Nuclear Luminosity Research Articles

The relative luminosities of the disk and the invisible of M82 a rediscussion of the polarization pattern

AbstractThe origin of the noncircular pattern of the polarization vectors in the halo of scattered light around M82 is discussed anew. This pattern had been interpreted by SOLINGER and MARKERT (1975) to indicate a high contribution of the disk to the illumination of the halo, whereas the blue colour of the halo demands a significant contribution from a very blue illuminating source, the nucleus. The discussion of SOLINGER and MARKERT has been modified in two respects: 1. an extinction in the disk M82, distributed similar to the stars, is assumed; this strengthens the disk's ability to turn the polarization vectors parallel to itself, and 2. an original polarization of the nuclear light parallel to the galaxy's plane is assumed; this also causes a corresponding turning of the polarization vectors.The new estimate of the nuclear luminosity relative to the disk luminosity is LN/LD = 0.7 ± 0.3 compared to 0.05 by SOLINGER and MARKERT. This luminosity ratio enables the nucleus to determine the colour of the scattered light near the minor axis at low and medium distances from the centre.

Induced nuclear emission-line activity in interacting spiral galaxies

view Abstract Citations (144) References (15) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Induced nuclear emission-line activity in interacting spiral galaxies. Kennicutt, R. C., Jr. ; Keel, W. C. Abstract The authors have investigated the effect of close galaxy-galaxy interactions on the level of nuclear activity in spiral galaxies by obtaining nuclear spectrophotometry for complete samples of multiple and single systems. Galaxies with nearby companions possess significantly higher nuclear emission-line luminosities and equivalent widths, and their nuclei exhibit a significantly higher level of ionization on average. A much higher fraction of galaxies with Seyfert or Seyfert type nuclei is found in the sample of multiple systems. Publication: The Astrophysical Journal Pub Date: April 1984 DOI: 10.1086/184243 Bibcode: 1984ApJ...279L...5K Keywords: Astronomical Spectroscopy; Interacting Galaxies; Nuclear Interactions; Seyfert Galaxies; Spiral Galaxies; Hydrogen Clouds; Spectral Line Width; Astrophysics full text sources ADS | data products SIMBAD (5) NED (3)

An X-ray survey of a complete sample of 3CR radio galaxies

view Abstract Citations (201) References (100) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS An X-ray survey of a complete sample of 3CR radio galaxies. Fabbiano, G. ; Miller, L. ; Trinchieri, G. ; Longair, M. ; Elvis, M. Abstract The X-ray survey of the galaxies, 40 in all, was made with the Einstein Observatory. By comparing the distributions of X-ray luminosities, it is found that 3CR galaxies with double radio morphology (FR 2) and optical emission-line spectra tend to be the more powerful X-ray emitters, with broad-line galaxies at the top of the distribution. It is also found that the X-ray luminosity is strongly correlated with the 5 GHz radio nuclear luminosity. Through an analysis of the complete optical and radio sample with the Spearman partial rank correlation technique, it is determined that nuclear radio luminosity at 5 GHz is correlated with both total radio luminosity at 178 MHz and with galaxy optical luminosity. Other weaker correlations are found of the X-ray luminosity with the total radio luminosity at 178 MHz and the optical luminosity of the galaxy. The results are seen as underlining the importance of nuclear phenomena in radio galaxies and indicating a nuclear origin of their X-ray emission. In addition, it is found that the 3CR emission-line galaxies are similar to both Seyfert galaxies and quasars with double radio morphology in their X-ray properties, strongly reinforcing a unified picture of active nuclei. Publication: The Astrophysical Journal Pub Date: February 1984 DOI: 10.1086/161676 Bibcode: 1984ApJ...277..115F Keywords: Galactic Nuclei; Luminosity; Radio Galaxies; X Ray Sources; Elliptical Galaxies; Galactic Radiation; Galactic Structure; Heao 2; Optical Emission Spectroscopy; Quasars; Seyfert Galaxies; Astrophysics full text sources ADS | data products SIMBAD (48) NED (42) Related Materials (1) Erratum: 1984ApJ...283..469F

Continuing formation of the central star cluster in M87

The rising velocity dispersion of the stars in the neighbourhood of the central luminosity spike observed1–3 in the elliptical radio galaxy M87 was originally considered to be evidence for the presence of a massive black hole4 (M ∼ 5×109M⊙). A later spectrum3 taken in good seeing, however, shows that most of the light in the spike is due to stars, which restricts any black hole model; the luminosity spike may be a star cluster formed from gas infalling from the outer regions of M875,6. Our analysis7 of Einstein Observatory X-ray data on M87 revealed a cooling inflow of gas occurring at the rate required to build such a cluster. We show here that the back-reaction on the flow of the nuclear luminosity is small unless M87 was much brighter in the past and we suggest that massive central star clusters may be common in the central galaxies in many clusters and, on a smaller scale, in many elliptical galaxies.

The nuclear luminosity and mass of type I seyfert galaxies

The nuclear mass M, bolometric luminosity L bol , and the Eddington luminosity L Edd are determined for fifty Type-I Seyfert galaxies from data on the luminosity and line-width of nuclear Balmer line H β , assuming a mass accretion flow model. It is emphasized that the full width at zero intensity (FWZI), rather than the full width at half maximum (FWHM) should be used to give the velocity in the central broad line region. The histograms of M and of L bol / L Edd are shown in Figs. 1 and 2, for ready comparison with Type-II Seyferts and QSOs. Adding the data on the X-ray luminosities L X for 38 Seyferts on our list, we have obtained the following correlations: L x(2–10KcV) α(FWZI) 2, with γ = 0.50, and L x(2–10KcV) α( M), with γ = 0.70 See Figs. 3 and 4. The implications of our statistical results are briefly discussed in terms of the spherically symmetric flow model of mass accretion.

An H-alpha forbidden N II survey of the nuclei of a complete sample of spiral galaxies

view Abstract Citations (232) References (23) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS An Half survey of the nuclei of a complete sample of spiral galaxies. Keel, W. C. Abstract New spectrophotometry of the nuclei of an optically complete sample of 93 spiral galaxies brighter than integrated magnitude brightness temperature of 12.0 is presented. All the nuclei exhibit emission lines. These are divided into those produced by stellar photoionization (H II regions) and low-ionization emission regions. In addition, five Seyfert nuclei occur in this sample, including one (NGC 4941) not previously identified. Relations between nuclear luminosity and emission-line luminosity, and between the character of the emission spectrum and line luminosity, are presented. Publication: The Astrophysical Journal Supplement Series Pub Date: July 1983 DOI: 10.1086/190866 Bibcode: 1983ApJS...52..229K Keywords: Forbidden Transitions; Galactic Nuclei; H Alpha Line; Seyfert Galaxies; Spiral Galaxies; Brightness Temperature; Emission Spectra; H Ii Regions; Line Spectra; Nebulae; Nitrogen; Spectrophotometry; Spectrum Analysis; Astrophysics full text sources ADS | data products SIMBAD (100) NED (100)

Secular evolution of cataclysmic binaries - Evolution of the secondary and the period gap

The evolution of low-mass main-sequence stars subject to mass loss at constant rates is followed, starting from several initial degrees of hydrogen depletion in the central regions and imposing several different rares of mass loss. During this evolution, stars of progressively smaller mass become fully convective. The behavior of convection along the computed sequences is a function both of the chemical stratification of the star and of the degree of departure from thermal equilibrium. Total mixing for stars initially not largely evolved occurs at Mapprox.0.4 M/sub sun/, and, according to the preceding history of the star, the mixing raises or decreases the /sup 3/He concentration in the core noticeably on a short time scale. The consequent sudden variation of the nuclear luminosity produces a thermal readjustment and a small radius increase or decrease. In more evolved initial models (central hydrogen mass fraction X/sub c/approx.0.30, toal mixing occurs only at Mapprox.0.2 M/sub sun/.

Kinematics of Nuclei of Sc Galaxies

For a sample of 21 Sc galaxies with a wide range of luminosities, of radii, and of masses, W. K. Ford and I have obtained spectra and determined rotation curves. By their kinematical behavior in their central regions, the Sc’s can be separated into two groups. Some galaxies, generally small and of low luminosity, have shallow central velocity gradients, reflecting their low central masses and densities. Other galaxies, most often large ones of high luminosity, have steep central velocity gradients. One reason this separation by central velocity gradients is of interest is because these galaxies exhibit other significant spectral differences which go hand-in-hand with the kinematical differences.The small, low luminosity galaxies show emission lines of Hα and [NII], with nuclear Ha sharp and stronger than [NII], and little or no stellar nuclear continuum, just as conventional HII regions. In contrast, the high luminosity galaxies show broad nuclear emission, with [NII] stronger than Ha. These galaxies have a strong red stellar continuum, arising from a red stellar population. The cause of the Hα[NII] intensity reversal in the nuclei of some galaxies remains unknown. However, the strong [NII] emission in generally high luminosity galaxies with massive nuclei, nuclei which show strong red continua, suggests that [Nil] intensity correlates with nuclear luminosity, and in turn with the density and velocity properties of the nuclear populations. We would expect high velocity dispersions and high bulge luminosities for galaxies with strong nuclear [NII] and steep central velocity gradients.

Evidence for a supermassive object in the nucleus of the galaxy M87 from SIT and CCD area photometry

Results are presented for broadband three-color (BVR) photometric observations of the peculiar elliptical radio galaxy M87, which were obtained with digital two-dimensional SIT and CCD detector systems on the Palomar 60-in. and 200-in. telescopes. The observations and the reduction procedures for the digital data are outlined, the luminosity profile of M87 is given, and a nuclear luminosity spike is found to be centered within 0.02 arcsec of the center of M87. Attempts are made to fit various theoretical models to the luminosity profile, and a satisfactory fit is obtained between the observed profile and a model involving a massive black hole in the galactic nucleus. A model-independent dynamical analysis of the central regions is performed which indicates that the nucleus of M87 contains a supermassive object of about 5 billion solar masses with a radius of no more than 100 pc and an M/L ratio of at least 60. The possible nature of this object is considered, and it is concluded that M87 is probably the most plausible candidate for a massive black hole in a galactic nucleus.

Extragalactic carbon monoxide

Observations of 2.6-mm carbon monoxide emission are reported for five galaxies: M82, NGC 253, M51, NGC 5236, and NGC 1068. An extensive map of the emission from M82 is presented, along with less extensive maps of NGC 253 and M51. Models for the CO distributions have been fitted to the mapping results for M82 and M51. Comparisons of OH, H2CO, and CO observations toward M82 and NGC 253 show that relative molecular abundances are similar to their Galactic values. The central CO profile in M82 closely resembles an averaged H-alpha emission profile for the same region. The estimated mass in molecular clouds is found to be greater than that in atomic hydrogen for most of the regions studied. Total CO column densities are estimated for the five galaxies, and a possible correlation is noted between these column densities and the nuclear 10-micron luminosities. Despite sensitive searches, no (C-13)O emission is observed toward NGC 253 and M82. These negative results imply either upper limits of about 10 for the optical depth of the (C-12)O features or lower limits to the C-12/C-13 abundance ratios of approximately 15 and 40 in M82 and NGC 253, respectively. Negative results for CO emission are reported for 24 other galaxies, including M31 and M63.

Unsteady Mass Loss in Close Binaries

The evolution of a system of 1.50M⊙ and 0.50M⊙ components with initial separation 3.00R⊙ is presented. The primary reaches its Roche lobe after 6.108 × 108 yr, and the mass loss rate grows quickly to ~ 1.1 × 10−7M⊙ yr−1. The deep convective envelope of the secondary contracts in response to accretion, however, and the system avoids contact, even though the main sequence mass-radius relationship crosses the Roche relationship at 0.758M⊙.The growth of the convective envelope of the primary with mass loss prevents thermaltimescale mass transfer from reaching any stable value. The mass loss rate continues to increase as a result of the tendency of the growing convective envelope to expand with mass loss. A Bath-type pulsational instability in the mass transfer rate is manifested as a longer-period thermal instability in the hydrostatic treatment. Eventually mass loss proceeds on a dynamical timescale, reaching 1.5 × 10−4M⊙yr−1. This is followed by a detached phase with the mass ratio not yet reversed, and a second dynamical episode leaving a 0.6666M⊙ + 1.3334M⊙ binary still in a semi-detached state. The original secondary, now more massive, has a surface luminosity of 0.0538L⊙ but a nuclear luminosity of 1540L⊙, and a convective core of 1.076M⊙ separated by a radiative zone of only 0.028M⊙ from its convective envelope.An attempt is made to follow the evolution of the secondary in the case where the stream energy, much greater than the intrinsic luminosity of the secondary, is dissipated spherically symmetrically at its surface. The outer envelope departs radically from the previous case, an optically deep radiative surface layer forming, and the convection zone splitting into two, the lower one remaining very massive. Because the mass transfer timescale is short compared with the thermal timescale of the secondary, however, it is concluded that the stream luminosity cannot significantly alter the evolution of the secondary.

The galaxy M82 - Nuclear luminosity as determined by the polarization pattern

The galaxy M82 - Nuclear luminosity as determined by the polarization pattern

Integrated Magnitudes and Colours of Bright Galaxies in the UBV System

Integrated V magnitudes and B–V , U–B colour indices are presented for 461 bright galaxies ( δ > −50°) observed between 1960 and 1968 mainly with the McDonald Observatory 91-cm reflector. The Catalogue includes over 1000 observations by 13 observers in 219 nights. The mean error of one observation is ±0.04 mag in V , ±0.030 in B–V , and ±0.045 in U–B . Colour indices statistically corrected for galactic reddening and redshift ( B–V ) 0 , ( U–B ) 0 , and for aperture and inclination effects ( B–V ) 0c , ( U–B ) 0c are also listed. The latter are derived from new solutions for the colour–aperture–ellipticity relation as a function of morphological type (Section 7). Mean corrected colour indices (and corresponding metallicity index) are tabulated for each galaxy type along the revised Hubble sequence (Section 8). The luminosity effect in the colours of elliptical and lenticular galaxies is once again verified (Section 9); no such effect is indicated for spirals. For the latter, negative colour residuals are quantitatively related to spectral estimates of emission line intensities both for general line emission (Section 10(a)) and for nuclear emission in Seyfert galaxies (Section 10(b)). A normalized mean relation between (negative) colour excess and aperture ratio depending only on nuclear luminosity is derived for the Seyfert galaxies. Other colour anomalies are noted in appendices to the Catalogue and briefly reviewed in Section 11. Typical magnitude–aperture relations are illustrated in Section 12. The full text of the above appears in Memoirs of the Royal Astronomical Society , Volume 77, Part 1.