Nuclear Luminosity Research Articles

Host Galaxies of Radio-Loud & Radio-Quiet AGN

A clear understanding of both the differences and similarities between the host galaxies of the three main classes of powerful active galaxy – radio-quiet quasars (RQQs), radio-loud quasars (RLQs) and radio galaxies (RGs) – is vital in any attempt to unify or relate the various manifestations of the AGN phenomenon. The unification of RLQs and RGs via orientation effects requires that the hosts of the two types be derived from the same population of galaxies. Meanwhile, the correlation between radio power and host morphology in nearby AGN, with radio-quiet objects (Seyferts) occurring in disc systems and radio-loud sources in ellipticals, is generally assumed to persist at higher redshifts and nuclear luminosities. However, in both cases the evidence remains ambiguous and, moreover, many previous studies have been based on poorly selected samples.

A nuclear Luminosity Function for Seyferts

Relations between various classes of AGN should show up when examining their LFs. For Seyfert galaxies, such studies have been affected by the prevalence of (essentially) integrated magnitudes. Proper nuclear magnitudes have been determined in an effort of CCD imaging, which enable an appropriate comparison with QSOs.

NEAR-INFRARED PROPERTIES OF QUASAR AND SEYFERT HOST GALAXIES

ABSTRACT We present near-infrared images of nearly 100 host galaxies of Active Galactic Nuclei (AGN). Our quasar sample is comprised of the 50 quasars from the Palomar Green Bright Quasar Survey with redshifts z\\≤ 0.3. We have restricted the redshift range to ensure adequate spatial resolution, galaxy detectability, and minimal distance-dependent effects, while still giving a large sample of objects. For lower-luminosity AGN we have chosen to image the CfA Seyfert sample. This sample is composed of 48 Seyferts, roughly equally divided among types 1, 1.5-1.9, and 2. This sample was spectroscopically selected, and, therefore, is not biased towards Seyferts with significant star formation. Taken together, these samples allow a statistical look at the continuity of host-galaxy properties over a factor of 10,000 in nuclear luminosity. We find the near-infrared light to be a good tracer of luminous mass in these galaxies. The Seyferts are found in galaxies of type S0 to Sc. The radio quiet quasars live in similar kinds of galaxies spanning the same range of mass centered around L*. However, for the most luminous quasars, there is a correlation between the minimum host-galaxy mass and the luminosity of the active nucleus. Radio-loud quasars are generally found in hosts more massive than an L* galaxy. We also detect a population of low-mass host galaxies with very low-luminosity Seyfert nuclei. The low luminosity quasars and the Seyferts both tend to lie in host galaxies seen preferentially face-on, which suggests there is a substantial amount of obscuration coplanar with the galaxian disk. The obscuration must be geometrically thick (thickness-to-radius ~1) and must cover a significant fraction of the narrow line region (r>100 pc). We have examined our images for signs of perturbations that could drive fuel toward the galaxy nucleus, but there are none we can identify at a significant level. The critical element for fueling is evidently not reflected clearly in the large scale distribution of luminous mass in the galaxy. We also present an infrared image of the jet of 3C 273 and compare it to visible and radio images from the literature.

Propagation of nuclear burning fronts on accreting neutron stars: X-ray bursts and sub-hertz noise

view Abstract Citations (124) References (84) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Propagation of Nuclear Burning Fronts on Accreting Neutron Stars: X-Ray Bursts and Sub-Hertz Noise Bildsten, Lars Abstract We identify a new regime of time dependent helium burning for high accretion rate neutron stars and suggest that this burning is the origin of the low-level luminosity variations (on timescales of 10-104 s, designated the 'very low-frequency noise'(VLFN) by van der Klis and collaborators) always detected in the brightest accreting X-ray sources. Only two nuclear burning regimes were previously recognized. At accretion rates in excess of the Eddington limit (dot-M approximately greater than (1-3) x 10-8 solar mass/yr), the accreted matter fuses steadily. At very low dot-M, the star's entire surface is rapidly (approximately less than 10 s) burned by a fast propagating convective burning front at regular intervals, giving quasi-periodic Type I X-ray bursts. We show that for the observationally interesting range of 5 x 10-10 solar mass/yr approximately less than dot-M approximately less than 10-8 solar mass/yr, parts of the stellar surface burn slowly. At these accretion rates, a local thermonuclear instability starts a fire which propagates horizontally at v approximately 300 cm/s. The fire propagates around the flammable surface in roughly the same time it takes to accrete enough fuel for the next instability (approximately 103-104, so that only a few fires are burning at once, giving rise to large luminosity flares. Nuclear burning is always time dependent for sub-Eddington local accretion rates: a local patch undergoes a recurrent cycle, accumulation fuel for hours until it becomes thermally unstable or is 'ignited' by a nearby burning region. The global pattern of burning and the resulting luminosity are thus very dependent on how fast nuclear fires spread around the star. The nuclear burning luminosity is not uniform over the stellar surface and so may provide a handle on measuring, or constraining, the spin periods of these neutron stars. Publication: The Astrophysical Journal Pub Date: January 1995 DOI: 10.1086/175128 Bibcode: 1995ApJ...438..852B Keywords: Accretion Disks; Combustion; Neutron Stars; Nuclear Reactions; Stellar Mass Accretion; X Rays; Helium; Stellar Atmospheres; Stellar Luminosity; Stellar Physics; Stellar Temperature; Astrophysics; ACCRETION; ACCRETION DISKS; INSTABILITIES; NUCLEAR REACTIONS; NUCLEOSYNTHESIS; ABUNDANCES; STARS: NEUTRON; X-RAYS: BURSTS full text sources ADS | data products SIMBAD (10)

Multiwavelength tests of the dusty torus model for Seyfert galaxies

view Abstract Citations (226) References (67) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Multiwavelength Tests of the Dusty Torus Model for Seyfert Galaxies Mulchaey, John S. ; Koratkar, Anuradha ; Ward, Martin J. ; Wilson, Andrew S. ; Whittle, Mark ; Antonucci, Robert R. J. ; Kinney, Anne L. ; Hurt, Todd Abstract We present a compilation of emission properties for a sample of 116 Seyfert galaxies based on both previously unpublished data and measurements available in the literature. These measurements include fluxes in the emission lines [O III] λ5007 and Hβ, as well as the infrared (25-60 microns), ultraviolet (1450 A), soft (0.2-4 keV), and hard (2-10 keV) X-ray continua. These data are used to try to distinguish between isotropic and anisotropic emission properties of Seyfert galaxies. The distribution functions of [O III] λ5007, infrared, and hard X-ray continuum are similar for Seyfert 1's and Seyfert 2's, consistent with these properties being isotropic. The ultraviolet and soft X-ray continua of Seyfert 2's are underluminous relative to the type 1's suggesting photons at these energies escape from the central source anisotropically. There is a correlation between the ultraviolet continuum and emission-line fluxes in Seyfert 1's consistent with the idea that the central engine is responsible for powering the line emission. No such correlation is found for the Seyfert 2's. Instead, the scatter in the plot of ultraviolet continuum versus line emission suggests the true nuclear continuum luminosity is not seen at Earth in these objects. These properties are consistent with those expected in the dusty torus model. Publication: The Astrophysical Journal Pub Date: December 1994 DOI: 10.1086/174933 Bibcode: 1994ApJ...436..586M Keywords: Active Galactic Nuclei; Astronomical Models; Emission Spectra; Infrared Spectra; Line Spectra; Seyfert Galaxies; Ultraviolet Spectra; Astronomical Spectroscopy; Infrared Astronomy; Mathematical Models; Ultraviolet Astronomy; Astrophysics; GALAXIES: ACTIVE; GALAXIES: NUCLEI; GALAXIES: SEYFERT; INFRARED: GALAXIES; ULTRAVIOLET: GALAXIES; X-RAYS: GALAXIES full text sources ADS | data products SIMBAD (117) NED (117) MAST (1)

Quasars and active galactic nuclei in rich environments. III - The rapid evolution of active galactic nucleus activity in rich clusters

view Abstract Citations (79) References (41) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Quasars and Active Galactic Nuclei in Rich Environments. III. The Rapid Evolution of Active Galactic Nucleus Activity in Rich Clusters Yee, H. K. C. ; Ellingson, E. Abstract The evolution of optical activity in radio-loud quasars and low- redshift radio galaxies in different galaxian environments is analyzed using data available in the literature. For any given luminosity function (LF) and its evolution, an envelope model of the distribution of points in the absolute magnitude-redshift plane can be constructed which predicts the expected loci of the brightest objects observable at different redshift. By applying such models to the distribution of optical nuclear luminosities from the active component of quasars and radio galaxies as a function of redshift, it is found that objects in similar environments from both classes can be described by a single optical LF and evolution law. Furthermore, the high-luminosity end of the LF and evolution for the active galactic nucleus component of the combined sample of radio-loud quasars and radio galaxies situated in poor environments is consistent with that of optically selected quasars. Quasars situated in rich galaxy clusters, however, are found to evolve ~5 times faster than their counterparts in poorer environments. The extrapolation of this rapid evolution is also consistent with the level of optical activity found in radio galaxies in rich clusters at low redshift. This suggests that radio galaxies can be considered as current- epoch low-luminosity counterparts to radio-loud quasars. This evolution scenario can account for the earlier finding that only the least active objects are found in rich environments at low redshifts; whereas at z ~0.6, extremely bright quasars are found in rich clusters. The rapid evolution of quasars in rich clusters is likely to be connected to the evolution of the physical conditions in the clusters. This rapid evolution, however does not extrapolate to redshifts higher than z~0.7, implying a drastic change in the evolution rate at this epoch. This may indicate a decrease in the cluster formation rate or a saturation effect in the quasar LF. Publication: The Astrophysical Journal Pub Date: July 1993 DOI: 10.1086/172806 Bibcode: 1993ApJ...411...43Y Keywords: Active Galactic Nuclei; Galactic Clusters; Galactic Evolution; Quasars; Radio Galaxies; Interacting Galaxies; Luminosity; Red Shift; Astrophysics; GALAXIES: ACTIVE; GALAXIES: CLUSTERING; GALAXIES: EVOLUTION; GALAXIES: NUCLEI; GALAXIES: QUASARS: GENERAL; RADIO CONTINUUM: GALAXIES full text sources ADS | data products NED (94) SIMBAD (93) Related Materials (2) Part 1: 1991ApJS...76..455E Part 2: 1991ApJ...371...49E

The origin of the optical polarizations of Seyfert 1 galaxies

A statistical study of the optical continuum polarizations of a sample of 68 optically selected Seyfert 1 galaxies is reported. The polarizations correlate with narrow H-alpha/H-beta, the 12 micron and 25 micron nuclear luminosities, with the nuclear 25/60 color and possibly the 112/60 and the 60/100 colors. They do not correlate with four broad-line reddening indicators, measures of asymmmetry in forbidden O III 5007, the 3.5 micron, 60 micron, and 100 micron luminosities, and the 12/3.5 and 12/25 nuclear colors. The only correlations found are with the properties of dust in the narrow-line region, and this indicates strongly that the polarization arises from scattering and extinction by dust that is outside or mixed with the narrow-line clouds. This same dust produces much of the 12 micron and 25 micron power of Seyfert 1s. 80 refs.

What is the difference between radio-loud and radio-quiet quasi-stellar objects?

Measures of the nuclear and host galaxy luminosities and colors and a morphological discussion of the host galaxies are presented for a sample of low-redshift, high-luminosity, radio-quiet QSOs whose redshift and luminosity distribution matches that of a radio-loud sample previously discussed. Radio-quiet QSOs are found to reside in galaxies which are smaller, fainter, and redder than the host galaxies of radio-loud QSOs. These properties are generally consistent with the suggestion that radio-quiet QSOs are located in spiral-type galaxies and radio-loud QSOs are located in more elliptical-type galaxies. Significantly less evidence is found for tidal interactions among the radio-quiet objects, although they appear to reside in somewhat richer environments in terms of nearby companions.

Radio-continuum observations of S�rsic-Pastoriza galaxies

Preliminary results of radio continuum observations of selected Sersic-Pastoriza galaxies are presented. Subjects reported are their radio properties at 6 and 20 cm, estimates of linear polarization and spectral indices and a discussion of possible relationships between nuclear morphology and radio luminosity.

The Twin-Nucleus Merging Galaxy MKN 266

We present results of observations of the double-nucleus galaxy Markarian 266 (NGC 5256) from 3 principal sources. These are 1:CCD imaging with the Canada-France-Hawaii telescope in broad and narrow bands. These indicate that the galaxy has extended, complex, faint outer plumes which indicate that a recent merger has occurred. The narrow-band images reveal remarkable knotty structure of the [O III] emitting gas, extending over the whole central part of the galaxy. This is not seen in Hα (see figure 1).2:21cm imaging with the VLA, covering velocity space near that of the optical nuclei. The continuum image reveals resolved triple structure, with the two outer peaks coincident with the optical nuclei. The 21cm velocity profiles indicate the presence of considerable H I absorption near the optical emission line velocities.3:Spatially resolved optical spectroscopy with the DAO 1.8m telescope. These data reveal the details of the [O III] velocity field and some of the physical parameters of the gas. The complexity and extended nature of the gas explains some conflicting redshift measurements in the literature. Together with the imaging data, we derive estimates of nuclear reddening and luminosity.

Line width-luminosity correlation for starburst galaxies

High-resolution spectroscopy and R-band CCD imagery are used to study the kinematics of galaxies with starburst nuclei. Good correlations are found between nuclear H-alpha emission line width and luminosity of the nucleus, and line width and host galaxy luminosity. The fundamental correlation appears to be with the nucleus, but the slope is shallower than the Tully-Fisher relation. This makes it a potentially more sensitive luminosity indicator. 13 references.

The optical luminosity function of quasars and low-luminosity active galactic nuclei

The optical luminosity function derived from quasars with M(B) less than -23 is extended to include the nuclear luminosities of Seyfert 1 galaxies. The model is fitted to the (total) luminosity data for active galaxies from a complete flux-limited survey. A good fit is obtained with dN/dL varying inversely as L exp -1.2, matching onto the steeper quasar luminosity function near M(B) = -22. Using a luminosity evolution model derived from quasar data, this feature compares well with the results from faint quasar surveys. 26 references.

21 CM emission in QSOs and active galaxies

view Abstract Citations (31) References (15) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS 21 CM Emission in QSOs and Active Galaxies Hutchings, J. B. ; Gower, Ann C. ; Price, Rob Abstract Observations of H I emission from galaxies containing QSOs and active nuclei, obtained with the Arecibo telescope, are reported, including new data on 17 objects, new detections in four of them, improved profiles in five more, and possible detections in several others. These results are discussed together with published observations of five other objects by the same telescope. This sample lies at higher luminosity and redshift than surveys of Seyfert galaxies. The line profiles are generally broad and asymmetric, probably due to contamination by associated or interacting galaxies. There is a close agreement with optical NLR redshifts, but a mismatch of some 50 km/s is suggested. Overall, the H I masses are lower than for normal galaxies, but they appear to correlate with the nuclear luminosity. This may connect fueling events and ionization by the nuclear radiation. Publication: The Astronomical Journal Pub Date: January 1987 DOI: 10.1086/114284 Bibcode: 1987AJ.....93....6H Keywords: Active Galaxies; Emission Spectra; Galactic Nuclei; Hydrogen; Quasars; Red Shift; Seyfert Galaxies; Interacting Galaxies; Line Spectra; Luminosity; Astrophysics; QUASARS; RADIO SOURCES: GALAXIES full text sources ADS | data products NED (23) SIMBAD (15)

Relationships Between Seyfert Galaxies, QSOs, and BL LACs

In this review, I will deal principally with the optical morphology of these three types of object, and attempt to outline similarities and essential differences. By this, I mean to include studies of the types of host galaxy, nuclear and galaxy luminosities and colours, interactions with other galaxies, and the general associations with other galaxies. Where relevant, I will refer to morphology at other wavelengths (generally radio), spectroscopy, and UV or X-ray properties. However, I expect these areas to be covered much more fully by other reviews and papers in this volume.

Far-infrared luminosities of Markarian starburst galaxies

Total far-infrared luminosities have been calculated from measured IRAS fluxes for a sample of optically selected galaxies and for a comparison sample of spiral galaxies. The starburst galaxies are notably more luminous in the far-infrared and have higher dust color temperatures than the comparison galaxies. The far-infrared light dominates the total luminosity of the starburst galaxies, and a significant amount of dust must be present. The far-infrared emission correlates well with total blue luminosity, nuclear blue luminosity, and nuclear H-alpha luminosity. The dust that produces the far-infrared light is probably heated predominantly by B rather than by O stars. 30 references.

On the nature of QSO host galaxies

view Abstract Citations (198) References (47) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the Nature of QSO Host Galaxies Smith, E. P. ; Heckman, T. M. ; Bothun, G. D. ; Romanishin, W. ; Balick, B. Abstract Results of an analysis of deep images of 31 low-redshift QSOs and lower luminosity QSO/AGNs obtained with the prime focus CCD system on the CTIO 4 m telescope are presented. The host galaxies of QSOs are generally luminous systems populating the exponential tail of the galaxy luminosity function. Seyfert galaxies are apparently less luminous than the hosts of radio-quiet QSOs. The radio-loud QSOs are more luminous than the radio-quiet QSO hosts. For the sample of QSOs and QSO/AGNs, there is a trend for the radio-loud hosts to be better fitted by elliptical galaxy models and for the radio-quiet hosts to be fitted by disk galaxies, suggesting that the dichotomy known to exist between Seyfert and radio galaxies extends to much higher levels of nuclear luminosity. These results strengthen the empirical basis for a continuity in properties between Seyfert galaxies and radio-quite QSOs and between radio galaxies and radio-loud QSOs. Publication: The Astrophysical Journal Pub Date: July 1986 DOI: 10.1086/164321 Bibcode: 1986ApJ...306...64S Keywords: Galactic Nuclei; Galactic Structure; Image Analysis; Quasars; Active Galactic Nuclei; Astronomical Spectroscopy; Cosmology; Data Processing; Galactic Evolution; Luminosity; Red Shift; Astrophysics; GALAXIES: NUCLEI; GALAXIES: PHOTOMETRY; GALAXIES: STRUCTURE; QUASARS; RADIO SOURCES: GALAXIES full text sources ADS | data products SIMBAD (30) NED (26)

Evolution of the Luminosity Function

In this review, the currently published, complete, spectroscopically identified samples of quasars are assembled to produce a composite luminosity function, independent of evolutionary assumptions. Two interpretations of the change with cosmic time provide reasonable fits to the data. Luminosity evolution implies a fixed population of host objects, with nuclear luminosity that fades with advancing cosmic time; some dependence of the timescale on intrinsic luminosity is required. Density evolution traces objects of comparable luminosity to find the change in space density, without a requirement of long lifetime. The change in co-moving volume density depends on luminosity; newer data suggest that somewhat stronger evolution is required at the low luminosity end than the models of Schmidt and Green allowed. Caution is advised in drawing direct physical conclusions about the evolution of individual quasars from mathematical representations of ensemble properties.

Differential population synthesis of early-type galaxies. II - Galaxy spectra, colors, and line strengths

view Abstract Citations (21) References (36) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Differential population synthesis of early-type galaxies. II. Galaxy spectra, colors and line strengths. Pickles, A. J. ; Visvanathan, N. Abstract Flux-calibrated spectra are presented for the nuclei of 12 elliptical and five lenticular galaxies in the Fornax Cluster (V0 = 1430 km/s). The continuous spectra have a resolution of 10-20 A and wavelength coverage extending from 3600 A to a maximum of 10,000 A. The galaxies have been selected to cover a large range (of about 6 mag) of absolute magnitude and provide a good, representative sample defining the color-magnitude diagram for the Fornax Cluster. Spectrophotometric colors derived on the Kron-Cousins UBVRI system are compared with published photoelectric photometry, and the variation with nuclear luminosity of several prominent line strengths is discussed. Publication: The Astrophysical Journal Pub Date: July 1985 DOI: 10.1086/163281 Bibcode: 1985ApJ...294..134P Keywords: Astronomical Photometry; Color-Magnitude Diagram; Elliptical Galaxies; Galactic Nuclei; Line Spectra; Metallicity; Balmer Series; Calibrating; Emission Spectra; H Alpha Line; Luminosity; Astrophysics full text sources ADS | data products SIMBAD (17) NED (16) Related Materials (2) Part 1: 1985ApJS...59...33P Part 3: 1985ApJ...296..340P

Multiaperture infrared photometry of the nuclei of spiral galaxies

view Abstract Citations (20) References (18) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Multiaperture infrared photometry of the nuclei of spiral galaxies. Cizdziel, P. J. ; Wynn-Williams, C. G. ; Becklin, E. E. Abstract Results of a multiaperture, 2.2- and 10-micron photometric survey of the nuclei of 25 nearby, low-inclination spiral galaxies are presented. The 10-micron nuclear luminosities, attributed to thermal reradiation by dust in regions of active star formation, and 10-micron/2.2-micron nuclear flux ratios, are examined as a function of the slope of 2.2-micron growth curve. No correlation is seen, suggesting that the contribution of young, red giants and supergiants to the near-infrared light of spiral nuclei is small. These results indicate that the 2.2-micron light of galaxies in the present sample is not radically altered by starbursts. Publication: The Astronomical Journal Pub Date: May 1985 DOI: 10.1086/113780 Bibcode: 1985AJ.....90..731C Keywords: Astronomical Photometry; Galactic Nuclei; Infrared Astronomy; Spiral Galaxies; Stellar Luminosity; Thermal Radiation; Far Infrared Radiation; H Alpha Line; Molecular Clouds; Red Giant Stars; Stellar Evolution; Stellar Flares; Astrophysics full text sources ADS | data products SIMBAD (27) NED (27)

Evidence for beamed radiation from QSOs

view Abstract Citations (18) References (12) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Evidence for beamed radiation from QSOs. Hutchings, J. B. ; Gower, A. C. Abstract Deep radio-continuum detection observations have been performed with the VLA on a representative sample of optically and X-ray selected QSOs of low redshift. Eight of 27 objects were detected as radio-continuum sources with core luminosities down to 10 to the 21st W/Hz. A further 15 had higher detection limits. The detected radio-source structures are all small, probably one-sided, and complex. The optical properties of the objects indicate that the ratio of nuclear to host galaxy luminosity is about 5 times higher in the radio-emitting objects, and that their nuclear luminosities are about 10 times higher. These and related statistics are used to argue that the optical and radio-continuum emission from these quasars is beamed towards this Galaxy. Publication: The Astronomical Journal Pub Date: March 1985 DOI: 10.1086/113745 Bibcode: 1985AJ.....90..405H Keywords: Astronomical Spectroscopy; Beams (Radiation); Continuous Spectra; Luminosity; Quasars; Radio Sources (Astronomy); Astronomical Maps; Emission Spectra; Galactic Nuclei; Red Shift; Visible Spectrum; X Ray Spectra; Astrophysics full text sources ADS | data products SIMBAD (40) NED (33)