5 research outputs found
Observing Supermassive Black Holes across cosmic time: from phenomenology to physics
In the last decade, a combination of high sensitivity, high spatial
resolution observations and of coordinated multi-wavelength surveys has
revolutionized our view of extra-galactic black hole (BH) astrophysics. We now
know that supermassive black holes reside in the nuclei of almost every galaxy,
grow over cosmological times by accreting matter, interact and merge with each
other, and in the process liberate enormous amounts of energy that influence
dramatically the evolution of the surrounding gas and stars, providing a
powerful self-regulatory mechanism for galaxy formation. The different
energetic phenomena associated to growing black holes and Active Galactic
Nuclei (AGN), their cosmological evolution and the observational techniques
used to unveil them, are the subject of this chapter. In particular, I will
focus my attention on the connection between the theory of high-energy
astrophysical processes giving rise to the observed emission in AGN, the
observable imprints they leave at different wavelengths, and the methods used
to uncover them in a statistically robust way. I will show how such a combined
effort of theorists and observers have led us to unveil most of the SMBH growth
over a large fraction of the age of the Universe, but that nagging
uncertainties remain, preventing us from fully understating the exact role of
black holes in the complex process of galaxy and large-scale structure
formation, assembly and evolution.Comment: 46 pages, 21 figures. This review article appears as a chapter in the
book: "Astrophysical Black Holes", Haardt, F., Gorini, V., Moschella, U and
Treves A. (Eds), 2015, Springer International Publishing AG, Cha
BASS. XXV. DR2 broad-line-based black hole mass estimates and biases from obscuration
We present measurements of broad emission lines and virial estimates of
supermassive black hole masses () for a large sample of ultra-hard
X-ray selected active galactic nuclei (AGNs) as part of the second data release
of the BAT AGN Spectroscopic Survey (BASS/DR2). Our catalog includes
estimates for a total 689 AGNs, determined from the H, H,
, and/or broad emission lines. The core
sample includes a total of 512 AGNs drawn from the 70-month Swift/BAT all-sky
catalog. We also provide measurements for 177 additional AGNs that are drawn
from deeper Swift/BAT survey data. We study the links between
estimates and line-of-sight obscuration measured from X-ray spectral analysis.
We find that broad H emission lines in obscured AGNs () are on average a factor of
weaker, relative to ultra-hard X-ray emission, and about \%
narrower than in unobscured sources (i.e., ). This indicates that the innermost part of the broad-line region is
preferentially absorbed. Consequently, current single-epoch
prescriptions result in severely underestimated (1 dex) masses for Type 1.9
sources (AGNs with broad H but no broad H) and/or sources with
. We provide simple multiplicative
corrections for the observed luminosity and width of the broad H
component ( and FWHM[bH]) in such sources to
account for this effect, and to (partially) remedy estimates for Type
1.9 objects. As key ingredient of BASS/DR2, our work provides the community
with the data needed to further study powerful AGNs in the low-redshift
Universe.Comment: published in ApJ
BASS. XXV. DR2 broad-line-based black hole mass estimates and biases from obscuration
Galaxie
The Sloan Digital Sky Survey-II Supernova Survey: Technical Summary
The Sloan Digital Sky Survey-II (SDSS-II) has embarked on a multi-year project to identify and measure light curves for intermediate-redshift (0.05 < z < 0.35) Type Ia supernovae (SNe Ia) using repeated five-band (ugriz) imaging over an area of 300 sq. deg. The survey region is a stripe 2.5° wide centered on the celestial equator in the Southern Galactic Cap that has been imaged numerous times in earlier years, enabling construction of a deep reference image for the discovery of new objects. Supernova imaging observations are being acquired between September 1 and November 30 of 2005-7. During the first two seasons, each region was imaged on average every five nights. Spectroscopic follow-up observations to determine supernova type and redshift are carried out on a large number of telescopes. In its first two three-month seasons, the survey has discovered and measured light curves for 327 spectroscopically confirmed SNe Ia, 30 probable SNe Ia, 14 confirmed SNe Ib/c, 32 confirmed SNe II, plus a large number of photometrically identified SNe Ia, 94 of which have host-galaxy spectra taken so far. This paper provides an overview of the project and briefly describes the observations completed during the first two seasons of operation