J/A+A/712/A47 CO-dark gas in compact emission-line galaxies (Liu+, 2026)
Ubiquitous CO faintness and the prevalence of CO-dark gas in compact
emission-line galaxies.
Liu S., Yin X., Luo A.-L., Zhang W., Yan P., Bo Q.
<Astron. Astrophys. 712, A47 (2026)>
=2026A&A...712A..47L 2026A&A...712A..47L (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, spectra ; Abundances ; Optical
Keywords: ISM: molecules - galaxies: dwarf - galaxies: ISM - galaxies: starburst
Abstract:
Green Pea and Blueberry galaxies are compact, low-metallicity
starbursts that provide nearby analogs of high-redshift star-forming
systems.
We investigate whether their weak CO emission reflects genuinely small
molecular reservoirs or CO-dark gas where independent tracers are
available.
We compiled 60 strong [OIII]λ5007 compact emission-line
galaxies with partially overlapping gas-tracer coverage: 12CO(1-0)
observations from the Delingha 13.7m telescope, HI 21cm data from
Arecibo, GBT, and FAST (ten detections and 41 upper limits), and
Herschel/PACS [CII] λ158um data (five detections and four
upper limits after excluding merger systems). Quantitative conclusions
are drawn only from detected or physically constraining subsets.
Molecular masses were estimated using a metallicity-dependent
CO-to-H2 conversion factor and the [CII]-to-H2 calibration for
low-metallicity dwarf galaxies. Two CO upper limits are deep enough to
constrain the expected molecular reservoir. We also removed major
mergers and examined the large-scale environment using the SDSS DR7
VoidFinder catalog.
For the five [CII]-detected sources, we find
MH2[CII]∼109.0-109.7M☉ and a median molecular gas
depletion time of τdep,H2∼0.16Gyr, shorter than the ∼1Gyr
typical of main-sequence galaxies. HI-detected sources have a median
atomic depletion time of τdep,H∼2.6Gyr. The detected subsets
show high gas fractions and short depletion times consistent with
rapid gas cycling, but the [CII] result remains limited by
small-number statistics. About 39% of the volume-matched sample lies
in cosmic voids.
CO alone misses a substantial fraction of the star-forming fuel in
these low-metallicity starbursts. Combined HI, [CII], and deep CO
constraints are needed to characterize their interstellar medium and
CO-dark molecular component.
Description:
This archive contains the LAMOST one-dimensional spectra used for the
optical emission-line measurements in the paper. The spectra are
provided as FITS files in the fits/subdirectory. The file lamost.dat
lists the object name, LAMOST designation, FITS file, observing
metadata, and the role of each spectrum in the paper.
The FITS files are the LAMOST DR12 reduced one-dimensional spectra.
Each file contains a primary header and a binary-table extension with
the columns FLUX, IVAR, WAVELENGTH, ANDMASK, ORMASK, and
NORMALIZATION, as distributed by LAMOST.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
lamost.dat 132 9 LAMOST spectra manifest
fits/* . 9 Individual fits spectra
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See also:
V/162 : LAMOST DR11 catalogs (Luo+, 2026)
Byte-by-byte Description of file: lamost.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- Name Short source name
12- 31 A20 --- LAMOST LAMOST designation
32- 43 A12 --- FileName spectrum FITS file name in subdirectory fits
45- 54 I10 --- OBSID LAMOST observation identifier
56- 65 F10.6 deg RAdeg Right ascension (J2000)
67- 75 F9.6 deg DEdeg Declination (J2000)
77- 83 F7.5 --- z LAMOST spectroscopic redshift
85- 89 I5 d MJD Modified Julian date
91- 92 I2 --- SpID LAMOST spectrograph identifier
94- 96 I3 --- Fiber LAMOST fiber identifier
98-120 A23 "datime" DateObs UTC start time of observation
122-125 A4 --- Used yes if adopted for line measurements
126-132 A7 --- Purpose Use in the manuscript
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Acknowledgements:
From Siqi Liu, liusiqi(at)ustb.edu.cn
Guoshoujing Telescope (the Large Sky Area Multi-Object Fiber
Spectroscopic Telescope, LAMOST) is a National Major Scientific
Project built by the Chinese Academy of Sciences. Funding for the
project has been provided by the National Development and Reform
Commission. LAMOST is operated and managed by the National
Astronomical Observatories, Chinese Academy of Sciences.
License: CC-BY-4.0
(End) Patricia Vannier [CDS] 17-Jun-2026