arXiv subjects

Charles L. Steinhardt

Publications and source records attributed to Charles L. Steinhardt.

62 records · Page 4Linked to original sources

arXiv2011

Do Anomalous Narrow Line Quasars Cast Doubt on Virial Mass Estimation?

Anomalous Narrow-Line Quasars (ANLs) are a population of quasars with narrow Hβ, and sometimes [O III] broader than ~1000 km/s, in total comprising \sim 10-30% (most likely ~25%) of Type I quasars at 0.2 < z < 0.8. We find that virial masses using the Hβand Mg II lines systematically differ for ANLs by an average of as much as 0.5 dex. Because the broad Hβcomponent width increases in ANLs but Mg II does not, we might suspect Hβ-based virial masses for ANLs are wrong but Mg II masses are correct. If this is due to an outflow reaching the lower-ionization potential Hβline, C IV masses will be similarly flawed. However, we cannot be certain of this explanation without followup work, and may be unable to identify which quasars are ANLs at z > 0.8. Therefore, it is essential that ANLs be well-understood and well-modeled in order to allow the use of virial mass estimators on large optical spectroscopic catalogs, particularly at z < 0.4 and z > 2.0 where only one broad line is available for use in mass estimation.

astro-ph.HE↗

arXiv2011

Effects of Biases in Virial Mass Estimation on Cosmic Synchronization of Quasar Accretion

Recent work using virial mass estimates and the quasar mass-luminosity plane has yielded several new puzzles regarding quasar accretion, including a sub-Eddington boundary on most quasar accretion, near-independence of the accretion rate from properties of the host galaxy, and a cosmic synchronization of accretion among black holes of a common mass. We consider how these puzzles might change if virial mass estimation turns out to have a systematic bias. As examples, we consider two recent claims of mass-dependent biases in MgII masses. Under any such correction, the surprising cosmic synchronization of quasar accretion rates and independence from the host galaxy remain. The slope and location of the sub-Eddington boundary are very sensitive to biases in virial mass estimation, and various mass calibrations appear to favor different possible physical explanations for feedback between the central black hole and its environment. The alternative mass estimators considered do not simply remove puzzling quasar behavior, but rather replace it with new puzzles that may be more difficult to solve than those using current virial mass estimators and the Shen et al. (2008) catalog.

astro-ph.HE↗

arXiv2011

Evolutionary Tracks of Individual Quasars in the Mass-Luminosity Plane

Previous work on the quasar mass-luminosity plane indicates the possibility that quasars of the same central black hole mass might follow a common evolutionary track, independent of the properties of the host galaxy. We consider two simple models for the evolution of individual quasars. Requiring these tracks to lie within the observed quasar locus at all redshifts strongly constrains the model parameters, but does allow some solutions. These solutions include a family of tracks with similar shape but different initial masses that might match the observed quasar distributions at all redshifts z < 2.0. This family of solutions is characterized by short (1-2 Gyr) lifetimes, a duty cycle in which the quasar is on at least 25% of the time, and a rapid decline in Eddington ratio, perhaps with L/L_Edd ~ t^-6 or steeper.

astro-ph.HE↗

arXiv2010

The Quasar Mass-Luminosity Plane I: A Sub-Eddington Limit for Quasars

We use 62185 quasars from the Sloan Digital Sky Survey Data Release 5 sample to explore the relationship between black hole mass and luminosity. Black hole masses were estimated based on the widths of their Hβ, MgII and CIV lines and adjacent continuum luminosities using standard virial mass estimate scaling laws. We find that, over the range 0.2 < z < 4.0, the most luminous low-mass quasars are at their Eddington luminosity, but the most luminous high-mass quasars in each redshift bin fall short of their Eddington luminosities, with the shortfall of the order of 10 or more at 0.2 < z < 0.6. We examine several potential sources of measurement uncertainty or bias and show that none of them can account for this effect. We also show the statistical uncertainty in virial mass estimation to have an upper bound of ~0.15 dex, smaller than the 0.4 dex previously reported. We also examine the highest mass quasars in every redshift bin in an effort to learn more about quasars that are about to cease their luminous accretion. We conclude that the quasar mass-luminosity locus contains a number of new puzzles that must be explained theoretically.

astro-ph.HE↗

arXiv2010

The Quasar Mass-Luminosity Plane III: Smaller Errors on Virial Mass Estimates

We use 62185 quasars from the Sloan Digital Sky Survey (SDSS) DR5 sample to explore the quasar mass-luminosity plane view of virial mass estimation. Previous work shows deviations of ~0.4 dex between virial and reverberation masses. The decline in quasar number density for the highest Eddington ratio quasars at each redshift provides an upper bound of between 0.13 and 0.29 dex for virial mass estimate statistical uncertainties. Across different redshift bins, the maximum possible MgII mass uncertainties average 0.15 dex, while Hβ uncertainties average 0.21 dex and CIV uncertainties average 0.27 dex. Any physical spread near the high-Eddington-ratio boundary will produce a more restrictive bound. A comparison of the sub-Eddington boundary slope using Hβ and MgII masses finds better agreement with uncorrected MgII masses than with recently proposed corrections. The best agreement for these bright objects is produced by a multiplicative correction by a factor of 1.19, smaller than the factor of 1.8 previously reported as producing the best agreement for the entire SDSS sample.

astro-ph.HE↗

arXiv2009

The Quasar Mass-Luminosity Plane II: High Mass Turnoff Evolution and a Synchronization Puzzle

We use 62,185 quasars from the Sloan Digital Sky Survey DR5 sample and standard virial mass scaling laws based on the widths of H beta, Mg II, and C IV lines and adjacent continuum luminosities to explore the maximum mass of quasars as a function of redshift, which we find to be sharp and evolving. This evolution is in the sense that high-mass black holes cease their luminous accretion at higher redshift than lower-mass black holes. Further, turnoff for quasars at any given mass is more highly synchronized than would be expected given the dynamics of their host galaxies. We investigate potential signatures of the quasar turnoff mechanism, including a dearth of high-mass quasars at low Eddington ratio. These new results allow a closer examination of several common assumptions used in modeling quasar accretion and turnoff.

astro-ph.HE↗

arXiv2004

Constraints on Field Theoretical Models for Variation of the Fine Structure Constant

Recent theoretical ideas and observational claims suggest that the fine structure constant alpha may be variable. We examine a spectrum of models in which alpha is a function of a scalar field. Specifically, we consider three scenarios: oscillating alpha, monotonic time variation of alpha, and time-independent alpha that is spatially varying. We examine the constraints imposed upon these theories by cosmological observations, particle detector experiments, and ``fifth force'' experiments. These constraints are very strong on models involving oscillation, but cannot compete with bounds from the Oklo sub-nuclear reactor on models with monotonic time-like variation of alpha. One particular model with spatial variation is consistent with all current experimental and observational measurements, including those from two seemingly conflicting measurements of the fine structure constant using the many multiplet method on absorption lines.

hep-ph↗

arXiv2003

Does the fine-structure constant vary with cosmological epoch?

We use the strong nebular lines of O III, 5007 A and 4959 A, to set a robust upper limit on the time dependence of the fine structure constant. We find |alpha^{-1} d alpha(t)/dt | < 2*10^{-13} yr, corresponding to Delta alpha/alpha(0) = (0.7 +- 1.4) * 10^{-4} for quasars with 0.16 < z < 0.80 obtained from the SDSS Early Data Release. Using a blind analysis, we show that the upper limit given here is invariant with respect to 17 different ways of selecting the sample and analyzing the data. As a by-product, we show that the ratio of transition probabilities for the 5007 A and the 4959 A lines is2.99 +- 0.02, in good agreement with (but more accurate than) theoretical estimates. We compare and contrast the O III emission line method used here with the Many-Multiplet method that has been used recently to suggest evidence for a time-dependent alpha. In an Appendix, we have analyzed the larger quasar sample from the SDSS Data Release One Sample and find Delta alpha/alpha(0) = (1.2 +- 0.7) * 10^{-4}.

astro-ph↗