J/ApJ/852/72 Luminosity functions of tidal disruption flares (van Velzen, 2018)
On the mass and luminosity functions of tidal disruption flares: rate
suppression due to black hole event horizons.
van Velzen S.
<Astrophys. J., 852, 72-72 (2018)>
=2018ApJ...852...72V 2018ApJ...852...72V (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies; Black holes; Stars, flare; Photometry, ugriz; Redshifts;
Velocity dispersion
Keywords: accretion, accretion disks; black hole physics;
galaxies: kinematics and dynamics; galaxies: nuclei;
supernovae: general
Abstract:
The tidal disruption of a star by a massive black hole is expected to
yield a luminous flare of thermal emission. About two dozen of these
stellar tidal disruption flares (TDFs) may have been detected in
optical transient surveys. However, explaining the observed properties
of these events within the tidal disruption paradigm is not yet
possible. This theoretical ambiguity has led some authors to suggest
that optical TDFs are due to a different process, such as a nuclear
supernova or accretion disk instabilities. Here we present a test of a
fundamental prediction of the tidal disruption event scenario: a
suppression of the flare rate due to the direct capture of stars by
the black hole. Using a recently compiled sample of candidate TDFs
with black hole mass measurements, plus a careful treatment of
selection effects in this flux-limited sample, we confirm that the
dearth of observed TDFs from high-mass black holes is statistically
significant. All the TDF impostor models we consider fail to explain
the observed mass function; the only scenario that fits the data is a
suppression of the rate due to direct captures. We find that this
suppression can explain the low volumetric rate of the luminous TDF
candidate ASASSN-15lh, thus supporting the hypothesis that this flare
belongs to the TDF family. Our work is the first to present the
optical TDF luminosity function. A steep power law is required to
explain the observed rest-frame g-band luminosity,
dN/dLg∝Lg-2.5. The mean event rate of the flares in our
sample is ∼1x10-4galaxy-1/yr, consistent with the theoretically
expected tidal disruption rate.
Description:
Our selection requirements and final stellar tidal disruption flare
(TDF) sample are similar to the candidate TDF samples presented
recently (Hung+ 2017ApJ...842...29H 2017ApJ...842...29H ; Wevers+ 2017MNRAS.471.1694W 2017MNRAS.471.1694W).
Three flares in our sample were found by searching for transients in
GALEX multiepoch imaging in the near-UV (NUV) and far-UV (FUV) bands:
GALEX-D3-13 (Gezari+ 2006ApJ...653L..25G 2006ApJ...653L..25G) GALEX-D1-9 (Gezari+ 2008,
J/ApJ/676/944), and GALEX-D23H-1 (Gezari+ 2009ApJ...698.1367G 2009ApJ...698.1367G). The
search was conducted using ∼5yr of GALEX observations of four
extragalactic fields (each covering ∼1deg2 of the sky).
Active galaxies were identified using the large body of archival
spectroscopic observations that are available for these fields,
complemented by spectroscopic follow-up observations where necessary.
See section 2.1.1.
Two flares in our sample, TDE1 and TDE2 (van Velzen+
2011ApJ...741...73V 2011ApJ...741...73V), were found by searching for transients in SDSS
Stripe 82 multiepoch imaging data (Frieman+ 2008AJ....135..338F 2008AJ....135..338F ;
Abazajian+ 2009, II/294), covering about 300deg2. This search used
the SDSS u, g, and r filters and selected nuclear transients from
inactive galaxies. See section 2.1.2.
Two flares in our sample originate from the Pan-STARRS (Chambers+
2016, II/349) Medium Deep (PS1 MD) fields: PS1-10jh (Gezari+
2012Natur.485..217G 2012Natur.485..217G) and PS1-11af (Chornock+ 2014ApJ...780...44C 2014ApJ...780...44C). See
section 2.1.3.
Three flares in our sample originate from the analysis of Arcavi+
(2014, J/ApJ/793/38) using the Palomar Transient Factory (PTF):
PTF-09ge, PTF-09djl, and PTF-09axc. These TDF candidates were obtained
by selecting nuclear transients from PTF imaging data that have
received spectroscopic follow-up observations. See section 2.1.4.
Three flares in our sample originate from iPTF, which is the successor
of PTF: iPTF-15af (N. Blagorodnova+ 2017, in preparation), iPTF-16axa
(Hung+ 2017ApJ...842...29H 2017ApJ...842...29H), and iPTF-16fnl (Blagorodnova+ 2017,
J/ApJ/844/46). The iPTF search was conducted with the same telescope
and camera as PTF, but cadence and follow-up strategy were different.
See section 2.1.5.
Four flares in our sample originate from ASAS-SN (Shappee+ 2014,
J/ApJ/788/48): ASASSN-14ae (Holoien+ 2014MNRAS.445.3263H 2014MNRAS.445.3263H), ASASSN-14li
(Holoien+ 2016MNRAS.455.2918H 2016MNRAS.455.2918H), ASASSN-15oi (Holoien+
2016MNRAS.463.3813H 2016MNRAS.463.3813H), and ASASSN-15lh (Dong+ 2016Sci...351..257D 2016Sci...351..257D). See
section 2.1.6.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 73 17 Sample of 17 candidate stellar tidal disruption
flares (TDFs)
table2.dat 83 17 Properties of the TDF host galaxies
mockgals.dat 145 6101944 Synthetic galaxy catalog (from FITS version
sent by the author; see table 5)
--------------------------------------------------------------------------------
Description of file on the FTP: mockgals.fits.gz is the original
FITS version (for table 5) sent by the author.
See also:
II/319 : UKIDSS-DR9 LAS, GCS and DXS Surveys (Lawrence+ 2012)
II/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009)
J/A+A/610/A14 : ASASSN-15lh MUSE host spectroscopy (Kruehler+, 2018)
J/ApJ/844/46 : Photometry of iPTF16fnl transient event (Blagorodnova+, 2017)
J/ApJS/229/32 : CANDELS: multiwavelength catalogs in the EGS (Stefanon+, 2017)
J/MNRAS/465/L114 : OGLE16aaa UVOT light curves (Wyrzykowski+, 2017)
J/ApJ/836/25 : Swift UVOT light curves of ASASSN-15lh (Margutti+, 2017)
J/MNRAS/463/3813 : ASASSN-15oi UBVI M2W1W2 light curves (Holoien+, 2016)
J/ApJ/793/38 : Palomar Transient Factory photometric obs. (Arcavi+, 2014)
J/ApJ/792/30 : NEOWISE magnitudes for near-Earth objects (Mainzer+, 2014)
J/ApJ/788/48 : X-ray through NIR photometry of NGC 2617 (Shappee+, 2014)
J/ApJ/676/944 : GALEX & CFHTLS cand. tidal disruption events (Gezari+, 2008)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 A12 --- Name Name of the TDF host galaxy
14- 15 I2 h RAh Hour of right ascension (J2000)
17- 18 I2 min RAm Minute of right ascension (J2000)
20- 24 F5.2 s RAs Second of right ascension (J2000)
26 A1 --- DE- Sign of declination (J2000)
27- 28 I2 deg DEd Degree of declination (J2000)
30- 31 I2 arcmin DEm Arcminute of declination (J2000)
33- 36 F4.1 arcsec DEs Arcsecond of declination (J2000)
38- 41 F4.1 mag mMax [16.2/22.4]? Maximum observed apparent
magnitude in Filt
43- 45 A3 --- Filt Filter
47 A1 --- f_mMax [*] *: peak of the light curve was not resolved
49- 52 F4.1 [10-7W] Lg [42.3/44.8]? Rest-frame g-band luminosity
54- 56 F3.1 10+4K Temp [1.2/5.6]? Observed blackbody temperature
58- 61 F4.1 [10-7W] Lbb [43.4/45.6]? Blackbody luminosity
63- 67 F5.3 --- z [0.01/0.5] Redshift
69- 73 F5.3 --- zMax [0.02/0.9] Maximum redshift where this flare
could have been detected given the survey
effective flux limit
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 A12 --- Name Name of the TDF host galaxy
14- 18 F5.2 mag gmag [15.2/23] Apparent corrected g-band magnitude (1)
20- 23 F4.2 mag e_gmag [0/0.3] gmag uncertainty (2)
25- 29 F5.2 mag rmag [14.7/21.4] Apparent corrected r-band
magnitude (1)
31- 34 F4.2 mag e_rmag [0/0.1] rmag uncertainty (2)
36- 40 F5.2 mag Kmag [14/20] Apparent corrected K-band magnitude (1)
42- 45 F4.2 mag e_Kmag [0.01/0.3] Kmag uncertainty (2)
47- 51 F5.1 mag rMag [-22.2/-18.6] r-band absolute magnitude in the
rest-frame of the host galaxy
53- 57 F5.1 mag gMag [-21.4/-18.1] g-band absolute magnitude in the
rest-frame of the host galaxy
59- 62 F4.1 [Msun] Mass [9.5/11] Total stellar mass of the galaxy (3)
64- 66 I3 km/s sigma [53/225]? Velocity dispersion σ (4)
68- 69 I2 km/s e_sigma [2/18]? sigma uncertainty
71- 73 F3.1 [Msun] MBH [5.7/8.3]? Black hole mass M{dot}
75- 77 F3.1 [Msun] e_MBH [0.4/0.6]? MBH uncertainty
79- 83 F5.3 --- zW17 [0.1/0.6] Maximum redshift for inclusion of the
galaxy in the Wevers+ (2017MNRAS.471.1694W 2017MNRAS.471.1694W)
sample
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Note (1): The apparent magnitudes (rmag, gmag, and Kmag) are corrected for
Galactic extinction using the
Schlafly & Finkbeiner (2011ApJ...737..103S 2011ApJ...737..103S) extinction maps.
Note (2): Uncertainties on the apparent magnitudes include only the statistical
uncertainty.
Note (3): The total stellar mass of the galaxy is estimated from the broadband
(ugrizJHK) photometry.
Note (4): The velocity dispersion (σ) measurements are from the sample of
Wevers+ (2017MNRAS.471.1694W 2017MNRAS.471.1694W) (with the exception of ASASSN-15lh
taken from Kruehler+ 2081, J/A+A/610/A14).
--------------------------------------------------------------------------------
Byte-by-byte Description of file: mockgals.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 F6.4 --- z [0.003/1] Redshift
8- 17 F10.6 deg RAdeg Right Ascension in decimal degrees (J2000)
19- 28 F10.6 deg DEdeg Declination in decimal degrees (J2000)
30- 37 E8.3 Msun mass [4e+06/1.1e+12] Total galaxy mass (1)
39- 46 E8.3 yr-1 B300 [2.5e-14/1] Specific SFR over past 300Myr (1)
48- 55 E8.3 yr-1 B1000 [4.8e-06/1] Specific SFR over past Gyr (1)
57- 64 E8.3 yr-1 sSFR [0/2.5e-08] Specific SFR from MPA-JHU catalog (2)
66- 71 F6.4 --- BT [0.01/1] Bulge-to-total ratio (3)
73- 79 F7.3 kpc r50 [0.1/140]? Effective radius
based on Sersic fit (4)
81- 84 F4.2 --- Sersic [0.2/6]? Sersic index (4)
86- 92 F7.2 km/s sigma [0.9/2142]? Velocity dispersion (5)
94- 99 F6.2 km/s sigmaS [0/850]? SDSS pipeline velocity dispersion (4)
101-107 F7.2 km/s e_sigmaS [-4/1307]? Uncertainty in sigmaS (6)
109-113 F5.2 [Msun] MBHs [-0.8/12.5]? log Black hole mass from sigma;
Eq. 8
115-119 F5.2 [Msun] MBHb [0.9/11]? log Black hole mass from bulge mass;
Eq. 9
121-125 F5.2 mag rmag [7.7/22.5]? Apparent r-band AB magnitude
127-132 F6.2 mag rMag [-25/-15.1]? Absolute, k-corrected r-band
AB magnitude
134-138 F5.2 mag gmag [8.3/27]? Apparent g-band AB magnitude
140-145 F6.2 mag gMag [-26.6/-14.6]? Absolute, k-corrected g-band
AB magnitude
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Note (1): From NYU-VAGC, based on ugrizJHK photometry.
Note (2): From the MPA-JHU catalog (their specsfrfibp50).
Note (3): Based on Lackner & Gunn (2012MNRAS.421.2277L 2012MNRAS.421.2277L) measurements
in the r-band
Note (4): From NYU-VAGC.
Note (5): Using the virial theorem; Eq. 6.
Note (6): This is the VDISP_ERR value in SDSS. The velocity dispersion is only
computed for galaxies and explicitly masking emission line regions.
Negative errors indicate an invalid fit.
-3 = set to 85km/s.
-4 = set to zero.
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History:
From electronic version of the journal for table 1 and 2.
From the author for Table 5 (= mockgals).
Acknowledgements:
Sjoert van Velzen [New York University]
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 17-Sep-2018