J/A+A/703/A295 Parent dwarf galaxy sample from Apertif HI survey (Siljeg+, 2025)
Gas-rich dwarf galaxy multiples in the Apertif HI survey.
Siljeg B., Adams E.A.K., Fraternali F., Hess K.M., Marasco A., Denes H.,
Garrido J., Lucero D.M., Morganti R., Sanchez-Exposito S.,
van der Hulst J.M.
<Astron. Astrophys. 703, A295 (2025)>
=2025A&A...703A.295S 2025A&A...703A.295S (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, radio ; H I data ; Galaxies, nearby ; Radio sources
Keywords: galaxies: dwarf - galaxies: groups: general - galaxies: interactions -
galaxies: star formation - galaxies: statistics
Abstract:
Dwarf-dwarf galaxy encounters are a key aspect of galaxy evolution as
they can ignite or temporarily suppress star formation in dwarfs and
can lead to dwarf mergers. However, the frequency and impact of dwarf
encounters remain poorly constrained due to limitations of
spectroscopic studies, e.g. surface-brightness incompleteness of
optical studies and poor spatial resolution of single-dish neutral
hydrogen (HI) surveys.
We aim to quantify the frequency of isolated gas-rich dwarf galaxy
multiples using the untargeted, interferometric Apertif HI survey and
study the impact of the interaction on star formation rates of
galaxies as a function of the on-sky separation.
Our parent dwarf sample consists of 2481 gas-rich galaxies with
stellar masses 106<M*/M☉<5*109, for which we identify close
companions based on projected separation (rp) and systemic velocity
difference (DelVsys). We explore both constant thresholds for rp
and DelVsys corresponding to 150kpc and 150km/s on all galaxies in
our sample, and mass-dependent thresholds based on a stellar-to-halo
mass relation.
We find the average number of companions per dwarf in our sample to be
13% (20%) when considering mass-dependent (constant) thresholds. In
the stellar mass regime of 2*108<M*/M☉<5*109, we find a
three times higher frequency (11.6%) of dwarf companions than
previously determined from optical spectroscopic studies, highlighting
the power of HI for finding dwarf multiples. Furthermore, we find
evidence for an increase in star formation rates (SFRs) of close dwarf
galaxy pairs of galaxies with similar stellar masses.
Description:
List of 2481 dwarf galaxies found in the 42% of the spatial footprint
of the Apertif HI survey. Some galaxies in this list were found within
the same Apertif HI detection (merged detections) and share the
Apertif name, but are listed individually in this table. The table
provides the global properties of all galaxies used in the
publication: Apertif source name, total number of galaxies within the
merged detection (if applicable), centroid of the stellar component,
systemic velocity, distance, stellar mass, HI mass, and star formation
rate.
The full source list from the Apertif survey is currently in
preparation and might contain different Apertif names for sources
presented here, as well as duplicate detections of these galaxies.
Hence, to find these sources in the future Apertif source list, the
two list would need to be crossmatched, preferentially using
centroiding of the stellar counterpart. Searching around 45 arcsec
around the stellar centroid generally finds all duplicate detections.
Merged detections in the full Apertif source list will only contain
measurements of stellar properties of one galaxy within the detection.
Hence, not all dwarfs in this list will have a match in the full
Apertif source list.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
dwarfs.dat 107 2481 Parent dwarf galaxy sample
--------------------------------------------------------------------------------
See also:
J/A+A/667/A39 : APERTIF DR1 continuum source catalog (Kutkin+, 2022)
Byte-by-byte Description of file: dwarfs.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 21 A21 --- Apertif Apertif name (1)
23- 24 A2 --- Ngalmerg Number of galaxies in merged detections (2)
26- 35 F10.6 deg RAdeg Right ascension (J2000.0)
37- 45 F9.6 deg DEdeg Declination (J2000.0)
47- 55 F9.3 km/s Vsys Systemic velocity of the galaxy
57- 62 F6.2 Mpc Dist Distance to the galaxy (3)
64- 68 F5.2 Mpc e_Dist Error on the distance (4)
70- 75 F6.3 [Msun] logMstar log10 of Stellar mass
77- 81 F5.3 [Msun] e_logMstar Uncertainty on logMstar
83- 88 F6.3 [Msun] logMHI log10 of HI mass
90- 94 F5.3 [Msun] e_logMHI Uncertainty on logMHI
96-101 F6.3 [Msun/yr] logSFR ?=- log10 of Star formation rate
103-107 F5.3 [Msun/yr] e_logSFR ?=- Uncertainty on logSFR
--------------------------------------------------------------------------------
Note (1): Apertif name is based on HI coordinates of the detection as
AHCJHHMMSS.s+DDMMSS.
Galaxies found in merged detections have a suffix _X, where X is an integer
number used simply to distinguish galaxies within the same Apertif detection.
Note (2): If a galaxy is part of the merged detection, Ngalmerg denotes the
total number of galaxies found in the same HI detection. Not all
galaxies within each merged detection ended up in the final sample.
Unclear merged detections contain letter 'u' after the number.
Note (3): Distances are determined using the linear density field model of
Valade et al. (2024NatAs...8.1610V 2024NatAs...8.1610V) calibrated on the Cosmicflows-4
database (Tully et al., 2023ApJ...944...94T 2023ApJ...944...94T, cat. J/ApJ/944/94).
Note (4): Error on the distance is computed using the prescription from
Haubner et al. (2025A&A...696A.185H 2025A&A...696A.185H).
--------------------------------------------------------------------------------
Acknowledgements:
From Barbara Siljeg, siljeg.barb(at)gmail.com
This source list was made possible by the combined efforts of the
Apertif team. In particular, I especially thank K.M. Hess, who ran
the source finding on Apertif data cubes, and A. Marasco, who
conducted photometric analysis of the stellar counterpart.
(End) Patricia Vannier [CDS] 29-Sep-2025