J/MNRAS/482/98 Search for outburst events in 1.4 million galaxies (Drake+, 2019)
Results of a systematic search for outburst events in 1.4 million galaxies.
Drake A.J., Djorgovski S.G., Graham M.J., Stern D., Mahabal A.A.,
Catelan M., Christensen E., Larson S.
<Mon. Not. R. Astron. Soc., 482, 98-117 (2019)>
=2019MNRAS.482...98D 2019MNRAS.482...98D (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, photometry ; Active gal. nuclei ; Supernovae
Keywords: galaxies: general - galaxies: active - galaxies: photometry -
supernovae: general
Abstract:
We present an analysis of 9yr of Catalina Surveys optical photometry
for 1.4 million spectroscopically confirmed SDSS galaxies. We find 717
outburst events that were not reported by ongoing transient surveys.
These events have time-scales ranging from weeks to years. More than
two-thirds of these new events are found in star-forming galaxies,
while such galaxies only constitute ∼20 per cent of our sample. Based
on the properties of the hosts and events, we find that almost all of
the new events are likely to be associated with regular supernovae.
However, a small number of long time-scale events are found among the
galaxies containing AGNs. These events have similar properties to
those recently found in the analyses of light curves of large samples
of AGNs. Given the lack of such events among more than a million
passive galaxies in the sample, we suggest that the long outbursts are
associated with supermassive black holes or their environments.
Description:
In order to investigate the general nature of flaring phenomena in
galaxies, it is necessary to begin with a large, clean, sample of
sources. Detection sensitivity requires that the sources have been
monitored with the time span and cadence required to discern such
events from other types of variability and noise sources. The
combination of photometry from the Catalina Surveys with SDSS
spectroscopy provides us with this for more than a million galaxies.
The Catalina Surveys consist of two separate surveys that use the same
data for different purposes. These consist of the Catalina Sky Survey3
that focuses on the discovery of Near-Earth Objects (NEOs; Larson et
al. 2003DPS....35.3604L 2003DPS....35.3604L), and the Catalina Real-time Transient Survey
(CRTS) which searches for optical transients (Drake et al.
2009ApJ...696..870D 2009ApJ...696..870D). The NEO survey began taking observations with
three telescopes in 2003. Within the Catalina photometric dataset, we
concentrate on photometry taken between 2007 January 1 and 2016 April
28. Most of the photometry used in this work is publicly available as
part of Catalina Surveys Data Release 2 (CSDR2).
The SDSS has operated for well over a decade and undertaken multiple
spectroscopic surveys. For this analysis, we selected spectroscopic
data from SDSS DR13 (Albareti et al. 2017ApJS..233...25A 2017ApJS..233...25A) as our
reference set. This was the most recent SDSS data release at the time
of the analysis and contains 4.4 million optical spectra of QSOs,
galaxies, and stars.
In Table 1, we present the parameters for each of the 692 new CSS
outburst candidates. In Table 2, we present the known properties for
each of the galaxies containing an outburst candidate.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 80 692 Properties of CSS outbursts
table2.dat 101 692 Properties of outburst host galaxies
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- ID CRTS outburst candidate ID (CRTSOBCNNN)
14- 21 F8.4 deg RAdeg Right ascension (J2000)
23- 30 F8.4 deg DEdeg Declination (J2000)
32- 36 F5.2 mag Vcssmag Apparent magnitude for the peak of the
outburst in pseudo-V magnitude
38- 43 F6.2 mag VcssMAG Absolute magnitude for the peak of the
outburst in pseudo-V magnitude
45- 51 F7.1 d MJD MJD of the outburst peak
53- 55 I3 d Lenght Time span over which the candidate outburst
was detected about 1σ
57- 61 F5.2 --- Signi Total significance in sigma of the detections
during the outburst time span
63- 68 F6.2 --- logP Probability of false detection assuming
normally distributed data
70- 71 I2 --- Nights Number of nights when the outburst was
detected above 1σ
73- 75 A3 --- Quality Quality of the outburst candidate based the
inspection of light curves and images as well
as the presence of detections in MLS data (1)
77- 80 A4 --- n_Quality Note on Quality (2)
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Note (1): Quality as follows:
I = high confidence event
II = moderate confidence event
III = low confidence event
Note (2): Note as follows:
a = Outburst is also detected in MLS observations
b = Source is resolved from the host galaxy
c = Long time-scale event
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 24 A24 --- Host SDSS ID of the outburst host galaxies
(SDSS_JHHMMSS.ss+DDMMSS.s)
26- 34 F9.5 deg RAdeg Right ascension (J2000)
36- 44 F9.5 deg DEdeg Declination (J2000)
46- 52 F7.5 --- z Redshift of the galaxies from SDSS
54- 59 F6.3 mag Vcssmag Apparent magnitude of the host based on CSS
photometry (pseudo-V magnitude) after
correcting for foreground extinction using
the Schlegel et al. (1998ApJ...500..525S 1998ApJ...500..525S)
reddening maps
61- 68 F8.4 mag VcssMAG Absolute magnitude (pseudo-V magnitude) of
the host based on CSS photometry after
correcting for foreground extinction using
the Schlegel et al. (1998ApJ...500..525S 1998ApJ...500..525S)
reddening maps
70- 74 I5 d MJD Date that the SDSS spectrum was obtained
76- 79 F4.1 [Msun/yr] SFR ? Star formation rate for the best-fitting
model to the SDSS spectrum
81- 85 F5.3 --- [Z/H] ? Metallicity (model values 0.004, 0.01,
0.02, 0.04) for the best-fitting model to
the SDSS spectrum
87- 93 F7.4 Gyr Age ? Age for the best-fitting model to the SDSS
spectrum
95- 99 F5.2 [Msun] Mass ? Host mass for the best-fitting model to the
SDSS spectrum
101 A1 --- n_Host [a ] a : Denotes whether a galaxy is an AGN
based on the spectrum and/or WISE
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 17-Jun-2022