Selection bias in the M_BH-sigma and M_BH-L correlations and its consequences

It is common to estimate black hole abundances by using a measured correlation between black hole mass and another more easily measured observable such as the velocity dispersion or luminosity of the surrounding bulge. The correlation is used to transform the distribution of the observable into an estimate of the distribution of black hole masses. However, different observables provide different estimates: the Mbh-sigma relation predicts fewer massive black holes than does the Mbh-L relation. This is because the sigma-L relation in black hole samples currently available is inconsistent with that in the SDSS sample, from which the distributions of L or sigma are based: the black hole samples have smaller L for a given sigma or have larger sigma for a given L. This is true whether L is estimated in the optical or in the NIR. If this is a selection rather than physical effect, then the Mbh-sigma and Mbh-L relations currently in the literature are also biased from their true values. We provide a framework for describing the effect of this bias. We then combine it with a model of the bias to make an estimate of the true intrinsic relations. While we do not claim to have understood the source of the bias, our simple model is able to reproduce the observed trends. If we have correctly modeled the selection effect, then our analysis suggests that the bias in the relation is likely to be small, whereas the relation is biased towards predicting more massive black holes for a given luminosity. In addition, it is likely that the Mbh-L relation is entirely a consequence of more fundamental relations between Mbh and sigma, and between sigma and L. The intrinsic relation we find suggests that at fixed luminosity, older galaxies tend to host more massive black holes.Comment: 12 pages, 7 figures. Accepted by ApJ. We have added a figure showing that a similar bias is also seen in the K-band. A new appendix describes the BH samples as well as the fits used in the main tex

The luminosity and stellar mass Fundamental Plane of early-type galaxies

From a sample of ~50000 early-type galaxies from the SDSS, we measured the traditional Fundamental Plane in four bands. We then replaced luminosity with stellar mass, and measured the "stellar mass" FP. The FP steepens slightly as one moves from shorter to longer wavelengths: the orthogonal fit has slope 1.40 in g and 1.47 in z. The FP is thinner at longer wavelengths: scatter is 0.062 dex in g, 0.054 dex in z. The scatter is larger at small galaxy sizes/masses; at large masses measurement errors account for essentially all of the observed scatter. The FP steepens further when luminosity is replaced with stellar mass, to slope ~ 1.6. The intrinsic scatter also reduces further, to 0.048 dex. Since color and stellar mass-to-light ratio are closely related, this explains why color can be thought of as the fourth FP parameter. However, the slope of the stellar mass FP remains shallower than the value of 2 associated with the virial theorem. This is because the ratio of dynamical to stellar mass increases at large masses as M_d^0.17. The face-on view of the stellar mass kappa-space suggests that there is an upper limit to the stellar density for a given dynamical mass, and this decreases at large masses: M_*/R_e^3 ~ M_d^-4/3. We also study how the estimated coefficients a and b of the FP are affected by other selection effects (e.g. excluding small sigma biases a high; excluding fainter L biases a low). These biases are seen in FPs which have no intrinsic curvature, so the observation that a and b scale with L and sigma is not, by itself, evidence that the Plane is warped. We show that the FP appears to curve sharply downwards at the small mass end, and more gradually downwards towards larger masses. Whereas the drop at small sizes is real, most of the latter effect is due to correlated errors.Comment: 17 pages, 15 figures, MNRAS in press. Added appendix on possible sample contamination by disk

The luminosities, sizes and velocity dispersions of Brightest Cluster Galaxies: Implications for formation history

The size-luminosity relation of early-type Brightest Cluster Galaxies (BCGs), R_e ~ L^0.88, is steeper than that for the bulk of the early-type galaxy population, for which R_e ~ L^0.68. In addition, although BCGs are hardly offset from the Fundamental Plane defined by the bulk of the early-type population, they show considerably smaller scatter. The larger than expected sizes of BCGs, and the increased homogeneity, are qualitatively consistent with models which seek to explain the colors of the most massive galaxies by invoking dry dissipationless mergers, since dissipation tends to reduce the sizes of galaxies, and wet mergers which result in star formation would tend to increase the scatter in luminosity at fixed size and velocity dispersion. Furthermore, BCGs define the same g-r color-magnitude relation as the bulk of the early-type population. If BCGs formed from dry mergers, then BCG progenitors must have been red for their magnitudes, suggesting that they hosted older stellar populations than typical for their luminosities. Our findings have two other consequences. First, the R_e-L relation of the early-type galaxy population as a whole (i.e., normal plus BCG) exhibits some curvature. Some of this curvature must be a consequence of the fact that an increasing fraction of the most luminous galaxies are BCGs. The second consequence is suggested by the fact that, despite following a steeper size-luminosity relation, BCGs tend to define a tight relation between dynamical mass R_e sigma^2/G and luminosity. As consequence, we find that BCGs define a shallower sigma-L relation than the bulk of the early-type galaxy population.Comment: 16 pages, 16 figures, AJ in pres

Curvature in the scaling relations of early-type galaxies

We select a sample of about 50,000 early-type galaxies from the Sloan Digital Sky Survey (SDSS), calibrate fitting formulae which correct for known problems with photometric reductions of extended objects, apply these corrections, and then measure a number of pairwise scaling relations in the corrected sample. We show that, because they are not seeing corrected, the use of Petrosian-based quantities in magnitude limited surveys leads to biases, and suggest that this is one reason why Petrosian-based analyses of BCGs have failed to find significant differences from the bulk of the early-type population. These biases are not present when seeing-corrected parameters derived from deVaucouleur fits are used. Most of the scaling relations we study show evidence for curvature: the most luminous galaxies have smaller velocity dispersions, larger sizes, and fainter surface brightnesses than expected if there were no curva-ture. These statements remain true if we replace luminosities with stellar masses; they suggest that dissipation is less important at the massive end. There is curvature in the dynamical to stellar mass relation as well: the ratio of dynamical to stellar mass increases as stellar mass increases, but it curves upwards from this scaling both at small and large stellar masses. In all cases, the curvature at low masses becomes apparent when the sample becomes dominated by objects with stellar masses smaller than 3 x 10^10 M_Sun. We quantify all these trends using second order polynomials; these generally provide significantly better description of the data than linear fits, except at the least luminous end.Comment: 15 pages, 17 figures, Accepted by MNRA

Sizes and ages of SDSS ellipticals: Comparison with hierarchical galaxy formation models

In a sample of about 45,700 early-type galaxies extracted from SDSS, we find that the shape, normalization, and dispersion around the mean size-stellar mass relation is the same for young and old systems, provided the stellar mass is greater than 3*10^10 Msun. This is difficult to reproduce in pure passive evolution models, which generically predict older galaxies to be much more compact than younger ones of the same stellar mass. However, this aspect of our measurements is well reproduced by hierarchical models of galaxy formation. Whereas the models predict more compact galaxies at high redshifts, subsequent minor, dry mergers increase the sizes of the more massive objects, resulting in a flat size-age relation at the present time. At lower masses, the models predict that mergers are less frequent, so that the expected anti-correlation between age and size is not completely erased. This is in good agreement with our data: below 3*10^10 Msun, the effective radius R_e is a factor of ~2 lower for older galaxies. These successes of the models are offset by the fact that the predicted sizes have other serious problems, which we discuss.Comment: 13 pages, 9 Figures, 1 Table. Accepted by MNRA

The Seventh Data Release of the Sloan Digital Sky Survey

This paper describes the Seventh Data Release of the Sloan Digital Sky Survey (SDSS), marking the completion of the original goals of the SDSS and the end of the phase known as SDSS-II. It includes 11663 deg^2 of imaging data, with most of the roughly 2000 deg^2 increment over the previous data release lying in regions of low Galactic latitude. The catalog contains five-band photometry for 357 million distinct objects. The survey also includes repeat photometry over 250 deg^2 along the Celestial Equator in the Southern Galactic Cap. A coaddition of these data goes roughly two magnitudes fainter than the main survey. The spectroscopy is now complete over a contiguous area of 7500 deg^2 in the Northern Galactic Cap, closing the gap that was present in previous data releases. There are over 1.6 million spectra in total, including 930,000 galaxies, 120,000 quasars, and 460,000 stars. The data release includes improved stellar photometry at low Galactic latitude. The astrometry has all been recalibrated with the second version of the USNO CCD Astrograph Catalog (UCAC-2), reducing the rms statistical errors at the bright end to 45 milli-arcseconds per coordinate. A systematic error in bright galaxy photometr is less severe than previously reported for the majority of galaxies. Finally, we describe a series of improvements to the spectroscopic reductions, including better flat-fielding and improved wavelength calibration at the blue end, better processing of objects with extremely strong narrow emission lines, and an improved determination of stellar metallicities. (Abridged)Comment: 20 pages, 10 embedded figures. Accepted to ApJS after minor correction

Exclusive Photoproduction of the Cascade (Xi) Hyperons

We report on the first measurement of exclusive Xi-(1321) hyperon photoproduction in gamma p --> K+ K+ Xi- for 3.2 < E(gamma) < 3.9 GeV. The final state is identified by the missing mass in p(gamma,K+ K+)X measured with the CLAS detector at Jefferson Laboratory. We have detected a significant number of the ground-state Xi-(1321)1/2+, and have estimated the total cross section for its production. We have also observed the first excited state Xi-(1530)3/2+. Photoproduction provides a copious source of Xi's. We discuss the possibilities of a search for the recently proposed Xi5-- and Xi5+ pentaquarks.Comment: submitted to Phys. Rev.

Endomembrane targeting of human OAS1 p46 augments antiviral activity

Many host RNA sensors are positioned in the cytosol to detect viral RNA during infection. However, most positive-strand RNA viruses replicate within a modified organelle co-opted from intracellular membranes of the endomembrane system, which shields viral products from cellular innate immune sensors. Targeting innate RNA sensors to the endomembrane system may enhance their ability to sense RNA generated by viruses that use these compartments for replication. Here, we reveal that an isoform of oligoadenylate synthetase 1, OAS1 p46, is prenylated and targeted to the endomembrane system. Membrane localization of OAS1 p46 confers enhanced access to viral replication sites and results in increased antiviral activity against a subset of RNA viruses including flaviviruses, picornaviruses, and SARS-CoV-2. Finally, our human genetic analysis shows that the OAS1 splice-site SNP responsible for production of the OAS1 p46 isoform correlates with protection from severe COVID-19. This study highlights the importance of endomembrane targeting for the antiviral specificity of OAS1 and suggests that early control of SARS-CoV-2 replication through OAS1 p46 is an important determinant of COVID-19 severity