift Survey (7CRS), and contains 47 radio sources. We have obtained 40 spectroscopic redshifts (~85 per cent completeness). Adding redshifts estimated for the seven other cases yields a median redshift zmed ~ 1.25. We find a significant population of objects with Fanaroff-Riley type I (FRI) like radio structures at radio luminosities above both the low-redshift FRI/II break and the break in the radio luminosity function. The redshift distribution and subpopulations of TOOT00 are broadly consistent with extrapolations from the 7CRS/6CE/3CRR data sets underlying the SKADS Simulated Skies Semi-Empirical Extragalactic Data base, S3-SEX.

The Kepler Light Curves of AGN: A Detailed Analysis

DOE PAGES

Smith, Krista Lynne; Mushotzky, Richard F.; Boyd, Patricia T.; ...

2018-04-25

Here, we present a comprehensive analysis of 21 light curves of Type 1 active galactic nuclei (AGN) from the Kepler spacecraft. First, we describe the necessity and development of a customized pipeline for treating Kepler data of stochastically variable sources like AGN. We then present the light curves, power spectral density functions (PSDs), and flux histograms. The light curves display an astonishing variety of behaviors, many of which would not be detected in ground-based studies, including switching between distinct flux levels. Six objects exhibit PSD flattening at characteristic timescales that roughly correlate with black hole mass. These timescales are consistentmore » with orbital timescales or free-fall accretion timescales. We check for correlations of variability and high-frequency PSD slope with accretion rate, black hole mass, redshift, and luminosity. We find that bolometric luminosity is anticorrelated with both variability and steepness of the PSD slope. We do not find evidence of the linear rms–flux relationships or lognormal flux distributions found in X-ray AGN light curves, indicating that reprocessing is not a significant contributor to optical variability at the 0.1%–10% level.« less

The Kepler Light Curves of AGN: A Detailed Analysis

NASA Astrophysics Data System (ADS)

Smith, Krista Lynne; Mushotzky, Richard F.; Boyd, Patricia T.; Malkan, Matt; Howell, Steve B.; Gelino, Dawn M.

2018-04-01

We present a comprehensive analysis of 21 light curves of Type 1 active galactic nuclei (AGN) from the Kepler spacecraft. First, we describe the necessity and development of a customized pipeline for treating Kepler data of stochastically variable sources like AGN. We then present the light curves, power spectral density functions (PSDs), and flux histograms. The light curves display an astonishing variety of behaviors, many of which would not be detected in ground-based studies, including switching between distinct flux levels. Six objects exhibit PSD flattening at characteristic timescales that roughly correlate with black hole mass. These timescales are consistent with orbital timescales or free-fall accretion timescales. We check for correlations of variability and high-frequency PSD slope with accretion rate, black hole mass, redshift, and luminosity. We find that bolometric luminosity is anticorrelated with both variability and steepness of the PSD slope. We do not find evidence of the linear rms–flux relationships or lognormal flux distributions found in X-ray AGN light curves, indicating that reprocessing is not a significant contributor to optical variability at the 0.1%–10% level.

Eight new Milky Way companions discovered in first-year Dark Energy Survey data

DOE PAGES

Bechtol, K.

2015-06-30

We report the discovery of eight new Milky Way companions inmore » $$\\sim 1800\\;{\\mathrm{deg}}^{2}$$ of optical imaging data collected during the first year of the Dark Energy Survey (DES). Each system is identified as a statistically significant over-density of individual stars consistent with the expected isochrone and luminosity function of an old and metal-poor stellar population. The objects span a wide range of absolute magnitudes (MV from $-2.2$ to $$-7.4\\;\\mathrm{mag}$$), physical sizes ($$10-170\\;\\mathrm{pc}$$), and heliocentric distances ($$30-330\\;\\mathrm{kpc}$$). Based on the low surface brightnesses, large physical sizes, and/or large Galactocentric distances of these objects, several are likely to be new ultra-faint satellite galaxies of the Milky Way and/or Magellanic Clouds. We introduce a likelihood-based algorithm to search for and characterize stellar over-densities, as well as identify stars with high satellite membership probabilities. As a result, we also present completeness estimates for detecting ultra-faint galaxies of varying luminosities, sizes, and heliocentric distances in the first-year DES data.« less

The Kepler Light Curves of AGN: A Detailed Analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, Krista Lynne; Mushotzky, Richard F.; Boyd, Patricia T.

Here, we present a comprehensive analysis of 21 light curves of Type 1 active galactic nuclei (AGN) from the Kepler spacecraft. First, we describe the necessity and development of a customized pipeline for treating Kepler data of stochastically variable sources like AGN. We then present the light curves, power spectral density functions (PSDs), and flux histograms. The light curves display an astonishing variety of behaviors, many of which would not be detected in ground-based studies, including switching between distinct flux levels. Six objects exhibit PSD flattening at characteristic timescales that roughly correlate with black hole mass. These timescales are consistentmore » with orbital timescales or free-fall accretion timescales. We check for correlations of variability and high-frequency PSD slope with accretion rate, black hole mass, redshift, and luminosity. We find that bolometric luminosity is anticorrelated with both variability and steepness of the PSD slope. We do not find evidence of the linear rms–flux relationships or lognormal flux distributions found in X-ray AGN light curves, indicating that reprocessing is not a significant contributor to optical variability at the 0.1%–10% level.« less

Toward a Unified View of Black-Hole High-Energy States

NASA Technical Reports Server (NTRS)

Nowak, Michael A.

1995-01-01

We present here a review of high-energy (greater than 1 keV) observations of seven black-hole candidates, six of which have estimated masses. In this review we focus on two parameters of interest: the ratio of 'nonthermal' to total luminosity as a function of the total luminosity divided by the Eddington luminosity, and the root-mean-square (rms) variability as a function of the nonthermal-to-total luminosity ratio. Below approx. 10% Eddington luminosity, the sources tend to be strictly nonthermal (the so called 'off' and 'low' states). Above this luminosity the sources become mostly thermal (the 'high' state). with the nonthermal component increasing with luminosity (the 'very high' and 'flare' states). There are important exceptions to this behavior, however, and no steady - as opposed to transient - source has been observed over a wide range of parameter space. In addition, the rms variability is positively correlated with the ratio of nonthermal to total luminosity, although there may be a minimum level of variability associated with 'thermal' states. We discuss these results in light of theoretical models and find that currently no single model describes the full range of black-hole high-energy behavior. In fact, the observations are exactly opposite from what one expects based upon simple notions of accretion disk instabilities.

Searching for faint AGN in the CDFS: an X-ray (Chandra) vs optical variability (HST) comparison.

NASA Astrophysics Data System (ADS)

Georgantopoulos, I.; Pouliasis, E.; Bonanos, A.; Sokolovsky, K.; Yang, M.; Hatzidimitriou, D.; Bellas, I.; Gavras, P.; Spetsieri, Z.

2017-10-01

X-ray surveys are believed to be the most efficient way to detect AGN. Recently though, optical variability studies are claimed to probe even fainter AGN. We are presenting results from an HST study aimed to identify Active Galactic Nuclei (AGN) through optical variability selection in the CDFS.. This work is part of the 'Hubble Catalogue of Variables'project of ESA that aims to identify variable sources in the Hubble Source Catalogue.' In particular, we used Hubble Space Telescope (HST) z-band images taken over 5 epochs and performed aperture photometry to derive the lightcurves of the sources. Two statistical methods (standard deviation & interquartile range) resulting in a final sample of 175 variable AGN candidates, having removed the artifacts by visual inspection and known stars and supernovae. The fact that the majority of the sources are extended and variable indicates AGN activity. We compare the efficiency of the method by comparing with the 7Ms Chandra detections. Our work shows that the optical variability probes AGN at comparable redshifts but at deeper optical magnitudes. Our candidate AGN (non detected in X-rays) have luminosities of L_x<6×10^{40} erg/sec at z˜0.7 suggesting that these are associated with low luminosity Seyferts and LINERS.

Obscured AGNs in Bulgeless Hosts discovered by WISE: The Case Study of SDSS J1224+5555

NASA Astrophysics Data System (ADS)

Satyapal, S.; Secrest, N. J.; Rothberg, B.; O'Connor, J. A.; Ellison, S. L.; Hickox, R. C.; Constantin, A.; Gliozzi, M.; Rosenberg, J. L.

2016-08-01

There is mounting evidence that supermassive black holes (SMBHs) form and grow in bulgeless galaxies. However, a robust determination of the fraction of active galactic nuclei (AGNs) in bulgeless galaxies, an important constraint to models of SMBH seed formation and merger-free models of AGN fueling, is unknown, since optical studies have been shown to be incomplete for AGNs in low-mass galaxies. In a recent study using the Wide-field Infrared Survey Explorer, we discovered hundreds of bulgeless galaxies that display mid-infrared signatures of extremely hot dust suggestive of powerful accreting massive black holes, despite having no signatures of black hole activity at optical wavelengths. Here we report X-ray follow-up observations of J122434.66+555522.3, a nearby (z = 0.052) isolated bulgeless galaxy that contains an unresolved X-ray source detected at the 3σ level by XMM-Newton with an observed luminosity uncorrected for intrinsic absorption of {L}2-10{keV}=(1.1+/- 0.4)× {10}40 erg s-1. Ground-based near-infrared spectroscopy with the Large Binocular Telescope and multiwavelength observations from ultraviolet to millimeter wavelengths together suggest that J1224+5555 harbors a highly absorbed AGN with an intrinsic absorption of {N}{{H}}\\gt {10}24 cm-2. The hard X-ray luminosity of the putative AGN corrected for absorption is {L}2-10{keV}˜ 3× {10}42 erg s-1, which, depending on the bolometric correction factor, corresponds to a bolometric luminosity of the AGN of {L}{bol}.˜ 6× {10}43-3 × 1044 {erg} {{{s}}}-1 and a lower mass limit for the black hole of {M}{BH}≃ 2× {10}6 {M}⊙ , based on the Eddington limit. While enhanced X-ray emission and hot dust can be produced by star formation in extremely low metallicity environments typical in dwarf galaxies, J1224+5555 has a stellar mass of ˜ 2.0× {10}10 {M}⊙ and an above solar metallicity (12 + {logO}/{{H}} = 9.11), typical of our WISE-selected bulgeless galaxy sample. While collectively these observations suggest the presence of an AGN, we caution that identifying obscured AGNs in the low-luminosity regime is challenging and often requires multiwavelength observations. These observations suggest that low-luminosity AGNs can be heavily obscured and reside in optically quiescent galaxies, adding to the growing body of evidence that the fraction of bulgeless galaxies with accreting black holes may be significantly underestimated based on optical studies.

The optical counterpart of GX 339-4, a possible black hole X-ray source

NASA Technical Reports Server (NTRS)

Grindlay, J. E.

1979-01-01

Optical studies of the galactic X-ray source GX 339-4 (4U 1658-48), which led to its recent identification as reported by Doxsey et al. (1979), are presented. Reddening and distance estimates are given, as well as evidence for optical variability on differing time scales. The emission-line spectra and UBV photometry suggest that GX 339-4 may be at about 8 kpc and have a main-sequence B star binary companion. Both the optical spectrum and optical/X-ray luminosity ratio for GX 339-4 may be similar to Cir X-1.

SILVERRUSH. VI. A simulation of Lyα emitters in the reionization epoch and a comparison with Subaru Hyper Suprime-Cam survey early data

NASA Astrophysics Data System (ADS)

Inoue, Akio K.; Hasegawa, Kenji; Ishiyama, Tomoaki; Yajima, Hidenobu; Shimizu, Ikkoh; Umemura, Masayuki; Konno, Akira; Harikane, Yuichi; Shibuya, Takatoshi; Ouchi, Masami; Shimasaku, Kazuhiro; Ono, Yoshiaki; Kusakabe, Haruka; Higuchi, Ryo; Lee, Chien-Hsiu

2018-06-01

The survey of Lyman α emitters (LAEs) with the Subaru Hyper Suprime-Cam, called SILVERRUSH (Ouchi et al. 2018, PASJ, 70, S13), is producing massive data of LAEs at z ≳ 6. Here we present LAE simulations to compare the SILVERRUSH data. In 1623 comoving Mpc3 boxes, where numerical radiative transfer calculations of reionization were performed, LAEs have been modeled with physically motivated analytic recipes as a function of halo mass. We have examined 23 models depending on the presence or absence of dispersion of halo Lyα emissivity, dispersion of the halo Lyα optical depth, τα, and halo mass dependence of τα. The unique free parameter in our model, a pivot value of τα, is calibrated so as to reproduce the z = 5.7 Lyα luminosity function (LF) of SILVERRUSH. We compare our model predictions with Lyα LFs at z = 6.6 and 7.3, LAE angular auto-correlation functions (ACFs) at z = 5.7 and 6.6, and LAE fractions in Lyman break galaxies at 5 < z < 7. The Lyα LFs and ACFs are reproduced by multiple models, but the LAE fraction turns out to be the most critical test. The dispersion of τα and the halo mass dependence of τα are essential to explain all observations reasonably. Therefore, a simple model of one-to-one correspondence between halo mass and Lyα luminosity with a constant Lyα escape fraction has been ruled out. Based on our best model, we present a formula to estimate the intergalactic neutral hydrogen fraction, x_{H I}, from the observed Lyα luminosity density at z ≳ 6. We finally obtain x_{H I}=0.5_{-0.3}^{+0.1} as a volume-average at z = 7.3.

SILVERRUSH. VI. A simulation of Lyα emitters in the reionization epoch and a comparison with Subaru Hyper Suprime-Cam survey early data

NASA Astrophysics Data System (ADS)

Inoue, Akio K.; Hasegawa, Kenji; Ishiyama, Tomoaki; Yajima, Hidenobu; Shimizu, Ikkoh; Umemura, Masayuki; Konno, Akira; Harikane, Yuichi; Shibuya, Takatoshi; Ouchi, Masami; Shimasaku, Kazuhiro; Ono, Yoshiaki; Kusakabe, Haruka; Higuchi, Ryo; Lee, Chien-Hsiu

2018-05-01

The survey of Lyman α emitters (LAEs) with the Subaru Hyper Suprime-Cam, called SILVERRUSH (Ouchi et al. 2018, PASJ, 70, S13), is producing massive data of LAEs at z ≳ 6. Here we present LAE simulations to compare the SILVERRUSH data. In 1623 comoving Mpc3 boxes, where numerical radiative transfer calculations of reionization were performed, LAEs have been modeled with physically motivated analytic recipes as a function of halo mass. We have examined 23 models depending on the presence or absence of dispersion of halo Lyα emissivity, dispersion of the halo Lyα optical depth, τα, and halo mass dependence of τα. The unique free parameter in our model, a pivot value of τα, is calibrated so as to reproduce the z = 5.7 Lyα luminosity function (LF) of SILVERRUSH. We compare our model predictions with Lyα LFs at z = 6.6 and 7.3, LAE angular auto-correlation functions (ACFs) at z = 5.7 and 6.6, and LAE fractions in Lyman break galaxies at 5 < z < 7. The Lyα LFs and ACFs are reproduced by multiple models, but the LAE fraction turns out to be the most critical test. The dispersion of τα and the halo mass dependence of τα are essential to explain all observations reasonably. Therefore, a simple model of one-to-one correspondence between halo mass and Lyα luminosity with a constant Lyα escape fraction has been ruled out. Based on our best model, we present a formula to estimate the intergalactic neutral hydrogen fraction, x_{H I}, from the observed Lyα luminosity density at z ≳ 6. We finally obtain x_{H I}=0.5_{-0.3}^{+0.1} as a volume-average at z = 7.3.

Stationary hydrodynamic models of Wolf-Rayet stars with optically thick winds.

NASA Astrophysics Data System (ADS)

Heger, A.; Langer, N.

1996-11-01

We investigate the influence of a grey, optically thick wind on the surface and internal structure of Wolf-Rayet (WR) stars. We calculate hydrodynamic models of chemically homogeneous helium stars with stationary outflows, solving the full set of stellar structure equations from the stellar center up to well beyond the sonic point of the wind, including the line force originating from absorption lines in a parameterized way. For specific assumptions about mass loss rate and wind opacity above our outer boundary, we find that the iron opacity peak may lead to local super-Eddington luminosities at the sonic point. By varying the stellar wind parameters over the whole physically plausible range, we show that the radius of the sonic point of the wind flow is always very close to the hydrostatic stellar radius obtained in WR star models which ignore the wind. However, our models confirm the possibility of large values for observable WR radii and correspondingly small effective temperatures found in earlier models. We show further that the energy which is contained in a typical WR wind can not be neglected. The stellar luminosity may be reduced by several 10%, which has a pronounced effect on the mass-luminosity relation, i. e., the WR masses derived for a given luminosity may be considerably larger. Thereby, also the momentum problem of WR winds is considerably reduced, as well as the scatter in the ˙(M) vs. M diagram for observed hydrogen-free WN stars.

Luminosity function of faint galaxies with ultraviolet continuum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stepanyan, D.A.

1985-05-01

The spatial density of faint galaxies with ultraviolet continuum in the Second Survey of the Byurakan Astrophysical Observatory is determined. The luminosity function of galaxies with ultraviolet continuum can be extended to objects fainter by 1-1.5 magnitudes. The spatial density of such galaxies in the interval of luminosities -16 /sup m/ .5 to -21 /sup m/ .5 is on the average 0.08 of the total density of field galaxies in the same interval of absolute magnitudes. The spatial density of low-luminosity galaxies with ultraviolet continuum is very high. In the interval from -12 /sup m/ .5 to -15 /sup m/more » .5 it is 0.23 Mpc/sup -3/.« less

An intermediate luminosity optical transient (ILOTs) model for the young stellar object ASASSN-15qi

NASA Astrophysics Data System (ADS)

Kashi, Amit; Soker, Noam

2017-07-01

We construct a scenario where the outburst of the young stellar object ASASSN-15qi is an intermediate luminosity optical transient (ILOT). In this scenario, a sub-Jupiter young planet was tidally destructed on to a young main-sequence (MS) star. The system is young, and therefore the radius of the planet is larger than its final value; consequently, its density is smaller. The lower density allows the tidal destruction of the young Saturn-like planet on to the MS star of mass ≈2.4 M⊙, resulting in the formation of a disc and a gravitationally powered ILOT. Unlike the case of the more energetic ILOT V838 Mon, the mass of the destructed planet is too low to inflate a giant envelope, and hence the merger remnant remains hot. If our suggested model holds, this ILOT possesses two interesting properties: (I) its luminosity and total energy are below those of novae; (II) it is not as red as other ILOTs. The unusual outburst of ASASSN-15qi - if indeed is an ILOT - further increases the diversity of the already heterogeneous group of ILOTs. We mark the region on the energy-time diagram occupied by such young ILOTs.

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.

A Uniformly Selected Sample of Low-mass Black Holes in Seyfert 1 Galaxies. II. The SDSS DR7 Sample

NASA Astrophysics Data System (ADS)

Liu, He-Yang; Yuan, Weimin; Dong, Xiao-Bo; Zhou, Hongyan; Liu, Wen-Juan

2018-04-01

A new sample of 204 low-mass black holes (LMBHs) in active galactic nuclei (AGNs) is presented with black hole masses in the range of (1–20) × 105 M ⊙. The AGNs are selected through a systematic search among galaxies in the Seventh Data Release (DR7) of the Sloan Digital Sky Survey (SDSS), and careful analyses of their optical spectra and precise measurement of spectral parameters. Combining them with our previous sample selected from SDSS DR4 makes it the largest LMBH sample so far, totaling over 500 objects. Some of the statistical properties of the combined LMBH AGN sample are briefly discussed in the context of exploring the low-mass end of the AGN population. Their X-ray luminosities follow the extension of the previously known correlation with the [O III] luminosity. The effective optical-to-X-ray spectral indices α OX, albeit with a large scatter, are broadly consistent with the extension of the relation with the near-UV luminosity L 2500 Å. Interestingly, a correlation of α OX with black hole mass is also found, with α OX being statistically flatter (stronger X-ray relative to optical) for lower black hole masses. Only 26 objects, mostly radio loud, were detected in radio at 20 cm in the FIRST survey, giving a radio-loud fraction of 4%. The host galaxies of LMBHs have stellar masses in the range of 108.8–1012.4 M ⊙ and optical colors typical of Sbc spirals. They are dominated by young stellar populations that seem to have undergone continuous star formation history.

ASASSN-15oi: a rapidly evolving, luminous tidal disruption event at 216 Mpc

NASA Astrophysics Data System (ADS)

Holoien, T. W.-S.; Kochanek, C. S.; Prieto, J. L.; Grupe, D.; Chen, Ping; Godoy-Rivera, D.; Stanek, K. Z.; Shappee, B. J.; Dong, Subo; Brown, J. S.; Basu, U.; Beacom, J. F.; Bersier, D.; Brimacombe, J.; Carlson, E. K.; Falco, E.; Johnston, E.; Madore, B. F.; Pojmanski, G.; Seibert, M.

2016-12-01

We present ground-based and Swift photometric and spectroscopic observations of the tidal disruption event (TDE) ASASSN-15oi, discovered at the centre of 2MASX J20390918-3045201 (d ≃ 216 Mpc) by the All-Sky Automated Survey for SuperNovae. The source peaked at a bolometric luminosity of L ≃ 1.3 × 1044 erg s-1 and radiated a total energy of E ≃ 6.6 × 1050 erg over the first ˜3.5 months of observations. The early optical/UV emission of the source can be fit by a blackbody with temperature increasing from T ˜ 2 × 104 K to T ˜ 4 × 104 K while the luminosity declines from L ≃ 1.3 × 1044 erg s-1 to L ≃ 2.3 × 1043 erg s-1, requiring the photosphere to be shrinking rapidly. The optical/UV luminosity decline during this period is most consistent with an exponential decline, L∝ e^{-(t-t_0)/τ}, with τ ≃ 46.5 d for t0 ≃ 57241.6 (MJD), while a power-law decline of L ∝ (t - t0)-α with t0 ≃ 57 212.3 and α = 1.62 provides a moderately worse fit. ASASSN-15oi also exhibits roughly constant soft X-ray emission that is significantly weaker than the optical/UV emission. Spectra of the source show broad helium emission lines and strong blue continuum emission in early epochs, although these features fade rapidly and are not present ˜3 months after discovery. The early spectroscopic features and colour evolution of ASASSN-15oi are consistent with a TDE, but the rapid spectral evolution is unique among optically selected TDEs.

Is the Ratio of Observed X-ray Luminosity to Bolometric Luminosity in Early-type Stars Really a Constant?

NASA Technical Reports Server (NTRS)

Waldron, W. L.

1985-01-01

The observed X-ray emission from early-type stars can be explained by the recombination stellar wind model (or base coronal model). The model predicts that the true X-ray luminosity from the base coronal zone can be 10 to 1000 times greater than the observed X-ray luminosity. From the models, scaling laws were found for the true and observed X-ray luminosities. These scaling laws predict that the ratio of the observed X-ray luminosity to the bolometric luminosity is functionally dependent on several stellar parameters. When applied to several other O and B stars, it is found that the values of the predicted ratio agree very well with the observed values.

THE CANADA-FRANCE HIGH-z QUASAR SURVEY: NINE NEW QUASARS AND THE LUMINOSITY FUNCTION AT REDSHIFT 6

DOE Office of Scientific and Technical Information (OSTI.GOV)

Willott, Chris J.; Crampton, David; Hutchings, John B.

2010-03-15

We present discovery imaging and spectroscopy for nine new z {approx} 6 quasars found in the Canada-France High-z Quasar Survey (CFHQS) bringing the total number of CFHQS quasars to 19. By combining the CFHQS with the more luminous Sloan Digital Sky Survey sample, we are able to derive the quasar luminosity function from a sample of 40 quasars at redshifts 5.74 < z < 6.42. Our binned luminosity function shows a slightly lower normalization and flatter slope than found in previous work. The binned data also suggest a break in the luminosity function at M {sub 1450} {approx} -25. Amore » double power-law maximum likelihood fit to the data is consistent with the binned results. The luminosity function is strongly constrained (1{sigma} uncertainty <0.1 dex) over the range -27.5 < M {sub 1450} < -24.7. The best-fit parameters are {phi}(M*{sub 1450}) = 1.14 x 10{sup -8} Mpc{sup -3} mag{sup -1}, break magnitude M*{sub 1450} = -25.13, and bright end slope {beta} = -2.81. However, the covariance between {beta} and M*{sub 1450} prevents strong constraints being placed on either parameter. For a break magnitude in the range -26 < M*{sub 1450} < -24, we find -3.8 < {beta} < -2.3 at 95% confidence. We calculate the z = 6 quasar intergalactic ionizing flux and show it is between 20 and 100 times lower than that necessary for reionization. Finally, we use the luminosity function to predict how many higher redshift quasars may be discovered in future near-IR imaging surveys.« less

Characterizing mid-ultraviolet to optical light curves of nearby type IIn supernovae

DOE PAGES

de la Rosa, Janie; Roming, Pete; Pritchard, Tyler; ...

2016-03-21

Here, we present early mid-ultraviolet and optical observations of Type IIn supernovae (SNe IIn) observed from 2007 to 2013. Our results focus on the properties of UV light curves: peak absolute magnitudes, temporal decay, and color evolution. During early times, this sample demonstrates that UV light decays faster than optical, and each event transitions from a predominantly UV-bright phase to an optically bright phase. In order to understand early UV behavior, we generate and analyze the sample's blackbody luminosity, temperature, and radius as the SN ejecta expand and cool. Since most of our observations were detected post maximum luminosity, wemore » introduce a method for estimating the date of peak magnitude. When our observations are compared based on filter, we find that even though these SNe IIn vary in peak magnitudes, there are similarities in UV decay rates. We use a simple semi-analytical SN model in order to understand the effects of the explosion environment on our UV observations. Understanding the UV characteristics of nearby SNe IIn during an early phase can provide valuable information about the environment surrounding these explosions, leading us to evaluating the diversity of observational properties in this subclass.« less

Luminosities of Radio Pulsars

NASA Astrophysics Data System (ADS)

Bagchi, Manjari

2013-08-01

Luminosity is an intrinsic property of radio pulsars related to the properties of the magnetospheric plasma and the beam geometry, and inversely proportional to the observing frequency. In traditional models, luminosity has been considered as a function of the spin parameters of pulsars. On the other hand, parameter independent models like power law and lognormal have been also used to fit the observed luminosities. Some of the older studies on pulsar luminosities neglected observational biases, but all of the recent studies tried to model observational effects as accurately as possible. Luminosities of pulsars in globular clusters (GCs) and in the Galactic disk have been studied separately. Older studies concluded that these two categories of pulsars have different luminosity distributions, but the most recent study concluded that those are the same. This paper reviews all significant works on pulsar luminosities and discusses open questions.

Continuing Long Term Optical and Infrared Reverberation Mapping of 17 Sloan Digital Sky Survey Quasars

NASA Astrophysics Data System (ADS)

Gorjian, Varoujan; Barth, Aaron; Brandt, Niel; Dawson, Kyle; Green, Paul; Ho, Luis; Horne, Keith; Jiang, Linhua; McGreer, Ian; Schneider, Donald; Shen, Yue; Tao, Charling

2018-05-01

Previous Spitzer reverberation monitoring projects searching for UV/optical light absorbed and re-emitted in the IR by dust have been limited to low luminosity active galactic nuclei (AGN) that could potentially show reverberation within a single cycle ( 1 year). Cycle 11-12's two year baseline allowed for the reverberation mapping of 17 high-luminosity quasars from the Sloan Digital Sky Survey Reverberation Mapping project. We continued this monitoring in Cycle 13 and now propose to extend this program in Cycle 14. By combining ground-based monitoring from Pan-STARRS, CFHT, and Steward Observatory telescopes with Spitzer data we have for the first time detected dust reverberation in quasars. By continuing observations with this unqiue combination of resources we should detect reverberation in more objects and reduce the uncertainties for the remaining sources.

Optical Rotation Curves and Linewidths for Tully-Fisher Applications

NASA Astrophysics Data System (ADS)

Courteau, Stephane

1997-12-01

We present optical long-slit rotation curves for 304 northern Sb-Sc UGC galaxies from a sample designed for Tully-Fisher (TF) applications. Matching r-band photometry exists for each galaxy. We describe the procedures of rotation curve (RC) extraction and construction of optical profiles analogous to 21 cm integrated linewidths. More than 20% of the galaxies were observed twice or more, allowing for a proper determination of systematic errors. Various measures of maximum rotational velocity to be used as input in the TF relation are tested on the basis of their repeatability, minimization of TF scatter, and match with 21 cm linewidths. The best measure of TF velocity, V2.2 is given at the location of peak rotational velocity of a pure exponential disk. An alternative measure to V2.2 which makes no assumption about the luminosity profile or shape of the rotation curve is Vhist, the 20% width of the velocity histogram, though the match with 21 cm linewidths is not as good. We show that optical TF calibrations yield internal scatter comparable to, if not smaller than, the best calibrations based on single-dish 21 cm radio linewidths. Even though resolved H I RCs are more extended than their optical counterpart, a tight match between optical and radio linewidths exists since the bulk of the H I surface density is enclosed within the optical radius. We model the 304 RCs presented here plus a sample of 958 curves from Mathewson et al. (1992, APJS, 81, 413) with various fitting functions. An arctan function provides an adequate simple fit (not accounting for non-circular motions and spiral arms). More elaborate, empirical models may yield a better match at the expense of strong covariances. We caution against physical or "universal" parametrizations for TF applications.

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.;

Phase-dependent Photometric and Spectroscopic Characterization of the MASTER-Net Optical Transient J212444.87+321738.3: An Oxygen-rich Mira

NASA Astrophysics Data System (ADS)

Ghosh, Supriyo; Mondal, Soumen; Das, Ramkrishna; Banerjee, D. P. K.; Ashok, N. M.; Hambsch, Franz-Josef; Dutta, Somnath

2018-05-01

We describe the time-dependent properties of a new spectroscopically confirmed Mira variable, which was discovered in 2013 as MASTER-Net Optical Transient J212444.87+321738.3 toward the Cygnus constellation. We have performed long-term optical/near-infrared (NIR) photometric and spectroscopic observations to characterize the object. From the optical/NIR light curves, we estimate a variability period of 465 ± 30 days. The wavelength-dependent amplitudes of the observed light curves range from ΔI ∼ 4 mag to ΔK ∼ 1.5 mag. The (J ‑ K) color index varies from 1.78 to 2.62 mag over phases. Interestingly, a phase lag of ∼60 days between optical and NIR light curves is also seen, as in other Miras. Our optical/NIR spectra show molecular features of TiO, VO, CO, and strong water bands that are a typical signature of oxygen-rich Mira. We rule out S- or C-type as ZrO bands at 1.03 and 1.06 μm and C2 band at 1.77 μm are absent. We estimate the effective temperature of the object from the Spectral Energy Distribution, and distance and luminosity from standard Period–Luminosity relations. The optical/NIR spectra display time-dependent atomic and molecular features (e.g., TiO, Na I, Ca I, H2O, CO), as commonly observed in Miras. Such spectroscopic observations are useful for studying pulsation variability in Miras.

Revisiting Optical Tidal Disruption Events with iPTF16axa

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hung, T.; Gezari, S.; Blagorodnova, N.

We report the discovery by the intermediate Palomar Transient Factory (iPTF) of a candidate tidal disruption event (TDE) iPTF16axa at z = 0.108 and present its broadband photometric and spectroscopic evolution from three months of follow-up observations with ground-based telescopes and Swift. The light curve is well fitted with a t -5/3 decay, and we constrain the rise time to peak to be <49 rest-frame days after disruption, which is roughly consistent with the fallback timescale expected for the ~5 × 10 6 M ⊙ black hole inferred from the stellar velocity dispersion of the host galaxy. The UV and optical spectral energy distribution is well described by a constant blackbody temperature of T ~ 3 × 10 4 K over the monitoring period, with an observed peak luminosity of 1.1 × 10 44 erg s -1. The optical spectra are characterized by a strong blue continuum and broad He ii and Hα lines, which are characteristic of TDEs. We compare the photometric and spectroscopic signatures of iPTF16axa with 11 TDE candidates in the literature with well-sampled optical light curves. Based on a single-temperature fit to the optical and near-UV photometry, most of these TDE candidates have peak luminosities confined between log(L [erg s -1]) = 43.4–44.4, with constant temperatures of a few ×104 K during their power-law declines, implying blackbody radii on the order of 10 times the tidal disruption radius, that decrease monotonically with time. For TDE candidates with hydrogen and helium emission, the high helium-to-hydrogen ratios suggest that the emission arises from high-density gas, where nebular arguments break down. In conclusion, we find no correlation between the peak luminosity and the black hole mass, contrary to the expectations for TDEs to havemore » $$\\dot{M}\\propto {M}_{\\mathrm{BH}}^{-1/2}$$.« less

Revisiting Optical Tidal Disruption Events with iPTF16axa

DOE PAGES

Hung, T.; Gezari, S.; Blagorodnova, N.; ...

2017-06-08

We report the discovery by the intermediate Palomar Transient Factory (iPTF) of a candidate tidal disruption event (TDE) iPTF16axa at z = 0.108 and present its broadband photometric and spectroscopic evolution from three months of follow-up observations with ground-based telescopes and Swift. The light curve is well fitted with a t -5/3 decay, and we constrain the rise time to peak to be <49 rest-frame days after disruption, which is roughly consistent with the fallback timescale expected for the ~5 × 10 6 M ⊙ black hole inferred from the stellar velocity dispersion of the host galaxy. The UV and optical spectral energy distribution is well described by a constant blackbody temperature of T ~ 3 × 10 4 K over the monitoring period, with an observed peak luminosity of 1.1 × 10 44 erg s -1. The optical spectra are characterized by a strong blue continuum and broad He ii and Hα lines, which are characteristic of TDEs. We compare the photometric and spectroscopic signatures of iPTF16axa with 11 TDE candidates in the literature with well-sampled optical light curves. Based on a single-temperature fit to the optical and near-UV photometry, most of these TDE candidates have peak luminosities confined between log(L [erg s -1]) = 43.4–44.4, with constant temperatures of a few ×104 K during their power-law declines, implying blackbody radii on the order of 10 times the tidal disruption radius, that decrease monotonically with time. For TDE candidates with hydrogen and helium emission, the high helium-to-hydrogen ratios suggest that the emission arises from high-density gas, where nebular arguments break down. In conclusion, we find no correlation between the peak luminosity and the black hole mass, contrary to the expectations for TDEs to havemore » $$\\dot{M}\\propto {M}_{\\mathrm{BH}}^{-1/2}$$.« less

The black hole candidate XTE J1752-223 towards and in quiescence: optical and simultaneous X-ray-radio observations

NASA Astrophysics Data System (ADS)

Ratti, E. M.; Jonker, P. G.; Miller-Jones, J. C. A.; Torres, M. A. P.; Homan, J.; Markoff, S.; Tomsick, J. A.; Kaaret, P.; Wijnands, R.; Gallo, E.; Özel, F.; Steeghs, D. T. H.; Fender, R. P.

2012-07-01

We present optical, X-ray and radio observations of the black hole transient (BHT) XTE J1752-223 towards and in quiescence. Optical photometry shows that the quiescent magnitude of XTE J1752-223 is fainter than 24.4 mag in the i' band. A comparison with measurements of the source during its 2009-2010 outburst shows that the outburst amplitude is more than 8 mag in the i' band. Known X-ray properties of the source combined with the faintness of the quiescence optical counterpart and the large outburst optical amplitude point towards a short orbital-period system (Porb≲ 6.8 h) with an M type (or later) mass donor, at a distance of 3.5 ≲d≲ 8 kpc. Simultaneous X-ray and radio data were collected with Chandra and the Expanded Very Large Array (EVLA), allowing constraints to be placed on the quiescent X-ray and radio flux of XTE J1752-223. Furthermore, using data covering the final stage of the outburst decay, we investigated the low-luminosity end of the X-ray-radio correlation for this source and compared it with other BHTs. We found that XTE J1752-223 adds to the number of outliers with respect to the 'standard' X-ray-radio luminosity relation. Furthermore, XTE J1752-223 is the second source, after the BHT H1743-322, that shows a transition from the region of the outliers towards the 'standard' correlation at low luminosity. Finally, we report on a faint, variable X-ray source we discovered with Chandra at an angular distance of ˜2.9 arcsec to XTE J1752-223 and at a position angle consistent with that of the radio jets previously observed from the BHT. We discuss the possibility that we detected X-ray emission associated with a jet from XTE J1752-223.

A New Compton-thick AGN in our Cosmic Backyard: Unveiling the Buried Nucleus in NGC 1448 with NuSTAR

NASA Astrophysics Data System (ADS)

Annuar, A.; Alexander, D. M.; Gandhi, P.; Lansbury, G. B.; Asmus, D.; Ballantyne, D. R.; Bauer, F. E.; Boggs, S. E.; Boorman, P. G.; Brandt, W. N.; Brightman, M.; Christensen, F. E.; Craig, W. W.; Farrah, D.; Goulding, A. D.; Hailey, C. J.; Harrison, F. A.; Koss, M. J.; LaMassa, S. M.; Murray, S. S.; Ricci, C.; Rosario, D. J.; Stanley, F.; Stern, D.; Zhang, W.

2017-02-01

NGC 1448 is one of the nearest luminous galaxies (L 8-1000μm > 109 L ⊙) to ours (z = 0.00390), and yet the active galactic nucleus (AGN) it hosts was only recently discovered, in 2009. In this paper, we present an analysis of the nuclear source across three wavebands: mid-infrared (MIR) continuum, optical, and X-rays. We observed the source with the Nuclear Spectroscopic Telescope Array (NuSTAR), and combined these data with archival Chandra data to perform broadband X-ray spectral fitting (≈0.5-40 keV) of the AGN for the first time. Our X-ray spectral analysis reveals that the AGN is buried under a Compton-thick (CT) column of obscuring gas along our line of sight, with a column density of N H(los) ≳ 2.5 × 1024 cm-2. The best-fitting torus models measured an intrinsic 2-10 keV luminosity of L {}2-10,{int} = (3.5-7.6) × 1040 erg s-1, making NGC 1448 one of the lowest luminosity CTAGNs known. In addition to the NuSTAR observation, we also performed optical spectroscopy for the nucleus in this edge-on galaxy using the European Southern Observatory New Technology Telescope. We re-classify the optical nuclear spectrum as a Seyfert on the basis of the Baldwin-Philips-Terlevich diagnostic diagrams, thus identifying the AGN at optical wavelengths for the first time. We also present high spatial resolution MIR observations of NGC 1448 with Gemini/T-ReCS, in which a compact nucleus is clearly detected. The absorption-corrected 2-10 keV luminosity measured from our X-ray spectral analysis agrees with that predicted from the optical [O III]λ5007 Å emission line and the MIR 12 μm continuum, further supporting the CT nature of the AGN.

Revisiting Optical Tidal Disruption Events with iPTF16axa

NASA Astrophysics Data System (ADS)

Hung, T.; Gezari, S.; Blagorodnova, N.; Roth, N.; Cenko, S. B.; Kulkarni, S. R.; Horesh, A.; Arcavi, I.; McCully, C.; Yan, Lin; Lunnan, R.; Fremling, C.; Cao, Y.; Nugent, P. E.; Wozniak, P.

2017-06-01

We report the discovery by the intermediate Palomar Transient Factory (iPTF) of a candidate tidal disruption event (TDE) iPTF16axa at z = 0.108 and present its broadband photometric and spectroscopic evolution from three months of follow-up observations with ground-based telescopes and Swift. The light curve is well fitted with a t -5/3 decay, and we constrain the rise time to peak to be <49 rest-frame days after disruption, which is roughly consistent with the fallback timescale expected for the ˜5 × 106 M ⊙ black hole inferred from the stellar velocity dispersion of the host galaxy. The UV and optical spectral energy distribution is well described by a constant blackbody temperature of T ˜ 3 × 104 K over the monitoring period, with an observed peak luminosity of 1.1 × 1044 erg s-1. The optical spectra are characterized by a strong blue continuum and broad He II and Hα lines, which are characteristic of TDEs. We compare the photometric and spectroscopic signatures of iPTF16axa with 11 TDE candidates in the literature with well-sampled optical light curves. Based on a single-temperature fit to the optical and near-UV photometry, most of these TDE candidates have peak luminosities confined between log(L [erg s-1]) = 43.4-44.4, with constant temperatures of a few ×104 K during their power-law declines, implying blackbody radii on the order of 10 times the tidal disruption radius, that decrease monotonically with time. For TDE candidates with hydrogen and helium emission, the high helium-to-hydrogen ratios suggest that the emission arises from high-density gas, where nebular arguments break down. We find no correlation between the peak luminosity and the black hole mass, contrary to the expectations for TDEs to have \\dot{M}\\propto {M}{BH}-1/2.

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.

WISE Discovery of Hyper Luminous Galaxies at z=2-4 and Their Implications for Galaxy and AGN Evolution

NASA Technical Reports Server (NTRS)

Tsai, Chao Wei; Eisenhardt, Peter; Wu, Jingwen; Bridge, Carrie; Assef, Roberto; Benford, Dominic; Blain, Andrew; Cutri, Roc; Griffith, Robert L.; Jarrett, Thomas;

Dust Grains and the Luminosity of Circumnuclear Water Masers in Active Galaxies

NASA Technical Reports Server (NTRS)

Collison, Alan J.; Watson, William D.

1995-01-01

In previous calculations for the luminosities of 22 GHz water masers, the pumping is reduced and ultimately quenched with increasing depth into the gas because of trapping of the infrared (approximately equals 30-150 micrometers), spectral line radiation of the water molecule. When the absorption (and reemission) of infrared radiation by dust grains is included, we demonstrate that the pumping is no longer quenched but remains constant with increasing optical depth. A temperature difference between the grains and the gas is required. Such conditions are expected to occur, for example, in the circumnuclear masing environments created by X-rays in active galaxies. Here, the calculated 22 GHz maser luminosities are increased by more than an order of magnitude. Application to the well-studied, circumnuclear masing disk in the galaxy NGC 4258 yields a maser luminosity near that inferred from observations if the observed X-ray flux is assumed to be incident onto only the inner surface of the disk.

The Ursa Major cluster of galaxies - III. Optical observations of dwarf galaxies and the luminosity function down to MR=-11

NASA Astrophysics Data System (ADS)

Trentham, Neil; Tully, R. Brent; Verheijen, Marc A. W.

2001-07-01

Results are presented of a deep optical survey of the Ursa Major cluster, a spiral-rich cluster of galaxies at a distance of 18.6Mpc which contains about 30 per cent of the light but only 5 per cent of the mass of the nearby Virgo cluster. Fields around known cluster members and a pattern of blind fields along the major and minor axes of the cluster were studied with mosaic CCD cameras on the Canada-France-Hawaii Telescope. The dynamical crossing time for the Ursa Major cluster is only slightly less than a Hubble time. Most galaxies in the local Universe exist in similar moderate-density environments. The Ursa Major cluster is therefore a good place to study the statistical properties of dwarf galaxies, since this structure is at an evolutionary stage representative of typical environments, yet has enough galaxies that reasonable counting statistics can be accumulated. The main observational results of our survey are as follows. (i) The galaxy luminosity function is flat, with a logarithmic slope α=-1.1 for -17

SN 2012fr: Ultraviolet, Optical, and Near-infrared Light Curves of a Type Ia Supernova Observed within a Day of Explosion

NASA Astrophysics Data System (ADS)

Contreras, Carlos; Phillips, M. M.; Burns, Christopher R.; Piro, Anthony L.; Shappee, B. J.; Stritzinger, Maximilian D.; Baltay, C.; Brown, Peter J.; Conseil, Emmanuel; Klotz, Alain; Nugent, Peter E.; Turpin, Damien; Parker, Stu; Rabinowitz, D.; Hsiao, Eric Y.; Morrell, Nidia; Campillay, Abdo; Castellón, Sergio; Corco, Carlos; González, Consuelo; Krisciunas, Kevin; Serón, Jacqueline; Tucker, Brad E.; Walker, E. S.; Baron, E.; Cain, C.; Childress, Michael J.; Folatelli, Gastón; Freedman, Wendy L.; Hamuy, Mario; Hoeflich, P.; Persson, S. E.; Scalzo, Richard; Schmidt, Brian; Suntzeff, Nicholas B.

2018-05-01

We present detailed ultraviolet, optical, and near-infrared light curves of the Type Ia supernova (SN) 2012fr, which exploded in the Fornax cluster member NGC 1365. These precise high-cadence light curves provide a dense coverage of the flux evolution from ‑12 to +140 days with respect to the epoch of B-band maximum ({t}{B\\max }). Supplementary imaging at the earliest epochs reveals an initial slow and nearly linear rise in luminosity with a duration of ∼2.5 days, followed by a faster rising phase that is well reproduced by an explosion model with a moderate amount of 56Ni mixing in the ejecta. From our analysis of the light curves, we conclude that: (i) the explosion occurred <22 hr before the first detection of the supernova, (ii) the rise time to peak bolometric (λ > 1800 Å) luminosity was 16.5 ± 0.6 days, (iii) the supernova suffered little or no host-galaxy dust reddening, (iv) the peak luminosity in both the optical and near-infrared was consistent with the bright end of normal Type Ia diversity, and (v) 0.60 ± 0.15 M ⊙ of 56Ni was synthesized in the explosion. Despite its normal luminosity, SN 2012fr displayed unusually prevalent high-velocity Ca II and Si II absorption features, and a nearly constant photospheric velocity of the Si II λ6355 line at ∼12,000 {km} {{{s}}}-1 that began ∼5 days before {t}{B\\max }. We also highlight some of the other peculiarities in the early phase photometry and the spectral evolution. SN 2012fr also adds to a growing number of Type Ia supernovae that are hosted by galaxies with direct Cepheid distance measurements. This paper includes data gathered with the 6.5 m Magellan Baade Telescope, located at Las Campanas Observatory, Chile.

The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. VIII. A Comparison to Cosmological Short-duration Gamma-Ray Bursts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fong, W.; Berger, E.; Blanchard, P. K.

Here, we present a comprehensive comparison of the properties of the radio through X-ray counterpart of GW170817 and the properties of short-duration gamma-ray bursts (GRBs). For this effort, we utilize a sample of 36 short GRBs spanning a redshift range ofmore » $$z \\approx 0.12-2.6$$ discovered over 2004-2017. We find that the counterpart to GW170817 has an isotropic-equivalent luminosity that is $$\\approx 3000$$ times less than the median value of on-axis short GRB X-ray afterglows, and $$\\gtrsim10^{4}$$ times less than that for detected short GRB radio afterglows. Moreover, the allowed jet energies and particle densities inferred from the radio and X-ray counterparts to GW170817 and on-axis short GRB afterglows are remarkably similar, suggesting that viewing angle effects are the dominant, and perhaps only, difference in their observed radio and X-ray behavior. From comparison to previous claimed kilonovae following short GRBs, we find that the optical and near-IR counterpart to GW170817 is comparatively under-luminous by a factor of $$\\approx 3-5$$, indicating a range of kilonova luminosities and timescales. A comparison of the optical limits following short GRBs on $$\\lesssim 1$$ day timescales also rules out a "blue" kilonova of comparable optical isotropic-equivalent luminosity in one previous short GRB. Finally, we investigate the host galaxy of GW170817, NGC4993, in the context of short GRB host galaxy stellar population properties. We find that NGC4993 is superlative in terms of its large luminosity, old stellar population age, and low star formation rate compared to previous short GRB hosts. Additional events within the Advanced LIGO/VIRGO volume will be crucial in delineating the properties of the host galaxies of NS-NS mergers, and connecting them to their cosmological counterparts.« less

The Geometry of the Infrared and X-Ray Obscurer in a Dusty Hyperluminous Quasar

NASA Astrophysics Data System (ADS)

Farrah, Duncan; Baloković, Mislav; Stern, Daniel; Harris, Kathryn; Kunimoto, Michelle; Walton, Dominic J.; Alexander, David M.; Arévalo, Patricia; Ballantyne, David R.; Bauer, Franz E.; Boggs, Steven; Brandt, William N.; Brightman, Murray; Christensen, Finn; Clements, David L.; Craig, William; Fabian, Andrew; Hailey, Charles; Harrison, Fiona; Koss, Michael; Lansbury, George B.; Luo, Bin; Paine, Jennie; Petty, Sara; Pitchford, Kate; Ricci, Claudio; Zhang, William

2016-11-01

We study the geometry of the active galactic nucleus (AGN) obscurer in IRAS 09104+4109, an IR-luminous, radio-intermediate FR-I source at z = 0.442, using infrared data from Spitzer and Herschel, X-ray data from NuSTAR, Swift, Suzaku, and Chandra, and an optical spectrum from Palomar. The infrared data imply a total rest-frame 1-1000 μm luminosity of 5.5 × 1046 erg s-1 and require both an AGN torus and a starburst model. The AGN torus has an anisotropy-corrected IR luminosity of 4.9 × 1046 erg s-1 and a viewing angle and half-opening angle both of approximately 36° from pole-on. The starburst has a star formation rate of (110 ± 34) M ⊙ yr-1 and an age of <50 Myr. These results are consistent with two epochs of luminous activity in IRAS 09104+4109: one approximately 150 Myr ago, and one ongoing. The X-ray data suggest a photon index of Γ ≃ 1.8 and a line-of-sight column density of N H ≃ 5 × 1023 cm-2. This argues against a reflection-dominated hard X-ray spectrum, which would have implied a much higher N H and luminosity. The X-ray and infrared data are consistent with a bolometric AGN luminosity of L bol ˜ (0.5-2.5) × 1047 erg s-1. The X-ray and infrared data are further consistent with coaligned AGN obscurers in which the line of sight “skims” the torus. This is also consistent with the optical spectra, which show both coronal iron lines and broad lines in polarized but not direct light. Combining constraints from the X-ray, optical, and infrared data suggest that the AGN obscurer is within a vertical height of 20 pc, and a radius of 125 pc, of the nucleus.

The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. VIII. A Comparison to Cosmological Short-duration Gamma-Ray Bursts

DOE PAGES

Fong, W.; Berger, E.; Blanchard, P. K.; ...

2017-10-16

Here, we present a comprehensive comparison of the properties of the radio through X-ray counterpart of GW170817 and the properties of short-duration gamma-ray bursts (GRBs). For this effort, we utilize a sample of 36 short GRBs spanning a redshift range ofmore » $$z \\approx 0.12-2.6$$ discovered over 2004-2017. We find that the counterpart to GW170817 has an isotropic-equivalent luminosity that is $$\\approx 3000$$ times less than the median value of on-axis short GRB X-ray afterglows, and $$\\gtrsim10^{4}$$ times less than that for detected short GRB radio afterglows. Moreover, the allowed jet energies and particle densities inferred from the radio and X-ray counterparts to GW170817 and on-axis short GRB afterglows are remarkably similar, suggesting that viewing angle effects are the dominant, and perhaps only, difference in their observed radio and X-ray behavior. From comparison to previous claimed kilonovae following short GRBs, we find that the optical and near-IR counterpart to GW170817 is comparatively under-luminous by a factor of $$\\approx 3-5$$, indicating a range of kilonova luminosities and timescales. A comparison of the optical limits following short GRBs on $$\\lesssim 1$$ day timescales also rules out a "blue" kilonova of comparable optical isotropic-equivalent luminosity in one previous short GRB. Finally, we investigate the host galaxy of GW170817, NGC4993, in the context of short GRB host galaxy stellar population properties. We find that NGC4993 is superlative in terms of its large luminosity, old stellar population age, and low star formation rate compared to previous short GRB hosts. Additional events within the Advanced LIGO/VIRGO volume will be crucial in delineating the properties of the host galaxies of NS-NS mergers, and connecting them to their cosmological counterparts.« less

Black Hole Demographics in and Nuclear Properties of Nearby Low Luminosity Radio Galaxies; Connections to Radio Activity?

NASA Technical Reports Server (NTRS)

Baum, S. A.; Kleijn, G. A. Verdoes; Xu, C.; ODea, C. P.; deZeeuw, P. T.

2004-01-01

We combine the results of an HST STIS and WFPC study of a complete sample of 21 nearby UGC low luminosity radio galaxies with the results of a radio VLA and VLBA study of the same sample. We examine the relationship between the stellar and gaseous properties of the galaxies on tens to hundreds of parsec scale with the properties of the radio jets on the same scale. From the VLA and VLBA data we constrain the physics of the outflowing radio plasma from the tens of parsecs to hundreds of kiloparsec scales. From the WFPC2 H alpha and dust images and the STIS kinematics of the near nuclear gas we obtain constraints on the orientation of near nuclear disks of gas and measures of the nuclear stellar, continuum point source, and line emission fluxes. Under the statistically supported assumption that the radio jet issues perpendicular to the disk, we use the orientation of the optical (large scale accretion?) disks to constrain the three-dimensional orientation of the radio ejection. From HST/STIS spectroscopy of the near-nuclear emission line gas we obtain measures/limits on the black hole masses. We examine correlations between the VLBA and VLA-scale radio emission, the nuclear line emission, and the nuclear optical and radio continuum emission. Though our sample is relatively small, it is uniquely well defined, spans a narrow range in redshift and we have a consistent set of high resolution data with which to carefully examine these relationships. We use the combined radio and optical data to: 1) Constrain the orientation, physics, and bulk outflow speed of the radio plasma; 2) Put limits on the mass accretion rate and study the relationship between black hole mass, radio luminosity, and near nuclear gaseous content; 3) Provide insight into the relationship between BL Lac objects and low luminosity radio galaxies.

The Geometry of the Infrared and X-Ray Obscurer in a Dusty Hyperluminous Quasar

NASA Technical Reports Server (NTRS)

Farrah, Duncan; Balokovic, Mislav; Stern, Daniel; Harris, Kathryn; Kunimoto, Michelle; Walton, Dominc J.; Alexander, David M.; Arevalo, Patricia; Ballantyne, David R.; Bauer, Franz E.;

Late Time Multi-Wavelength Observations of Swift J1644+5734: A Luminous Optical/IR Bump and Quiescent X-Ray Emission

NASA Technical Reports Server (NTRS)

Levan, A. J.; Tanvir, N. R.; Brown, G. C.; Metzger, B.D.; Page, K. L.; Cenko, S. B.; O'Brien, P. T.; Lyman, J. D.; Wiersema, K.; Stanway, E. R.;

The nature of the embedded population in the Rho Ophiuchi dark cloud - Mid-infrared observations

NASA Technical Reports Server (NTRS)

Lada, C. J.; Wilking, B. A.

1984-01-01

In combination with previous IR and optical data, the present 10-20 micron observations of previously identified members of the embedded population of the Rho Ophiuchi dark cloud allow determinations to be made of the broadband energy distributions for 32 of the 44 sources. The majority of the sources are found to emit the bulk of their luminosity in the 1-20 micron range, and to be surrounded by dust shells. Because they are, in light of these characteristics, probably premain-sequence in nature, relatively accurate bolometric luminosities for these objects can be obtained through integration of their energy distributions. It is found that 44 percent of the sources are less luminous than the sun, and are among the lowest luminosity premain-sequence/protostellar objects observed to date.

Detection of H I, OH, CO, and optical imaging of the distant galaxy IRAS 12112 + 0305

NASA Technical Reports Server (NTRS)

Mirabel, I. F.; Kazes, I.; Sanders, D. B.

1988-01-01

The detection of H I absorption and OH and CO emission from the galaxy IRAS 12112 + 0305, which is receding from the sun at about 7 percent of the speed of light is reported. This galaxy, which appears to be an ongoing merger, radiates about 2 x 10 to the 12th solar luminosities in the infrared. The H I, OH, and CO spectra are indicative of large turbulent motions. From the millimeter wave CO observations, a total mass of molecular gas of 4 x 10 to the 10th solar masses is inferred. The OH emission in the 1667 MHz line is the most luminous extragalactic OH maser reported so far, with an isotropic luminosity of 1800 solar luminosities.

Spectroscopic observations of the symbiotic binary RW Hydrae

NASA Technical Reports Server (NTRS)

Kenyon, Scott J.; Fernandez-Castro, Telmo

1987-01-01

Ultraviolet/optical spectrophotometry and infrared photometry show that the symbiotic binary RW Hya is comprised of an M giant (with L of about 1000 solar luminosities) and a compact object (with L of about 200 solar luminosities) which resembles the central star of a planetary nebula. The luminosity of the hot component is produced by a nuclear shell source which is replenished by the wind of the red giant at a rate of about 10 to the -8th solar mass/yr. Results indicate that the binary is surrounded by an H II region (of radius of about 10 AU) which gives rise to the observed emission lines and radio emission. The He(2+) and O(2+) regions are found to be confined to the immediate vicinity of the hot component.

Numerical calculations of spectral turnover and synchrotron self-absorption in CSS and GPS radio sources

NASA Astrophysics Data System (ADS)

Jeyakumar, S.

2016-06-01

The dependence of the turnover frequency on the linear size is presented for a sample of Giga-hertz Peaked Spectrum and Compact Steep Spectrum radio sources derived from complete samples. The dependence of the luminosity of the emission at the peak frequency with the linear size and the peak frequency is also presented for the galaxies in the sample. The luminosity of the smaller sources evolve strongly with the linear size. Optical depth effects have been included to the 3D model for the radio source of Kaiser to study the spectral turnover. Using this model, the observed trend can be explained by synchrotron self-absorption. The observed trend in the peak-frequency-linear-size plane is not affected by the luminosity evolution of the sources.

VizieR Online Data Catalog: The CLASS blazar survey. I. (Marcha+, 2001)

NASA Astrophysics Data System (ADS)

Marcha, M. J.; Caccianiga, A.; Browne, I. W. A.; Jackson, N.

2002-04-01

This paper presents a new complete and well-defined sample of flat-spectrum radio sources (FSRS) selected from the Cosmic Lens All-Sky Survey (CLASS), with the further constraint of a bright (mag<=17.5) optical counterpart. The sample has been designed to produce a large number of low-luminosity blazars in order to test the current unifying models in the low-luminosity regime. In this first paper the new sample is presented and the radio properties of the 325 sources contained therein are discussed. (1 data file).

Tidal interactions and infrared-bright QSOs

NASA Technical Reports Server (NTRS)

Hutchings, J. B.; Neff, S. G.

1988-01-01

Deep direct images of five IRAS-selected QSOs with similar IR luminosities and spectral indices have been analyzed. The present objects possess IR luminosities similar to those of the IRAS flux-lined sample of ultraluminous galaxies, but have IR spectral indices similar to those of normal QSOs. Four of the objects are in strong tidal interaction and have blue host galaxies and reddened nuclei. It is suggested that these objects are QSOs and AGN in an intermediate stage of their activity, which lies between that of ultraluminous galaxies and optically selected QSOs.

VLA observations of unidentified Leiden-Berkeley Deep-Survey sources - Luminosity and redshift dependence of spectral properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kapahi, V.K.; Kulkarni, V.K.

1990-05-01

VLA observations of a complete subset of the Leiden-Berkeley Deep Survey sources that have S(1.4 GHz) greater than 10 mJy and are not optically identified down to F=22 mag are reported. By comparing the spectral and structural properties of the sources with samples from the literature, an attempt was made to disentangle the luminosity and redshift dependence of the spectral indices of extended emission in radio galaxies and of the incidence of compact steep-spectrum sources. It is found that the fraction of compact sources among those with a steep spectrum is related primarily to redshift, being much larger at highmore » redshifts for sources of similar radio luminosity. Only a weak and marginally significant dependence of spectral indices of the extended sources on luminosity and redshift is found in samples selected at 1.4 and 2.7 GHz. It is pointed out that the much stronger correlation of spectral indices with luminosity may be arising partly from spectral curvature, and partly due to the preferential inclusion of very steep-spectrum sources from high redshift in low-frequency surveys. 54 refs.« less

Probing stellar mass build-up in galaxies at z=4-7 with CANDELS and S-CANDELS

NASA Astrophysics Data System (ADS)

Song, Mimi; Finkelstein, Steven L.; Ashby, Matthew; Merlin, Emiliano

2015-01-01

Over the last few years the advent of the Hubble Space Telescope (HST) Wide Field Camera 3 has enabled us to build statistically significant samples of galaxies out to z=8. We have subsequently witnessed remarkable progress in our understanding of galaxy evolution in the early universe. However, our understanding of the galaxy stellar mass growth in this era has been limited due to the lack of rest-frame optical data at a comparable depth as the HST data. Here we present results on the galaxy stellar mass function at z=4-7 from a sample of ~7500 galaxies over an area of ~280 square arcmin in the CANDELS GOODS-South and North fields, as well as the Hubble Ultra Deep Field. Utilizing deep IRAC data from the S-CANDELS and IUDF10 programs to robustly constrain the stellar masses of galaxies in our sample, we measure the stellar-mass to rest-frame ultraviolet (UV) luminosity trends in each of our redshift bins. We convolve these trends with recent measurements of the rest-frame ultraviolet luminosity function to derive the stellar mass functions. Contrary to initial studies at these redshifts, we find steeper low-mass-end slopes (-1.6 at z=4, and -2.0 at z=7), similar to recent simulations. Our results provide the most accurate estimates to date of the cosmic stellar mass density over the first two billion years after the Big Bang.

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 as many ionizing photons as the radio H II regions themselves. Allowing for the ionizing radiation that is absorbed by dust (about 25% of the total), we find that the maximum ionizing photon luminosity of a Galactic OB association is Su ~= 4.9 × 1051 photons s-1, corresponding to an Hα luminosity of about 5 × 1039 ergs s-1. The total ionizing luminosity of this distribution of OB associations can account for the thermal radio emission and the N II far-infrared emission of the Galaxy. The number of massive stars in the associations is consistent with estimates of the rate of massive star supernovae in the Galaxy. Associations produce several generations of stars over their lifetimes, and the largest associations are predicted to produce about 7000 supernova progenitors. Fitting the surface density of associations to an exponential of the form d\\Nscra(\\Nscr*)/dA~ exp (-R/HR) with a scale length HR = 3.5 kpc gives a number of OB associations in the solar neighborhood that is consistent with observation. The H II envelopes contribute to pulsar dispersion measures and can account for the increased dispersion measure observed in the inner Galaxy.

The MUSE Hubble Ultra Deep Field Survey. VI. The faint-end of the Lyα luminosity function at 2.91 < z < 6.64 and implications for reionisation

NASA Astrophysics Data System (ADS)

Drake, A. B.; Garel, T.; Wisotzki, L.; Leclercq, F.; Hashimoto, T.; Richard, J.; Bacon, R.; Blaizot, J.; Caruana, J.; Conseil, S.; Contini, T.; Guiderdoni, B.; Herenz, E. C.; Inami, H.; Lewis, J.; Mahler, G.; Marino, R. A.; Pello, R.; Schaye, J.; Verhamme, A.; Ventou, E.; Weilbacher, P. M.

2017-11-01

We present the deepest study to date of the Lyα luminosity function in a blank field using blind integral field spectroscopy from MUSE. We constructed a sample of 604 Lyα emitters (LAEs) across the redshift range 2.91 < z < 6.64 using automatic detection software in the Hubble Ultra Deep Field. The deep data cubes allowed us to calculate accurate total Lyα fluxes capturing low surface-brightness extended Lyα emission now known to be a generic property of high-redshift star-forming galaxies. We simulated realistic extended LAEs to fully characterise the selection function of our samples, and performed flux-recovery experiments to test and correct for bias in our determination of total Lyα fluxes. We find that an accurate completeness correction accounting for extended emission reveals a very steep faint-end slope of the luminosity function, α, down to luminosities of log10L erg s-1< 41.5, applying both the 1 /Vmax and maximum likelihood estimators. Splitting the sample into three broad redshift bins, we see the faint-end slope increasing from -2.03-0.07+ 1.42 at z ≈ 3.44 to -2.86-∞+0.76 at z ≈ 5.48, however no strong evolution is seen between the 68% confidence regions in L∗-α parameter space. Using the Lyα line flux as a proxy for star formation activity, and integrating the observed luminosity functions, we find that LAEs' contribution to the cosmic star formation rate density rises with redshift until it is comparable to that from continuum-selected samples by z ≈ 6. This implies that LAEs may contribute more to the star-formation activity of the early Universe than previously thought, as any additional intergalactic medium (IGM) correction would act to further boost the Lyα luminosities. Finally, assuming fiducial values for the escape of Lyα and LyC radiation, and the clumpiness of the IGM, we integrated the maximum likelihood luminosity function at 5.00

HIFLUGCS: X-ray luminosity-dynamical mass relation and its implications for mass calibrations with the SPIDERS and 4MOST surveys

NASA Astrophysics Data System (ADS)

Zhang, Yu-Ying; Reiprich, Thomas H.; Schneider, Peter; Clerc, Nicolas; Merloni, Andrea; Schwope, Axel; Borm, Katharina; Andernach, Heinz; Caretta, César A.; Wu, Xiang-Ping

2017-03-01

We present the relation of X-ray luminosity versus dynamical mass for 63 nearby clusters of galaxies in a flux-limited sample, the HIghest X-ray FLUx Galaxy Cluster Sample (HIFLUGCS, consisting of 64 clusters). The luminosity measurements are obtained based on 1.3 Ms of clean XMM-Newton data and ROSAT pointed observations. The masses are estimated using optical spectroscopic redshifts of 13647 cluster galaxies in total. We classify clusters into disturbed and undisturbed based on a combination of the X-ray luminosity concentration and the offset between the brightest cluster galaxy and X-ray flux-weighted center. Given sufficient numbers (I.e., ≥45) of member galaxies when the dynamical masses are computed, the luminosity versus mass relations agree between the disturbed and undisturbed clusters. The cool-core clusters still dominate the scatter in the luminosity versus mass relation even when a core-corrected X-ray luminosity is used, which indicates that the scatter of this scaling relation mainly reflects the structure formation history of the clusters. As shown by the clusters with only few spectroscopically confirmed members, the dynamical masses can be underestimated and thus lead to a biased scaling relation. To investigate the potential of spectroscopic surveys to follow up high-redshift galaxy clusters or groups observed in X-ray surveys for the identifications and mass calibrations, we carried out Monte Carlo resampling of the cluster galaxy redshifts and calibrated the uncertainties of the redshift and dynamical mass estimates when only reduced numbers of galaxy redshifts per cluster are available. The resampling considers the SPIDERS and 4MOST configurations, designed for the follow-up of the eROSITA clusters, and was carried out for each cluster in the sample at the actual cluster redshift as well as at the assigned input cluster redshifts of 0.2, 0.4, 0.6, and 0.8. To follow up very distant clusters or groups, we also carried out the mass calibration based on the resampling with only ten redshifts per cluster, and redshift calibration based on the resampling with only five and ten redshifts per cluster, respectively. Our results demonstrate the power of combining upcoming X-ray and optical spectroscopic surveys for mass calibration of clusters. The scatter in the dynamical mass estimates for the clusters with at least ten members is within 50%.

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).

Polarimetry of optically selected BL Lacertae candidates from the SDSS

NASA Astrophysics Data System (ADS)

Heidt, J.; Nilsson, K.

2011-05-01

We present and discuss polarimetric observations of 182 targets drawn from an optically selected sample of 240 probable BL Lac candidates out of the SDSS compiled by Collinge et al. (2005, AJ, 129, 2542). In contrast to most other BL Lac candidate samples extracted from the SDSS, its radio- and/or X-ray properties have not been taken into account for its derivation. Thus, because its selection is based on optical properties alone, it may be less prone to selection effects inherent in other samples derived at different frequencies, so it offers a unique opportunity to extract the first unbiased BL Lac luminosity function that is suitably large in size. We found 124 out of 182 targets (68%) to be polarized, 95 of the polarized targets (77%) to be highly polarized (>4%). The low-frequency peaked BL Lac candidates in the sample are on average only slightly more polarized than the high-frequency peaked ones. Compared to earlier studies, we found a high duty cycle in high polarization (˜ 66+2-14% to be >4% polarized) in high-frequency peaked BL Lac candidates. This may come from our polarization analysis, which minimizes the contamination by host galaxy light. No evidence of radio-quiet BL Lac objects in the sample was found. Our observations show that the probable sample of BL Lac candidates of Collinge et al. (2005) indeed contains a large number of bona fide BL Lac objects. High S/N spectroscopy and deep X-ray observations are required to construct the first luminosity function of optically selected BL Lac objects and to test more stringently for any radio-quiet BL Lac objects in the sample. Based on observations collected with the NTT on La Silla (Chile) operated by the European Southern Observatory in the course of the observing proposal 082.B-0133.Based on observations collected at the Centro Astronómico Hispano Alemán (CAHA), operated jointly by the Max-Planck-Institut für Astronomie and the Instituto de Astrofisica de Andalucia (CSIC).Based on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias.Table 1 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/529/A162

Classification of X-ray sources in the direction of M31

NASA Astrophysics Data System (ADS)

Vasilopoulos, G.; Hatzidimitriou, D.; Pietsch, W.

2012-01-01

M31 is our nearest spiral galaxy, at a distance of 780 kpc. Identification of X-ray sources in nearby galaxies is important for interpreting the properties of more distant ones, mainly because we can classify nearby sources using both X-ray and optical data, while more distant ones via X-rays alone. The XMM-Newton Large Project for M31 has produced an abundant sample of about 1900 X-ray sources in the direction of M31. Most of them remain elusive, giving us little signs of their origin. Our goal is to classify these sources using criteria based on properties of already identified ones. In particular we construct candidate lists of high mass X-ray binaries, low mass X-ray binaries, X-ray binaries correlated with globular clusters and AGN based on their X-ray emission and the properties of their optical counterparts, if any. Our main methodology consists of identifying particular loci of X-ray sources on X-ray hardness ratio diagrams and the color magnitude diagrams of their optical counterparts. Finally, we examined the X-ray luminosity function of the X-ray binaries populations.

NuSTAR Observations of Heavily Obscured Quasars Selected by WISE

NASA Astrophysics Data System (ADS)

Yan, Wei

2017-08-01

A key goal of the Nuclear Spectroscopic Telescope Array (NuSTAR) program is to find and characterize heavily obscured quasars, luminous accreting supermassive black holes hidden by gas and dust. Based on mid-infrared (IR) photometry from Wide-Field Infrared Survey Explorer (WISE) and optical photometry from the Sloan Digital Sky Surveys, we have selected a large population of obscured quasars; here we report the NuSTAR observations of four WISE-selected heavily obscured quasars for which we have optical spectroscopy from the Southern African Large Telescope and KECK Telescope. Three of four objects are undetected with NuSTAR, while the fourth has only a marginal detection. We confirm our objects have observed hard X-ray (10-40 keV) luminosities at or below ~1043 erg s-1. We compare IR and X-ray luminosities to obtain estimates of hydrogen column NH based on the suppression of the hard X-ray emission. We estimate NH to be at or greater than 1025 cm-2, confirming that WISE and optical selection can identify very heavily obscured quasars that may be missed in X-ray surveys.

Upgrade of the ATLAS Tile Calorimeter Electronics

NASA Astrophysics Data System (ADS)

Moreno, Pablo; ATLAS Tile Calorimeter System

2016-04-01

The Tile Calorimeter (TileCal) is the hadronic calorimeter covering the central region of the ATLAS experiment at LHC. The TileCal readout consists of 9852 channels. The bulk of its upgrade will occur for the High Luminosity LHC phase (Phase II) where the peak luminosity will increase 5× compared to the design luminosity (1034 cm-2s-1) at center of mass energy of 14 TeV. The TileCal upgrade aims at replacing the majority of the on- and off-detector electronics to the extent that all calorimeter signals will be digitized and sent to the off-detector electronics in the counting room. To achieve the required reliability, redundancy has been introduced at different levels. Three different options are presently being investigated for the front-end electronic upgrade. Extensive test beam studies will determine which option will be selected. 10.24 Gbps optical links are used to read out all digitized data to the counting room while 4.8 Gbps down-links are used for synchronization, configuration and detector control. For the off-detector electronics a pre-processor (sROD) is being developed, which takes care of the initial trigger processing while temporarily storing the main data flow in pipeline and de-randomizer memories. Field Programmable Gate Arrays are extensively used for the logic functions off- and on-detector. One demonstrator prototype module with the new calorimeter module electronics, but still compatible with the present system, is planned to be inserted in ATLAS at the end of 2015.

ROSAT observations of Coma Cluster galaxies

NASA Technical Reports Server (NTRS)

Dow, K. L.; White, S. D. M.

1995-01-01

The approximately 86 ks ROSAT Position Sensitive Proportional Counter (PSPC) image of the Coma Cluster is deeper than any previous X-ray observation of a galaxy cluster. We search for X-ray emission from 35 individual galaxies in a magnitude-limited sample, all of which lie within 20 arcmins of the optical axis in at least one of the four Coma pointings. We detect seven galaxies in the 0.4-2.4 keV band at a significance level exceeding 3 sigma, and a further four at above 2 sigma. Although we can set only upper limits on the individual flux from each of the other galaxies, we are able to measure their mean flux by stacking the observations. The X-ray luminosities of the seven detections range from 6.2 x 10(exp 40) to 1.5 x 10(exp 42) ergs/s (0.4-2.4 keV for H(sub 0) = 50 km/s/Mpc). For galaxies with a blue absolute magnitude of about -21 we find a mean X-ray luminosity of 1.3 x 10(exp 40) ergs/s. The ratio of X-ray to optical luminosity is substantially smaller for such subjects than for the brightest galaxies in the cluster. The X-ray luminosities of the four brightest galaxies are ill-defined, however, because of ambiguity in distinguishing galaxy emission from cluster emission. Each object appears to be related to significant structure in the diffuse intracluster medium. We also investigate emission in the softer 0.2-0.4 keV band where detections are less significant because of the higher background, and we discuss the properties of a number of interesting individual sources. The X-ray luminosities of the Coma galaxies are similar to those of galaxies in the Virgo Cluster and in other regions with relatively low galaxy density. We conclude that large-scale environmental effects do not significantly enhance or suppress the average X-ray emission from galaxies, but that individual objects vary in luminosity substantially in a way which may depend on the detailed history of their environment.

An X-ray/SDSS sample. I. Multi-phase outflow incidence and dependence on AGN luminosity

NASA Astrophysics Data System (ADS)

Perna, M.; Lanzuisi, G.; Brusa, M.; Mignoli, M.; Cresci, G.

2017-07-01

Aims: The connection between the growth of super-massive black holes (SMBHs) and the evolution of their host galaxies is nowadays well established, although the underlying mechanisms explaining their mutual relations are still debated. Multi-phase fast, massive outflows have been postulated to play a crucial role in this process. The aim of this work is to constrain the nature and the fraction of outflowing gas in active galactic nuclei (AGNs) as well as the nuclear conditions possibly at the origin of such phenomena. Methods: We present a large spectroscopic sample of X-ray detected SDSS AGNs at z< 0.8 with a high signal-to-noise ratio in the [O III]λ5007 line to unveil the faint wings of the emission profile associated with AGN-driven outflows. We used X-ray and optical flux ratio diagnostics to select the sample. We derived physical and kinematic characterization by re-analysing optical (and X-ray) spectra. Results: We derive the incidence of ionized ( 40%) and atomic (<1%) outflows covering a wide range of AGN bolometric luminosity from 1042 to 1046 erg/s. We also derive bolometric luminosities and X-ray bolometric corrections to test whether the presence of outflows is associated with an X-ray loudness, as suggested by our recent results obtained by studying high-z QSOs. Conclusions: We study the relations between the outflow velocity inferred from [O III] kinematic analysis and different AGN power tracers, such as black hole mass (MBH), [O III], and X-ray luminosity. We show a well-defined positive trend between outflow velocity and LX, for the first time, over a range of 5 order of magnitudes. Overall, we find that in the QSO-luminosity regime and at MBH> 108M⊙ the fraction of AGNs with outflows becomes >50%. Finally, we discuss our results about X-ray bolometric corrections and outflow incidence in cold and ionized phases in the context of an evolutionary sequence allowing two distinct stages for the feedback phase: first, an initial stage characterized by X-ray/optical obscured AGNs, in which the atomic gas is still present in the ISM and the outflow processes involve all the gas components and, second, a later stage associated with unobscured AGNs, in which the line of sight has been cleaned and the cold components have been heated or exhausted.

THE INTRINSIC EDDINGTON RATIO DISTRIBUTION OF ACTIVE GALACTIC NUCLEI IN STAR-FORMING GALAXIES FROM THE SLOAN DIGITAL SKY SURVEY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jones, Mackenzie L.; Hickox, Ryan C.; Black, Christine S.

An important question in extragalactic astronomy concerns the distribution of black hole accretion rates of active galactic nuclei (AGNs). Based on observations at X-ray wavelengths, the observed Eddington ratio distribution appears as a power law, while optical studies have often yielded a lognormal distribution. There is increasing evidence that these observed discrepancies may be due to contamination by star formation and other selection effects. Using a sample of galaxies from the Sloan Digital Sky Survey Data Release 7, we test whether or not an intrinsic Eddington ratio distribution that takes the form of a Schechter function is consistent with previousmore » work suggesting that young galaxies in optical surveys have an observed lognormal Eddington ratio distribution. We simulate the optical emission line properties of a population of galaxies and AGNs using a broad, instantaneous luminosity distribution described by a Schechter function near the Eddington limit. This simulated AGN population is then compared to observed galaxies via their positions on an emission line excitation diagram and Eddington ratio distributions. We present an improved method for extracting the AGN distribution using BPT diagnostics that allows us to probe over one order of magnitude lower in Eddington ratio, counteracting the effects of dilution by star formation. We conclude that for optically selected AGNs in young galaxies, the intrinsic Eddington ratio distribution is consistent with a possibly universal, broad power law with an exponential cutoff, as this distribution is observed in old, optically selected galaxies and X-rays.« less

The Einstein database of IPC x-ray observations of optically selected and radio-selected quasars, 1.

NASA Technical Reports Server (NTRS)

Wilkes, Belinda J.; Tananbaum, Harvey; Worrall, D. M.; Avni, Yoram; Oey, M. S.; Flanagan, Joan

1994-01-01

We present the first volume of the Einstein quasar database. The database includes estimates of the X-ray count rates, fluxes, and luminosities for 514 quasars and Seyfert 1 galaxies observed with the Imaging Proportional Counter (IPC) aboard the Einstein Observatory. All were previously known optically selected or radio-selected objects, and most were the targets of the X-ray observations. The X-ray properties of the Active Galactic Nuclei (AGNs) have been derived by reanalyzing the IPC data in a systematic manner to provide a uniform database for general use by the astronomical community. We use the database to extend earlier quasar luminosity studies which were made using only a subset of the currently available data. The database can be accessed on internet via the SAO Einstein on-line system ('Einline') and is available in ASCII format on magnetic tape and DOS diskette.

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.

The Problem of Spectral Mimicry of Supergiants

NASA Astrophysics Data System (ADS)

Klochkova, V. G.; Chentsov, E. L.

2018-01-01

The phenomenon of spectral mimicry refers to the fact that hypergiants and post-AGB supergiants—stars of different masses in fundamentally different stages of their evolution—have similar optical spectra, and also share certain other characteristics (unstable extended atmospheres, expanding dust-gas envelopes, high IR excesses). As a consequence, it is not always possible to distinguish post-AGB stars from hypergiants based on individual spectral observations in the optical. Examples of spectral mimicry are analyzed using uniform, high-quality spectral material obtained on the 6-m telescope of the Special Astrophysical Observatory in the course of long-term monitoring of high-luminosity stars. It is shown that unambiguously resolving the mimicry problem for individual stars requires the determination of a whole set of parameters: luminosity, wind parameters, spectral energy distribution, spectral features, velocity field in the atmosphere and circumstellar medium, behavior of the parameters with time, and the chemical composition of the atmosphere.

Pulsating stars in ω Centauri. Near-IR properties and period-luminosity relations

NASA Astrophysics Data System (ADS)

Navarrete, Camila; Catelan, Márcio; Contreras Ramos, Rodrigo; Alonso-García, Javier; Gran, Felipe; Dékány, István; Minniti, Dante

2017-09-01

ω Centauri (NGC 5139) contains many variable stars of different types, including the pulsating type II Cepheids, RR Lyrae and SX Phoenicis stars. We carried out a deep, wide-field, near-infrared (IR) variability survey of ω Cen, using the VISTA telescope. We assembled an unprecedented homogeneous and complete J and KS near-IR catalog of variable stars in the field of ω Cen. In this paper we compare optical and near-IR light curves of RR Lyrae stars, emphasizing the main differences. Moreover, we discuss the ability of near-IR observations to detect SX Phoenicis stars given the fact that the amplitudes are much smaller in these bands compared to the optical. Finally, we consider the case in which all the pulsating stars in the three different variability types follow a single period-luminosity relation in the near-IR bands.

RECONCILING AGN-STAR FORMATION, THE SOLTAN ARGUMENT, AND MEIER’S PARADOX

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garofalo, David; Kim, Matthew I.; Christian, Damian J.

2016-02-01

We provide a theoretical context for understanding the recent work of Kalfountzou et al. showing that star formation is enhanced at lower optical luminosity in radio-loud quasars. Our proposal for coupling the assumption of collimated FRII quasar-jet-induced star formation with lower accretion optical luminosity also explains the observed jet power peak in active galaxies at higher redshift compared to the peak in accretion power, doing so in a way that predicts the existence of a family of radio-quiet active galactic nuclei associated with rapidly spinning supermassive black holes at low redshift, as mounting observations suggest. The relevance of this work liesmore » in its promise to explain the observed cosmological evolution of accretion power, jet power, and star formation in a way that is both compatible with the Soltan argument and resolves the so-called “Meier Paradox.”.« less

Global properties of infrared bright galaxies

NASA Technical Reports Server (NTRS)

Young, Judith S.; Xie, Shuding; Kenney, Jeffrey D. P.; Rice, Walter L.

1989-01-01

Infrared flux densities of 182 galaxies, including 50 galaxies in the Virgo cluster, were analyzed using IRAS data for 12, 25, 60, and 100 microns, and the results were compared with data listed in the Point Source Catalog (PSC, 1985). In addition, IR luminosities, L(IRs), colors, and warm dust masses were derived for these galaxies and were compared with the interstellar gas masses and optical luminosities of the galaxies. It was found that, for galaxies whose optical diameter measures between 5 and 8 arcmin, the PSC flux densities are underestimated by a factor of 2 at 60 microns, and by a factor of 1.5 at 100 microns. It was also found that, for 49 galaxies, the mass of warm dust correlated well with the H2 mass, and that L(IR) correlated with L(H-alpha), demonstrating that the L(IR) measures the rate of star formation in these galaxies.

Evidence for a mass-dependent AGN Eddington ratio distribution via the flat relationship between SFR and AGN luminosity

NASA Astrophysics Data System (ADS)

Bernhard, E.; Mullaney, J. R.; Aird, J.; Hickox, R. C.; Jones, M. L.; Stanley, F.; Grimmett, L. P.; Daddi, E.

2018-05-01

The lack of a strong correlation between AGN X-ray luminosity (LX; a proxy for AGN power) and the star formation rate (SFR) of their host galaxies has recently been attributed to stochastic AGN variability. Studies using population synthesis models have incorporated this by assuming a broad, universal (i.e. does not depend on the host galaxy properties) probability distribution for AGN specific X-ray luminosities (i.e. the ratio of LX to host stellar mass; a common proxy for Eddington ratio). However, recent studies have demonstrated that this universal Eddington ratio distribution fails to reproduce the observed X-ray luminosity functions beyond z ˜ 1.2. Furthermore, empirical studies have recently shown that the Eddington ratio distribution may instead depend upon host galaxy properties, such as SFR and/or stellar mass. To investigate this further, we develop a population synthesis model in which the Eddington ratio distribution is different for star-forming and quiescent host galaxies. We show that, although this model is able to reproduce the observed X-ray luminosity functions out to z ˜ 2, it fails to simultaneously reproduce the observed flat relationship between SFR and X-ray luminosity. We can solve this, however, by incorporating a mass dependency in the AGN Eddington ratio distribution for star-forming host galaxies. Overall, our models indicate that a relative suppression of low Eddington ratios (λEdd ≲ 0.1) in lower mass galaxies (M* ≲ 1010 - 11 M⊙) is required to reproduce both the observed X-ray luminosity functions and the observed flat SFR/X-ray relationship.

Binary Systems and the Initial Mass Function

NASA Astrophysics Data System (ADS)

Malkov, O. Yu.

2017-07-01

In the present paper we discuss advantages and disadvantages of binary stars, which are important for star formation history determination. We show that to make definite conclusions of the initial mass function shape, it is necessary to study binary population well enough to correct the luminosity function for unresolved binaries; to construct the mass-luminosity relation based on wide binaries data, and to separate observational mass functions of primaries, of secondaries, and of unresolved binaries.

Towards A Complete Census of Compton-thick AGN and N_H Distribution in the Local Universe

NASA Astrophysics Data System (ADS)

Annuar, A.; Gandhi, P.; Alexander, D.; Asmus, D.; Goulding, A.; Harrison, C.; Lansbury, G.

2014-07-01

Many studies have shown that Compton-thick AGNs (CTAGNs) provide important contribution to the cosmic X-ray background spectrum (˜25% at 20keV). They are expected to dominate the Seyfert 2 population in the local universe, yet only ˜20 bona fide CTAGNs are known. We present an updated census of CTAGN population in the local universe using a volume-limited AGN sample complete to D=15Mpc. Intrinsic relations between 2-10keV X-ray luminosity and mid-IR emission at 12μm, [OIV]λ25.68μm and [NeV]λ14.32μm are investigated, and it is found that the emission at 12μm has the tightest correlation with the X-ray luminosity.Candidates for CTAGN are then selected using this relation and by comparing their 12μm luminosity with the observed X-ray luminosity.We also investigate the Compton-thick nature of these sources using the optical [OIII]λ5007{A}:X-ray diagnostic for comparison, and find that 35-50% of the sample are Compton-thick,of which 10-20% would be missed with the optical approach.Finally, we estimate the intrinsic N_{H} distribution of AGN population in the local universe from this analysis, and show that up to 70% of the sources are heavily obscured (N_{H}>10^{23} cm^{-2}), with ≥50% lying in the Compton-thick regime (N_{H}>10^{24} cm^{-2}).This work provides a well-defined local benchmark for AGN obscuration studies.

Design of the large hadron electron collider interaction region

NASA Astrophysics Data System (ADS)

Cruz-Alaniz, E.; Newton, D.; Tomás, R.; Korostelev, M.

2015-11-01

The large hadron electron collider (LHeC) is a proposed upgrade of the Large Hadron Collider (LHC) within the high luminosity LHC (HL-LHC) project, to provide electron-nucleon collisions and explore a new regime of energy and luminosity for deep inelastic scattering. The design of an interaction region for any collider is always a challenging task given that the beams are brought into crossing with the smallest beam sizes in a region where there are tight detector constraints. In this case integrating the LHeC into the existing HL-LHC lattice, to allow simultaneous proton-proton and electron-proton collisions, increases the difficulty of the task. A nominal design was presented in the the LHeC conceptual design report in 2012 featuring an optical configuration that focuses one of the proton beams of the LHC to β*=10 cm in the LHeC interaction point to reach the desired luminosity of L =1033 cm-2 s-1 . This value is achieved with the aid of a new inner triplet of quadrupoles at a distance L*=10 m from the interaction point. However the chromatic beta beating was found intolerable regarding machine protection issues. An advanced chromatic correction scheme was required. This paper explores the feasibility of the extension of a novel optical technique called the achromatic telescopic squeezing scheme and the flexibility of the interaction region design, in order to find the optimal solution that would produce the highest luminosity while controlling the chromaticity, minimizing the synchrotron radiation power and maintaining the dynamic aperture required for stability.

Multiwavength Observations of the Black Hole X-Ray Binary A0620-00 in Quiescence

NASA Astrophysics Data System (ADS)

Dinçer, Tolga; Bailyn, Charles D.; Miller-Jones, James C. A.; Buxton, Michelle; MacDonald, Rachel K. D.

2018-01-01

We present results from simultaneous multiwavelength X-ray, radio, and optical/near-infrared observations of the quiescent black hole X-ray binary A0620-00 performed in 2013 December. We find that the Chandra flux has brightened by a factor of 2 since 2005, and by a factor of 7 since 2000. The spectrum has not changed significantly over this time, being consistent with a power law of {{Γ }}=2.07+/- 0.13 and a hydrogen column of {N}H=(3.0+/- 0.5)× {10}21 {{cm}}-2. Very Large Array observations of A0620-00 at three frequencies, over the interval of 5.25–22.0 GHz, have provided us with the first broadband radio spectrum of a quiescent stellar mass black hole system at X-ray luminosities as low as 10‑8 times the Eddington luminosity. Compared to previous observations, the source has moved to lower radio and higher X-ray luminosity, shifting it perpendicular to the standard track of the radio/X-ray correlation for X-ray binaries. The radio spectrum is inverted with a spectral index α =0.74+/- 0.19 ({S}ν \\propto {ν }α ). This suggests that the peak of the spectral energy distribution is likely to be between 1012 and 1014 Hz, and that the near-IR and optical flux contain significant contributions from the star, the accretion flow, and from the outflow. Decomposing these components may be difficult, but holds the promise of revealing the interplay between accretion and jet in low luminosity systems.

Calibrating Star Formation in WISE Using Total Infrared Luminosity

NASA Astrophysics Data System (ADS)

Cluver, M. E.; Jarrett, T. H.; Dale, D. A.; Smith, J.-D. T.; August, Tamlyn; Brown, M. J. I.

2017-11-01

We present accurate resolved WISE photometry of galaxies in the combined SINGS and KINGFISH sample. The luminosities in the W3 12 μm and W4 23 μm bands are calibrated to star formation rates (SFRs) derived using the total infrared luminosity, avoiding UV/optical uncertainties due to dust extinction corrections. The W3 relation has a 1σ scatter of 0.15 dex that is over nearly 5 orders of magnitude in SFR and 12 μm luminosity, and a range in host stellar mass from dwarfs (107 {M}⊙ ) to ˜ 3× {M}{\\star } (1011.5 {M}⊙ ) galaxies. In the absence of deep silicate absorption features and powerful active galactic nuclei, we expect this to be a reliable SFR indicator chiefly due to the broad nature of the W3 band. By contrast, the W4 SFR relation shows more scatter (1σ =0.18 dex). Both relations show reasonable agreement with radio-continuum-derived SFRs and excellent accordance with so-called “hybrid” Hα + 24 μm and FUV+24 μm indicators. Moreover, the WISE SFR relations appear to be insensitive to the metallicity range in the sample. We also compare our results with IRAS-selected luminous infrared galaxies, showing that the WISE relations maintain concordance, but systematically deviate for the most extreme galaxies. Given the all-sky coverage of WISE and the performance of the W3 band as an SFR indicator, the {L}12μ {{m}} SFR relation could be of great use to studies of nearby galaxies and forthcoming large-area surveys at optical and radio wavelengths.

The Local Universe as Seen in the Far-Infrared and Far-Ultraviolet: A Global Point of View of the Local Recent Star Formation

NASA Astrophysics Data System (ADS)

Buat, V.; Takeuchi, T. T.; Iglesias-Páramo, J.; Xu, C. K.; Burgarella, D.; Boselli, A.; Barlow, T.; Bianchi, L.; Donas, J.; Forster, K.; Friedman, P. G.; Heckman, T. M.; Lee, Y.-W.; Madore, B. F.; Martin, D. C.; Milliard, B.; Morissey, P.; Neff, S.; Rich, M.; Schiminovich, D.; Seibert, M.; Small, T.; Szalay, A. S.; Welsh, B.; Wyder, T.; Yi, S. K.

2007-12-01

We select far-infrared (FIR: 60 μm) and far-ultraviolet (FUV: 530 Å) samples of nearby galaxies in order to discuss the biases encountered by monochromatic surveys (FIR or FUV). Very different volumes are sampled by each selection, and much care is taken to apply volume corrections to all the analyses. The distributions of the bolometric luminosity of young stars are compared for both samples: they are found to be consistent with each other for galaxies of intermediate luminosities, but some differences are found for high (>5×1010 Lsolar) luminosities. The shallowness of the IRAS survey prevents us from securing a comparison at low luminosities (<2×109 Lsolar). The ratio of the total infrared (TIR) luminosity to the FUV luminosity is found to increase with the bolometric luminosity in a similar way for both samples up to 5×1010 Lsolar. Brighter galaxies are found to have a different behavior according to their selection: the LTIR/LFUV ratio of the FUV-selected galaxies brighter than 5×1010 Lsolar reaches a plateau, whereas LTIR/LFUV continues to increase with the luminosity of bright galaxies selected in FIR. The volume-averaged specific star formation rate (SFR per unit galaxy stellar mass, SSFR) is found to decrease toward massive galaxies within each selection. The mean values of the SSFR are found to be larger than those measured for optical and NIR-selected samples over the whole mass range for the FIR selection, and for masses larger than 1010 Msolar for the FUV selection. Luminous and massive galaxies selected in FIR appear as active as galaxies with similar characteristics detected at z~0.7.

Far-infrared photometry of compact extragalactic objects - Detection of 3C 345

NASA Technical Reports Server (NTRS)

Harvey, P. M.; Wilking, B. A.; Joy, M.

1982-01-01

The first detection of a quasar between 10 and 1000 microns is reported. The observation permits (1) the determination of the intersection of the optical/infrared and millimeter continua; (2) more precise determination of the total luminosity; (3) the placing of limits on the contribution of any thermal dust emission to the total luminosity. The quasar is the first object ever to have been observed whose energy distribution peaks at wavelength of about 100 microns without a large contribution to the total luminosity from thermal dust emission. The observed flux density of 2.2 + or - 0.5 Jy at 100 microns and an upper limit of 0.5 + or - 0.6 Jy at 50 microns clearly define the overall energy distribution and show the quasar to be a powerful far-infrared source.

Radiatively driven relativistic spherical winds under relativistic radiative transfer

NASA Astrophysics Data System (ADS)

Fukue, J.

2018-05-01

We numerically investigate radiatively driven relativistic spherical winds from the central luminous object with mass M and luminosity L* under Newtonian gravity, special relativity, and relativistic radiative transfer. We solve both the relativistic radiative transfer equation and the relativistic hydrodynamical equations for spherically symmetric flows under the double-iteration processes, to obtain the intensity and velocity fields simultaneously. We found that the momentum-driven winds with scattering are quickly accelerated near the central object to reach the terminal speed. The results of numerical solutions are roughly fitted by a relation of \\dot{m}=0.7(Γ _*-1)\\tau _* β _* β _out^{-2.6}, where \\dot{m} is the mass-loss rate normalized by the critical one, Γ* the central luminosity normalized by the critical one, τ* the typical optical depth, β* the initial flow speed at the central core of radius R*, and βout the terminal speed normalized by the speed of light. This relation is close to the non-relativistic analytical solution, \\dot{m} = 2(Γ _*-1)\\tau _* β _* β _out^{-2}, which can be re-expressed as β _out^2/2 = (Γ _*-1)GM/c^2 R_*. That is, the present solution with small optical depth is similar to that of the radiatively driven free outflow. Furthermore, we found that the normalized luminosity (Eddington parameter) must be larger than unity for the relativistic spherical wind to blow off with intermediate or small optical depth, i.e. Γ _* ≳ \\sqrt{(1+β _out)^3/(1-β _out)}. We briefly investigate and discuss an isothermal wind.

Low-luminosity stellar mass functions in globular clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Richer, H.B.; Fahlman, G.G.; Buonanno, R.

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)more » 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.« less

Gamma-Ray Burst Host Galaxies Have "Normal" Luminosities.

PubMed

Schaefer

2000-04-10

The galactic environment of gamma-ray bursts can provide good evidence about the nature of the progenitor system, with two old arguments implying that the burst host galaxies are significantly subluminous. New data and new analysis have now reversed this picture: (1) Even though the first two known host galaxies are indeed greatly subluminous, the next eight hosts have absolute magnitudes typical for a population of field galaxies. A detailed analysis of the 16 known hosts (10 with redshifts) shows them to be consistent with a Schechter luminosity function with R*=-21.8+/-1.0, as expected for normal galaxies. (2) Bright bursts from the Interplanetary Network are typically 18 times brighter than the faint bursts with redshifts; however, the bright bursts do not have galaxies inside their error boxes to limits deeper than expected based on the luminosities for the two samples being identical. A new solution to this dilemma is that a broad burst luminosity function along with a burst number density varying as the star formation rate will require the average luminosity of the bright sample (>6x1058 photons s-1 or>1.7x1052 ergs s-1) to be much greater than the average luminosity of the faint sample ( approximately 1058 photons s-1 or approximately 3x1051 ergs s-1). This places the bright bursts at distances for which host galaxies with a normal luminosity will not violate the observed limits. In conclusion, all current evidence points to gamma-ray burst host galaxies being normal in luminosity.

The galaxy luminosity function around groups

NASA Astrophysics Data System (ADS)

González, R. E.; Padilla, N. D.; Galaz, G.; Infante, L.

2005-11-01

We present a study on the variations of the luminosity function of galaxies around clusters in a numerical simulation with semi-analytic galaxies, attempting to detect these variations in the 2dF Galaxy Redshift Survey. We subdivide the simulation box into equal-density regions around clusters, which we assume can be achieved by selecting objects at a given normalized distance (r/rrms, where rrms is an estimate of the halo radius) from the group centre. The semi-analytic model predicts important variations in the luminosity function out to r/rrms~= 5. In brief, variations in the mass function of haloes around clusters (large dark matter haloes with M > 1012h-1Msolar) lead to cluster central regions that present a high abundance of bright galaxies (high M* values) as well as low-luminosity galaxies (high α) at r/rrms~= 3 there is a lack of bright galaxies, which shows the depletion of galaxies in the regions surrounding clusters (minimum in M* and α), and a tendency to constant luminosity function parameters at larger cluster-centric distances. We take into account the observational biases present in the real data by reproducing the peculiar velocity effect on the redshifts of galaxies in the simulation box, and also by producing mock catalogues. We find that excluding from the analysis galaxies which in projection are close to the centres of the groups provides results that are qualitatively consistent with the full simulation box results. When we apply this method to mock catalogues of the 2dF Galaxy Redshift Survey (2dFGRS) and the 2PIGG catalogue of groups, we find that the variations in the luminosity function are almost completely erased by the Finger of God effect; only a lack of bright galaxies at r/rrms~= 3 can be marginally detected in the mock catalogues. The results from the real 2dFGRS data show a clearer detection of a dip in M* and α for r/rrms= 3, consistent with the semi-analytic predictions.

Radio-Optical Alignments in a Low Radio Luminosity Sample

NASA Technical Reports Server (NTRS)

Lacy, Mark; Ridgway, Susan E.; Wold, Margrethe; Lilje, Per B.; Rawlings, Steve

1999-01-01

We present an optically-based study of the alignment between the radio axes and the optical major axes of eight z approximately 0.7 radio galaxies in a 7C sample. The radio galaxies in this sample are approximately 20-times less radio luminous than 3C galaxies at the same redshift, and are significantly less radio-luminous than any other well-defined samples studied to date. Using Nordic Optical Telescope images taken in good seeing conditions at rest-frame wavelengths just longward of the 4000A break, we find a statistically significant alignment effect in the 7C sample. Furthermore, in two cases where the aligned components are well separated from the host we have been able to confirm spectroscopically that they are indeed at the same redshift as the radio galaxy. However, a quantitative analysis of the alignment in this sample and in a corresponding 3C sample from HST (Hubble Space Telescope) archival data indicates that the percentage of aligned flux may be lower and of smaller spatial scale in the 7C sample. Our study suggests that alignments on the 50-kpc scale are probably closely related to the radio luminosity, whereas those on the 15 kpc scale are not. We discuss these results in the context of popular models for the alignment effect.

A catalogue of optical to X-ray spectral energy distributions of z ≈ 2 quasars observed with Swift - I. First results

NASA Astrophysics Data System (ADS)

Lawther, D.; Vestergaard, M.; Raimundo, S.; Grupe, D.

2017-06-01

We present the Swift optical to X-ray spectral energy distributions (SEDs) of 44 quasars at redshifts z ≈ 2 observed by Swift, part of a larger program to establish and characterize the optical through X-ray SEDs of moderate-redshift quasars. Here, we outline our analysis approach and present preliminary analysis and results for the first third of the full quasar sample. Not all quasars in the sample are detected in X-rays; all of the X-ray-detected objects so far are radio loud. As expected for radio-loud objects, they are X-ray bright relative to radio-quiet quasars of comparable optical luminosities, with an average αox =1.39 ± 0.03 (where αox is the power-law slope connecting the monochromatic flux at 2500 Å and at 2 keV), and display hard X-ray spectra. We find integrated 3000 Å-25 keV accretion luminosities of between 0.7 × 1046 erg s-1 and 5.2 × 1047 erg s-1. Based on single-epoch spectroscopic virial black hole mass estimates, we find that these quasars are accreting at substantial Eddington fractions, 0.1 ≲ L/LEdd ≲ 1.

ASCA Observations of "Type 2" LINERs Evidence for a Stellar Source of Ionization

NASA Technical Reports Server (NTRS)

Terashima, Yuichi; Ho, Luis C.; Ptak, Andrew F.; Mushotzky, Richard F.; Serlemitsos, Peter J.; Yaqoob, Tahir; Kunieda, Hideyo

1999-01-01

We present ASCA observations of LINERs without broad H.alpha emission in their optical spectra. The sample of "type 2" LINERs consists of NGC 404, 4111, 4192, 4457, and 4569. We have detected X-ray emission from all the objects except for NGC 404; among the detected objects are two so-called transition objects (NGC 4192 and NGC 4569), which have been postulated to be composite nuclei having both an H II region and a LINER component. The images of NGC 4111 and NGC 4569 in the soft (0.5-2 keV) and hard (2-7 keV) X-ray bands are extended on scales of several kpc. The X-ray spectra of NGC 4111, NGC 4457 and NGC 4569 are well fitted by a two-component model that consists of soft thermal emission with kT approximately 0.65 keV and a hard component represented by a power law (photon index approximately 2) or by thermal bremsstrahlung emission (kT approximately several keV). The extended hard X-rays probably come from discrete sources, while the soft emission most likely originates from hot gas produced by active star formation in the host galaxy. We have found no clear evidence for the presence of active galactic nuclei (AGNs) in the sample. Using black hole masses estimated from host galaxy bulge luminosities, we obtain an upper limit on the implied Eddington ratios less than 5 x 10(exp -5). If an AGN component is the primary ionization source of the optical emission lines, then it must be heavily obscured with a column density significantly larger than 10(exp 23)/sq cm, since the observed X-ray luminosity is insufficient to drive the luminosities of the optical emission lines. Alternatively, the optical emission could be ionized by a population of exceptionally hot stars. This interpretation is consistent with the small [O I] lambda6300/H.alpha ratios observed in these sources, the ultraviolet spectral characteristics in the cases where such information exists, and the X-ray results reported here. We also analyze the X-ray properties of NGC 4117, a low-luminosity Seyfert 2 galaxy serendipitously observed in the field of NGC 4111.

AKARI IRC 2.5-5 μm spectroscopy of infrared galaxies over a wide luminosity range

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ichikawa, Kohei; Ueda, Yoshihiro; Imanishi, Masatoshi

2014-10-20

We present the result of a systematic infrared 2.5-5 μm spectroscopic study of 22 nearby infrared galaxies over a wide infrared luminosity range (10{sup 10} L {sub ☉} < L {sub IR} < 10{sup 13} L {sub ☉}) obtained from the AKARI Infrared Camera (IRC). The unique band of the AKARI IRC spectroscopy enables us to access both the 3.3 μm polycyclic aromatic hydrocarbon (PAH) emission feature from star-forming activity and the continuum of torus-dust emission heated by an active galactic nucleus (AGN). Applying our AGN diagnostics to the AKARI spectra, we discover 14 buried AGNs. The large fraction ofmore » buried AGNs suggests that AGN activity behind the dust is almost ubiquitous in ultra-/luminous infrared galaxies (U/LIRGs). We also find that both the fraction and energy contribution of buried AGNs increase with infrared luminosity from 10{sup 10} L {sub ☉} to 10{sup 13} L {sub ☉}, including normal infrared galaxies with L {sub IR} < 10{sup 11} L {sub ☉}. The energy contribution from AGNs in the total infrared luminosity is only ∼7% in LIRGs and ∼20% in ULIRGs, suggesting that the majority of the infrared luminosity originates from starburst activity. Using the PAH emission, we investigate the luminosity relation between star formation and AGNs. We find that these infrared galaxies exhibit higher star formation rates than optically selected Seyfert galaxies with the same AGN luminosities, implying that infrared galaxies could be an early evolutionary phase of AGN.« less

Collapsar γ-ray bursts: how the luminosity function dictates the duration distribution

NASA Astrophysics Data System (ADS)

Petropoulou, Maria; Barniol Duran, Rodolfo; Giannios, Dimitrios

2017-12-01

Jets in long-duration γ-ray bursts (GRBs) have to drill through the collapsing star in order to break out of it and produce the γ-ray signal while the central engine is still active. If the breakout time is shorter for more powerful engines, then the jet-collapsar interaction acts as a filter of less luminous jets. We show that the observed broken power-law GRB luminosity function is a natural outcome of this process. For a theoretically motivated breakout time that scales with jet luminosity as L-χ with χ ∼ 1/3-1/2, we show that the shape of the γ-ray duration distribution can be uniquely determined by the GRB luminosity function and matches the observed one. This analysis has also interesting implications about the supernova-central engine connection. We show that not only successful jets can deposit sufficient energy in the stellar envelope to power the GRB-associated supernovae, but also failed jets may operate in all Type Ib/c supernovae.

Wedge Absorbers for Final Cooling for a High-Energy High-Luminosity Lepton Collider

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neuffer, David; Mohayai, Tanaz; Snopok, Pavel

2016-06-01

A high-energy high-luminosity muon collider scenario requires a "final cooling" system that reduces transverse emittance to ~25 microns (normalized) while allowing longitudinal emittance increase. Ionization cooling using high-field solenoids (or Li Lens) can reduce transverse emittances to ~100 microns in readily achievable configurations, confirmed by simulation. Passing these muon beams at ~100 MeV/c through cm-sized diamond wedges can reduce transverse emittances to ~25 microns, while increasing longitudinal emittance by a factor of ~5. Implementation will require optical matching of the exiting beam into downstream acceleration systems.

The host galaxy/AGN connection in nearby early-type galaxies. Is there a miniature radio-galaxy in every "core" galaxy?

NASA Astrophysics Data System (ADS)

Balmaverde, B.; Capetti, A.

2006-02-01

This is the second of a series of three papers exploring the connection between the multiwavelength properties of AGN in nearby early-type galaxies and the characteristics of their hosts. We selected two samples with 5 GHz VLA radio flux measurements down to 1 mJy, reaching levels of radio luminosity as low as 1036 erg s-1. In Paper I we presented a study of the surface brightness profiles for the 65 objects with available archival HST images out of the 116 radio-detected galaxies. We classified early-type galaxies into "core" and "power-law" galaxies, discriminating on the basis of the slope of their nuclear brightness profiles, following the Nukers scheme. Here we focus on the 29 core galaxies (hereafter CoreG). We used HST and Chandra data to isolate their optical and X-ray nuclear emission. The CoreG invariably host radio-loud nuclei, with an average radio-loudness parameter of Log R = L5 {GHz} / LB ˜ 3.6. The optical and X-ray nuclear luminosities correlate with the radio-core power, smoothly extending the analogous correlations already found for low luminosity radio-galaxies (LLRG) toward even lower power, by a factor of ˜ 1000, covering a combined range of 6 orders of magnitude. This supports the interpretation of a common non-thermal origin of the nuclear emission also for CoreG. The luminosities of the nuclear sources, most likely dominated by jet emission, set firm upper limits, as low as L/L_Edd ˜ 10-9 in both the optical and X-ray band, on any emission from the accretion process. The similarity of CoreG and LLRG when considering the distributions host galaxies luminosities and black hole masses, as well as of the surface brightness profiles, indicates that they are drawn from the same population of early-type galaxies. LLRG represent only the tip of the iceberg associated with (relatively) high activity levels, with CoreG forming the bulk of the population. We do not find any relationship between radio-power and black hole mass. A minimum black hole mass of M_BH = 108 M⊙ is apparently associated with the radio-loud nuclei in both CoreG and LLRG, but this effect must be tested on a sample of less luminous galaxies, likely to host smaller black holes. In the unifying model for BL Lacs and radio-galaxies, CoreG likely represent the counterparts of the large population of low luminosity BL Lac now emerging from the surveys at low radio flux limits. This suggests the presence of relativistic jets also in these quasi-quiescent early-type "core" galaxies.

The NGC 7742 star cluster luminosity function: a population analysis revisited

NASA Astrophysics Data System (ADS)

de Grijs, Richard; Ma, Chao

2018-02-01

We re-examine the properties of the star cluster population in the circumnuclear starburst ring in the face-on spiral galaxy NGC 7742, whose young cluster mass function has been reported to exhibit significant deviations from the canonical power law. We base our reassessment on the clusters’ luminosities (an observational quantity) rather than their masses (a derived quantity), and confirm conclusively that the galaxy’s starburst-ring clusters—and particularly the youngest subsample, {log}(t {{{yr}}}-1)≤ 7.2—show evidence of a turnover in the cluster luminosity function well above the 90% completeness limit adopted to ensure the reliability of our results. This confirmation emphasizes the unique conundrum posed by this unusual cluster population.

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.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krolewski, Alex G.; Eisenstein, Daniel J., E-mail: akrolewski@college.harvard.edu

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 quasarsmore » 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.« less

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 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/590/A80

Interpreting the cosmic far-infrared background anisotropies using a gas regulator model

NASA Astrophysics Data System (ADS)

Wu, Hao-Yi; Doré, Olivier; Teyssier, Romain; Serra, Paolo

2018-04-01

Cosmic far-infrared background (CFIRB) is a powerful probe of the history of star formation rate (SFR) and the connection between baryons and dark matter across cosmic time. In this work, we explore to which extent the CFIRB anisotropies can be reproduced by a simple physical framework for galaxy evolution, the gas regulator (bathtub) model. This model is based on continuity equations for gas, stars, and metals, taking into account cosmic gas accretion, star formation, and gas ejection. We model the large-scale galaxy bias and small-scale shot noise self-consistently, and we constrain our model using the CFIRB power spectra measured by Planck. Because of the simplicity of the physical model, the goodness of fit is limited. We compare our model predictions with the observed correlation between CFIRB and gravitational lensing, bolometric infrared luminosity functions, and submillimetre source counts. The strong clustering of CFIRB indicates a large galaxy bias, which corresponds to haloes of mass 1012.5 M⊙ at z = 2, higher than the mass associated with the peak of the star formation efficiency. We also find that the far-infrared luminosities of haloes above 1012 M⊙ are higher than the expectation from the SFR observed in ultraviolet and optical surveys.

Mini-Survey of SDSS OIII AGN with Swift

NASA Technical Reports Server (NTRS)

Angelina, Lorella; George, Ian

2007-01-01

There is a common wisdom that every massive galaxy has a massive block hole. However, most of these objects either are not radiating or until recently have been very difficult to detect. The Sloan Digital Sky Survey (SDSS) data, based on the [OIII] line indicate that perhaps up to 20% of all galaxies may be classified as AGN a surprising result that must be checked with independent data. X-ray surveys have revealed that hard X-ray selected AGN show a strong luminosity dependent evolution and their luminosity function (LF) shows a dramatic break towards low Lx (at all z). This is seen for all types of AGN, but is stronger for the broad-line objects. In sharp contrast, the local LF of (optically-selected samples) shows no such break and no differences between narrow and broad-line objects. Assuming both hard X-ray and [OIII] emission are fair indicators of AGN activity, it is important to understand this discrepancy. We present here the results of a mini-survey done with Swift on a selected sample of SDSS selected AGN. The objects have been sampled at different L([OIII]) to check the relation with the Lx observed with Swift.

No evidence for a significant AGN contribution to cosmic hydrogen reionization

NASA Astrophysics Data System (ADS)

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

2018-03-01

We reinvestigate a claimed sample of 22 X-ray detected active galactic nuclei (AGN) at redshifts z > 4, which has reignited the debate as to whether young galaxies or AGN reionized the Universe. These sources lie within the Great Observatories Origins Deep Survey-South (GOODS-S)/Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey (CANDELS) field, and we examine both the robustness of the claimed X-ray detections (within the Chandra 4Ms imaging) and perform an independent analysis of the photometric redshifts of the optical/infrared counterparts. We confirm the reality of only 15 of the 22 reported X-ray detections, and moreover find that only 12 of the 22 optical/infrared counterpart galaxies actually lie robustly at z > 4. Combining these results we find convincing evidence for only seven X-ray AGN at z > 4 in the GOODS-S field, of which only one lies at z > 5. We recalculate the evolving far-ultraviolet (1500 Å) luminosity density produced by AGN at high redshift, and find that it declines rapidly from z ≃ 4 to z ≃ 6, in agreement with several other recent studies of the evolving AGN luminosity function. The associated rapid decline in inferred hydrogen ionizing emissivity contributed by AGN falls an order-of-magnitude short of the level required to maintain hydrogen ionization at z ≃ 6. We conclude that all available evidence continues to favour a scenario in which young galaxies reionized the Universe, with AGN making, at most, a very minor contribution to cosmic hydrogen reionization.

VizieR Online Data Catalog: Transits observed in OGLE 2001-2003 (Udalski+, 2002-2004)

NASA Astrophysics Data System (ADS)

Udalski, A.; Paczynski, B.; Zebrun, K.; Szymanski, M.; Kubiak, M.; Soszinski, I.; Szewczyk, O.; Wyrzykowski, L.; Pietrzynski, G.

2003-11-01

We present results of an extensive photometric search for planetary and low-luminosity object transits in the Galactic disk stars commencing the third phase of the Optical Gravitational Lensing Experiment - OGLE-III. (1 data file).

Galaxy and Mass Assembly (GAMA): ugriz galaxy luminosity functions

NASA Astrophysics Data System (ADS)

Loveday, J.; Norberg, P.; Baldry, I. K.; Driver, S. P.; Hopkins, A. M.; Peacock, J. A.; Bamford, S. P.; Liske, J.; Bland-Hawthorn, J.; Brough, S.; Brown, M. J. I.; Cameron, E.; Conselice, C. J.; Croom, S. M.; Frenk, C. S.; Gunawardhana, M.; Hill, D. T.; Jones, D. H.; Kelvin, L. S.; Kuijken, K.; Nichol, R. C.; Parkinson, H. R.; Phillipps, S.; Pimbblet, K. A.; Popescu, C. C.; Prescott, M.; Robotham, A. S. G.; Sharp, R. G.; Sutherland, W. J.; Taylor, E. N.; Thomas, D.; Tuffs, R. J.; van Kampen, E.; Wijesinghe, D.

2012-02-01

Galaxy and Mass Assembly (GAMA) is a project to study galaxy formation and evolution, combining imaging data from ultraviolet to radio with spectroscopic data from the AAOmega spectrograph on the Anglo-Australian Telescope. Using data from Phase 1 of GAMA, taken over three observing seasons, and correcting for various minor sources of incompleteness, we calculate galaxy luminosity functions (LFs) and their evolution in the ugriz passbands. At low redshift, z < 0.1, we find that blue galaxies, defined according to a magnitude-dependent but non-evolving colour cut, are reasonably well fitted over a range of more than 10 magnitudes by simple Schechter functions in all bands. Red galaxies, and the combined blue plus red sample, require double power-law Schechter functions to fit a dip in their LF faintwards of the characteristic magnitude M* before a steepening faint end. This upturn is at least partly due to dust-reddened disc galaxies. We measure the evolution of the galaxy LF over the redshift range 0.002 < z < 0.5 both by using a parametric fit and by measuring binned LFs in redshift slices. The characteristic luminosity L* is found to increase with redshift in all bands, with red galaxies showing stronger luminosity evolution than blue galaxies. The comoving number density of blue galaxies increases with redshift, while that of red galaxies decreases, consistent with prevailing movement from blue cloud to red sequence. As well as being more numerous at higher redshift, blue galaxies also dominate the overall luminosity density beyond redshifts z≃ 0.2. At lower redshifts, the luminosity density is dominated by red galaxies in the riz bands, and by blue galaxies in u and g.

Identification and properties of host galaxies of RCR radio sources

NASA Astrophysics Data System (ADS)

Zhelenkova, O. P.; Soboleva, N. S.; Majorova, E. K.; Temirova, A. V.

2013-01-01

FIRST and NVSS radio maps are used to cross identify the radio sources of the RCR catalog, which is based on observational data obtained in several runs of the "Cold" survey, with the SDSS and DPOSS digital optical sky surveys and the 2MASS, LAS UKIDSS, and WISE infrared surveys. Digital images in various filters and the coadded gri-band SDSS images, red and infrared DPOSS images, JHK-band UKIDSS images, and JHK-band 2MASS images are analyzed for the sources with no optical candidates found in the above catalogs. Our choice of optical candidates was based on the data on the structure of the radio source, its photometry, and spectroscopy (where available). We found reliable identifications for 86% of the radio sources; possible counterparts for 8% of the sources, and failed to find any optical counterparts for 6% of the sources because their host objects proved to be fainter than the limiting magnitude of the corresponding surveys. A little over half of all the identifications proved to be galaxies; about one quarter were quasars, and the types of the remaining objects were difficult to determine because of their faintness. A relation between the luminosity and the radioloudness index was derived and used to estimate the 1.4 and 3.94 GHz luminosities for the sources with unknown redshifts. We found 3% and 60% of all the RCR radio sources to be FRI-type objects ( L ≲ 1024 W/Hz at 1.4 GHz) and powerful FRII-type galaxies ( L ≳ 1026.5 W/Hz), respectively, whereas the rest are sources including objects of the FRI, FRII, and mixed FRI-FRII types. Unlike quasars, galaxies show a trend of decreasing luminosity with decreasing flux density. Note that identification would be quite problematic without the software and resources of the virtual observatory.

Fundamental Properties of O-Type Stars

NASA Technical Reports Server (NTRS)

Heap, Sara R.; Lanz, Thierry; Hubeny, Ivan

2006-01-01

We present a comprehensive analysis of high-resolution, far-ultraviolet HST STIS, FUSE, and optical spectra of 18 O stars in the Small Magellanic Cloud. Our analysis is based on the OSTAR2002 grid of NLTE metal-line-blanketed model atmospheres calculated with our code TLUSTY. We systematically explore and present the sensitivity of various UV and optical lines to different stellar parameters. We have obtained consistent fits of the UV and the optical spectrum to derive the effective temperature, surface gravity, surface composition, and microturbulent velocity of each star. Stellar radii, masses, and luminosities follow directly. For stars of the same spectral subtype, we find a general good agreement between effective temperature determinations obtained with TLUSTY, CMFGEN, and FASTWIND models, which are all lower than the standard T(sub eff) calibration of O stars. We propose a new calibration between the spectral type and effective temperature based on our results from UV metal lines, as well as optical hydrogen and helium lines. The lower effective temperatures translate into ionizing luminosities that are smaller by a factor of 3 compared to luminosities inferred from previous standard calibrations. The chemical composition analysis reveals that the surface of about 80% of the program stars is moderately to strongly enriched in nitrogen, while showing the original helium, carbon, and oxygen abundances. Our results support the new stellar evolution models that predict that the surface of fast rotating stars becomes nitrogen-rich during the main-sequence phase because of rotationally induced mixing. Enrichment factors are, however, larger than predicted by stellar evolution models. Most stars exhibit the "mass discrepancy" problem, which we interpret as a result of fast rotation that lowers the measured effective gravity. Nitrogen enrichment and low spectroscopic masses are therefore two manifestations of fast rotation. Our study thus emphasizes the importance of rotation in our understanding of the properties of massive stars and provides a framework for investigating populations of low-metallicity massive stars at low and high redshifts.

LUMINOSITY FUNCTIONS OF LMXBs IN CENTAURUS A: GLOBULAR CLUSTERS VERSUS THE FIELD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Voss, Rasmus; Gilfanov, Marat; Sivakoff, Gregory R.

2009-08-10

We study the X-ray luminosity function (XLF) of low-mass X-ray binaries (LMXB) in the nearby early-type galaxy Centaurus A, concentrating primarily on two aspects of binary populations: the XLF behavior at the low-luminosity limit and the comparison between globular cluster and field sources. The 800 ksec exposure of the deep Chandra VLP program allows us to reach a limiting luminosity of {approx}8 x 10{sup 35} erg s{sup -1}, about {approx}2-3 times deeper than previous investigations. We confirm the presence of the low-luminosity break of the overall LMXB XLF at log(L{sub X} ) {approx} 37.2-37.6, below which the luminosity distribution followsmore » a dN/d(ln L) {approx} const law. Separating globular cluster and field sources, we find a statistically significant difference between the two luminosity distributions with a relative underabundance of faint sources in the globular cluster population. This demonstrates that the samples are drawn from distinct parent populations and may disprove the hypothesis that the entire LMXB population in early-type galaxies is created dynamically in globular clusters. As a plausible explanation for this difference in the XLFs, we suggest an enhanced fraction of helium-accreting systems in globular clusters, which are created in collisions between red giants and neutron stars. Due to the four times higher ionization temperature of He, such systems are subject to accretion disk instabilities at {approx}20 times higher mass accretion rate and, therefore, are not observed as persistent sources at low luminosities.« less

Radiative GRMHD simulations of accretion and outflow in non-magnetized neutron stars and ultraluminous X-ray sources

NASA Astrophysics Data System (ADS)

Abarca, David; Kluźniak, Wlodek; Sądowski, Aleksander

2018-06-01

We run two GRRMHD simulations of super-Eddington accretion disks around a black hole and a non-magnetized, non-rotating neutron star. The neutron star was modeled using a reflective inner boundary condition. We observe the formation of a transition layer in the inner region of the disk in the neutron star simulation which leads to a larger mass outflow rate and a lower radiative luminosity over the black hole case. Sphereization of the flow leads to an observable luminosity at infinity around the Eddington value when viewed from all directions for the neutron star case, contrasting to the black hole case where collimation of the emission leads to observable luminosities about an order of magnitude higher when observed along the disk axis. We find the outflow to be optically thick to scattering, which would lead to the obscuring of any neutron star pulsations observed in corresponding ULXs.

Extended CO (J = 7-6) emission from Orion molecular cloud 1 - Hot ambient gas, two hot-outflow sources

NASA Astrophysics Data System (ADS)

Schmid-Burgk, J.; Densing, R.; Krugel, E.; Nett, H.; Roser, H. P.; Schafer, F.; Schwaab, G.; van der Wal, P.; Wattenbach, R.

1989-05-01

Observations of a 6 x 8-arcmin region at the core of Orion molecular cloud 1 are reported. Data obtained in the 806-GHz line of CO using the NASA Kuiper Airborne Observatory on September 15 and 17, 1986 are presented graphically and analyzed in detail. The results indicate a region of density 10,000/cu cm or greater and temperature of about 50 K extending several arcmin from the core; the total luminosities due to CO (J = 7-6) and to dust are estimated as 10 and 100,000 solar luminosities, respectively. Particular attention is given to the dust-embedded IR cluster BN-KL (with high-velocity outflow suggesting small optical depths) and a second more prominent feature about 2 arcmin to the south (with outflow of about 1 solar mass of material at 500-1000 K, radiating about 0.25 solar luminosity in CO 7-6).

The Abundance of Low-Luminosity Lyα Emitters at High Redshift

NASA Astrophysics Data System (ADS)

Santos, Michael R.; Ellis, Richard S.; Kneib, Jean-Paul; Richard, Johan; Kuijken, Konrad

2004-05-01

We derive the luminosity function of high-redshift Lyα-emitting sources from a deep, blind, spectroscopic survey that utilized strong-lensing magnification by intermediate-redshift clusters of galaxies. We observed carefully selected regions near nine clusters, consistent with magnification factors generally greater than 10 for the redshift range 4.5L)~L-1 over 1041-1042.5 ergs s-1. When combined with the results of other surveys, limited at higher luminosities, our results suggest evidence for the suppression of star formation in low-mass halos, as predicted in popular models of galaxy formation. 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.

Detecting the Attenuation of Blazar Gamma-ray Emission by Extragalactic Background Light with GLAST

NASA Technical Reports Server (NTRS)

Chen, Andrew; Ritz, Steven

1999-01-01

Gamma rays with energy above 10 GeV interact with optical-UV photons resulting in pair production. Therefore, a large sample of high redshift sources of these gamma rays can be used to probe the extragalactic background starlight (EBL) by examining the redshift dependence of the attenuation of the flux above 10 GeV. GLAST, the next generation high-energy gamma-ray telescope, will for the first time have the unique capability to detect thousands of gamma-ray blazars up to redshifts of at least z = 4, with enough angular resolution to allow identification of a large fraction of their optical counterparts. By combining recent determinations of the gamma-ray blazar luminosity function, recent calculations of the high energy gamma-ray opacity due to EBL absorption, and the expected GLAST instrument performance to produce simulated samples of blazars that GLAST would detect, including their redshifts and fluxes, we demonstrate that these blazars have the potential to be a highly effective probe of the EBL.

FRESH ACTIVITY IN OLD SYSTEMS: RADIO AGNs IN FOSSIL GROUPS OF GALAXIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hess, Kelley M.; Wilcots, Eric M.; Hartwick, Victoria L., E-mail: hess@ast.uct.ac.za, E-mail: ewilcots@astro.wisc.edu, E-mail: vhartwick@wisc.edu

2012-08-15

We present the first systematic 1.4 GHz Very Large Array radio continuum survey of fossil galaxy group candidates. These are virialized systems believed to have assembled over a gigayear in the past through the merging of galaxy group members into a single, isolated, massive elliptical galaxy and featuring an extended hot X-ray halo. We use new photometric and spectroscopic data from Sloan Digital Sky Survey Data Release 7 to determine that three of the candidates are clearly not fossil groups. Of the remaining 30 candidates, 67% contain a radio-loud (L{sub 1.4GHz} > 10{sup 23} W Hz{sup -1}) active galactic nucleusmore » (AGN) at the center of their dominant elliptical galaxy. We find a weak correlation between the radio luminosity of the AGN and the X-ray luminosity of the halo suggesting that the AGN contributes to energy deposition into the intragroup medium. We only find a correlation between the radio and optical luminosity of the central elliptical galaxy when we include X-ray-selected, elliptically dominated non-fossil groups, indicating a weak relationship between AGN strength and the mass assembly history of the groups. The dominant elliptical galaxy of fossil groups is on average roughly an order of magnitude more luminous than normal group elliptical galaxies in optical, X-ray, and radio luminosities and our findings are consistent with previous results that the radio-loud fraction in elliptical galaxies is linked to the stellar mass of a population. The current level of activity in fossil groups suggests that AGN fueling continues long after the last major merger. We discuss several possibilities for fueling the AGN at the present epoch.« less

CXOGBS J173620.2-293338: A candidate symbiotic X-ray binary associated with a bulge carbon star

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hynes, Robert I.; Britt, C. T.; Johnson, C. B.

2014-01-01

The Galactic Bulge Survey (GBS) is a wide but shallow X-ray survey of regions above and below the Plane in the Galactic Bulge. It was performed using the Chandra X-ray Observatory's ACIS camera. The survey is primarily designed to find and classify low luminosity X-ray binaries. The combination of the X-ray depth of the survey and the accessibility of optical and infrared counterparts makes this survey ideally suited to identification of new symbiotic X-ray binaries (SyXBs) in the Bulge. We consider the specific case of the X-ray source CXOGBS J173620.2-293338. It is coincident to within 1 arcsec with a verymore » red star, showing a carbon star spectrum and irregular variability in the Optical Gravitational Lensing Experiment data. We classify the star as a late C-R type carbon star based on its spectral features, photometric properties, and variability characteristics, although a low-luminosity C-N type cannot be ruled out. The brightness of the star implies it is located in the Bulge, and its photometric properties are overall consistent with the Bulge carbon star population. Given the rarity of carbon stars in the Bulge, we estimate the probability of such a close chance alignment of any GBS source with a carbon star to be ≲ 10{sup –3}, suggesting that this is likely to be a real match. If the X-ray source is indeed associated with the carbon star, then the X-ray luminosity is around 9 × 10{sup 32} erg s{sup –1}. Its characteristics are consistent with a low luminosity SyXB, or possibly a low accretion rate white dwarf symbiotic.« less

1.4 GHz on the Fundamental Plane of black hole activity

NASA Astrophysics Data System (ADS)

Saikia, Payaswini; Körding, Elmar; Dibi, Salome

2018-06-01

The Fundamental Plane (FP) of black hole activity is an empirical relationship between the O III/X-ray luminosity depicting the accretion power, the radio luminosity as a probe of the instantaneous jet power and the mass of the black hole. For the first time, we use the 1.4 GHz FIRST radio luminosities on the optical FP, to investigate whether or not Faint Images of the Radio Sky at Twenty-Centimetres (FIRST) fluxes can trace nuclear activity. We use an SDSS-FIRST cross-correlated sample of 10 149 active galaxies and analyse their positioning on the optical FP. We focus on various reasons that can cause the discrepancy between the observed FIRST radio fluxes and the theoretically expected core radio fluxes, and show that FIRST fluxes are heavily contaminated by non-nuclear, extended components and other environmental factors. We show that the subsample of `compact sources', which should have negligible lobe contribution, statistically follow the FP when corrected for relativistic beaming, while all the other sources lie above the plane. The sample of low-ionization nuclear emission-line regions (LINERs), which should have negligible lobe and beaming contribution, also follow the FP. A combined fit of the low-luminosity AGN and the X-ray binaries, with the LINERs, results in the relation log LR = 0.77 log L_{O III} + 0.69 log M. Assuming that the original FP relation is correct, we conclude that 1.4 GHz FIRST fluxes do not trace the pure `core' jet and instantaneous nuclear activity in the AGN, and one needs to be careful while using it on the FP of black hole activity.

Unveiling the Composite Nature of Dust-Obscured Galaxies (DOGs) with Herschel

NASA Astrophysics Data System (ADS)

Riguccini, Laurie A.; Le Floc'h, Emeric; Mullaney, James

2015-08-01

DOGs are bright 24um-selected sources with extreme obscuration at optical wavelengths. Some of them are characterized by a rising power-law continuum of hot dust (T_D ~ 200-1000 K) in the near-IR emission indicating that their mid-IR luminosity is dominated by an AGN. Whereas DOGs with a fainter 24um flux display a stellar bump and their mid-IR luminosity is believed to be mainly powered by dusty star-formation. Another explanation is that the mid-IR emission still comes from AGN activity but the torus emission is so obscured that it becomes negligible with respect to the emission from the host component.In an effort to characterize the nature of the physical processes underlying their IR emission, we focus on DOGs (F24/FR>982) within the COSMOS field with Herschel data and derive their far-IR properties (e.g., total IR luminosities; mid-to-far IR colors; dust temperatures and masses and AGN contribution) based on SED fitting.Of particular interest are the 24um-bright DOGs (F24>1mJy). They present bluer far-IR/mid-IR colors than the rest of the sample, unveiling the potential presence of an AGN. The AGN contribution to the total 8-1000um flux increases as a function of the rest-frame 8um-luminosity irrespective of the redshift, with a stronger contribution at lower redshift. This confirms that faint DOGs (F24<1mJy) are dominated by star-formation while brighter DOGs show a larger contribution from an AGN.Is this FIR-selection technique allowing us to probe a new population of obscured AGN? Or does it corresponds to already known AGN in the X-rays, NIR or radio? The wealth of multi wavelength data in COSMOS will allow us to describe our results here.

HUBBLE FRONTIER FIELDS FIRST COMPLETE CLUSTER DATA: FAINT GALAXIES AT z ∼ 5-10 FOR UV LUMINOSITY FUNCTIONS AND COSMIC REIONIZATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ishigaki, Masafumi; Ouchi, Masami; Ono, Yoshiaki

2015-01-20

We present comprehensive analyses of faint dropout galaxies up to z ∼ 10 with the first full-depth data set of the A2744 lensing cluster and parallel fields observed by the Hubble Frontier Fields (HFF) program. We identify 54 dropouts at z ∼ 5-10 in the HFF fields and enlarge the size of the z ∼ 9 galaxy sample obtained to date. Although the number of highly magnified (μ ∼ 10) galaxies is small because of the tiny survey volume of strong lensing, our study reaches the galaxies' intrinsic luminosities comparable to the deepest-field HUDF studies. We derive UV luminosity functionsmore » with these faint dropouts, carefully evaluating by intensive simulations the combination of observational incompleteness and lensing effects in the image plane, including magnification, distortion, and multiplication of images, with the evaluation of mass model dependencies. Our results confirm that the faint-end slope, α, is as steep as –2 at z ∼ 6-8 and strengthen the evidence for the rapid decrease of UV luminosity densities, ρ{sub UV}, at z > 8 from the large z ∼ 9 sample. We examine whether the rapid ρ{sub UV} decrease trend can be reconciled with the large Thomson scattering optical depth, τ{sub e}, measured by cosmic microwave background experiments, allowing a large space of free parameters, such as an average ionizing photon escape fraction and a stellar-population-dependent conversion factor. No parameter set can reproduce both the rapid ρ{sub UV} decrease and the large τ {sub e}. It is possible that the ρ{sub UV} decrease moderates at z ≳ 11, that the free parameters significantly evolve toward high z, or that there exist additional sources of reionization such as X-ray binaries and faint active galactic nuclei.« less

REVIEWS OF TOPICAL PROBLEMS: Masses of black holes in binary stellar systems

NASA Astrophysics Data System (ADS)

Cherepashchuk, Anatolii M.

1996-08-01

Mass determination methods and their results for ten black holes in X-ray binary systems are summarised. A unified interpretation of the radial velocity and optical light curves allows one to reliably justify the close binary system model and to prove the correctness of determination of the optical star mass function fv(m).The orbit plane inclination i can be estimated from an analysis of optical light curve of the system, which is due mainly to the ellipsoidal shape of the optical star (the so-called ellipticity effect). The component mass ratio q = mx/mv is obtained from information about the distance to the binary system as well as from data about rotational broadening of absorption lines in the spectrum of the optical star. These data allow one to obtain from the value of fv(m) a reliable value of the black hole mass mx or its low limit, as well as the optical star mass mv. An independent estimate of the optical star mass mv obtained from information about its spectral class and luminosity gives us test results. Additional test comes from information about the absence or presence of X-ray eclipses in the system. Effects of the non-zero dimension of the optical star, its pear-like shape, and X-ray heating on the absorption line profiles and the radial velocity curve are investigated. It is very significant that none of ten known massive (mx > 3M\\odot) X-ray sources considered as black hole candidates is an X-ray pulsar or an X-ray burster of the first kind.

Recalculating the quasar luminosity function of the extended Baryon Oscillation Spectroscopic Survey

NASA Astrophysics Data System (ADS)

Caditz, David M.

2017-12-01

Aims: The extended Baryon Oscillation Spectroscopic Survey (eBOSS) of the Sloan Digital Sky Survey provides a uniform sample of over 13 000 variability selected quasi-stellar objects (QSOs) in the redshift range 0.68

The mysterious age invariance of the planetary nebula luminosity function bright cut-off

NASA Astrophysics Data System (ADS)

Gesicki, K.; Zijlstra, A. A.; Miller Bertolami, M. M.

2018-05-01

Planetary nebulae mark the end of the active life of 90% of all stars. They trace the transition from a red giant to a degenerate white dwarf. Stellar models1,2 predicted that only stars above approximately twice the solar mass could form a bright nebula. But the ubiquitous presence of bright planetary nebulae in old stellar populations, such as elliptical galaxies, contradicts this: such high-mass stars are not present in old systems. The planetary nebula luminosity function, and especially its bright cut-off, is almost invariant between young spiral galaxies, with high-mass stars, and old elliptical galaxies, with only low-mass stars. Here, we show that new evolutionary tracks of low-mass stars are capable of explaining in a simple manner this decades-old mystery. The agreement between the observed luminosity function and computed stellar evolution validates the latest theoretical modelling. With these models, the planetary nebula luminosity function provides a powerful diagnostic to derive star formation histories of intermediate-age stars. The new models predict that the Sun at the end of its life will also form a planetary nebula, but it will be faint.

The fraction of AGNs in major merger galaxies and its luminosity dependence

NASA Astrophysics Data System (ADS)

Weigel, Anna K.; Schawinski, Kevin; Treister, Ezequiel; Trakhtenbrot, Benny; Sanders, David B.

2018-05-01

We use a phenomenological model which connects the galaxy and active galactic nucleus (AGN) populations to investigate the process of AGNs triggering through major galaxy mergers at z ˜ 0. The model uses stellar mass functions as input and allows the prediction of AGN luminosity functions based on assumed Eddington ratio distribution functions (ERDFs). We show that the number of AGNs hosted by merger galaxies relative to the total number of AGNs increases as a function of AGN luminosity. This is due to more massive galaxies being more likely to undergo a merger and does not require the assumption that mergers lead to higher Eddington ratios than secular processes. Our qualitative analysis also shows that to match the observations, the probability of a merger galaxy hosting an AGN and accreting at a given Eddington value has to be increased by a factor ˜10 relative to the general AGN population. An additional significant increase of the fraction of high Eddington ratio AGNs among merger host galaxies leads to inconsistency with the observed X-ray luminosity function. Physically our results imply that, compared to the general galaxy population, the AGN fraction among merger galaxies is ˜10 times higher. On average, merger triggering does however not lead to significantly higher Eddington ratios.

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.

A Correlation Between the Intrinsic Brightness and Average Decay Rate of Gamma-Ray Burst X-Ray Afterglow Light Curves

NASA Technical Reports Server (NTRS)

Racusin, J. L.; Oates, S. R.; De Pasquale, M.; Kocevski, D.

2016-01-01

We present a correlation between the average temporal decay (alpha X,avg, greater than 200 s) and early-time luminosity (LX,200 s) of X-ray afterglows of gamma-ray bursts as observed by the Swift X-ray Telescope. Both quantities are measured relative to a rest-frame time of 200 s after the gamma-ray trigger. The luminosity â€" average decay correlation does not depend on specific temporal behavior and contains one scale-independent quantity minimizing the role of selection effects. This is a complementary correlation to that discovered by Oates et al. in the optical light curves observed by the Swift Ultraviolet Optical Telescope. The correlation indicates that, on average, more luminous X-ray afterglows decay faster than less luminous ones, indicating some relative mechanism for energy dissipation. The X-ray and optical correlations are entirely consistent once corrections are applied and contamination is removed. We explore the possible biases introduced by different light-curve morphologies and observational selection effects, and how either geometrical effects or intrinsic properties of the central engine and jet could explain the observed correlation.

The NuSTAR Serendipitous Survey: The 40-month Catalog and the Properties of the Distant High-energy X-Ray Source Population

NASA Astrophysics Data System (ADS)

Lansbury, G. B.; Stern, D.; Aird, J.; Alexander, D. M.; Fuentes, C.; Harrison, F. A.; Treister, E.; Bauer, F. E.; Tomsick, J. A.; Baloković, M.; Del Moro, A.; Gandhi, P.; Ajello, M.; Annuar, A.; Ballantyne, D. R.; Boggs, S. E.; Brandt, W. N.; Brightman, M.; Chen, C.-T. J.; Christensen, F. E.; Civano, F.; Comastri, A.; Craig, W. W.; Forster, K.; Grefenstette, B. W.; Hailey, C. J.; Hickox, R. C.; Jiang, B.; Jun, H. D.; Koss, M.; Marchesi, S.; Melo, A. D.; Mullaney, J. R.; Noirot, G.; Schulze, S.; Walton, D. J.; Zappacosta, L.; Zhang, W. W.

2017-02-01

We present the first full catalog and science results for the Nuclear Spectroscopic Telescope Array (NuSTAR) serendipitous survey. The catalog incorporates data taken during the first 40 months of NuSTAR operation, which provide ≈20 Ms of effective exposure time over 331 fields, with an areal coverage of 13 deg2, and 497 sources detected in total over the 3-24 keV energy range. There are 276 sources with spectroscopic redshifts and classifications, largely resulting from our extensive campaign of ground-based spectroscopic follow-up. We characterize the overall sample in terms of the X-ray, optical, and infrared source properties. The sample is primarily composed of active galactic nuclei (AGNs), detected over a large range in redshift from z = 0.002 to 3.4 (median of < z> =0.56), but also includes 16 spectroscopically confirmed Galactic sources. There is a large range in X-ray flux, from {log}({f}3-24{keV}/{erg} {{{s}}}-1 {{cm}}-2)≈ -14 to -11, and in rest-frame 10-40 keV luminosity, from {log}({L}10-40{keV}/{erg} {{{s}}}-1)≈ 39 to 46, with a median of 44.1. Approximately 79% of the NuSTAR sources have lower-energy (<10 keV) X-ray counterparts from XMM-Newton, Chandra, and Swift XRT. The mid-infrared (MIR) analysis, using WISE all-sky survey data, shows that MIR AGN color selections miss a large fraction of the NuSTAR-selected AGN population, from ≈15% at the highest luminosities ({L}{{X}}> {10}44 erg s-1) to ≈80% at the lowest luminosities ({L}{{X}}< {10}43 erg s-1). Our optical spectroscopic analysis finds that the observed fraction of optically obscured AGNs (I.e., the type 2 fraction) is {F}{Type2}={53}-15+14 % , for a well-defined subset of the 8-24 keV selected sample. This is higher, albeit at a low significance level, than the type 2 fraction measured for redshift- and luminosity-matched AGNs selected by <10 keV X-ray missions.

THE GEOMETRY OF THE INFRARED AND X-RAY OBSCURER IN A DUSTY HYPERLUMINOUS QUASAR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Farrah, Duncan; Harris, Kathryn; Baloković, Mislav

2016-11-01

We study the geometry of the active galactic nucleus (AGN) obscurer in IRAS 09104+4109, an IR-luminous, radio-intermediate FR-I source at z = 0.442, using infrared data from Spitzer and Herschel , X-ray data from NuSTAR , Swift , Suzaku , and Chandra , and an optical spectrum from Palomar. The infrared data imply a total rest-frame 1–1000 μ m luminosity of 5.5 × 10{sup 46} erg s{sup −1} and require both an AGN torus and a starburst model. The AGN torus has an anisotropy-corrected IR luminosity of 4.9 × 10{sup 46} erg s{sup −1} and a viewing angle and half-openingmore » angle both of approximately 36° from pole-on. The starburst has a star formation rate of (110 ± 34) M {sub ⊙} yr{sup −1} and an age of <50 Myr. These results are consistent with two epochs of luminous activity in IRAS 09104+4109: one approximately 150 Myr ago, and one ongoing. The X-ray data suggest a photon index of Γ ≃ 1.8 and a line-of-sight column density of N {sub H} ≃ 5 × 10{sup 23} cm{sup −2}. This argues against a reflection-dominated hard X-ray spectrum, which would have implied a much higher N {sub H} and luminosity. The X-ray and infrared data are consistent with a bolometric AGN luminosity of L {sub bol} ∼ (0.5–2.5) × 10{sup 47} erg s{sup −1}. The X-ray and infrared data are further consistent with coaligned AGN obscurers in which the line of sight “skims” the torus. This is also consistent with the optical spectra, which show both coronal iron lines and broad lines in polarized but not direct light. Combining constraints from the X-ray, optical, and infrared data suggest that the AGN obscurer is within a vertical height of 20 pc, and a radius of 125 pc, of the nucleus.« less

Star and Dust Formation Activities in AzTEC-3, a Starburst Galaxy at z = 5.3

NASA Astrophysics Data System (ADS)

Dwek, Eli; Staguhn, Johannes G.; Arendt, Richard G.; Capak, Peter L.; Kovacs, Attila; Benford, Dominic J.; Fixsen, Dale; Karim, Alexander; Leclercq, Samuel; Maher, Stephen F.; Moseley, Samuel H.; Schinnerer, Eva; Sharp, Elmer H.

2011-09-01

Analyses of high-redshift ultraluminous infrared (IR) galaxies traditionally use the observed optical to submillimeter spectral energy distribution (SED) and estimates of the dynamical mass as observational constraints to derive the star formation rate (SFR), the stellar mass, and age of these objects. An important observational constraint neglected in the analysis is the mass of dust giving rise to the IR emission. In this paper we add this constraint to the analysis of AzTEC-3. Adopting an upper limit to the mass of stars and a bolometric luminosity for this object, we construct different stellar and chemical evolutionary scenarios, constrained to produce the inferred dust mass and observed luminosity before the associated stellar mass exceeds the observational limit. We use the PÉGASE population synthesis code and a chemical evolution model to follow the evolution of the galaxy's SED and its stellar and dust masses as a function of galactic age for seven different stellar initial mass functions (IMFs). We find that the model with a Top Heavy IMF provided the most plausible scenario consistent with the observational constraints. In this scenario the dust formed over a period of ~200 Myr, with an SFR of ~500 M sun yr-1. These values for the age and SFR in AzTEC-3 are significantly higher and lower, respectively, from those derived without the dust mass constraint. However, this scenario is not unique, and others cannot be completely ruled out because of the prevailing uncertainties in the age of the galaxy, its bolometric luminosity, and its stellar and dust masses. A robust result of our models is that all scenarios require most of the radiating dust mass to have been accreted in molecular clouds. Our new procedure highlights the importance of a multiwavelength approach, and of the use of dust evolution models in constraining the age and the star formation activity and history in galaxies.

STAR AND DUST FORMATION ACTIVITIES IN AzTEC-3, A STARBURST GALAXY AT z = 5.3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dwek, Eli; Staguhn, Johannes G.; Arendt, Richard G.

2011-09-01

Analyses of high-redshift ultraluminous infrared (IR) galaxies traditionally use the observed optical to submillimeter spectral energy distribution (SED) and estimates of the dynamical mass as observational constraints to derive the star formation rate (SFR), the stellar mass, and age of these objects. An important observational constraint neglected in the analysis is the mass of dust giving rise to the IR emission. In this paper we add this constraint to the analysis of AzTEC-3. Adopting an upper limit to the mass of stars and a bolometric luminosity for this object, we construct different stellar and chemical evolutionary scenarios, constrained to producemore » the inferred dust mass and observed luminosity before the associated stellar mass exceeds the observational limit. We use the PEGASE population synthesis code and a chemical evolution model to follow the evolution of the galaxy's SED and its stellar and dust masses as a function of galactic age for seven different stellar initial mass functions (IMFs). We find that the model with a Top Heavy IMF provided the most plausible scenario consistent with the observational constraints. In this scenario the dust formed over a period of {approx}200 Myr, with an SFR of {approx}500 M{sub sun} yr{sup -1}. These values for the age and SFR in AzTEC-3 are significantly higher and lower, respectively, from those derived without the dust mass constraint. However, this scenario is not unique, and others cannot be completely ruled out because of the prevailing uncertainties in the age of the galaxy, its bolometric luminosity, and its stellar and dust masses. A robust result of our models is that all scenarios require most of the radiating dust mass to have been accreted in molecular clouds. Our new procedure highlights the importance of a multiwavelength approach, and of the use of dust evolution models in constraining the age and the star formation activity and history in galaxies.« less

The Luminosity Function and Star Formation Rate between Redshifts of 0.07 and 1.47 for Narrowband Emitters in the Subaru Deep Field

NASA Astrophysics Data System (ADS)

Ly, Chun; Malkan, Matt A.; Kashikawa, Nobunari; Shimasaku, Kazuhiro; Doi, Mamoru; Nagao, Tohru; Iye, Masanori; Kodama, Tadayuki; Morokuma, Tomoki; Motohara, Kentaro

2007-03-01

SDF line-emitting galaxies in four narrowband filters at low and intermediate redshifts are presented. Broadband colors, follow-up optical spectroscopy, and multiple NB filters are used to distinguish Hα, [O II], and [O III] emitters at z=0.07-1.47 to construct their LFs. These LFs are derived down to faint magnitudes, allowing for an 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 LF. Prior to dust extinction corrections, the [O III] and [O II] LFs agree reasonably well with those of Hippelein et al. The z=0.08 Hα LF, which reaches 2 orders of magnitude fainter than Gallego et al., is steeper by 25%. This indicates that there are more low-luminosity star-forming galaxies for z<0.1. The faint-end slope α and φ* show a strong redshift evolution, while L* shows little evolution. The evolution in α indicates that low-luminosity galaxies have a stronger evolution compared to brighter ones. Integrated SFR densities are derived via Hα, [O III], and [O II] for 0.071, the SFR densities are similar. The latter is consistent with previous UV and [O II] measurements. Below z<0.4, the SFR densities are consistent with several Hα, [O II], and UV measurements, but others are a factor of 2 higher. For example, the z=0.066-0.092 LF agrees with Jones & Bland-Hawthorn, but at z=0.24 and 0.40, their number densities are twice as high. This discrepancy can be explained by cosmic variance. Based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

An X-Ray Survey of the Open Cluster NGC 6475 (M7) with ROSAT

NASA Technical Reports Server (NTRS)

Prosser, Charles F.; Stauffer, John R.; Caillault, J.-P.; Balachandran, Suchitra; Stern, Robert A.; Randich, Sofia

1995-01-01

A ROSAT x-ray survey, with complimentary optical photometry, of the open cluster NGC 6475 has enabled the detection of approx. 50 late-F to K0 and approx. 70 K/M dwarf new candidate members, providing the first reliable detection of low-mass stars in this low. galactic latitude, 220 Myr old cluster. The x-ray observations reported here have a typical limiting sensitivity of L(sub x) approx. equal to 10(exp 29) erg/s. The detection frequency of early type cluster members is consistent with the hypothesis that the x-ray emitting early type stars are binary systems with an unseen, low-mass secondary producing the x rays. The ratio between x-ray and bolometric luminosity among NGC 6475 members saturates at a spectral-type/color which is intermediate between that in much younger and in much older clusters, consistent with rotational spindown of solar-type stars upon their arrival on the ZAMS. The upper envelope of x-ray luminosity as a function of spectral type is comparable to that of the Pleiades, with the observed spread in x-ray luminosity among low-mass members being likely due to the presence of binaries and relatively rapid rotators. However, the list of x-ray selected candidate members is likely biased against low-mass, slowly rotating single stars. While some preliminary spectroscopic information is given in an appendix, further spectroscopic observations of the new candidate members will aid in interpreting the coronal activity among solar-type NGC 6475 members and their relation to similar stars in older and younger open clusters.

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.

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 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.

An expanded set of brown dwarf and very low mass star models

NASA Technical Reports Server (NTRS)

Burrows, A.; Hubbard, W. B.; Saumon, D.; Lunine, J. I.

1993-01-01

We present in this paper updated and improved theoretical models of brown dwarfs and late M dwarfs. The evolution and characteristics of objects between 0.01 and 0.2 solar mass are exhaustively investigated and special emphasis is placed on their properties at early ages. The dependence on the helium fraction, deuterium fraction, and metallicity of the masses, effective temperature and luminosities at the edge of the hydrogen main sequence are calculated. We derive luminosity functions for representative mass functions and compare our predictions to recent cluster data. We show that there are distinctive features in the theoretical luminosity functions that can serve as diagnostics of brown dwarf physics. A zero-metallicity model is presented as a bound to or approximation of a putative extreme halo population.

Spectroscopic constraints on the form of the stellar cluster mass function

NASA Astrophysics Data System (ADS)

Bastian, N.; Konstantopoulos, I. S.; Trancho, G.; Weisz, D. R.; Larsen, S. S.; Fouesneau, M.; Kaschinski, C. B.; Gieles, M.

2012-05-01

This contribution addresses the question of whether the initial cluster mass function (ICMF) has a fundamental limit (or truncation) at high masses. The shape of the ICMF at high masses can be studied using the most massive young (<10 Myr) clusters, however this has proven difficult due to low-number statistics. In this contribution we use an alternative method based on the luminosities of the brightest clusters, combined with their ages. The advantages are that more clusters can be used and that the ICMF leaves a distinct pattern on the global relation between the cluster luminosity and median age within a population. If a truncation is present, a generic prediction (nearly independent of the cluster disruption law adopted) is that the median age of bright clusters should be younger than that of fainter clusters. In the case of an non-truncated ICMF, the median age should be independent of cluster luminosity. Here, we present optical spectroscopy of twelve young stellar clusters in the face-on spiral galaxy NGC 2997. The spectra are used to estimate the age of each cluster, and the brightness of the clusters is taken from the literature. The observations are compared with the model expectations of Larsen (2009, A&A, 494, 539) for various ICMF forms and both mass dependent and mass independent cluster disruption. While there exists some degeneracy between the truncation mass and the amount of mass independent disruption, the observations favour a truncated ICMF. For low or modest amounts of mass independent disruption, a truncation mass of 5-6 × 105 M⊙ is estimated, consistent with previous determinations. Additionally, we investigate possible truncations in the ICMF in the spiral galaxy M 83, the interacting Antennae galaxies, and the collection of spiral and dwarf galaxies present in Larsen (2009, A&A, 494, 539) based on photometric catalogues taken from the literature, and find that all catalogues are consistent with having a truncation in the cluster mass functions. However for the case of the Antennae, we find a truncation mass of a few × 106M⊙ , suggesting a dependence on the environment, as has been previously suggested.

A Correlation Between Changes in Solar Luminosity and Differential Radius Measurements

NASA Technical Reports Server (NTRS)

Kroll, R. J.; Hill, H. A.; Beardsley, B. J.

1990-01-01

Solar luminosity variations occurring during solar cycle 21 can be attributed in large part to the presence of sunspots and faculae. Nevertheless, there remains a residual portion of the luminosity variation distinctly unaccounted for by these phenomena of solar activity. At the Santa Catalina Laboratory for Experimental Relativity by Astrometry (SCLERA), observations of the solar limb are capable of detecting changes in the solar limb darkening function by monitoring a quantity known as the differential radius. These observations are utilized in such a way that the effects of solar activity are minimized in order to reveal the more fundamental structure of the photosphere. The results of observations made during solar cycle 21 at various solar latitudes indicate that a measurable change did occur in the global photospheric limb darkening function. It is proposed that the residual luminosity change is associated in part with this change in limb darkening.

Six months of multiwavelength follow-up of the tidal disruption candidate ASASSN-14li and implied TDE rates from ASAS-SN

DOE PAGES

Holoien, Thomas W. -S.; Kochanek, C. S.; Prieto, J. L.; ...

2015-11-25

In this paper, we present ground-based and Swift photometric and spectroscopic observations of the candidate tidal disruption event (TDE) ASASSN-14li, found at the centre of PGC 043234 (d ≃ 90 Mpc) by the All-Sky Automated Survey for SuperNovae (ASAS-SN). The source had a peak bolometric luminosity of L ≃ 10 44 erg s -1 and a total integrated energy of E ≃ 7 × 10 50 erg radiated over the ~6 months of observations presented. The UV/optical emission of the source is well fitted by a blackbody with roughly constant temperature of T ~ 35 000 K, while the luminositymore » declines by roughly a factor of 16 over this time. The optical/UV luminosity decline is broadly consistent with an exponential decline, L∝e -t/t0, with t 0 ≃ 60 d. ASASSN-14li also exhibits soft X-ray emission comparable in luminosity to the optical and UV emission but declining at a slower rate, and the X-ray emission now dominates. Spectra of the source show broad Balmer and helium lines in emission as well as strong blue continuum emission at all epochs. Finally, we use the discoveries of ASASSN-14li and ASASSN-14ae to estimate the TDE rate implied by ASAS-SN, finding an average rate of r ≃ 4.1 × 10 -5 yr -1 per galaxy with a 90 per cent confidence interval of (2.2–17.0) × 10 -5 yr -1 per galaxy. ASAS-SN found roughly 1 TDE for every 70 Type Ia supernovae in 2014, a rate that is much higher than that of other surveys.« less

Probing the Physical Properties of High Redshift Optically Obscured Galaxies in the Bootes NOAO Deep Wide Field Survey using the Infrared Spectrograph on Spitzer

NASA Astrophysics Data System (ADS)

Higdon, S. J. U.; Weedman, D.; Higdon, J. L.; Houck, J. R.; Soifer, B. T.; Armus, L.; Charmandaris, V.; Herter, T. L.; Brandl, B. R.; Brown, M. J. I.; Dey, A.; Jannuzi, B.; Le Floc'h, E.; Rieke, M.

2004-12-01

We have surveyed a field covering 8.4 degrees2 within the NOAO Deep Wide Field Survey region in Boötes with the Multiband Imaging Photometer on the Spitzer Space Telescope to a limiting 24 um flux density of 0.3 mJy, identifying ˜ 22,000 point sources. Thirty one sources from this survey with F(24 um) > 0.75 mJy , which are optically ``invisible'' (R > 26) or very faint (I > 24) have been observed with the low-resolution modules of the Infrared Spectrograph on SST. The spectra were extracted using the IRS SMART spectral analysis package in order to optimize their signal to noise. A suite of mid-IR spectral templates of well known galaxies, observed as part of the IRS GTO program, is used to perform formal fits to the spectral energy distribution of the Boötes sources. These fits enable us to measure their redshift, to calculate the depth of the 9.7 um silicate feature along with the strength of 7.7 um PAH, as well as to estimate their bolometric luminosities. We compare the mid-IR slope, the measured PAH luminosity, and the optical depth of these sources with those of galaxies in the local Universe. As a result we are able to estimate the contribution of a dust enshrouded active nucleus to the mid-IR and bolometric luminosity of these systems. This work is based [in part] on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407. Support for this work was provided by NASA through Contract Number 1257184 issued by JPL/Caltech.

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.

Quasar evolution and the growth of black holes

NASA Technical Reports Server (NTRS)

Small, Todd A.; Blandford, Roger D.

1992-01-01

A 'minimalist' model of AGN evolution is analyzed that links the measured luminosity function to an elementary description of black hole accretion. The observed luminosity function of bright AGN is extrapolated and simple prescriptions for the growth and luminosity of black holes are introduced to infer quasar birth rates, mean fueling rates, and relict black hole distribution functions. It is deduced that the mean accretion rate scales as (M exp -1./5)(t exp -6.7) and that, for the most conservative model used, the number of relict black holes per decade declines only as M exp -0.4 for black hole masses between 3 x 10 exp 7 and 3 x 10 exp 9 solar masses. If all sufficiently massive galaxies pass through a quasar phase with asymptotic black hole mass a monotonic function of the galaxy mass, then it is possible to compare the space density of galaxies with estimated central masses to that of distant quasars.

Einstein X-ray survey of the Pleiades - The dependence of X-ray emission on stellar age

NASA Technical Reports Server (NTRS)

Micela, G.; Sciortino, S.; Serio, S.; Vaiana, G. S.; Bookbinder, J.; Golub, L.; Harnden, F. R., Jr.; Rosner, R.

1985-01-01

The data obtained with two pointed observations of 1 deg by 1 deg fields of the Pleiades region have been analyzed, and the results are presented. The maximum-likelihood X-ray luminosity functions for the Pleiades G and K stars in the cluster are derived, and it is shown that, for the G stars, the Pleiades X-ray luminosity function is significantly brighter than the corresponding function for Hyades G dwarf stars. This finding indicates a dependence of X-ray luminosity on stellar age, which is confirmed by comparison of the same data with median X-ray luminosities of pre-main sequence and local disk population dwarf G stars. It is suggested that the significantly larger number of bright X-ray sources associated with G stars than with K stars, the lack of detection of M stars, and the relatively rapid rotation of the Pleiades K stars can be explained in terms of the onset of internal differential rotation near the convective envelope-radidative core interface after the spin-up phase during evolution to the main sequence.

Einstein Observatory survey of X-ray emission from solar-type stars - The late F and G dwarf stars

NASA Technical Reports Server (NTRS)

Maggio, A.; Sciortino, S.; Vaiana, G. S.; Majer, P.; Bookbinder, J.

1987-01-01

Results of a volume-limited X-ray survey of stars of luminosity classes IV and V in the spectral range F7-G9 observed with the Einstein Observatory are presented. Using survival analysis techniques, the stellar X-ray luminosity function in the 0.15-4.0 keV energy band for both single and multiple sources. It is shown that the difference in X-ray luminosity between these two classes of sources is consistent with the superposition of individual components in multiple-component systems, whose X-ray properties are similar to those of the single-component sources. The X-ray emission of the stars in our sample is well correlated with their chromospheric CA II H-K line emission and with their projected equatorial rotational velocity. Comparison of the X-ray luminosity function constructed for the sample of the dG stars of the local population with the corresponding functions derived elsewhere for the Hyades, the Pleiades, and the Orion Ic open cluster confirms that the level of X-ray emission decreases with stellar age.

Models of the hard X-ray spectrum of AM Herculis and implications for the accretion rate

NASA Technical Reports Server (NTRS)

Swank, J. H.; Fabian, A. C.; Ross, R. R.

1983-01-01

Phenomenological fits to the hard X-ray spectrum of AM Herculis left unexplained the high equivalent width (0.8 + or - 0.1 keV) of Fe K alpha emission. A purely thermal origin implies a much steeper spectrum than was observed. With Monte Carlo calculations, scattering and fluorescent line production in a cold or partially ionized accretion column of hard X-rays emitted at the base were investigated. The strength of the iron emission and the flat spectral continuum can be explained by the effects of fluorescence and absorption within the accretion column and the surface of the white dwarf on a thermal X-ray spectrum. Thomson optical depths across the column in the range 0.2 to 0.7 are acceptable. The accretion rate and gravitational power can be deduced from the optical depth across the column, if the column size is known, and, together with the observed hard X-ray and polarized light luminosities, imply a lower limit for the luminosity in the UV to soft X-ray range, for which the observations give model-dependent values. Estimates of the column size differ by a factor of 40. Small spot sizes and low luminosities would be consistent with the soft component being the expected reprocessed bremsstrahlung and cyclotron radiation, although the constraint of matching the spectrum confines one to solutions with fluxes exceeding 20% the Eddington limits.

Modeling the Infrared Reverberation Response of the Circumnuclear Dusty Torus in AGNs: The Effects of Cloud Orientation and Anisotropic Illumination

DOE Office of Scientific and Technical Information (OSTI.GOV)

Almeyda, Triana; Robinson, Andrew; Richmond, Michael

The obscuring circumnuclear torus of dusty molecular gas is one of the major components of active galactic nuclei (AGN). The torus can be studied by analyzing the time response of its infrared (IR) dust emission to variations in the AGN continuum luminosity, a technique known as reverberation mapping. The IR response is the convolution of the AGN ultraviolet/optical light curve with a transfer function that contains information about the size, geometry, and structure of the torus. Here, we describe a new computer model that simulates the reverberation response of a clumpy torus. Given an input optical light curve, the codemore » computes the emission of a 3D ensemble of dust clouds as a function of time at selected IR wavelengths, taking into account light travel delays. We present simulated dust emission responses at 3.6, 4.5, and 30 μ m that explore the effects of various geometrical and structural properties, dust cloud orientation, and anisotropy of the illuminating radiation field. We also briefly explore the effects of cloud shadowing (clouds are shielded from the AGN continuum source). Example synthetic light curves have also been generated, using the observed optical light curve of the Seyfert 1 galaxy NGC 6418 as input. The torus response is strongly wavelength-dependent, due to the gradient in cloud surface temperature within the torus, and because the cloud emission is strongly anisotropic at shorter wavelengths. Anisotropic illumination of the torus also significantly modifies the torus response, reducing the lag between the IR and optical variations.« less

Modeling Photodisintegration-induced TeV Photon Emission from Low-luminosity Gamma-Ray Bursts

NASA Astrophysics Data System (ADS)

Liu, Xue-Wen; Wu, Xue-Feng; Lu, Tan

2012-05-01

Ultra-high-energy cosmic-ray heavy nuclei have recently been considered as originating from nearby low-luminosity gamma-ray bursts that are associated with Type Ibc supernovae. Unlike the power-law decay in long duration gamma-ray bursts, the light curve of these bursts exhibits complex UV/optical behavior: shock breakout dominated thermal radiation peaks at about 1 day, and, after that, nearly constant emission sustained by radioactive materials for tens of days. We show that the highly boosted heavy nuclei at PeV energy interacting with the UV/optical photon field will produce considerable TeV photons via the photodisintegration/photo-de-excitation process. It was later predicted that a thermal-like γ-ray spectrum peaks at about a few TeV, which may serve as evidence of nucleus acceleration. The future observations by the space telescope Fermi and by the ground atmospheric Cherenkov telescopes such as H.E.S.S., VERITAS, and MAGIC will shed light on this prediction.

Comparison of the far-infrared and carbon monoxide emission in Heiles' Cloud 2 and B18

NASA Technical Reports Server (NTRS)

Snell, Ronald L.; Schloerb, F. Peter; Heyer, Mark H.

1989-01-01

A comparison is made of the far-IR emission detected by IRAS at 60 and 100 microns and the emission from C(-13)O in B18 and Heiles' Cloud 2. The results show that both these clouds have extended emission at the studied wavelengths and that this emission is correlated with the integrated intensity of (C-13)O emission. The dust temperature and optical depth, the gas column density, the mass of gas and dust, and the far-IR luminosity are derived and presented. The analysis shows that the dust optical depth is much better correlated with the gas column density than with the far-IR intensity. The dust temperature is found to be anticorrelated with the gas column density, suggesting that these clouds are externally heated by the interstellar radiation field. The far-IR luminosity-to-mass ratios for the clouds are substantially less than the average for the inner Galaxy.

Planets, Planetary Nebulae, and Intermediate Luminosity Optical Transients (ILOTs)

NASA Astrophysics Data System (ADS)

Soker, Noam

2018-05-01

I review some aspects related to the influence of planets on the evolution of stars before and beyond the main sequence. Some processes include the tidal destruction of a planet on to a very young main sequence star, on to a low mass main sequence star, and on to a brown dwarf. This process releases gravitational energy that might be observed as a faint intermediate luminosity optical transient (ILOT) event. I then summarize the view that some elliptical planetary nebulae are shaped by planets. When the planet interacts with a low mass upper asymptotic giant branch (AGB) star it both enhances the mass loss rate and shapes the wind to form an elliptical planetary nebula, mainly by spinning up the envelope and by exciting waves in the envelope. If no interaction with a companion, stellar or sub-stellar, takes place beyond the main sequence, the star is termed a Jsolated star, and its mass loss rates on the giant branches are likely to be much lower than what is traditionally assumed.

Construction of the optical part of a time-of-flight detector prototype for the AFP detector

DOE PAGES

Nozka, L.; Adamczyk, L.; Avoni, G.; ...

2016-11-22

We present the construction of the optical part of the ToF (time-of-flight) subdetector prototype for the AFP (ATLAS Forward Proton) detector. The ToF detector in conjunction with a 3D silicon pixel tracker will tag and measure protons originating in central exclusive interactions p + p → p + X + p, where the two outgoing protons are scattered in the very forward directions. The ToF is required to reduce so-called pileup backgrounds that arise from multiple proton interactions in the same bunch crossing at high luminosity. The background can fake the signal of interest, and the extra rejection from themore » ToF allows the proton tagger to operate at the high luminosity required for measurement of the processes. The prototype detector uses fused silica bars emitting Cherenkov radiation as a relativistic particle passes through it. Finally, the emitted Cherenkov photons are detected by a micro-channel plate multi-anode Photomultiplier Tube (MCP-PMT) and processed by fast electronics.« less

IRAS 14348-1447, an ultraluminous pair of colliding, gas-rich galaxies - The birth of a quasar?

NASA Technical Reports Server (NTRS)

Sanders, D. B.; Soifer, B. T.; Scoville, N. Z.

1988-01-01

Ground-baed observations of the object IRAS 14348-1447, which was discovered with the Infrared Astronomical Satellite, show that it is an extremely luminous colliding galaxy system that emits more than 95 percent of its energy at FIR wavelengths. IRAS 14348-1447, which is receeding from the sun at 8 percent of the speed of light, has a bolometric luminosity more than 100 times larger than that of the Galaxy, and is therefore as luminous as optical quasars. New optical, infrared, and spectroscopic measurements suggest that the dominant luminosity source is a dust-enshrouded quasar. The fuel for the intense activity is an enormous supply of molecular gas. Carbon monoxide emission has been detected at a wavelength of 2.6 millimeters by means of a new, more sensitive receiver recently installed on the 12-meter telescope of the National Radio Astronomy Observatory. IRAS 14348-1447 is the most distant and luminous source of carbon monoxide line emission yet detected.

Construction of the optical part of a time-of-flight detector prototype for the AFP detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nozka, L.; Adamczyk, L.; Avoni, G.

We present the construction of the optical part of the ToF (time-of-flight) subdetector prototype for the AFP (ATLAS Forward Proton) detector. The ToF detector in conjunction with a 3D silicon pixel tracker will tag and measure protons originating in central exclusive interactions p + p → p + X + p, where the two outgoing protons are scattered in the very forward directions. The ToF is required to reduce so-called pileup backgrounds that arise from multiple proton interactions in the same bunch crossing at high luminosity. The background can fake the signal of interest, and the extra rejection from themore » ToF allows the proton tagger to operate at the high luminosity required for measurement of the processes. The prototype detector uses fused silica bars emitting Cherenkov radiation as a relativistic particle passes through it. Finally, the emitted Cherenkov photons are detected by a micro-channel plate multi-anode Photomultiplier Tube (MCP-PMT) and processed by fast electronics.« less

Effect of luminosity on color discrimination of dichromatic marmosets (Callithrix jacchus).

PubMed

Freitag, Fabio Batista; Pessoa, Daniel Marques Almeida

2012-02-01

Psychophysical data have shown that under mesopic conditions cones and rods can interact, improving color vision. Since electrophysiological data have suggested that rods of dichromatic marmosets appear to be active at higher luminance, we aimed to investigate the effect of different levels of sunlight on the foraging abilities of male dichromatic marmosets. Captive marmosets were observed under three different conditions, with respect to their performance in detecting colored food items against a green background. Compared to high and low light intensities, intermediate luminosities significantly increased detection of orange targets by male dichromats, an indication of rod intrusion. © 2012 Optical Society of America

Morphological and Star Formation Evolution to z = 1

NASA Astrophysics Data System (ADS)

Hammer, F.

The decrease, since z = 1, of the rest-frame UV luminosity density is related to global changes in morphology, color and emission lines properties of galaxies. This is apparently followed by a similar decrease of the rest-frame IR luminosity density. I discuss the relative contribution from the different galaxy morphological types to the observed evolution. The main contributors are compact galaxies observed in large number at optical wavelengths, and the sparse population of extincted & powerful starbursts observed by ISO. This latter population is made of large and massive galaxies mostly found in interacting systems, some of which could be leading to the formation of massive ellipticals at z < 1.

Characterisation of a candidate dual AGN

NASA Astrophysics Data System (ADS)

Lena, D.; Panizo-Espinar, G.; Jonker, P. G.; Torres, M.; Heida, M.

2018-05-01

We present Chandra and optical observations of a candidate dual AGN discovered serendipitously while searching for recoiling black holes via a cross-correlation between the serendipitous XMM source catalog (2XMMi) and SDSS-DR7 galaxies with a separation no larger than ten times the sum of their Petrosian radii. The system has a stellar mass ratio M1/M2 ≈ 0.7. One of the galaxies (Source 1) shows clear evidence for AGN activity in the form of hard X-ray emission and optical emission-line diagnostics typical of AGN ionisation. The nucleus of the other galaxy (Source 2) has a soft X-ray spectrum, bluer colours, and optical emission line ratios dominated by stellar photoionisation with a "composite" signature, which might indicate the presence of a weak AGN. When plotted on a diagram with X-ray luminosity vs [OIII] luminosity both nuclei fall within the locus defined by local Seyfert galaxies. From the optical spectrum we estimate the electron densities finding n1 < 27 e- cm-3 and n2 ≈ 200 e- cm-3. From a 2D decomposition of the surface brightness distribution we infer that both galaxies host rotationally supported bulges (Sersic index <1). While the active nature of Source 1 can be established with confidence, whether the nucleus of Source 2 is active remains a matter of debate. Evidence that a faint AGN might reside in its nucleus is, however, tantalising.

Evolution of Galaxy Luminosity and Stellar-Mass Functions since $z=1$ with the Dark Energy Survey Science Verification Data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Capozzi, D.; et al.

We present the first study of the evolution of the galaxy luminosity and stellar-mass functions (GLF and GSMF) carried out by the Dark Energy Survey (DES). We describe the COMMODORE galaxy catalogue selected from Science Verification images. This catalogue is made ofmore » $$\\sim 4\\times 10^{6}$$ galaxies at $$0« less

Practical way to avoid spurious geometrical contributions in Brillouin light scattering experiments at variable scattering angles.

PubMed

Battistoni, Andrea; Bencivenga, Filippo; Fioretto, Daniele; Masciovecchio, Claudio

2014-10-15

In this Letter, we present a simple method to avoid the well-known spurious contributions in the Brillouin light scattering (BLS) spectrum arising from the finite aperture of collection optics. The method relies on the use of special spatial filters able to select the scattered light with arbitrary precision around a given value of the momentum transfer (Q). We demonstrate the effectiveness of such filters by analyzing the BLS spectra of a reference sample as a function of scattering angle. This practical and inexpensive method could be an extremely useful tool to fully exploit the potentiality of Brillouin acoustic spectroscopy, as it will easily allow for effective Q-variable experiments with unparalleled luminosity and resolution.

An Interferometric Study of the Post-AGB Binary 89 Herculis. 1: Spatially Resolving the Continuum Circumstellar Environment at Optical and Near-IR Wavelengths with the VLTI, NPOI, IOTA, PTI, and the CHARA Array

DTIC Science & Technology

2013-01-01

evolution of binaries as well as the structure of circumstellar disks. Aims. A multiwavelength high angular resolution study of the prototypical object...optical to mid-IR wave- lengths. For YSOs this has led to the discovery of an empiri- cal size-luminosity relation (Millan-Gabet et al. 2001; Monnier...Millan-Gabet 2002), which in turn has led to the current paradigm (Dullemond & Monnier 2010) of a passive dusty disk with an optically thin cavity and the

Plain fundamentals of Fundamental Planes: analytics and algorithms

NASA Astrophysics Data System (ADS)

Sheth, Ravi K.; Bernardi, Mariangela

2012-05-01

Estimates of the coefficients a and b of the Fundamental Plane relation R∝σa Ib depend on whether one minimizes the scatter in the R direction, or orthogonal to the plane. We provide explicit expressions for a and b (and confidence limits) in terms of the covariances between log R, log σ and log I. Our expressions quantify the origin of the difference between the direct, inverse and orthogonal fit coefficients. They also show how to account for correlated errors, how to quantify the difference between the plane in a magnitude-limited survey and one which is volume limited, how to determine whether a scaling relation will be biased when using an apparent magnitude-limited survey, how to remove this bias and why some forms of the z≈ 0 plane appear to be less affected by selection effects, but that this does not imply that they will remain unaffected at high redshift. Finally, they show why, to a good approximation, the three vectors associated with the plane, one orthogonal to and the other two in it, can all be written as simple combinations of a and b. Essentially, this is a consequence of the fact that the distribution of surface brightness is much broader than that of velocity dispersions, and velocity dispersion and surface brightness are only weakly correlated. Why this should be so for galaxies is a fundamental open question about the physics of early-type galaxy formation. We argue that if luminosity evolution is differential, and sizes and velocity dispersions do not evolve, then this is just an accident: velocity dispersion and surface brightness must have been correlated in the past. On the other hand, if the (lack of) correlation is similar to that at the present time, then differential luminosity evolution must have been accompanied by structural evolution. A model in which the luminosities of low-luminosity galaxies evolve more rapidly than do those of higher luminosity galaxies is able to produce the observed decrease in a (by a factor of 2 at z˜ 1) while having b decrease by only about 20 per cent. In such a model, the dynamical mass-to-light ratio is a steeper function of mass at higher z. Our analysis is more generally applicable to any other correlations between three variables: e.g. the colour-magnitude-σ relation, the luminosity and velocity dispersion of a galaxy and the mass of its black hole or the relation between the X-ray luminosity, Sunyaev-Zeldovich decrement and optical richness of a cluster. Furthermore, for completeness, we show how our analysis generalizes further to correlations between more than three variables.

A Database of Young Star Clusters for Five Hundred Galaxies

NASA Astrophysics Data System (ADS)

Evans, Jessica; Whitmore, B. C.; Lindsay, K.; Chandar, R.; Larsen, S.

2009-01-01

The study of young massive stellar clusters has faced a series of observational challenges, such as the use of inconsistent data sets and low number statistics. To rectify these shortcomings, this project will use the source lists developed as part of the Hubble Legacy Archive to obtain a large, uniform database of super star clusters in nearby star-forming galaxies in order to address two fundamental astronomical questions: 1) To what degree is the cluster luminosity (and mass) function of star clusters universal? 2) What fraction of super star clusters are "missing" in optical studies (i.e., are hidden by dust)? The archive's recent data release (Data Release 2 - September, 2008) will help us achieve the large sample necessary (N 50 galaxies for multi-wavelength, N 500 galaxies for ACS F814W). The uniform data set will comprise of ACS, WFPC2, and NICMOS data, with DAOphot used for object detection. This database will also support comparisons with new Monte-Carlo simulations that have independently been developed in the past few years, and will be used to test the Whitmore, Chandar, Fall (2007) framework designed to understand the demographics of star clusters in all star forming galaxies. The catalogs will increase the number of galaxies with measured mass and luminosity functions by an order of magnitude, and will provide a powerful new tool for comparative studies, both ours and the community's. The poster will describe our preliminary investigation for the first 30 galaxies in the sample.

On the determination of the number of O stars in H II regions and starburst galaxies

NASA Technical Reports Server (NTRS)

Vacca, William D.

1994-01-01

The hot star population in H II regions, H II galaxies, and starburst galaxies is often described in terms of the number of 'equivalent' O stars of a single representative subtype and luminosity class needed to produce the ionizing luminosity deduced from the nebular recombination lines in the optical spectra. In this paper we define conversion factors eta(sub 0), eta(sub 1), and zeta(sub 5000) with which the total number of O V stars and their flux contribution at 5000 A can be derived from the number of these 'equivalent' stars. These quantities depend primarily on three parameters: the slope and upper mass limit of the stellar mass function and the metallicity of the region. Using the latest stellar atmosphere and evolution models, we calculate eta(sub 0), eta(sub 1), and zeta(sub 5000) for a large number of values of these parameters. The results are presented in tabular as well as graphical form. We apply our results to two H II regions for which the hot star population are known and find that the predicted numbers of O stars agree well the observed counts. In addition, we describe a method by which the values of eta(sub 0) and eta(sub 1) and the observed emission-line fluxes can be used to place constraints on the allowed values of the slope and upper mass limit of the stellar mass function in a region.

Type II supernovae in low luminosity host galaxies

NASA Astrophysics Data System (ADS)

Gutiérrez, C. P.; Anderson, J. P.; Sullivan, M.; Dessart, L.; González-Gaitan, S.; Galbany, L.; Dimitriadis, G.; Arcavi, I.; Bufano, F.; Chen, T.-W.; Dennefeld, M.; Gromadzki, M.; Haislip, J. B.; Hosseinzadeh, G.; Howell, D. A.; Inserra, C.; Kankare, E.; Leloudas, G.; Maguire, K.; McCully, C.; Morrell, N.; E, F. Olivares; Pignata, G.; Reichart, D. E.; Reynolds, T.; Smartt, S. J.; Sollerman, J.; Taddia, F.; Takáts, K.; Terreran, G.; Valenti, S.; Young, D. R.

2018-06-01

We present an analysis of a new sample of type II core-collapse supernovae (SNe II) occurring within low-luminosity galaxies, comparing these with a sample of events in brighter hosts. Our analysis is performed comparing SN II spectral and photometric parameters and estimating the influence of metallicity (inferred from host luminosity differences) on SN II transient properties. We measure the SN absolute magnitude at maximum, the light-curve plateau duration, the optically thick duration, and the plateau decline rate in the V -band, together with expansion velocities and pseudo-equivalent-widths (pEWs) of several absorption lines in the SN spectra. For the SN host galaxies, we estimate the absolute magnitude and the stellar mass, a proxy for the metallicity of the host galaxy. SNe II exploding in low luminosity galaxies display weaker pEWs of Fe II λ5018, confirming the theoretical prediction that metal lines in SN II spectra should correlate with metallicity. We also find that SNe II in low-luminosity hosts have generally slower declining light curves and display weaker absorption lines. We find no relationship between the plateau duration or the expansion velocities with SN environment, suggesting that the hydrogen envelope mass and the explosion energy are not correlated with the metallicity of the host galaxy. This result supports recent predictions that mass-loss for red supergiants is independent of metallicity.

VizieR Online Data Catalog: FIR data of IR-bright dust-obscured galaxies (DOGs) (Toba+, 2017)

NASA Astrophysics Data System (ADS)

Toba, Y.; Nagao, T.; Wang, W.-H.; Matsuhara, H.; Akiyama, M.; Goto, T.; Koyama, Y.; Ohyama, Y.; Yamamura, I.

2017-11-01

We investigate the star-forming activity of a sample of infrared (IR)-bright dust-obscured galaxies (DOGs) that show an extreme red color in the optical and IR regime, (i-[22])AB>7.0. Combining an IR-bright DOG sample with the flux at 22μm>3.8mJy discovered by Toba & Nagao (2016ApJ...820...46T) with the IRAS faint source catalog version 2 and AKARI far-IR (FIR) all-sky survey bright source catalog version 2, we selected 109 DOGs with FIR data. For a subsample of seven IR-bright DOGs with spectroscopic redshifts (0.07

Far-infrared Properties of Infrared-bright Dust-obscured Galaxies Selected with IRAS and AKARI Far-infrared All-sky Survey

NASA Astrophysics Data System (ADS)

Toba, Yoshiki; Nagao, Tohru; Wang, Wei-Hao; Matsuhara, Hideo; Akiyama, Masayuki; Goto, Tomotsugu; Koyama, Yusei; Ohyama, Youich; Yamamura, Issei

2017-05-01

We investigate the star-forming activity of a sample of infrared (IR)-bright dust-obscured galaxies (DOGs) that show an extreme red color in the optical and IR regime, {(I-[22])}{AB}> 7.0. Combining an IR-bright DOG sample with the flux at 22 μm > 3.8 mJy discovered by Toba & Nagao with the IRAS faint source catalog version 2 and AKARI far-IR (FIR) all-sky survey bright source catalog version 2, we selected 109 DOGs with FIR data. For a subsample of seven IR-bright DOGs with spectroscopic redshifts (0.07< z< 1.0) that were obtained from the literature, we estimated their IR luminosity, star formation rate (SFR), and stellar mass based on the spectral energy distribution fitting. We found that (1) the WISE 22 μm luminosity at the observed frame is a good indicator of IR luminosity for IR-bright DOGs and (2) the contribution of the active galactic nucleus to IR luminosity increases with IR luminosity. By comparing the stellar mass and SFR relation for our DOG sample and the literature, we found that most of the IR-bright DOGs lie significantly above the main sequence of star-forming galaxies at similar redshift, indicating that the majority of IRAS- or AKARI-detected IR-bright DOGs are starburst galaxies.

LoCuSS: connecting the dominance and shape of brightest cluster galaxies with the assembly history of massive clusters

NASA Astrophysics Data System (ADS)

Smith, Graham P.; Khosroshahi, Habib G.; Dariush, A.; Sanderson, A. J. R.; Ponman, T. J.; Stott, J. P.; Haines, C. P.; Egami, E.; Stark, D. P.

2010-11-01

We study the luminosity gap, Δm12, between the first- and second-ranked galaxies in a sample of 59 massive (~1015Msolar) galaxy clusters, using data from the Hale Telescope, the Hubble Space Telescope, Chandra and Spitzer. We find that the Δm12 distribution, p(Δm12), is a declining function of Δm12 to which we fitted a straight line: p(Δm12) ~ -(0.13 +/- 0.02)Δm12. The fraction of clusters with `large' luminosity gaps is p(Δm12 >= 1) = 0.37 +/- 0.08, which represents a 3σ excess over that obtained from Monte Carlo simulations of a Schechter function that matches the mean cluster galaxy luminosity function. We also identify four clusters with `extreme' luminosity gaps, Δm12 >= 2, giving a fraction of . More generally, large luminosity gap clusters are relatively homogeneous, with elliptical/discy brightest cluster galaxies (BCGs), cuspy gas density profiles (i.e. strong cool cores), high concentrations and low substructure fractions. In contrast, small luminosity gap clusters are heterogeneous, spanning the full range of boxy/elliptical/discy BCG morphologies, the full range of cool core strengths and dark matter concentrations, and have large substructure fractions. Taken together, these results imply that the amplitude of the luminosity gap is a function of both the formation epoch and the recent infall history of the cluster. `BCG dominance' is therefore a phase that a cluster may evolve through and is not an evolutionary `cul-de-sac'. We also compare our results with semi-analytic model predictions based on the Millennium Simulation. None of the models is able to reproduce all of the observational results on Δm12, underlining the inability of the current generation of models to match the empirical properties of BCGs. We identify the strength of active galactic nucleus feedback and the efficiency with which cluster galaxies are replenished after they merge with the BCG in each model as possible causes of these discrepancies.

Fundamental properties of Fanaroff-Riley type II radio galaxies investigated via Monte Carlo simulations

NASA Astrophysics Data System (ADS)

Kapińska, A. D.; Uttley, P.; Kaiser, C. R.

2012-08-01

Radio galaxies and quasars are among the largest and most powerful single objects known and are believed to have had a significant impact on the evolving Universe and its large-scale structure. We explore the intrinsic and extrinsic properties of the population of Fanaroff-Riley type II (FR II) objects, i.e. their kinetic luminosities, lifetimes and the central densities of their environments. In particular, the radio and kinetic luminosity functions of these powerful radio sources are investigated using the complete, flux-limited radio catalogues of the Third Cambridge Revised Revised Catalogue (3CRR) and Best et al. We construct multidimensional Monte Carlo simulations using semi-analytical models of FR II source time evolution to create artificial samples of radio galaxies. Unlike previous studies, we compare radio luminosity functions found with both the observed and simulated data to explore the best-fitting fundamental source parameters. The new Monte Carlo method we present here allows us to (i) set better limits on the predicted fundamental parameters of which confidence intervals estimated over broad ranges are presented and (ii) generate the most plausible underlying parent populations of these radio sources. Moreover, as has not been done before, we allow the source physical properties (kinetic luminosities, lifetimes and central densities) to co-evolve with redshift, and we find that all the investigated parameters most likely undergo cosmological evolution. Strikingly, we find that the break in the kinetic luminosity function must undergo redshift evolution of at least (1 + z)3. The fundamental parameters are strongly degenerate, and independent constraints are necessary to draw more precise conclusions. We use the estimated kinetic luminosity functions to set constraints on the duty cycles of these powerful radio sources. A comparison of the duty cycles of powerful FR IIs with those determined from radiative luminosities of active galactic nuclei of comparable black hole mass suggests a transition in behaviour from high to low redshifts, corresponding to either a drop in the typical black hole mass of powerful FR IIs at low redshifts, or a transition to a kinetically dominated, radiatively inefficient FR II population.

Bias Properties of Extragalactic Distance Indicators. VIII. H0 from Distance-limited Luminosity Class and Morphological Type-Specific Luminosity Functions for SB, SBC, and SC Galaxies Calibrated Using Cepheids

NASA Astrophysics Data System (ADS)

Sandage, Allan

1999-12-01

Relative, reduced to absolute, magnitude distributions are obtained for Sb, Sbc, and Sc galaxies in the flux-limited Revised Shapley-Ames Catalog (RSA2) for each van den Bergh luminosity class (L), within each Hubble type (T). The method to isolate bias-free subsets of the total sample is via Spaenhauer diagrams, as in previous papers of this series. The distance-limited type and class-specific luminosity functions are normalized to numbers of galaxies per unit volume (105 Mpc3), rather than being left as relative functions, as in Paper V. The functions are calculated using kinematic absolute magnitudes, based on an arbitrary trial value of H0=50. Gaussian fits to the individual normalized functions are listed for each T and L subclass. As in Paper V, the data can be freed from the T and L dependencies by applying a correction of 0.23T+0.5L to the individual absolute magnitudes. Here, T=3 for Sb, 4 for Sbc, and 5 for Sc galaxies, and the L values range from 1 to 6 as the luminosity class changes from I to III-IV. The total luminosity function, obtained by combining the volume-normalized Sb, Sbc, and Sc individual luminosity functions, each corrected for the T and L dependencies, has an rms dispersion of 0.67 mag, similar to much of the Tully-Fisher parameter space. Absolute calibration of the trial kinematic absolute magnitudes is made using 27 galaxies with known T and L that also have Cepheid distances. This permits the systematic correction to the H0=50 kinematic absolute magnitudes of 0.22+/-0.12 mag, givingH0=55+/-3(internal) km s-1 Mpc-1 . The Cepheid distances are based on the Madore/Freedman Cepheid period-luminosity (PL) zero point that requires (m-M)0=18.50 for the LMC. Using the modern LMC modulus of (m-M)0=18.58 requires a 4% decrease in H0, giving a final value of H0=53+/-7 (external) by this method. These values of H0, based here on the method of luminosity functions, are in good agreement with (1) H0=55+/-5 by Theureau and coworkers from their bias-corrected Tully-Fisher method of ``normalized distances'' for field galaxies; (2) H0=56+/-4 from the method through the Virgo Cluster, as corrected to the global kinematic frame (Tammann and coworkers); and (3) H0=58+/-5 from Cepheid-calibrated Type Ia supernovae (Saha and coworkers). Our value here also disagrees with the final value from the NASA ``Key Project'' group value of H0=70+/-7. Analysis of the total flux-limited sample of Sb, Sbc, and Sc galaxies in the RSA2 by the present method, but uncorrected for selection bias, would give an incorrect value of H0=71 using the same Cepheid calibration. The effect of the bias is pernicious at the 30% level; either it must be corrected by the methods in the papers of this series, or the data must be restricted to the distance-limited subset of any sample, as is done here.

A cross-correlation-based estimate of the galaxy luminosity function

NASA Astrophysics Data System (ADS)

van Daalen, Marcel P.; White, Martin

2018-06-01

We extend existing methods for using cross-correlations to derive redshift distributions for photometric galaxies, without using photometric redshifts. The model presented in this paper simultaneously yields highly accurate and unbiased redshift distributions and, for the first time, redshift-dependent luminosity functions, using only clustering information and the apparent magnitudes of the galaxies as input. In contrast to many existing techniques for recovering unbiased redshift distributions, the output of our method is not degenerate with the galaxy bias b(z), which is achieved by modelling the shape of the luminosity bias. We successfully apply our method to a mock galaxy survey and discuss improvements to be made before applying our model to real data.

Age of Local Galactic Disk from the Wdlf for Cpmbs

NASA Astrophysics Data System (ADS)

Smith, J. Allyn; Oswalt, Terry D.; Wood, Matt A.; Silvestri, Nicole M.

We present the white dwarf luminosity function (WDLF) for common proper motion systems. This WDLF was derived using the 1/Vmax method pioneered by Schmidt (1975) and detailed by Liebert Dahn and Monet (1988). New cooling models were used to determine the luminosities of the white dwarfs and the age of the local Galactic disk. Comparison to WDLFs developed using older colling models (Wood 1995) will be examined for changes in the derived disk age. Kinematic data is available for a subset of the WDs in the sample. Separate luminosity functions will be examined for each of the statistically significant subsets. JAS acknowledges support from NASA GSRP Fellowship NGT-51086.

IRAS observations of the Rho Ophiuchi infrared cluster - Spectral energy distributions and luminosity function

NASA Technical Reports Server (NTRS)

Wilking, Bruce A.; Lada, Charles J.; Young, Eric T.

1989-01-01

High-sensitivity IRAS coadded survey data, coupled with new high-sensitivity near-IR observations, are used to investigate the nature of embedded objects over an 4.3-sq-pc area comprising the central star-forming cloud of the Ophiuchi molecular complex; the area encompasses the central cloud of the Rho Ophiuchi complex and includes the core region. Seventy-eight members of the embedded cluster were identified; spectral energy distributions were constructed for 53 objects and were compared with theoretical models to gain insight into their evolutionary status. Bolometric luminosities could be estimated for nearly all of the association members, leading to a revised luminosity function for this dust-embedded cluster.

M Dwarfs from Hubble Space Telescope Star Counts. IV.

NASA Astrophysics Data System (ADS)

Zheng, Zheng; Flynn, Chris; Gould, Andrew; Bahcall, John N.; Salim, Samir

2001-07-01

We study a sample of about 1400 disk M dwarfs that are found in 148 fields observed with the Wide Field Camera 2 (WFC2) on the Hubble Space Telescope and 162 fields observed with pre-repair Planetary Camera 1 (PC1), of which 95 of the WFC2 fields are newly analyzed. The method of maximum likelihood is applied to derive the luminosity function and the Galactic disk parameters. At first, we use a local color-magnitude relation and a locally determined mass-luminosity relation in our analysis. The results are consistent with those of previous work but with considerably reduced statistical errors. These small statistical errors motivate us to investigate the systematic uncertainties. Considering the metallicity gradient above the Galactic plane, we introduce a modified color-magnitude relation that is a function of Galactic height. The resultant M dwarf luminosity function has a shape similar to that derived using the local color-magnitude relation but with a higher peak value. The peak occurs at MV~12, and the luminosity function drops sharply toward MV~14. We then apply a height-dependent mass-luminosity function interpolated from theoretical models with different metallicities to calculate the mass function. Unlike the mass function obtained using local relations, which has a power-law index α=0.47, the one derived from the height-dependent relations tends to be flat (α=-0.10). The resultant local surface density of disk M dwarfs (12.2+/-1.6 Msolar pc-2) is somewhat smaller than the one obtained using local relations (14.3+/-1.3 Msolar pc-2). Our measurement favors a short disk scale length, H=2.75+/-0.16 (statistical)+/-0.25 (systematic) kpc. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

Up and Down the Black Hole Radio/X-Ray Correlation: The 2017 Mini-outbursts from Swift J1753.5-0127

NASA Astrophysics Data System (ADS)

Plotkin, R. M.; Bright, J.; Miller-Jones, J. C. A.; Shaw, A. W.; Tomsick, J. A.; Russell, T. D.; Zhang, G.-B.; Russell, D. M.; Fender, R. P.; Homan, J.; Atri, P.; Bernardini, F.; Gelfand, J. D.; Lewis, F.; Cantwell, T. M.; Carey, S. H.; Grainge, K. J. B.; Hickish, J.; Perrott, Y. C.; Razavi-Ghods, N.; Scaife, A. M. M.; Scott, P. F.; Titterington, D. J.

2017-10-01

The candidate black hole X-ray binary Swift J1753.5-0127 faded to quiescence in 2016 November after a prolonged outburst that was discovered in 2005. Nearly three months later, the system displayed renewed activity that lasted through 2017 July. Here, we present radio and X-ray monitoring over ≈ 3 months of the renewed activity to study the coupling between the jet and the inner regions of the disk/jet system. Our observations cover low X-ray luminosities that have not historically been well-sampled ({L}{{X}}≈ 2× {10}33{--}{10}36 {erg} {{{s}}}-1; 1-10 keV), including time periods when the system was both brightening and fading. At these low luminosities, Swift J1753.5-0127 occupies a parameter space in the radio/X-ray luminosity plane that is comparable to “canonical” systems (e.g., GX 339-4), regardless of whether the system was brightening or fading, even though during its ≳11 year outburst, Swift J1753.5-0127 emitted less radio emission from its jet than expected. We discuss implications for the existence of a single radio/X-ray luminosity correlation for black hole X-ray binaries at the lowest luminosities ({L}{{X}}≲ {10}35 {erg} {{{s}}}-1), and we compare to supermassive black holes. Our campaign includes the lowest luminosity quasi-simultaneous radio/X-ray detection to date for a black hole X-ray binary during its rise out of quiescence, thanks to early notification from optical monitoring combined with fast responses from sensitive multiwavelength facilities.

The duration of reionization constrains the ionizing sources

NASA Astrophysics Data System (ADS)

Sharma, Mahavir; Theuns, Tom; Frenk, Carlos

2018-06-01

We investigate how the nature of the galaxies that reionized the Universe affects the duration of reionization. We contrast two sets of models: one in which galaxies on the faint side of the luminosity function dominate the ionizing emissivity, and a second in which the galaxies on the bright side of the luminosity function dominate. The faint end of the luminosity function evolves slowly, therefore the transition from mostly neutral to mostly ionized state takes a much longer time in the first set of models compared to the second. Existing observational constraints on the duration of this transition are relatively weak, but taken at face value prefer the model in which galaxies on the bright side play a major role. Measurements of the kinetic Sunyaev-Zeldovich effect in the cosmic microwave background from the epoch of reionization also point in the same direction.

Inflow Generated X-ray Corona Around Supermassive Black Holes and Unified Model for X-ray Emission

NASA Astrophysics Data System (ADS)

Wang, Lile; Cen, Renyue

2016-01-01

Three-dimensional hydrodynamic simulations, covering the spatial domain from hundreds of Schwarzschild radii to 2 pc around the central supermassive black hole of mass 108 M⊙, with detailed radiative cooling processes, are performed. Generically found is the existence of a significant amount of shock heated, high temperature (≥108 K) coronal gas in the inner (≤104 rsch) region. It is shown that the composite bremsstrahlung emission spectrum due to coronal gas of various temperatures are in reasonable agreement with the overall ensemble spectrum of AGNs and hard X-ray background. Taking into account inverse Compton processes, in the context of the simulation-produced coronal gas, our model can readily account for the wide variety of AGN spectral shape, which can now be understood physically. The distinguishing feature of our model is that X-ray coronal gas is, for the first time, an integral part of the inflow gas and its observable characteristics are physically coupled to the concomitant inflow gas. One natural prediction of our model is the anti-correlation between accretion disk luminosity and spectral hardness: as the luminosity of SMBH accretion disk decreases, the hard X-ray luminosity increases relative to the UV/optical luminosity.

Morphology and luminosity segregation of galaxies in nearby loose groups

NASA Astrophysics Data System (ADS)

Girardi, M.; Rigoni, E.; Mardirossian, F.; Mezzetti, M.

2003-08-01

We study morphology and luminosity segregation of galaxies in loose groups. We analyze the two catalogs of groups identified in the Nearby Optical Galaxy (NOG) sample, by means of hierarchical and percolation ``friends-of-friends'' methods (HG and PG catalogs, respectively). In the first part of our analysis we consider 387 and 436 groups of HG and PG and compare morphology- (luminosity-) weighted to unweighted group properties: velocity dispersion, mean pairwise distance, and mean groupcentric distance of member galaxies. The second part of our analysis is based on two ensemble systems, one for each catalog, built by suitably combining together galaxies of all groups (1584 and 1882 galaxies for HG and PG groups). We find that earlier-type (brighter) galaxies are more clustered and lie closer to the group centers, both in position and in velocity, than later-type (fainter) galaxies. Spatial segregations are stronger than kinematical segregations. These effects are generally detected at the >˜ 3-sigma level. Luminosity segregation is shown to be independent of morphology segregation. Our main conclusions are strengthened by the detection of segregation in both hierarchical and percolation catalogs. Our results agree with a continuum of segregation properties of galaxies in systems, from low-mass groups to massive clusters.

Multiwavelength Properties of the X-Ray Sources in the Groth-Westphal Strip Field

NASA Astrophysics Data System (ADS)

Miyaji, Takamitsu; Sarajedini, Vicki; Griffiths, Richard E.; Yamada, Toru; Schurch, Matthew; Cristóbal-Hornillos, David; Motohara, Kentaro

2004-06-01

We summarize the multiwavelength properties of X-ray sources detected in the 80 ks XMM-Newton observation of the Groth-Westphal strip, a contiguous strip of 28 Hubble Space Telescope Wide Field Planetary Camera 2 (WFPC2) images. Among the ~150 X-ray sources detected in the XMM-Newton field of view, 23 are within the WFPC2 fields. Ten spectroscopic redshifts are available from the Deep Extragalactic Evolutionary Probe and Canada-France Redshift Survey projects. Four of these show broad Mg II emission and can be classified as type 1 active galactic nuclei (AGNs). Two of those without any broad lines, nevertheless, have [Ne V] emission, which is an unambiguous signature of AGN activity. One is a narrow-line Seyfert 1 and the other a type 2 AGN. As a follow-up, we have made near-infrared spectroscopic observations using the OHS/CISCO spectrometer for five of the X-ray sources for which we found no indication of AGN activity in the optical spectrum. We have detected Hα+[N II] emission in four of them. A broad Hα component and/or a large [N II]/Hα ratio is seen, suggestive of AGN activity. Nineteen sources have been detected in the Ks band, and four of these are extremely red objects (EROs) (I814-Ks>4). The optical counterparts for the majority of the X-ray sources are bulge-dominated. The I814-Ks color of these bulge-dominated hosts are indeed consistent with evolving elliptical galaxies, while contaminations from star formation/AGNs seems to be present in their V606-I814 color. Assuming that the known local relations among the bulge luminosity, central velocity dispersion, and the mass of the central blackhole still hold at z~1, we compare the AGN luminosity with the Eddington luminosity of the central blackhole mass. The AGN bolometric luminosity to Eddington luminosity ratio ranges from 0.3% to 10%. Based on observations from the XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA member states and NASA. Also based on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

The Keck/OSIRIS Nearby AGN Survey (KONA). I. The Nuclear K-band Properties of Nearby AGN

NASA Astrophysics Data System (ADS)

Müller-Sánchez, F.; Hicks, E. K. S.; Malkan, M.; Davies, R.; Yu, P. C.; Shaver, S.; Davis, B.

2018-05-01

We introduce the Keck OSIRIS Nearby AGN survey (KONA), a new adaptive optics-assisted integral-field spectroscopic survey of Seyfert galaxies. KONA permits at ∼0.″1 resolution a detailed study of the nuclear kinematic structure of gas and stars in a representative sample of 40 local bona fide active galactic nucleus (AGN). KONA seeks to characterize the physical processes responsible for the coevolution of supermassive black holes and galaxies, principally inflows and outflows. With these IFU data of the nuclear regions of 40 Seyfert galaxies, the KONA survey will be able to study, for the first time, a number of key topics with meaningful statistics. In this paper we study the nuclear K-band properties of nearby AGN. We find that the K-band (2.1 μm) luminosities of the compact Seyfert 1 nuclei are correlated with the hard X-ray luminosities, implying a non-stellar origin for the majority of the continuum emission. The best-fit correlation is log L K = 0.9log L 2–10 keV + 4 over three orders of magnitude in both K-band and X-ray luminosities. We find no strong correlation between 2.1 μm luminosity and hard X-ray luminosity for the Seyfert 2 galaxies. The spatial extent and spectral slope of the Seyfert 2 galaxies indicate the presence of nuclear star formation and attenuating material (gas and dust), which in some cases is compact and in some galaxies extended. We detect coronal-line emission in 36 galaxies and for the first time in 5 galaxies. Finally, we find 4/20 galaxies that are usually classified as Seyfert 2 based on their optical spectra exhibit a broad component of Brγ emission, and one galaxy (NGC 7465) shows evidence of a double nucleus. Based on observations 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.

Resolving the faint end of the satellite luminosity function for the nearest elliptical Centaurus A

NASA Astrophysics Data System (ADS)

Crnojevic, Denija

2014-10-01

We request HST/ACS imaging to follow up 15 new faint candidate dwarfs around the nearest elliptical Centaurus A (3.8 Mpc). The dwarfs were found via a systematic ground-based (Magellan/Megacam) survey out to ~150 kpc, designed to directly confront the "missing satellites" problem in a wholly new environment. Current Cold Dark Matter models for structure formation fail to reproduce the shallow slope of the satellite luminosity function in spiral-dominated groups for which dwarfs fainter than M_V<-14 have been surveyed (the Local Group and the nearby, interacting M81 group). Clusters of galaxies show a better agreement with cosmological predictions, suggesting an environmental dependence of the (poorly-understood) physical processes acting on the evolution of low mass galaxies (e.g., reionization). However, the luminosity function completeness for these rich environments quickly drops due to the faintness of the satellites and to the difficult cluster membership determination. We target a yet unexplored "intermediate" environment, a nearby group dominated by an elliptical galaxy, ideal due to its proximity: accurate (10%) distance determinations for its members can be derived from resolved stellar populations. The proposed observations of the candidate dwarfs will confirm their nature, group membership, and constrain their luminosities, metallicities, and star formation histories. We will obtain the first complete census of dwarf satellites of an elliptical down to an unprecedented M_V<-9. Our results will crucially constrain cosmological predictions for the faint end of the satellite luminosity function to achieve a more complete picture of the galaxy formation process.

The Luminosity Function of Star Clusters in 20 Star-Forming Galaxies Based on Hubble Legacy Archive Photometry

NASA Astrophysics Data System (ADS)

Bowers, Ariel; Whitmore, B. C.; Chandar, R.; Larsen, S. S.

2014-01-01

Luminosity functions have been determined for star cluster populations in 20 nearby (4 - 30 Mpc), star-forming galaxies based on ACS source lists generated by the Hubble Legacy Archive (http://hla.stsci.edu). 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 luminosity function can be approximated by a power-law, dN/dL ∝ Lα, with an average value for α of -2.37 and rms scatter = 0.18. A comparison of fitting results based on methods which 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 steper luminosity functions. Our uniform database results in a small scatter (0.5 magnitude) in the correlation between the magnitude of the brightest cluster (Mbrightest) and Log of the number of clusters brighter than MI = -9 (Log N). We also examine the magnitude of the brightest cluster vs. Log SFR for a sample including LIRGS and ULIRGS.

Analysis of RGU Photometry in Selected Area 51

NASA Astrophysics Data System (ADS)

Bilir, S.; Karaali, S.; Buser, R.

2004-09-01

A low-latitude anticenter field (l=189 °, b=+21 °) is investigated by using the full calibration tools of RGU photometry. The observed RGU data are reduced to the standard system and the separation of dwarfs and evolved stars is carried out by an empirical method. Stars are categorized into three metallicity classes, i.e. -0.25<[M/H]≤+0.50, $-1.00<[M/H]≤-0.25, and [M/H]≤-1.00 dex, and their absolute magnitudes are determined by the corresponding color-magnitude diagrams. The unusually large scattering in the two-color diagrams is reduced by excluding 153 extra-galactic objects, identifying them compared with the charts of Basel Astronomical Institute and University of Minnesota, and by the criterion and algorithm of Gaidos et al. [1]. The local logarithmic space density for giants, D*(0)=6.75, lies within the local densities of Gliese and Gliese & Jahreiss. The local luminosity function in our work for the absolute magnitude interval 3

THE DISTRIBUTION OF FAINT SATELLITES AROUND CENTRAL GALAXIES IN THE CANADA-FRANCE-HAWAII TELESCOPE LEGACY SURVEY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, C. Y.; Jing, Y. P.; Li, Cheng

2012-11-20

We investigate the radial number density profile and the abundance distribution of faint satellites around central galaxies in the low-redshift universe using the Canada-France-Hawaii Telescope (CFHT) Legacy Survey. We consider three samples of central galaxies with magnitudes of M {sub r} = -21, -22, and -23 selected from the Sloan Digital Sky Survey group catalog of Yang et al. The satellite distribution around these central galaxies is obtained by cross-correlating these galaxies with the photometric catalog of the CFHT Legacy Survey. The projected radial number density of the satellites obeys a power-law form with the best-fit logarithmic slope of -1.05,more » independent of both the central galaxy luminosity and the satellite luminosity. The projected cross-correlation function between central and satellite galaxies exhibits a non-monotonic trend with satellite luminosity. It is most pronounced for central galaxies with M {sub r} = -21, where the decreasing trend of clustering amplitude with satellite luminosity is reversed when satellites are fainter than central galaxies by more than 2 mag. A comparison with the satellite luminosity functions in the Milky Way (MW) and M31 shows that the MW/M31 system has about twice as many satellites as around a typical central galaxy of similar luminosity. The implications for theoretical models are briefly discussed.« less

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.;

ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: CO Luminosity Functions and the Evolution of the Cosmic Density of Molecular Gas

NASA Astrophysics Data System (ADS)

Decarli, Roberto; Walter, Fabian; Aravena, Manuel; Carilli, Chris; Bouwens, Rychard; da Cunha, Elisabete; Daddi, Emanuele; Ivison, R. J.; Popping, Gergö; Riechers, Dominik; Smail, Ian R.; Swinbank, Mark; Weiss, Axel; Anguita, Timo; Assef, Roberto J.; Bauer, Franz E.; Bell, Eric F.; Bertoldi, Frank; Chapman, Scott; Colina, Luis; Cortes, Paulo C.; Cox, Pierre; Dickinson, Mark; Elbaz, David; Gónzalez-López, Jorge; Ibar, Edo; Infante, Leopoldo; Hodge, Jacqueline; Karim, Alex; Le Fevre, Olivier; Magnelli, Benjamin; Neri, Roberto; Oesch, Pascal; Ota, Kazuaki; Rix, Hans-Walter; Sargent, Mark; Sheth, Kartik; van der Wel, Arjen; van der Werf, Paul; Wagg, Jeff

2016-12-01

In this paper we use ASPECS, the ALMA Spectroscopic Survey in the Hubble Ultra Deep Field in band 3 and band 6, to place blind constraints on the CO luminosity function and the evolution of the cosmic molecular gas density as a function of redshift up to z ˜ 4.5. This study is based on galaxies that have been selected solely through their CO emission and not through any other property. In all of the redshift bins the ASPECS measurements reach the predicted “knee” of the CO luminosity function (around 5 × 109 K km s-1 pc2). We find clear evidence of an evolution in the CO luminosity function with respect to z ˜ 0, with more CO-luminous galaxies present at z ˜ 2. The observed galaxies at z ˜ 2 also appear more gas-rich than predicted by recent semi-analytical models. The comoving cosmic molecular gas density within galaxies as a function of redshift shows a drop by a factor of 3-10 from z ˜ 2 to z ˜ 0 (with significant error bars), and possibly a decline at z > 3. This trend is similar to the observed evolution of the cosmic star formation rate density. The latter therefore appears to be at least partly driven by the increased availability of molecular gas reservoirs at the peak of cosmic star formation (z ˜ 2).

The Structure of the Young Star Cluster NGC 6231. I. Stellar Population

NASA Astrophysics Data System (ADS)

Kuhn, Michael A.; Medina, Nicolás; Getman, Konstantin V.; Feigelson, Eric D.; Gromadzki, Mariusz; Borissova, Jordanka; Kurtev, Radostin

2017-09-01

NGC 6231 is a young cluster (age ˜2-7 Myr) dominating the Sco OB1 association (distance ˜1.59 kpc) with ˜100 O and B stars and a large pre-main-sequence stellar population. We combine a reanalysis of archival Chandra X-ray data with multiepoch near-infrared (NIR) photometry from the VISTA Variables in the Vía Lactéa (VVV) survey and published optical catalogs to obtain a catalog of 2148 probable cluster members. This catalog is 70% larger than previous censuses of probable cluster members in NGC 6231. It includes many low-mass stars detected in the NIR but not in the optical and some B stars without previously noted X-ray counterparts. In addition, we identify 295 NIR variables, about half of which are expected to be pre-main-sequence stars. With the more complete sample, we estimate a total population in the Chandra field of 5700-7500 cluster members down to 0.08 {M}⊙ (assuming a universal initial mass function) with a completeness limit at 0.5 {M}⊙ . A decrease in stellar X-ray luminosities is noted relative to other younger clusters. However, within the cluster, there is little variation in the distribution of X-ray luminosities for ages less than 5 Myr. The X-ray spectral hardness for B stars may be useful for distinguishing between early-B stars with X-rays generated in stellar winds and B-star systems with X-rays from a pre-main-sequence companion (>35% of B stars). A small fraction of catalog members have unusually high X-ray median energies or reddened NIR colors, which might be explained by absorption from thick or edge-on disks or being background field stars.

Search for early gamma-ray production in supernovae located in a dense circumstellar medium with the Fermi Lat

DOE PAGES

Ackermann, M.; Arcavi, I.; Baldini, L.; ...

2015-07-09

Supernovae (SNe) exploding in a dense circumstellar medium (CSM) are hypothesized to accelerate cosmic rays in collisionless shocks and emit GeV γ-rays and TeV neutrinos on a timescale of several months. We perform the first systematic search for γ-ray emission in Fermi Large Area Telescope data in the energy range frommore » $$100\\;\\mathrm{MeV}$$ to $$300\\;\\mathrm{GeV}$$ from the ensemble of 147 SNe Type IIn exploding in a dense CSM. Here, we search for a γ-ray excess at each SNe location in a one-year time window. In order to enhance a possible weak signal, we simultaneously study the closest and optically brightest sources of our sample in a joint-likelihood analysis in three different time windows (1 year, 6 months, and 3 months). For the most promising source of the sample, SN 2010jl (PTF 10aaxf), we repeat the analysis with an extended time window lasting 4.5 years. We do not find a significant excess in γ-rays for any individual source nor for the combined sources and provide model-independent flux upper limits for both cases. Additionally, we derive limits on the γ-ray luminosity and the ratio of γ-ray-to-optical luminosity ratio as a function of the index of the proton injection spectrum assuming a generic γ-ray production model. Furthermore, we present detailed flux predictions based on multi-wavelength observations and the corresponding flux upper limit at a 95% confidence level (CL) for the source SN 2010jl (PTF 10aaxf).« less

Physical properties and H-ionizing-photon production rates of extreme nearby star-forming regions

NASA Astrophysics Data System (ADS)

Chevallard, Jacopo; Charlot, Stéphane; Senchyna, Peter; Stark, Daniel P.; Vidal-García, Alba; Feltre, Anna; Gutkin, Julia; Jones, Tucker; Mainali, Ramesh; Wofford, Aida

2018-06-01

Measurements of the galaxy UV luminosity function at z ≳ 6 suggest that young stars hosted in low-mass star-forming galaxies produced the bulk of hydrogen-ionizing photons necessary to reionize the intergalactic medium (IGM) by redshift z ˜ 6. Whether star-forming galaxies dominated cosmic reionization, however, also depends on their stellar populations and interstellar medium properties, which set, among other things, the production rate of H-ionizing photons, ξ _{ion}^\\star, and the fraction of these escaping into the IGM. Given the difficulty of constraining with existing observatories the physical properties of z ≳ 6 galaxies, in this work we focus on a sample of ten nearby objects showing UV spectral features comparable to those observed at z ≳ 6. We use the new-generation BEAGLE tool to model the UV-to-optical photometry and UV/optical emission lines of these Local `analogues' of high-redshift galaxies, finding that our relatively simple, yet fully self-consistent, physical model can successfully reproduce the different observables considered. Our galaxies span a broad range of metallicities and are characterised by high ionization parameters, low dust attenuation, and very young stellar populations. Through our analysis, we derive a novel diagnostic of the production rate of H-ionizing photons per unit UV luminosity, ξ _{ion}^\\star, based on the equivalent width of the bright [O III]49595007 line doublet, which does not require measurements of H-recombination lines. This new diagnostic can be used to estimate ξ _{ion}^\\star from future direct measurements of the [O III]49595007 line using JWST/NIRSpec (out to z ˜ 9.5), and by exploiting the contamination by Hβ +[O III]{4959}{5007}} of photometric observations of distant galaxies, for instance from existing Spitzer/IRAC data and from future ones with JWST/NIRCam.

Toward Understanding the Fanaroff-Riley Dichotomy in Radio Source Morphology and Power

NASA Astrophysics Data System (ADS)

Baum, Stefi A.; Zirbel, Esther L.; O'Dea, Christopher P.

1995-09-01

In Paper I we presented the results of a study of the interrelationships between host galaxy magnitude, optical line luminosity, and radio luminosity in a large sample of Fanaroff-Riley classes 1 and 2 (FR 1 and FR 2) radio galaxies. We report several important differences between the FR 1 and FR 2 radio galaxies. At the same host galaxy magnitude or radio luminosity, the FR 2's produce substantially more optical line emission (by roughly an order of magnitude or more) than do FR 1's. Similarly, FR 2 sources produce orders of magnitude more line luminosity than do radio-quiet galaxies of the same optical magnitude, while FR 1 sources and radio-quiet galaxies of the same optical magnitude produce similar line luminosities. Combining these results with previous results from the literature, we conclude that while the emission-line gas in the FR 2's is indeed photoionized by a nuclear UV continuum source from the AGN, the emission-line gas in the FR 1's may be energized predominantly by processes associated with the host galaxy itself. The apparent lack of a strong UV continuum source from the central engine in FR 1 sources can be understood in two different ways. In the first scenario, FR l's are much more efficient at covering jet bulk kinetic energy into radio luminosity than FR 2's, such that an FR 1 has a much lower bolometric AGN luminosity (hence nuclear UV continuum source) than does an FR 2 of the same radio luminosity. We discuss the pros and cons of this model and conclude that the efficiency differences needed between FR 2 and FR 1 radio galaxies are quite large and may lead to difficulties with the interpretation since it would suggest that FR 2 radio source deposit very large amounts of kinetic energy into the ISM Intracluster Medium. However, this interpretation remains viable. Alternatively, it may be that the AGNs in FR 1 sources simply produce far less radiant UV energy than do those in FR 2 sources. That is, FR 1 sources may funnel a higher fraction of the total energy output from the AGNs into jet kinetic energy versus radiant energy than do FR 2 sources. If this interpretation is correct, then this suggests that there is a fundamental difference in the central engine and/or in the immediate "accretion region" around the engine in FR 1 and FR 2 radio galaxies. We note also the absence of FR 1 sources with nuclear broad line regions and suggest that the absence of the BLR is tied to the absence of the "isotropic" nuclear UV continuum source in FR 1 sources. We put forth the possibility that the FR 1/FR 2 dichotomy (i.e., the observed differences in the properties of low- and high-power radio sources) is due to qualitative differences in the structural properties of the central engines in these two types of sources. Following early work by Rees et al. (1982), we suggest the possibility that FR 1 sources are produced when the central engine is fed at a lower accretion rate, leading to the creation of a source in which the ratio of radiant to jet bulk kinetic energy is low, while FR 2 sources are produced when the central engine is fed at a higher accretion rate, causing the central engine to deposit a higher fraction of its energy in radiant energy. We further suggest the possibility that associated differences in the spin properties of the central black hole between FR 1 (lower spin) and FR 2 (higher spin) sources may be responsible for the different collimation properties and Mach numbers of the jets produced by these two types of radio-loud galaxies. This scenario, although currently clearly speculative, is nicely consistent with our current picture of the triggering, feeding, environments, and evolution of powerful radio galaxies. This model allows for evolution of these properties with time for example, the mass accretion rate and BH spin may decline with time causing an FR 2 radio source or quasar to evolve into a FR 1 radio source.

The CALYMHA survey: Lyα luminosity function and global escape fraction of Lyα photons at z = 2.23

NASA Astrophysics Data System (ADS)

Sobral, David; Matthee, Jorryt; Best, Philip; Stroe, Andra; Röttgering, Huub; Oteo, Iván; Smail, Ian; Morabito, Leah; Paulino-Afonso, Ana

2017-04-01

We present the CAlibrating LYMan-α with Hα (CALYMHA) pilot survey and new results on Lyman α (Lyα) selected galaxies at z ˜ 2. We use a custom-built Lyα narrow-band filter at the Isaac Newton Telescope, designed to provide a matched volume coverage to the z = 2.23 Hα HiZELS survey. Here, we present the first results for the COSMOS and UDS fields. Our survey currently reaches a 3σ line flux limit of ˜4 × 10-17 erg s-1 cm-2, and a Lyα luminosity limit of ˜1042.3 erg s-1. We find 188 Lyα emitters over 7.3 × 105 Mpc3, but also find significant numbers of other line-emitting sources corresponding to He II, C III] and C IV emission lines. These sources are important contaminants, and we carefully remove them, unlike most previous studies. We find that the Lyα luminosity function at z = 2.23 is very well described by a Schechter function up to LLy α ≈ 1043 erg s-1 with L^{ast }=10^{42.59^{+0.16}_{-0.08}} erg s-1, φ ^{ast }=10^{-3.09^{+0.14}_{-0.34}} Mpc-3 and α = -1.75 ± 0.25. Above LLy α ≈ 1043 erg s-1, the Lyα luminosity function becomes power-law like, driven by X-ray AGN. We find that Lyα-selected emitters have a high escape fraction of 37 ± 7 per cent, anticorrelated with Lyα luminosity and correlated with Lyα equivalent width. Lyα emitters have ubiquitous large (≈40 kpc) Lyα haloes, ˜2 times larger than their Hα extents. By directly comparing our Lyα and Hα luminosity functions, we find that the global/overall escape fraction of Lyα photons (within a 13 kpc radius) from the full population of star-forming galaxies is 5.1 ± 0.2 per cent at the peak of the star formation history. An extra 3.3 ± 0.3 per cent of Lyα photons likely still escape, but at larger radii.

Multiwavelength Study of Active Galaxies

NASA Astrophysics Data System (ADS)

Singh, Veeresh

2010-08-01

Seyfert galaxies are a subclass of active galaxies and are categorized as nearby, low luminosity, radio-quiet Active Galactic Nuclei (AGN) hosted in spiral or lenticular galaxies. Demographically, Seyfert galaxies may account for ~ 10% of the entire population of active galaxies in the nearby universe. Seyfert galaxies are classified mainly into two subclasses named as `type 1' and `type 2' Seyferts, based on the presence and absence of broad permitted emission lines in their optical spectra, respectively. Detection of broad permitted emission lines in some Seyfert type 2s observed in the polarized light laid the foundation of the Seyfert unification scheme, which hypothesizes that Seyfert type 1s and type 2s belong to the same parent population and appear different solely due to the differing orientations of the obscuring material having a torus-like geometry around the AGN (Antonucci and Miller 1985; Antonucci 1993). The primary objective of this thesis work is to examine the validity and limitations of the orientation and obscuration based Seyfert unification scheme using multiwavelength (mainly X-ray and radio) observations. The key issue in testing the Seyfert unification scheme has been acquiring a well defined rigorously selected Seyfert sample. I have argued that the Seyfert samples based on flux limited surveys at optical, IR, UV and X-ray are likely to be biased against obscured and faint sources. In order to test the predictions of Seyfert unification scheme I use a sample based on properties (i.e., cosmological redshift, [OIII] emission line luminosity, absolute bulge magnitude, absolute stellar magnitude of the host galaxy and the Hubble stage of the host galaxy) that are independent to the orientation of the obscuring torus, host galaxy and the AGN axis. Furthermore, two Seyfert subtypes of our sample have matched distributions in the orientation-independent properties and this ensures the intrinsic similarity between two Seyfert subtypes within the framework of the unification scheme. In other words, it is ensured that the two subtypes being compared are not selected from entirely different parts of the evolution function (redshift, luminosity, bulge magnitude, stellar luminosity of the host galaxy and Hubble type of the host galaxy). To study the X-ray spectral properties of two Seyfert subtypes I use the XMM-Newton pn data. The 0.5 - 10 keV X-ray spectra of Seyfert galaxies are generally best fitted with a model consists of: an absorbed power law with exponential cut-off which contains cold absorption from the Galactic hydrogen column density together with absorption from neutral gas at the redshift of the source; a narrow Gaussian line fitted to the Fe K_alpha line at 6.4 keV; a soft excess component characterized by either a steep power law and/or a thermal plasma model with temperature kT and in some cases, reflection component characterized by the reflection from an isotropically illuminated cold slab, (model `pexrav' in XSPEC) is required. Partial covering of the primary AGN power law component is also required for the best fit in some sources. There are several type 2 sources in our sample in which the hard (2.0 - 10.0 keV) part of the X-ray spectrum is best fitted with a reflection component alone (`pexrav' model). The statistical comparisons of the X-ray spectral properties show that in compared to Seyfert type 1s, the type 2s exhibit lower X-ray luminosities in soft (0.5 - 2.0 keV) and hard (2.0 - 10.0) X-ray bands, higher X-ray absorbing column densities, higher equivalent widths of Fe K line, and lower flux ratios of hard X-ray (2.0 - 10.0 keV) to [OIII]. In both the Seyfert subtypes, the X-ray luminosity is moderately correlated with the pc-scale, kpc-scale radio luminosities and [OIII] line luminosity, in a similar fashion. A large fraction ~ 60 - 70% of type 2 Seyferts of our sample are likely to be Compton-thick and as a case study of a Compton-thick AGN, we studied the broad-band 0.5 - 50 keV X-ray spectral properties of NGC 5135 using Suzaku (XIS and HID) data to unveil the nature and geometry of obscuring torus. To test the predictions of the Seyfert unification scheme in the radio regime, I studied the radio properties of Seyfert galaxies using Giant Meterwave Radio Telescope (GMRT) observations carried out at 240 MHz/610 MHz, and NRAO VLA Sky Survey observations at 1.4 GHz and VLA 5 GHz observations from the literature. The four point (240 MHz, 610 MHz, 1.4 GHz, 5.0 GHz) integrated radio spectra of the two Seyfert subtypes are similar and fairly steep (i.e., spectral index ~ -0.7). Radio luminosity distributions at 240 MHz, 610 MHz, 1.4 GHz and 5.0 GHz are also similar for the Seyfert type 1s and type 2s. The study on radio - IR luminosity correlations shows that for both the Seyfert subtypes, the total 610 MHz and 240 MHz radio luminosities are moderately correlated with near-IR, mid-IR luminosities while the correlation becomes poorer with far-IR luminosities. Furthermore, the 12 micron, 25 micron, 60 micron and 100 micron IR luminosity distributions are also statistically simil! ar for the Seyfert type 1s and type 2s. I conclude that the statistical comparisons of the X-ray, radio and IR properties of the two Seyfert subtypes of our sample are consistent with the obscuration and orientation based unification scheme.

The Production of Cold Gas Within Galaxy Outflows

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scannapieco, Evan

2017-03-01

I present a suite of three-dimensional simulations of the evolution of initially hot material ejected by starburst-driven galaxy outflows. The simulations are conducted in a comoving frame that moves with the material, tracking atomic/ionic cooling, Compton cooling, and dust cooling and destruction. Compton cooling is the most efficient of these processes, while the main role of atomic/ionic cooling is to enhance density inhomogeneities. Dust, on the other hand, has little effect on the outflow evolution, and is rapidly destroyed in all the simulations except for the case with the smallest mass flux. I use the results to construct a simplemore » steady-state model of the observed UV/optical emission from each outflow. The velocity profiles in this case are dominated by geometric effects, and the overall luminosities are extremely strong functions of the properties of the host system, as observed in ultra-luminous infrared galaxies (ULIRGs). Furthermore the luminosities and maximum velocities in several models are consistent with emission-line observations of ULIRGs, although the velocities are significantly greater than observed in absorption-line studies. It may be that absorption line observations of galaxy outflows probe entrained cold material at small radii, while emission-line observations probe cold material condensing from the initially hot medium at larger distances.« less

An X-ray Investigation of the NGC 346 Field in the SMC (2): The Field Population

NASA Technical Reports Server (NTRS)

Naze, Y.; Hartwell, J. M.; Stevens, I. R.; Manfroid, J.; Marchenko, S.; Corcoran, M. F.; Moffat, A. F. J.; Skalkowski, G.

2003-01-01

We present results from a Chandra observation of the NGC 346 cluster, which is the ionizing source of N66, the most luminous HII region and the largest star formation region in the SMC. In the first part of this investigation, we have analysed the X-ray properties of the cluster itself and the remarkable star HD 5980. But the field contains additional objects of interest. In total, 79 X-ray point sources were detected in the Chandra observation: this is more than five times the number of sources detected by previous X-ray surveys. We investigate here their characteristics in detail. The sources possess rather high hardness ratios, and their cumulative luminosity function is steeper than that for the rest of the SMC at higher .luminosities. Their absorption columns suggest that most of the sources belong to NGC346. Using new UBV RI imaging with the ESO 2.2m telescope, we also discovered possible counterparts for 36 of these X-ray sources and estimated a B spectral type for a large number of these counterparts. This tends to suggest that most of the X-ray sources in the field are in fact X-ray binaries. Finally, some objects show X-ray and/or optical variability, with a need for further monitoring.

The difference between radio-loud and radio-quiet active galaxies

NASA Astrophysics Data System (ADS)

Wilson, A. S.; Colbert, E. J. M.

1995-01-01

The recent development of unified theories of active galactic nuclei (AGNs) has indicated that there are two physically distinct classes of these objects--radio-loud and radio-quiet. Despite differences, the (probable) thermal emissions from the AGNs (continua and lines from X-ray to infrared wavelengths) are quite similar to the two classes of object. We argue that this last result suggests that the black hole masses and mass accretion rates in the two classes are not greatly different, and that the difference between the classes is associated with the spin of the black hole. We assume that the normal process of accretion through a disk does not lead to rapidly spinning holes and propose that galaxies (e.g., spirals) which have not suffered a recent major merger event contain nonrotating or only slowly rotating black holes. When two such galaxies merge, the two black holes are known to form a binary and we assume that they eventually coalesce. The ratio of the number of radio-loud to radio-quiet AGNs at a given thermal (e.g., optical) luminosity is determined by the galaxy merger rate. Comparisons between the predicted and observed radio luminosity functions constrain the efficiencies with which jet power is extracted from the spinning hole and radio emission is produced by the jet.

A supermassive black hole in an ultra-compact dwarf galaxy.

PubMed

Seth, Anil C; van den Bosch, Remco; Mieske, Steffen; Baumgardt, Holger; den Brok, Mark; Strader, Jay; Neumayer, Nadine; Chilingarian, Igor; Hilker, Michael; McDermid, Richard; Spitler, Lee; Brodie, Jean; Frank, Matthias J; Walsh, Jonelle L

2014-09-18

Ultra-compact dwarf galaxies are among the densest stellar systems in the Universe. These systems have masses of up to 2 × 10(8) solar masses, but half-light radii of just 3-50 parsecs. Dynamical mass estimates show that many such dwarfs are more massive than expected from their luminosity. It remains unclear whether these high dynamical mass estimates arise because of the presence of supermassive black holes or result from a non-standard stellar initial mass function that causes the average stellar mass to be higher than expected. Here we report adaptive optics kinematic data of the ultra-compact dwarf galaxy M60-UCD1 that show a central velocity dispersion peak exceeding 100 kilometres per second and modest rotation. Dynamical modelling of these data reveals the presence of a supermassive black hole with a mass of 2.1 × 10(7) solar masses. This is 15 per cent of the object's total mass. The high black hole mass and mass fraction suggest that M60-UCD1 is the stripped nucleus of a galaxy. Our analysis also shows that M60-UCD1's stellar mass is consistent with its luminosity, implying a large population of previously unrecognized supermassive black holes in other ultra-compact dwarf galaxies.

Primeval galaxies and cold dark matter

NASA Technical Reports Server (NTRS)

Silk, Joseph; Szalay, Alexander S.

1987-01-01

In the context of the cold dark matter theory for the large-scale matter distribution, the onset of galaxy formation is a gradual process, with star formation being initiated at z = about 10 and reaching a peak for luminous galaxies at z = about 1. The mass function of galaxy cores matches the observed quasar luminosity function at z = 2-3. Primeval galaxies are envisaged as a collection of many interacting and merging clumps, attaining a peak luminosity that is an order of magnitude below that achieved in models in which galaxy formation is initiated abruptly. Hence, ongoing searches for primeval galaxies would not necessarily have been successful unless they are designed to find moderately low-luminosity, low-surface-brigtness extended objects at low redshift.

LFlGRB: Luminosity function of long gamma-ray bursts

NASA Astrophysics Data System (ADS)

Paul, Debdutta

2018-04-01

LFlGRB models the luminosity function (LF) of long Gamma Ray Bursts (lGRBs) by using a sample of Swift and Fermi lGRBs to re-derive the parameters of the Yonetoku correlation and self-consistently estimate pseudo-redshifts of all the bursts with unknown redshifts. The GRB formation rate is modeled as the product of the cosmic star formation rate and a GRB formation efficiency for a given stellar mass.

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.

MAD ADAPTIVE OPTICS IMAGING OF HIGH-LUMINOSITY QUASARS: A PILOT PROJECT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liuzzo, E.; Falomo, R.; Paiano, 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. Wemore » 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.« less

Ultraviolet Opacity and Fluorescence in Supernova Envelopes

NASA Technical Reports Server (NTRS)

Li, Hongwei; McCray, Richard

1996-01-01

By the time the expanding envelope of a Type 2 supernova becomes transparent in the optical continuum, most of the gamma-ray luminosity produced by radioactive Fe/Co/Ni clumps propagates into the hydrogen/helium envelope and is deposited there, if at all. The resulting fast electrons excite He 1 and H 1, the two- photon continua of which are the dominant internal sources of ultraviolet radiation. The UV radiation is blocked by scattering in thousands of resonance lines of metals and converted by fluorescence into optical and infrared emission lines that escape freely. We describe results of Monte Carlo calculations that simulate non-LTE scattering and fluorescence in more than five million allowed lines of Ca, Sc, Ti, V, Cr, Mn, Fe, Co, and Ni. For a model approximating conditions in the envelope of SN 1987A, the calculated emergent spectrum resembles the observed one. For the first 2 yr after explosion, the ultraviolet radiation (lambda less than or approximately equals 3000) is largely blocked and converted into a quasi continuum of many thousands of weak optical and infrared emission lines and some prominent emission features, such as the Ca 2 lambdalambda8600 triplet. Later, as the envelope cools and expands, it becomes more transparent, and an increasing fraction of the luminosity emerges in the UV band.

Luminosity determination in pp collisions at $$\\sqrt{s} = 7$$ TeV using the ATLAS detector at the LHC

DOE PAGES

Aad, G.; Abbott, B.; Abdallah, J.; ...

2011-04-27

Measurements of luminosity obtained using the ATLAS detector during early running of the Large Hadron Collider (LHC) at √s = 7 TeV are presented. The luminosity is independently determined using several detectors and multiple algorithms, each having different acceptances, systematic uncertainties and sensitivity to background. The ratios of the luminosities obtained from these methods are monitored as a function of time and of μ, the average number of inelastic interactions per bunch crossing. Residual time- and μ-dependence between the methods is less than 2% for 0 < μ < 2.5. Absolute luminosity calibrations, performed using beam separation scans, have amore » common systematic uncertainty of ±11%, dominated by the measurement of the LHC beam currents. After calibration, the luminosities obtained from the different methods differ by at most ±2%. The visible cross sections measured using the beam scans are compared to predictions obtained with the PYTHIA and PHOJET event generators and the ATLAS detector simulation.« less

Precision Luminosity of LHC Proton-Proton Collisions at 13 TeV Using Hit Counting With TPX Pixel Devices

NASA Astrophysics Data System (ADS)

Sopczak, André; Ali, Babar; Asawatavonvanich, Thanawat; Begera, Jakub; Bergmann, Benedikt; Billoud, Thomas; Burian, Petr; Caicedo, Ivan; Caforio, Davide; Heijne, Erik; Janeček, Josef; Leroy, Claude; Mánek, Petr; Mochizuki, Kazuya; Mora, Yesid; Pacík, Josef; Papadatos, Costa; Platkevič, Michal; Polanský, Štěpán; Pospíšil, Stanislav; Suk, Michal; Svoboda, Zdeněk

2017-03-01

A network of Timepix (TPX) devices installed in the ATLAS cavern measures the LHC luminosity as a function of time as a stand-alone system. The data were recorded from 13-TeV proton-proton collisions in 2015. Using two TPX devices, the number of hits created by particles passing the pixel matrices was counted. A van der Meer scan of the LHC beams was analyzed using bunch-integrated luminosity averages over the different bunch profiles for an approximate absolute luminosity normalization. It is demonstrated that the TPX network has the capability to measure the reduction of LHC luminosity with precision. Comparative studies were performed among four sensors (two sensors in each TPX device) and the relative short-term precision of the luminosity measurement was determined to be 0.1% for 10-s time intervals. The internal long-term time stability of the measurements was below 0.5% for the data-taking period.

The Discovery of Low-Luminosity BL Lacs

NASA Astrophysics Data System (ADS)

Rector, Travis A.; Stocke, John T.

1995-12-01

Many of the properties of BL Lacs have become explicable in terms of the ``relativistic beaming'' hypothesis whereby BL Lacs are ``highly beamed'' FR-I radio galaxies (i.e. our line of sight to these objects is nearly along the jet axis). Further, radio-selected BL Lacs (RBLs) are believed to be seen nearly ``on-axis'' (the line-of-sight angle theta ~ 8deg ) while X-ray selected BL Lacs (XBLs) are seen at larger angles (theta ~ 30deg ; the X-ray emitting jet is believed to be less collimated). However, a major problem with this model was that a transition population between beamed BL Lacs and unbeamed FR-Is had not been detected. Low-luminosity BL Lacs may be such a transition population, and were predicted to exist by Browne and Marcha (1993). We present ROSAT HRI images, VLA radio maps and optical spectra which confirm the existence of low-luminosity BL Lacs, objects which were previously mis-identified in the EMSS catalog as clusters of galaxies. Thus our results strengthen the relativistic beaming hypothesis.

Radio properties of type 1.8 and 1.9 Seyfert galaxies

NASA Technical Reports Server (NTRS)

Ulvestad, James S.

1986-01-01

A number of type 1.8 and 1.9 Seyfert galaxies have been observed at the VLA in order to compare their properties with those of the other types of Seyfert galaxy. The observed types have radio luminosities in the range of 10 to the 39th-40.5th args/s, with the median near 10 to the 40th ergs/s. Most of these galaxies have radio sources with diameters of about 500 pc or less. The ratio of radio luminosity to featureless optical continuum luminosity in the Seyfert 1.8/12.9 galaxies and Seyfert 1.2/1.5 galaxies is intermediate between the values for Seyfert 1 and Seyfert 2 galaxies. The infrared-to-radio ratio decreases along the sequence from Seyfert 1 galaxies, through intermediate Seyfert galaxies, to Seyfert 2 galaxies. This systematic statistical difference in the ratio of two aspect-independent quantities implies that the differences among the Seyfert classes cannot be attributed solely to differences in viewing angle.

Two classes of fast-declining Type Ia supernovae

NASA Astrophysics Data System (ADS)

Dhawan, Suhail; Leibundgut, B.; Spyromilio, J.; Blondin, S.

2017-06-01

We aim to characterise a sample of fast-declining Type Ia supernovae (SN Ia) using their bolometric and near-infrared (NIR) properties. Based on these properties, we find that fast-declining SN Ia separate into two categories based on their bolometric and NIR properties. The peak bolometric luminosity (Lmax), the phase of the first maximum relative to the optical, the NIR peak luminosity, and the occurrence of a second maximum in the NIR distinguish a group of very faint SN Ia. Fast-declining supernovae show a large range of peak bolometric luminosities (Lmax differing by up to a factor of 8). All fast-declining SN Ia with Lmax < 0.3× 1043 erg s-1 are spectroscopically classified as 91bg-like and show only a single NIR peak. SNe with Lmax > 0.5× 1043 erg s-1 appear to smoothly connect to normal SN Ia. The total ejecta mass (Mej) values for SNe with enough late time data are ≲1 M⊙, indicating a sub-Chandrasekhar mass progenitor for these SNe.