Radius-luminosity Relation Research Articles

Radius‐dependent Luminosity Evolution of Blue Galaxies in GOODS‐N

We examine the radius-luminosity (R-L) relation for blue galaxies in the Team Keck Redshift Survey (TKRS) of GOODS-N. We compare with a volume-limited, Sloan Digital Sky Survey sample and find that the R-L relation has evolved to lower surface brightness since z=1. Based on the detection limits of GOODS this can not be explained by incompleteness in low surface-brightness galaxies. Number density arguments rule out a pure radius evolution. It can be explained by a radius dependent decline in B-band luminosity with time. Assuming a linear shift in M_B with z, we use a maximum likelihood method to quantify the evolution. Under these assumptions, large (R_{1/2} > 5 kpc), and intermediate sized (3 < R_{1/2} < 5 kpc) galaxies, have experienced Delta M_B =1.53 (-0.10,+0.13) and 1.65 (-0.18, +0.08) magnitudes of dimming since z=1. A simple exponential decline in star formation with an e-folding time of 3 Gyr can result in this amount of dimming. Meanwhile, small galaxies, or some subset thereof, have experienced more evolution, 2.55 (+/- 0.38) magnitudes. This factor of ten decline in luminosity can be explained by sub-samples of starbursting dwarf systems that fade rapidly, coupled with a decline in burst strength or frequency. Samples of bursting, luminous, blue, compact galaxies at intermediate redshifts have been identified by various previous studies. If there has been some growth in galaxy size with time, these measurements are upper limits on luminosity fading.

Implications of Quasar Black Hole Masses at High Redshifts

We investigated a sample of 15 luminous high-redshift quasars (3.3 z 5.1) to measure the mass of their supermassive black holes (SMBH) and compare, for the first time, results based on C IV, Mg II, and H? emission lines at high redshifts. Assuming gravitationally bound orbits as dominant broad-line region gas motion, we determine black hole masses in the range of Mbh 2 ? 108 up to Mbh 4 ? 1010 M?. While the black hole mass estimates based on C IV and H? agree well, Mg II typically indicates a factor of ~5 times lower SMBH masses. A flatter slope of the H? radius-luminosity relation, a possibly steeper slope of the Mg II radius-luminosity relation, and a slightly larger radius of the Mg II broad-line region than for H? could relax the discrepancy. In spite of these uncertainties, the C IV, Mg II, and H? emission lines consistently indicate supermassive black hole masses of several times 109 M? at redshifts up to z = 5.1. Assuming logarithmic growth by spherical accretion with a mass-to-energy conversion efficiency of = 0.1 and an Eddington ratio Lbol/Ledd calculated for each quasar individually, we estimate black hole growth times of the order of several ~100 Myr which are smaller than the age of the universe at the corresponding redshift. Assuming high-mass seed black holes (M = 103-105 M?) the SMBHs in the z 3.5 quasars began to grow at redshifts z 4, while for the quasars with z 4.5 they started at z 6 to 10. These estimated timescales for forming SMBHs at high redshifts, together with previous studies indicating high quasar metallicities, suggest that the main SMBH growth phase occurs roughly contemporaneously with a period of violent and extensive star formation in protogalactic nuclei.

On the Nature of Low‐Luminosity Narrow‐Line Active Galactic Nuclei

There is clear observational evidence that some narrow-line (type 2) active galactic nuclei (AGNs) have a hidden broad-line region (BLR) and are thus intrinsically broad-line (type 1) AGNs. Does this AGN unification apply for all type 2 AGNs? Indirect arguments suggest that some type 2 AGNs, i.e., AGNs having no obscured BLR, do exist, but it is not clear why the BLR is missing in these AGNs. Here we point out a possible natural explanation. The observed radius-luminosity relation for the BLR implies an increasing line width with decreasing luminosity for a given black hole mass (MBH). In addition, there appears to be an upper limit to the observed width of broad emission lines in AGNs of Δvmax ~ 25,000 km s-1, which may reflect a physical limit above which the BLR may not be able to survive. Thus, at a low enough luminosity the BLR radius shrinks below the Δvmax radius, leaving no region where the BLR can exist, although the AGN may remain otherwise normal. The implied minimum bolometric luminosity required to sustain a BLR with Δv < 25,000 km s-1 is Lmin ~ 1041.8(MBH/108 M☉)2. All AGNs with L < Lmin are expected to be type 2 AGNs, i.e., narrow-line AGNs without a hidden BLR. Predictions for the true nature of low-luminosity AGNs in two samples of nearby galaxies are provided. These can be used to test the above Lmin conjecture and the predictions of other models for the size and origin of the BLR.

The radius-mass relation for clusters of galaxies - Cosmological scenarios versus observations

The relationship between the characteristic radii and masses (luminosities) of rich clusters of galaxies is studied using N-body simulations in comparison with observations. Various scenarios for the formation of the large-scale structure of the universe within the gravitational instability picture are considered, including hierarchical clustering, pancake, and hybrid scenarios. A well-defined radius-mass relation is found for the simulated clusters in each model, the slope of which depends on the form of the initial density fluctuation spectrum. The radius-luminosity relation is also studied for a sample of 29 Abell clusters, and a well-defined correlation is found to exist, R is proportional to L^0.51 +/= 0.07^. If M/L is roughly the same among clusters, and if the distributions of light and mass are similar, then best agreement with the observations is found for an initial spectrum with an effective slope -1 &lt;= n &lt;= 0 on the scale of protoclusters, as is expected in such scenarios as cold dark matter, isocurvature baryonic models, and certain hybrid scenarios. The pancake scenario, on the other hand, may have difficulty reproducing the observed radius-luminosity relation.

V ZW 311 - The once and future cD

view Abstract Citations (49) References (23) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS VZW 311 : the once and future CD ? Schneider, D. P. ; Gunn, J. E. Abstract Recent observations indicate that 'cannibalism' among first-ranked cluster ellipticals almost certainly occurs. Nearly 30% of first-ranked galaxies have multiple nuclei, the merger time scales for which are all very short. Dynamical evidence from the structure of the galaxies themselves, such as the radius-luminosity relation having the form predicted by simple cannibalism models to quite high accuracy, concurs with the merger predictions. The present investigation is concerned with a multiple-nucleus system, the peculiar central 'galaxy' in the poor cluster V Zw 311 (Zwicky 1971), which is also 407 in the catalog of Abell (1958). This remarkable object has many compact nuclei embedded in a luminous matrix. At least nine condensations with luminosities comparable to the outlying cluster galaxies make up the central object. Attention is given to the spectroscopic observations, details of photometry, and three different dynamical systems, including the inner nuclei, the envelope, and the cluster as a whole. Publication: The Astrophysical Journal Pub Date: December 1982 DOI: 10.1086/160475 Bibcode: 1982ApJ...263...14S Keywords: Elliptical Galaxies; Galactic Clusters; Galactic Evolution; Galactic Nuclei; Galactic Structure; Astronomical Maps; Luminosity; Peculiar Galaxies; Red Shift; Spectrophotometry; Spectrum Analysis; Astrophysics full text sources ADS | data products SIMBAD (18) NED (17)