J/A+A/680/A98 A LOFAR sample of OCRS in dwarf galaxies (Vohl+, 2023)
A LOFAR sample of luminous compact sources coincident with nearby dwarf
galaxies.
Vohl D., Vedantham H.K., Hessels J.W.T., Bassa C.G., Cook D.O., Kaplan D.L.,
Shimwell T.W., Zhang C.
<Astron. Astrophys. 680, A98 (2023)>
=2023A&A...680A..98V 2023A&A...680A..98V (SIMBAD/NED BibCode)
ADC_Keywords: Radio sources ; Galaxies, nearby
Keywords: stars: neutron - stars: black holes - galaxies: dwarf -
radio continuum: general
Abstract:
The vast majority of extra-galactic, compact continuum radio sources
are associated with star formation or jets from (super)massive black
holes and, as such, are more likely to be found in association with
starburst galaxies or early type galaxies. Recently, two new
populations of radio sources have been identified: (a) compact and
persistent sources (PRS) associated with fast radio bursts (FRB) in
dwarf galaxies and (b) compact sources in dwarf galaxies that could
belong to the long-sought population of intermediate-mass black holes.
Despite the interesting aspects of these newly found sources, the
current sample size is small, limiting scrutiny of the underlying
population. Here, we present a search for compact radio sources
coincident with dwarf galaxies. We search the LOFAR Two-meter Sky
Survey (LoTSS) -- the most sensitive low-frequency (144MHz central
frequency) large-area survey for optically thin synchrotron emission
to date. Exploiting LoTSS' high spatial resolution (6arcsec) and low
astrometric uncertainty (∼0.2arcsec), we match its compact sources to
the compiled sample of dwarf galaxies in the Census of the Local
Universe -- an H Alpha survey with the Palomar Observatory's 48-inch
Samuel Oschin Telescope. We identify 29 over-luminous compact radio
sources, evaluate the probability of chance alignment within the
sample, investigate the potential nature of these sources, and
evaluate their volumetric density and volumetric rate. While optical
line-ratio diagnostics on the nebular lines from the host galaxies
prefer a star-formation origin (against an AGN origin), future high
angular resolution radio data is necessary to ascertain the origin of
the radio sources. We discuss planned strategies to differentiate them
between candidate FRB hosts and intermediate-mass black holes.
Description:
Tables 1 and 3, which describe 29 over-luminous compact radio sources.
One of these source (ILT J125940.18+275123.5) is judged to be a likely
chance association. Please refer to article for further details.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 126 29 Properties of the selected candidates
table3.dat 98 12 Fluxes for candidates matched in at least one
ancillary radio survey
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See also:
J/A+A/659/A1 : LOFAR Two-metre Sky Survey (LoTSS) DR2 (Shimwell+, 2022)
J/A+A/664/A83 : Nearby galaxies in LoTSS-DR2 (Heesen+, 2022)
J/A+A/669/A8 : Nearby galaxies in LoTSS-DR2. II. (Heesen+, 2023)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 23 A23 --- Source Source name in LoTSS DR2
(ILT JHHMMSS.ss+DDMMSS.s)
25- 50 A26 --- Host Host galaxy name in CLU
52- 54 F3.1 arcsec ProjOff Projected offset between the radio source
and Hα source coordinates in arcsec
56- 58 F3.1 arcsec e_ProjOff Projected offset in arcsec uncertainty
60- 63 I4 pc ProjOffpc Projected offset between the radio source
and Hα source coordinates (pc)
65- 70 F6.4 pc e_ProjOffpc Projected offset in pc uncertainty
72- 78 A7 --- z Redshift
80 A1 --- n_z [kmn] Distance method (1)
82- 86 F5.2 mJy Sint Integrated flux density at 144MHz
88- 91 F4.2 mJy e_Sint Integrated flux density at 144MHz
uncertainty
93- 97 F5.2 [W/Hz] logL Radio luminosity at 144MHz
98-102 F5.2 [Msun/yr] logSFR Star formation rate
104-108 F5.2 [Msun/yr] e_logSFR [] Star formation rate uncertainty
110-114 F5.2 --- sigma ? Standard deviation above the L-SFR
relation
116-120 F5.2 --- alpha ? Radio spectral index
122-126 F5.2 --- Rg ? Radio loudness
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Note (1): Distance method as follows:
k = kinematic
m = median (redshift-independent)
n = narrowband (Hα)
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 23 A23 --- Source Source name in LoTSS DR2
(ILT JHHMMSS.ss+DDMMSS.s)
25- 29 F5.2 mJy Sint-LoTSS LoTSS 144MHz integrated flux density
31- 34 F4.2 mJy e_Sint-LoTSS LoTSS 144MHz integrated flux density
uncertainty
36- 39 F4.2 mJy Sint-RACS ?=- RACS (Rapid ASKAP Continuum Survey)
700-1800MHz integrated flux density
41- 44 F4.2 mJy e_Sint-RACS ?=- RACS 700-1800MHz integrated flux density
uncertainty
46- 50 F5.2 mJy Sint-FIRST ?=- FIRST 1.4GHz integrated flux density
52- 55 F4.2 mJy e_Sint-FIRST ?=- FIRST 1.4GHz integrated flux density
uncertainty
57- 61 F5.2 mJy Sint-NVSS ?=- NVSS 1.4GHz integrated flux density
63- 66 F4.2 mJy e_Sint-NVSS ?=- NVSS 1.4GHz integrated flux density
uncertainty
68- 71 F4.2 mJy Sint-VLASS ?=- VLASS 3GHz integrated flux density
73- 76 F4.2 mJy e_Sint-VLASS ?=- VLASS 3GHz integrated flux density
uncertainty
77 A1 --- n_Sint-VLASS [*] Note on Sint_VLASS (1)
79- 82 F4.1 --- alpha Radio spectral index
84- 87 F4.2 --- e_alpha Radio spectral index uncertainty
89- 92 F4.1 --- alpha-hf ?=- Radio spectral index fitted between
1.4 and 3GHz
94- 97 F4.2 --- e_alpha-hf ?=- Radio spectral index fitted between
1.4 and 3GHz uncertainty
98 A1 --- n_alpha-hf [*] Note on alpha-hf (2)
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Note (1): Note as follows:
* = value is estimated based on cutout image from CIRADA Image Cutout Web
Service
Note (2): Note as follows:
* = spectral index includes estimates from CIRADA Cutouts
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History:
From Dany Vohl, d.vohl(at)uva.nl
Acknowledgements:
This work was carried out in part through funding from the European
Open Science Cloud (EOSC) Future, an EU-funded H2020 project.
LOFAR is the Low Frequency Array designed and constructed by ASTRON.
It has observing, data processing, and data storage facilities in
several countries, which are owned by various parties (each with their
own funding sources), and which are collectively operated by the ILT
foundation under a joint scientific policy. The ILT resources have
benefited from the following recent major funding sources: CNRS-INSU,
Observatoire de Paris and Universite d'Orleans, France; BMBF,
MIWF-NRW, MPG, Germany; Science Foundation Ireland (SFI), Department
of Business, Enterprise and Innovation (DBEI), Ireland; NWO, The
Netherlands; The Science and Technology Facilities Council, UK;
Ministry of Science and Higher Education, Poland; The Istituto
Nazionale di Astrofisica (INAF), Italy.
(End) Patricia Vannier [CDS] 10-Oct-2023