scholarly journals Spectral variability of a sample of extreme variability quasars and implications for the Mg ii broad-line region

2020 ◽  
Vol 493 (4) ◽  
pp. 5773-5787 ◽  
Author(s):  
Qian Yang ◽  
Yue Shen ◽  
Yu-Ching Chen ◽  
Xin Liu ◽  
James Annis ◽  
...  
Keyword(s):  
Dynamic Range ◽  
Sloan Digital Sky Survey ◽  
Spectral Variability ◽  
Dark Energy Survey ◽  
Line Region ◽  
Sky Survey ◽  
Balmer Lines ◽  
Extreme Variability ◽  
Single Epoch ◽  
Energy Survey

ABSTRACT We present new Gemini/GMOS optical spectroscopy of 16 extreme variability quasars (EVQs) that dimmed by more than 1.5 mag in the g band between the Sloan Digital Sky Survey (SDSS) and the Dark Energy Survey epochs (separated by a few years in the quasar rest frame). These EVQs are selected from quasars in the SDSS Stripe 82 region, covering a redshift range of 0.5 < z < 2.1. Nearly half of these EVQs brightened significantly (by more than 0.5 mag in the g band) in a few years after reaching their previous faintest state, and some EVQs showed rapid (non-blazar) variations of greater than 1–2 mag on time-scales of only months. To increase sample statistics, we use a supplemental sample of 33 EVQs with multi-epoch spectra from SDSS that cover the broad Mg ii λ2798 line. Leveraging on the large dynamic range in continuum variability between the multi-epoch spectra, we explore the associated variations in the broad Mg ii line, whose variability properties have not been well studied before. The broad Mg ii flux varies in the same direction as the continuum flux, albeit with a smaller amplitude, which indicates at least some portion of Mg ii is reverberating to continuum changes. However, the full width at half-maximum (FWHM) of Mg ii does not vary accordingly as continuum changes for most objects in the sample, in contrast to the case of the broad Balmer lines. Using the width of broad Mg ii to estimate the black hole mass with single epoch spectra therefore introduces a luminosity-dependent bias.

scholarly journals Extreme Variability Quasars from the Sloan Digital Sky Survey and the Dark Energy Survey

2018 ◽  
Vol 854 (2) ◽  
pp. 160 ◽  
Author(s):  
N. Rumbaugh ◽  
Yue Shen ◽  
Eric Morganson ◽  
Xin Liu ◽  
M. Banerji ◽  
...  
Keyword(s):  
Dark Energy ◽  
Sloan Digital Sky Survey ◽  
Dark Energy Survey ◽  
Sky Survey ◽  
Extreme Variability ◽  
Energy Survey

scholarly journals Candidate Periodically Variable Quasars from the Dark Energy Survey and the Sloan Digital Sky Survey

2020 ◽  
Author(s):  
Yu-Ching Chen ◽  
Xin Liu ◽  
Wei-Ting Liao ◽  
A Miguel Holgado ◽  
Hengxiao Guo ◽  
...  
Keyword(s):  
Black Holes ◽  
Dark Energy ◽  
Detection Rate ◽  
Sloan Digital Sky Survey ◽  
Light Curves ◽  
Close Binary ◽  
Single Frequency ◽  
Dark Energy Survey ◽  
Sky Survey ◽  
Energy Survey

Abstract Periodically variable quasars have been suggested as close binary supermassive black holes. We present a systematic search for periodic light curves in 625 spectroscopically confirmed quasars with a median redshift of 1.8 in a 4.6 deg2 overlapping region of the Dark Energy Survey Supernova (DES-SN) fields and the Sloan Digital Sky Survey Stripe 82 (SDSS-S82). Our sample has a unique 20-year long multi-color (griz) light curve enabled by combining DES-SN Y6 observations with archival SDSS-S82 data. The deep imaging allows us to search for periodic light curves in less luminous quasars (down to r ∼23.5 mag) powered by less massive black holes (with masses ≳ 108.5M⊙) at high redshift for the first time. We find five candidates with significant (at >99.74% single-frequency significance in at least two bands with a global p-value of ∼7 × 10−4–3× 10−3 accounting for the look-elsewhere effect) periodicity with observed periods of ∼3–5 years (i.e., 1–2 years in rest frame) having ∼4–6 cycles spanned by the observations. If all five candidates are periodically variable quasars, this translates into a detection rate of ${\sim }0.8^{+0.5}_{-0.3}$% or ${\sim }1.1^{+0.7}_{-0.5}$ quasar per deg2. Our detection rate is 4–80 times larger than those found by previous searches using shallower surveys over larger areas. This discrepancy is likely caused by differences in the quasar populations probed and the survey data qualities. We discuss implications on the future direct detection of low-frequency gravitational waves. Continued photometric monitoring will further assess the robustness and characteristics of these candidate periodic quasars to determine their physical origins.

scholarly journals The Milky Way’s total satellite population and constraining the mass of the warm dark matter particle

2018 ◽  
Vol 14 (S344) ◽  
pp. 109-113 ◽  
Author(s):  
Oliver Newton ◽  
Marius Cautun ◽  
Adrian Jenkins ◽  
Carlos S. Frenk ◽  
John C. Helly
Keyword(s):  
Dark Matter ◽  
Dark Matter Particle ◽  
Statistical Error ◽  
Sloan Digital Sky Survey ◽  
Dark Energy Survey ◽  
Satellite Galaxy ◽  
Sky Survey ◽  
Galaxy Luminosity Function ◽  
Energy Survey ◽  
Rule Out

AbstractThe Milky Way’s (MW) satellite population is a powerful probe of warm dark matter (WDM) models as the abundance of small substructures is very sensitive to the properties of the WDM particle. However, only a partial census of the MW’s complement of satellite galaxies exists because surveys of the MW’s close environs are incomplete both in depth and in sky coverage. We present a new Bayesian analysis that combines the sample of satellites recently discovered by the Dark Energy Survey (DES) with those found in the Sloan Digital Sky Survey (SDSS) to estimate the total satellite galaxy luminosity function down to Mv = 0. We find that there should be at least $124_{ - 27}^{ + 40}$ (68% CL, statistical error) satellites as bright or brighter than Mv = 0 within 300 kpc of the Sun, with only a weak dependence on MW halo mass. When it comes online the Large Synoptic Survey Telescope should detect approximately half of this population. We also show that WDM models infer the same number of satellites as in ΛCDM, which will allow us to rule out those models that produce insufficient substructure to be viable.

Statistics, Data Mining, and Machine Learning in Astronomy

2014 ◽  
Author(s):  
Željko Ivezic ◽  
Andrew J. Connolly ◽  
Jacob T VanderPlas ◽  
Alexander Gray
Keyword(s):  
Sloan Digital Sky Survey ◽  
Data Sets ◽  
Complex Data ◽  
Dark Energy Survey ◽  
Astronomical Surveys ◽  
Sky Survey ◽  
Different Types ◽  
Complex Data Sets ◽  
Coding Standards ◽  
Energy Survey

As telescopes, detectors, and computers grow ever more powerful, the volume of data at the disposal of astronomers and astrophysicists will enter the petabyte domain, providing accurate measurements for billions of celestial objects. This book provides a comprehensive and accessible introduction to the cutting-edge statistical methods needed to efficiently analyze complex data sets from astronomical surveys such as the Panoramic Survey Telescope and Rapid Response System, the Dark Energy Survey, and the upcoming Large Synoptic Survey Telescope. It serves as a practical handbook for graduate students and advanced undergraduates in physics and astronomy, and as an indispensable reference for researchers. The book presents a wealth of practical analysis problems, evaluates techniques for solving them, and explains how to use various approaches for different types and sizes of data sets. For all applications described in the book, Python code and example data sets are provided. The supporting data sets have been carefully selected from contemporary astronomical surveys (for example, the Sloan Digital Sky Survey) and are easy to download and use. The accompanying Python code is publicly available, well documented, and follows uniform coding standards. Together, the data sets and code enable readers to reproduce all the figures and examples, evaluate the methods, and adapt them to their own fields of interest.

scholarly journals Discovery of a Candidate Binary Supermassive Black Hole in a Periodic Quasar from Circumbinary Accretion Variability

2020 ◽  
Author(s):  
Wei-Ting Liao ◽  
Yu-Ching Chen ◽  
Xin Liu ◽  
A Miguel Holgado ◽  
Hengxiao Guo ◽  
...  
Keyword(s):  
Galaxy Formation ◽  
Sloan Digital Sky Survey ◽  
Light Curves ◽  
P Value ◽  
Kinematic Effect ◽  
Dark Energy Survey ◽  
Sky Survey ◽  
Laser Interferometer Space Antenna ◽  
The Look ◽  
Energy Survey

Abstract Binary supermassive black holes (BSBHs) are expected to be a generic byproduct from hierarchical galaxy formation. The final coalescence of BSBHs is thought to be the loudest gravitational wave (GW) siren, yet no confirmed BSBH is known in the GW-dominated regime. While periodic quasars have been proposed as BSBH candidates, the physical origin of the periodicity has been largely uncertain. Here we report discovery of a periodicity (P=1607±7 days) at 99.95% significance (with a global p-value of ∼10−3 accounting for the look elsewhere effect) in the optical light curves of a redshift 1.53 quasar, SDSS J025214.67−002813.7. Combining archival Sloan Digital Sky Survey data with new, sensitive imaging from the Dark Energy Survey, the total ∼20-yr time baseline spans ∼4.6 cycles of the observed 4.4-yr (restframe 1.7-yr) periodicity. The light curves are best fit by a bursty model predicted by hydrodynamic simulations of circumbinary accretion disks. The periodicity is likely caused by accretion rate modulation by a milli-parsec BSBH emitting GWs, dynamically coupled to the circumbinary accretion disk. A bursty hydrodynamic variability model is statistically preferred over a smooth, sinusoidal model expected from relativistic Doppler boost, a kinematic effect proposed for PG1302−102. Furthermore, the frequency dependence of the variability amplitudes disfavors Doppler boost, lending independent support to the circumbinary accretion variability hypothesis. Given our detection rate of one BSBH candidate from circumbinary accretion variability out of 625 quasars, it suggests that future large, sensitive synoptic surveys such as the Vera C. Rubin Observatory Legacy Survey of Space and Time may be able to detect hundreds to thousands of candidate BSBHs from circumbinary accretion with direct implications for Laser Interferometer Space Antenna.

scholarly journals Physical properties of emitting plasma near massive black holes: the Broad Line Region

2006 ◽  
Vol 2 (S238) ◽  
pp. 383-384
Author(s):  
D. Ilić ◽  
G. La Mura ◽  
L. Č Popović ◽  
A. I. Shapovalova ◽  
S. Ciroi ◽  
...  
Keyword(s):  
Galactic Nuclei ◽  
Sloan Digital Sky Survey ◽  
Time Variability ◽  
Broad Line ◽  
Boltzmann Plot ◽  
Massive Black Holes ◽  
Broad Line Region ◽  
Line Region ◽  
Sky Survey ◽  
Balmer Lines

AbstractWe apply the Boltzmann-Plot (BP) method to the Balmer lines to estimate the physical propertiesin the Broad Line Region of Active Galactic Nuclei. We study the Balmer lines of a sample of 90 AGN from Sloan Digital Sky Survey database, as well as the time variability of the BP parameter A of NGC 5548.

scholarly journals Are sdAs helium core stars?

2017 ◽  
Vol 26 (1) ◽  
Author(s):  
Ingrid Pelisoli ◽  
S. O. Kepler ◽  
Detlev Koester
Keyword(s):  
Main Sequence ◽  
Galactic Disk ◽  
Physical Nature ◽  
Sloan Digital Sky Survey ◽  
Distance Modulus ◽  
Main Sequence Stars ◽  
Sky Survey ◽  
Balmer Lines ◽  
Low Mass ◽  
Binary Evolution

AbstractEvolved stars with a helium core can be formed by non-conservative mass exchange interaction with a companion or by strong mass loss. Their masses are smaller than 0.5 M⊙. In the database of the Sloan Digital Sky Survey (SDSS), there are several thousand stars which were classified by the pipeline as dwarf O, B and A stars. Considering the lifetimes of these classes on the main sequence, and their distance modulus at the SDSS bright saturation, if these were common main sequence stars, there would be a considerable population of young stars very far from the galactic disk. Their spectra are dominated by Balmer lines which suggest effective temperatures around 8 000-10 000 K. Several thousand have significant proper motions, indicative of distances smaller than 1 kpc. Many show surface gravity in intermediate values between main sequence and white dwarf, 4.75 < log g < 6.5, hence they have been called sdA stars. Their physical nature and evolutionary history remains a puzzle. We propose they are not H-core main sequence stars, but helium core stars and the outcomes of binary evolution. We report the discovery of two new extremely-low mass white dwarfs among the sdAs to support this statement.

scholarly journals Clustering and Halo Occupation Distribution of Active Galactic Nuclei

2013 ◽  
Vol 9 (S304) ◽  
pp. 243-243
Author(s):  
Takamitsu Miyaji ◽  
M. Krumpe ◽  
A. Coil ◽  
H. Aceves ◽  
B. Husemann
Keyword(s):  
Cross Correlation ◽  
Dynamic Range ◽  
Signal To Noise Ratio ◽  
Sloan Digital Sky Survey ◽  
Dark Matter Halo ◽  
Bias Parameter ◽  
X Ray ◽  
Sky Survey ◽  
Galaxy Population ◽  
Halo Occupation Distribution

AbstractWe present the results of our series of studies on correlation function and halo occupation distribution of AGNs utilizing data the ROSAT All-Sky Survey (RASS) and the Sloan Digital Sky Survey (SDSS) in the redshift range of 0.07<z<0.36. In order to improve the signal-to-noise ratio, we take cross-correlation approach, where cross-correlation functions (CCF) between AGNs and much more numerous AGNs are analyzed. The calculated CCFs are analyzed using the Halo Occupation Distribution (HOD) model, where the CCFs are divided into the term contributed by the AGN-galaxy pairs that reside in one dark matter halo (DMH), (the 1-halo term) and those from two different DMHs (the 2-halo term). The 2-halo term is the indicator of the bias parameter, which is a function of the typical mass of the DMHs in which AGNs reside. The combination of the 1-halo and 2-halo terms gives, not only the typical DMH mass, but also how the AGNs are distributed among the DMHs as a function of mass separately for those at the center of the DMHs and satellites. The main results are as follows: (1) the range of typical mass of the DMHs in various sub-samples of AGNs log (MDMH/h−1MΘ) ~ 12.4–13.4, (2) we found a dependence of the AGN bias parameter on the X-ray luminosity of AGNs, while the optical luminosity dependence is not significant probably due to smaller dynamic range in luminosity for the optically-selected sample, and (3) the growth of the number of AGNs per DMH (N (MDMH)) with MDMH is shallow, or even may be flat, contrary to that of the galaxy population in general, which grows with MDMH proportionally, suggesting a suppression of AGN triggering in denser environment. In order to investigate the origin of the X-ray luminosity dependence, we are also investigating the dependence of clustering on the black hole mass and the Eddington ratio, we also present the results of this investigation.

scholarly journals Producing a BOSS CMASS sample with DES imaging

2019 ◽  
Vol 489 (2) ◽  
pp. 2887-2906 ◽  
Author(s):  
S Lee ◽  
E M Huff ◽  
A J Ross ◽  
A Choi ◽  
C Hirata ◽  
...  
Keyword(s):  
Sloan Digital Sky Survey ◽  
Joint Analysis ◽  
Dark Energy Survey ◽  
Sky Survey ◽  
Angular Correlation Function ◽  
Galaxy Sample ◽  
Celestial Equator ◽  
The Difference ◽  
Galaxy Bias ◽  
Validation Tests

ABSTRACT We present a sample of galaxies with the Dark Energy Survey (DES) photometry that replicates the properties of the BOSS CMASS sample. The CMASS galaxy sample has been well characterized by the Sloan Digital Sky Survey (SDSS) collaboration and was used to obtain the most powerful redshift-space galaxy clustering measurements to date. A joint analysis of redshift-space distortions (such as those probed by CMASS from SDSS) and a galaxy–galaxy lensing measurement for an equivalent sample from DES can provide powerful cosmological constraints. Unfortunately, the DES and SDSS-BOSS footprints have only minimal overlap, primarily on the celestial equator near the SDSS Stripe 82 region. Using this overlap, we build a robust Bayesian model to select CMASS-like galaxies in the remainder of the DES footprint. The newly defined DES-CMASS (DMASS) sample consists of 117 293 effective galaxies covering $1244\,\deg ^2$. Through various validation tests, we show that the DMASS sample selected by this model matches well with the BOSS CMASS sample, specifically in the South Galactic cap (SGC) region that includes Stripe 82. Combining measurements of the angular correlation function and the clustering-z distribution of DMASS, we constrain the difference in mean galaxy bias and mean redshift between the BOSS CMASS and DMASS samples to be $\Delta b = 0.010^{+0.045}_{-0.052}$ and $\Delta z = \left(3.46^{+5.48}_{-5.55} \right) \times 10^{-3}$ for the SGC portion of CMASS, and $\Delta b = 0.044^{+0.044}_{-0.043}$ and $\Delta z= (3.51^{+4.93}_{-5.91}) \times 10^{-3}$ for the full CMASS sample. These values indicate that the mean bias of galaxies and mean redshift in the DMASS sample are consistent with both CMASS samples within 1σ.

scholarly journals The Sloan Digital Sky Survey Reverberation Mapping Project: Estimating Masses of Black Holes in Quasars with Single-epoch Spectroscopy

2020 ◽  
Vol 903 (2) ◽  
pp. 112
Author(s):  
Elena Dalla Bontà ◽  
Bradley M. Peterson ◽  
Misty C. Bentz ◽  
W. N. Brandt ◽  
S. Ciroi ◽  
...  
Keyword(s):  
Black Holes ◽  
Sloan Digital Sky Survey ◽  
Reverberation Mapping ◽  
Sky Survey ◽  
Single Epoch
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