Updated Analysis of a “Dark” Galaxy and Its Blue Companion in the Virgo Cloud H I 1225 + 01

Matsuoka, Yoshiki; Ienaka, N.; Oyabu, Shinki; Wada, K.; Takino, S.

doi:10.1088/0004-6256/144/6/159

Cited by 14 publications

(13 citation statements)

References 42 publications

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“…ratios than the one that we find in Coma P. For example, Matsuoka et al (2012) find that the northeastern component of the system HI 1225+01 is more extreme than Coma P, although Coma P is of lower surface brightness. Similarly, some of the recently discovered resolved stellar populations of the UCHVC population discovered by ALFALFA (Adams et al , 2016 have M H I /M ratios in excess of 100 (Janesh et al , 2017.…”

Section: Contextualizing Coma Pcontrasting

confidence: 71%

The Enigmatic (Almost) Dark Galaxy Coma P: The Atomic Interstellar Medium

Ball

Cannon

Adams

et al. 2018

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We present new high-resolution H I spectral line imaging of Coma P, the brightest H I source in the system HI 1232 +20. This galaxy with extremely low surface brightness was first identified in the ALFALFA survey as an "(Almost) Dark" object: a clearly extragalactic H I source with no obvious optical counterpart in existing optical survey data (although faint ultraviolet emission was detected in archival GALEX imaging). Using a combination of data from the Westerbork Synthesis Radio Telescope and the Karl G. Jansky Very Large Array, we investigate the H I morphology and kinematics at a variety of physical scales. The H I morphology is irregular, reaching only moderate maxima in mass surface density (peak M 10 H I s~ pc −2 ). Gas of lower surface brightness extends to large radial distances, with the H I diameter measured at 4.0±0.2 kpc inside the M 1  pc −2 level. We quantify the relationships between mass surface density of H I gas and star formation on timescales of ∼100-200 Myr as traced by GALEX far-ultraviolet emission. While Coma P has regions of dense H I gas reaching the N 10 I I scaling relation. It is either too large for its H I mass, has too low an H I mass for its H I size, or the two H I components artificially extend its H I size. Coma P lies within the empirical scatter at the faint end of the baryonic Tully-Fisher relation, although the complexity of the H I dynamics complicates the interpretation. Along with its large ratio of H I to stellar mass, the collective H I characteristics of Coma P make it unusual among known galaxies in the nearby universe.

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Section: Contextualizing Coma Pcontrasting

confidence: 71%

The Enigmatic (Almost) Dark Galaxy Coma P: The Atomic Interstellar Medium

Ball

Cannon

Adams

et al. 2018

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“…As previously suggested in S13, there is evidence that a small number of our galaxies may be candidates for dark galaxies and a significant fraction of the sample are low-mass dwarf galaxies. Recent studies by Matsuoka et al (2012) show that images as deep as mR = 30 do not detect the source which is initially detected in HI 21-cm data. They additionally do not detect any nebular emission lines from this dark region, though the optically detected component of this galaxy to the NE does have strong emission detected.…”

Section: Dwarf Galaxies and Dark Halos?mentioning

confidence: 97%

“…Ten of these 35 have no detectable galaxy in imaging after PSF subtraction (IDs 3,6,8,13,20,23,32,34,39,and 47). These targets may be good candidates for dark galaxies (Matsuoka et al 2012;Rhode et al 2013). This leaves 18 targets with no detectable absorption, only seven of which have no visible galaxy in imaging (IDs 5,9,11,12,30,38,and 44).…”

Section: Absorption Line Measurementsmentioning

confidence: 99%

Galactic nebular lines in the fibre spectra of background QSOs: reaching a hundred QSO–galaxy pairs with spectroscopic and photometric measurements

Straka

Noterdaeme

Srianand

et al. 2015

Monthly Notices of the Royal Astronomical Society

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We present photometric and spectroscopic measurements of 53 QSO-galaxy pairs from the Sloan Digital Sky Survey, where nebular emission lines from a 0 < z < 0.84 foreground galaxy are detected in the fiber spectra of a background QSO, bringing the overall sample to 103 QSO-galaxy pairs detected in the SDSS. We here study the nature of these systems. Detected foreground galaxies appear at impact parameters between 0.37 kpc and 12.68 kpc. The presence of oxygen and Balmer emission lines allows us to determine the emission line metallicities for our sample, which are on average super-solar in value. Star formation rates for our sample are in the range 0.01 − 12 M yr −1 . We utilize photometric redshift fitting techniques to estimate the M * values of our galaxies (log M * = 7.34 -11.54), and extrapolate this relationship to those galaxies with no imaging detections. Where available, we measure the absorption features present in the QSO spectrum due to the foreground galaxy and the relationships between their rest equivalent widths. We report an anti-correlation between impact parameter and E(B-V) (g−i) , as well as a correlation between galaxy color (u − r) and E(B-V) (g−i) . We find that our sample is one of late-type, star forming galaxies comparable to field galaxies in a similar redshift range, providing important clues to better understand absorption systems. These galaxies represent a sample of typical galaxies in the local Universe for which abundances, extinction, morphology, and absorption properties may be measured using background QSOs with great potential for follow-up observations.

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“…However, though broadly similar, the specific properties of the two sources show important differences. The optical counterpart to HI 1225+01 is bluer in color than AGC 229101 (with g − r ∼ 0; (Matsuoka et al 2012)), and it has active star formation (Salzer et al 1991) and is much more compact and likely less massive than AGC 229101, with a stellar mass of approximately 10 6 solar masses (Matsuoka et al 2012). Furthermore, the H i distribution of HI1225+01 has an even larger physical extent than does the H i gas in AGC 229101; in HI1225+01, the centers of the two clumps are separated by about 100 kpc and stretch over nearly 200 kpc.…”

Section: The Extreme Nature Of Agc 229101mentioning

confidence: 97%

“…The source has two H i components, with a total H i mass of approximately 2 × 10 9 solar masses, similar to the H i mass of AGC 229101. Moreover, the northeast clump of HI 1225+01 has a low surface brightness, blue optical counterpart while the other clump has no identified stellar emission (Salzer et al 1991;Matsuoka et al 2012).…”

Section: The Extreme Nature Of Agc 229101mentioning

confidence: 99%

The ALFALFA Almost-Dark Galaxy AGC~229101: A Two Billion Solar Mass HI Cloud with a Very Low Surface Brightness Optical Counterpart

Leisman,

Rhode,

Ball

et al. 2021

Preprint

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We present results from deep H i and optical imaging of AGC 229101, an unusual H i source detected at v helio = 7116 km s −1 in the ALFALFA survey. Initially classified as a candidate "dark" source because it lacks a clear optical counterpart in SDSS or DSS2 imaging, AGC 229101 has 10 9.31±0.05 M of H i, but an H i line width of only 43±9 km s −1 . Low resolution WSRT imaging and higher resolution VLA B-array imaging show that the source is significantly elongated, stretching over a projected length of ∼80 kpc. The HI imaging resolves the source into two parts of roughly equal mass. WIYN pODI optical imaging reveals a faint, blue optical counterpart coincident with the northern portion of the H i. The peak surface brightness of the optical source is only µ g ∼ 26.6 mag arcsec −2 , well below the typical cutoff that defines the isophotal edge of a galaxy, and its estimated stellar mass is only 10 7.32±0.33 M , yielding an overall neutral gas-to-stellar mass ratio of M HI /M * = 98 +111 −52 . We demonstrate the extreme nature of this object by comparing its properties to those of other H i-rich sources in ALFALFA and the literature. We also explore potential scenarios that might explain the existence of AGC 229101, including a tidal encounter with neighboring objects and a merger of two dark H i clouds.

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Updated Analysis of a “Dark” Galaxy and Its Blue Companion in the Virgo Cloud H I 1225 + 01

Cited by 14 publications

References 42 publications

The Enigmatic (Almost) Dark Galaxy Coma P: The Atomic Interstellar Medium

The Enigmatic (Almost) Dark Galaxy Coma P: The Atomic Interstellar Medium

Galactic nebular lines in the fibre spectra of background QSOs: reaching a hundred QSO–galaxy pairs with spectroscopic and photometric measurements

The ALFALFA Almost-Dark Galaxy AGC~229101: A Two Billion Solar Mass HI Cloud with a Very Low Surface Brightness Optical Counterpart

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