J/ApJ/888/36 SDSS/FIRST dwarf galaxies with VLA high res. obs. (Reines+, 2020)
A new sample of (wandering) massive black holes in dwarf galaxies from
high-resolution radio observations.
Reines A.E., Condon J.J., Darling J., Greene J.E.
<Astrophys. J., 888, 36-36 (2020)>
=2020ApJ...888...36R 2020ApJ...888...36R (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, radio; Redshifts; Magnitudes, absolute; Optical; Colors;
Active gal. nuclei; Black holes
Keywords: Intermediate-mass black holes; Dwarf galaxies; Radio sources
Very Large Array; Active galactic nuclei; AGN host galaxies
Dwarf irregular galaxies; Supermassive black holes
Abstract:
We present a sample of nearby dwarf galaxies with radio-selected
accreting massive black holes (BHs), the majority of which are
non-nuclear. We observed 111 galaxies using sensitive, high-resolution
observations from the Karl G. Jansky Very Large Array (VLA) in its
most extended A-configuration at X band (∼8-12GHz), yielding a typical
angular resolution of ∼0.25" and rms noise of ∼15µJy. Our targets
were selected by crossmatching galaxies with stellar masses
M*≤3x109M☉ and redshifts z<0.055 in the NASA-Sloan Atlas
with the VLA Faint Images of the Radio Sky at Twenty centimeters
Survey. With our new high-resolution VLA observations, we detect
compact radio sources toward 39 galaxies and carefully evaluate
possible origins for the radio emission, including thermal
HII regions, supernova remnants, younger radio supernovae, background
interlopers, and active galactic nuclei (AGNs) in the target galaxies.
We find that 13 dwarf galaxies almost certainly host active massive
BHs, despite the fact that only one object was previously identified
as having optical signatures of an AGN. We also identify a candidate
dual radio AGN in a more massive galaxy system. The majority of the
radio-detected BHs are offset from the center of the host galaxies,
with some systems showing signs of interactions/mergers. Our results
indicate that massive BHs need not always live in the nuclei of dwarf
galaxies, confirming predictions from simulations. Moreover, searches
attempting to constrain BH seed formation using observations of dwarf
galaxies need to account for such a population of "wandering" BHs.
Description:
As in Reines+ (2013, J/ApJ/775/116), we construct our parent sample of
dwarf galaxies from the NASA-Sloan Atlas (NSA; version v012), which
is a catalog of images and parameters of SDSS galaxies with redshifts
z<0.055 (D≲225Mpc). Redshifts primarily come from SDSS DR8 spectra.
Our parent sample includes 43707 objects.
We select a subsample of dwarf galaxies detected in the VLA Faint
Images of the Radio Sky at Twenty-centimeters (FIRST) Survey
(see VIII/92).
See Section 2.
Our 111 target dwarf galaxies were observed with the VLA in the most
extended A-configuration in 2014 from February 20 to May 31 (PI: Reines;
Project 14A-220). Continuum observations were carried out at X band
with 2x2GHz basebands centered at 9.0 and 10.65GHz. See Section 3.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 126 111 Observed dwarf galaxy sample with FIRST detections
table2.dat 116 111 VLA observations
table3.dat 83 48 Compact radio sources detected toward target galaxies
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See also:
V/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015)
VIII/92 : The FIRST Survey Catalog, Version 2014Dec17 (Helfand+ 2015)
J/ApJ/393/149 : W49N H2O maser outflow: distance and kinematics (Winn+, 1992)
J/ApJ/670/92 : New sample of low-mass black holes in AGN (Greene+, 2007)
J/ApJ/703/370 : Radio SNRs in nearby galaxies (Chomiuk+, 2009)
J/ApJ/755/167 : Low-mass black holes in SDSS Seyfert 1 galaxies (Dong+, 2012)
J/ApJ/775/116 : z<0.06 active BH galaxies from SDSS-DR8 (Reines+, 2013)
J/ApJ/799/72 : Binary AGNs from the VLA Stripe 82 survey (Fu+, 2015)
J/ApJ/813/82 : z<0.06 broad-line AGN emission-line measures (Reines+, 2015)
J/MNRAS/454/3722 : AGN in nearby low-mass galaxies (Sartori+, 2015)
J/A+A/593/A86 : Arp 220 LOFAR radio images at 150MHz (Varenius+, 2016)
J/A+A/602/A28 : IR signature of CMBH in nearby dwarf galaxies (Marleau+, 2017)
J/ApJ/872/148 : 2MASX/NVSS gal. brighter than K20fe=12.25 (Condon+, 2019)
J/A+A/623/A173 : SNe/SNRs in starburst galaxy Arp 220 (Varenius+, 2019)
http://www.nsatlas.org/ : NASA-Sloan Atlas home page
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [1/111] Running identification number
7- 16 A10 --- Name Target galaxy (JHHMM+DDMM)
20- 25 I6 --- NSAID [7/171025] NASA-Sloan Atlas identification
number
29- 37 F9.5 deg RAdeg [4.5/360] Right Ascension (J2000) (1)
43- 51 F9.5 deg DEdeg [-10.1/62.5] Declination (J2000) (1)
58- 63 F6.4 --- z [0.0029/0.05] Redshift (1)
67- 70 F4.2 [Msun] logM* [7.5/9.5] Log stellar mass (1)
77- 82 F6.2 mag gMag [-20/-13.2] Absolute g-band magnitude (1)(2)
91- 95 F5.2 mag g-r [-0.6/1.1] The (g-r) color index (1)(2)
101-105 F5.2 kpc r50 [0.18/10.4] Petrosian 50% light radius (1)
109-111 F3.1 --- n [0.5/6] Sersic index (1)
116-120 F5.2 mJy S [0.45/20.7] FIRST 1.4GHz radio flux density
124-126 F3.1 arcsec offset [0/4.8] FIRST/optical positional offset
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Note (1): From the NSA and assume h=0.73.
Note (2): Magnitudes are K-corrected to rest-frame values using kcorrect v4_2
and corrected for foreground Galactic extinction.
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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- 3 I3 --- Seq [1/111] Running identification number
8- 17 A10 --- Name Target galaxy (JHHMM+DDMM)
22- 31 A10 "Y-M-D" Date Date observed
36- 40 A5 --- Fluxcal Flux and bandpass calibrator
45- 54 A10 --- Phasecal Phase calibrator (JHHMM+DDMM)
60- 68 A9 arcsec2 Beam9 Synthesized beam size at 9GHz (lower baseband)
74- 76 I3 deg PA9 [-86/88] Beam position angle at 9GHz
82- 83 I2 uJy/beam rms9 [12/29] RMS noise in 9 GHz image
93-101 A9 arcsec2 Beam10 Synthesized beam size at 10.65GHz
(upper baseband)
107-109 I3 deg PA10 [-90/88] Beam position angle at 10.65GHz
115-116 I2 uJy/beam rms10 [13/36] RMS noise in 10.65 GHz image
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq Galaxy identification number
4 A1 --- m_Seq Component on Seq
6- 15 A10 --- Name Target galaxy (JHHMM+DDMM)
17- 25 F9.5 deg RAdeg Radio right ascension (J2000)
27- 34 F8.5 deg DEdeg Radio declination (J2000)
36- 38 F3.1 arcsec Offset [0/4.9] Offset from optical center of the galaxy
40- 44 I5 uJy S9GHz [63/21831] Flux density at 9GHz
46- 48 I3 uJy e_S9GHz [10/200] S9GHz uncertainty (1)
50- 53 F4.1 [W/Hz] logL9GHz [18.5/22.4] Log spectral luminosity at 9GHz
55- 58 F4.1 --- alpha [-3.1/0.4]? Spectral index
(Sν∝να) (2)
60- 62 F3.1 --- e_alpha [0.1/4.2]? alpha uncertainty
64- 68 A5 --- PS Designation as a point source (or not),
determined from IMFIT
70- 79 A10 --- Note Note (3)
81- 83 A3 --- Comm Comment (4)
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Note (1): This does not include the 5% calibration error.
Note (2): Spectral index determined from flux densities at 9.00 and 10.65GHz,
if source is detected in the 10.65GHz image.
Note (3): Radio source as follows:
Sample A = 28 confirmed dwarf galaxies with 35 compact radio sources
Sample B = 7 galaxies with unreliable redshifts with 9 compact radio sources
Background = 4 background objects with point-like optical counterparts
(IDs 46, 47, 50, 96; see Figure 3 and the Appendix).
Note (4): Code as follows:
AGN = radio sources that are too luminous to be consistent with
star formation (20 occurrences).
SF = radio sources consistent with star formation (24 occurrences).
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Nomenclature note:
Radio sources are <[RCD2020] JDDD.ddddd+DD.ddddd> in Simbad.
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 23-Jun-2021