scholarly journals The ALFALFA Almost Dark Galaxy AGC 229101: A 2 Billion Solar Mass H i Cloud with a Very Low Surface Brightness Optical Counterpart

2021 ◽  
Vol 162 (6) ◽  
pp. 274
Author(s):  
Lukas Leisman ◽  
Katherine L. Rhode ◽  
Catherine Ball ◽  
Hannah J. Pagel ◽  
John M. Cannon ◽  
...  
Keyword(s):  
Optical Imaging ◽  
Surface Brightness ◽  
Stellar Mass ◽  
Equal Mass ◽  
Optical Counterpart ◽  
Solar Mass ◽  
Optical Source ◽  
Very Large Array ◽  
Neutral Gas ◽  
Sky Survey

Abstract 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 Arecibo Legacy Fast ALFA (ALFALFA) blind H i survey. Initially classified as a candidate “dark” source because it lacks a clear optical counterpart in Sloan Digital Sky Survey (SDSS) or Digitized Sky Survey 2 (DSS2) imaging, AGC 229101 has 109.31±0.05 M ⊙ of H i, but an H i line width of only 43 ± 9 km s−1. Low-resolution Westerbork Synthesis Radio Telescope (WSRT) imaging and higher-resolution Very Large Array (VLA) B-array imaging show that the source is significantly elongated, stretching over a projected length of ∼80 kpc. The H i imaging resolves the source into two parts of roughly equal mass. WIYN partially populated One Degree Imager (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 107.32±0.33 M ⊙, yielding an overall neutral gas-to-stellar mass ratio of M/M * = 98 − 52 + 111 . We demonstrate the extreme nature of this object by comparing its properties with 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.

scholarly journals Deep Observations with the Parkes 21-cm Multibeam System

1999 ◽  
Vol 16 (1) ◽  
pp. 66-69 ◽  
Author(s):  
M. J. Disney ◽  
P. J. Boyce ◽  
G. D. Banks ◽  
R. F. Minchin ◽  
A. E. Wright
Keyword(s):  
Preliminary Analysis ◽  
Surface Brightness ◽  
Signal To Noise Ratio ◽  
Optical Counterpart ◽  
Signal To Noise ◽  
Beam System ◽  
Sky Survey ◽  
Low Surface Brightness ◽  
Noise Ratio

AbstractWe report on a preliminary analysis of a 5600 sec per point survey of 32 square degrees in Centaurus, carried out with the Parkes 13-beam system. The signal-to-noise ratio is found to improve as for the whole integration. We have detected 102 HI sources between +250 and +12,700 km s−1 either by eye or by using the new galaxy-finding algorithm PICASSO. Over half of these are new HI detections. Around a dozen of these are not associated with catalogued galaxies and, in two of these cases, we have not identified an optical counterpart on the Digitized Sky Survey. Arguments are put forward to explain why deep integrations are needed to find low surface brightness objects.

scholarly journals The quantity of dark matter in early-type galaxies and its relation to the environment

2019 ◽  
Vol 488 (1) ◽  
pp. 1320-1331 ◽  
Author(s):  
A Nigoche-Netro ◽  
G Ramos-Larios ◽  
P Lagos ◽  
E de la Fuente ◽  
A Ruelas-Mayorga ◽  
...  
Keyword(s):  
Dark Matter ◽  
Surface Brightness ◽  
Stellar Mass ◽  
Sloan Digital Sky Survey ◽  
Early Type ◽  
Dynamical Mass ◽  
Redshift Range ◽  
Sky Survey ◽  
The Impact ◽  
Mass Functions

ABSTRACT We study the behaviour of the dynamical and stellar mass inside the effective radius of early-type galaxies (ETGs) as a function of environment considering Newtonian dynamics, different surface-brightness profiles, different initial mass functions (IMF), and different redshift ranges. We use several samples of ETGs – ranging from 19 000 to 98 000 objects – from the ninth data release of the Sloan Digital Sky Survey. We assume that any difference between the dynamical and stellar mass is due to dark matter and/or a non-universal IMF. The main results, considering samples in the redshift range 0.0024 ≤ z ≤ 0.35, are as follows: (i) the amount of dark matter inside ETGs depends on the environment; (ii) ETGs in low-density environments span a wider dark matter range than ETGs in dense environments; (iii) the amount of dark matter inside ETGs in the most dense environments will be less than approximately 55–75 per cent of the dynamical mass; (iv) the accurate value of this upper limit depends on the impact of the IMF on the stellar mass estimation; (v) in the case of an ETG sample which is approximately complete for log(MVirial/MSun) > 10.5 and in the redshift range 0.04 ≤ z ≤ 0.08, we find that the amount of dark matter in the most dense environments will be less than approximately 60–65 per cent of the dynamical mass.

scholarly journals Discovery of a large H i ring around the quiescent galaxy AGC 203001

2019 ◽  
Author(s):  
Omkar Bait ◽  
Sushma Kurapati ◽  
Pierre-Alain Duc ◽  
Jean-Charles Cuillandre ◽  
Yogesh Wadadekar ◽  
...  
Keyword(s):  
Star Formation ◽  
Optical Imaging ◽  
Radio Telescope ◽  
Surface Brightness ◽  
Optical Emission ◽  
Optical Counterpart ◽  
Density Waves ◽  
Brightness Level ◽  
Ring Galaxies ◽  
The Impact

Abstract Here we report the discovery with the Giant Metrewave Radio Telescope of an extremely large (∼115 kpc in diameter) H i ring, located around a massive quenched galaxy, AGC 203001, but off-centered, with respect to it. This ring does not have any bright extended optical counterpart unlike several other known ring galaxies. Our deep g, r, and i optical imaging of the H i ring, using the MegaCam instrument on the Canada-France-Hawaii Telescope, shows however several regions with faint optical emission at a surface brightness level of ∼28 mag/arcsec2. Such an extended H i structure is very rare with only one other case known so far – the Leo ring. Conventionally, off-centered rings have been explained by a collision with an “intruder” galaxy leading to expanding density waves of gas and stars in the form of a ring. However, in such a scenario the impact also leads to large amounts of star formation in the ring which is not observed in the ring presented in this paper. We discuss possible scenarios for the formation of such H i dominated rings.

scholarly journals Deep optical imaging of the dark galaxy candidate AGESVC1 282

2020 ◽  
Vol 642 ◽  
pp. L10
Author(s):  
Michal Bílek ◽  
Oliver Müller ◽  
Ana Vudragović ◽  
Rhys Taylor
Keyword(s):  
Surface Brightness ◽  
Stellar Mass ◽  
Virgo Cluster ◽  
Sloan Digital Sky Survey ◽  
Dark Matter Halos ◽  
Mass Ratio ◽  
Stellar Content ◽  
Dark Clouds ◽  
Sky Survey ◽  
Galaxy Environment

The blind H I survey Arecibo Galaxy Environment Survey (AGES) detected several unresolved sources in the Virgo cluster, which do not have optical counterparts in the Sloan Digital Sky Survey. The origin of these dark clouds is unknown. They might be crucial objects since they could be the so-called dark galaxies, that is, the dark matter halos without stellar content that are expected from cosmological simulations. In order to reveal the nature of the dark clouds, we took a deep optical image of one them, AGESVC1 282, with the newly-commissioned 1.4 m Milanković Telescope. After observing it for 10.4 h in the L-filter, the image reached a surface-brightness limit of about 29.1 mag arcsec−2 in V. No optical counterpart was detected. We placed an upper limit on the V-band luminosity of the object of 1.1 × 107 L⊙, giving a stellar mass below 1.4 × 107 M⊙ and a H I-to-stellar mass ratio above 3.1. By inspecting archival H I observations of the surrounding region, we found that none of the standard explanations for optically dark H I clouds fits the available constraints on this object.

scholarly journals CN Com: a Typical RS Canum Venaticorum Star

1995 ◽  
Vol 151 ◽  
pp. 106-107
Author(s):  
G.A. Richter ◽  
J. Greiner
Keyword(s):  
Time Interval ◽  
Optical Counterpart ◽  
X Ray ◽  
Sky Survey ◽  
Error Circle

CN Com = CSV 6907 was dicovered by Romano (1958). First we note that the GCVS (and Simbad) coordinates are wrong by ≈2′. Using the finding chart of Romano (1958) and the APM data (digitized POSS), the correct coordinates of CN Com are R.A.(2000.0) = 12h19m47s.0, DEC(2000.0) = +16°30′50″.CN Com is only 8″ distant from the ROSAT X-ray source RX J1219.7+1630 detected during the All-Sky-Survey at a PSPC countrate of 0.022 cts/s. Due to the positional proximity and the absence of other optical objects brighter than 20rmm within the about 30″ error circle, CN Com is very probably the optical counterpart of RX J1219.7+1630.CN Com was investigated on some 600 photographic plates (Sonneberg astrographs 400/1600 mm and 400/2000 mm) of the fields 26 Com and 5 Com, covering the time interval from 1962 to 1994 (with only a very few plates from the years 1967-1974).

scholarly journals The weak imprint of environment on the stellar populations of galaxies

2020 ◽  
Vol 500 (4) ◽  
pp. 4469-4490 ◽  
Author(s):  
James Trussler ◽  
Roberto Maiolino ◽  
Claudia Maraston ◽  
Yingjie Peng ◽  
Daniel Thomas ◽  
...  
Keyword(s):  
Environmental Effects ◽  
Unique Feature ◽  
Stellar Populations ◽  
Stellar Mass ◽  
Sloan Digital Sky Survey ◽  
Star Forming ◽  
Sky Survey ◽  
Satellite Galaxies ◽  
Projected Distance ◽  
Environmental Dependence

ABSTRACT We investigate the environmental dependence of the stellar populations of galaxies in Sloan Digital Sky Survey Data Release 7 (SDSS DR7). Echoing earlier works, we find that satellites are both more metal-rich (<0.1 dex) and older (<2 Gyr) than centrals of the same stellar mass. However, after separating star-forming, green valley, and passive galaxies, we find that the true environmental dependence of both stellar metallicity (<0.03 dex) and age (<0.5 Gyr) is in fact much weaker. We show that the strong environmental effects found when galaxies are not differentiated result from a combination of selection effects brought about by the environmental dependence of the quenched fraction of galaxies, and thus we strongly advocate for the separation of star-forming, green valley, and passive galaxies when the environmental dependence of galaxy properties are investigated. We also study further environmental trends separately for both central and satellite galaxies. We find that star-forming galaxies show no environmental effects, neither for centrals nor for satellites. In contrast, the stellar metallicities of passive and green valley satellites increase weakly (<0.05 and <0.08 dex, respectively) with increasing halo mass, increasing local overdensity and decreasing projected distance from their central; this effect is interpreted in terms of moderate environmental starvation (‘strangulation’) contributing to the quenching of satellite galaxies. Finally, we find a unique feature in the stellar mass–stellar metallicity relation for passive centrals, where galaxies in more massive haloes have larger stellar mass (∼0.1 dex) at constant stellar metallicity; this effect is interpreted in terms of dry merging of passive central galaxies and/or progenitor bias.

scholarly journals Delayed Stellar Mass Assembly in the Low Surface Brightness Dwarf Galaxy KDG 215

2018 ◽  
Vol 864 (1) ◽  
pp. L14 ◽  
Author(s):  
John M. Cannon ◽  
Zili Shen ◽  
Kristen B. W. McQuinn ◽  
Joshua Bartz ◽  
Lilly Bralts-Kelly ◽  
...  
Keyword(s):  
Surface Brightness ◽  
Dwarf Galaxy ◽  
Stellar Mass ◽  
Low Surface Brightness ◽  
Mass Assembly

scholarly journals Surface Photometry of Spiral Galaxy NGC 5005 and Elliptical Galaxy NGC 4278

2018 ◽  
Vol 15 (3) ◽  
pp. 314-323
Author(s):  
Baghdad Science Journal
Keyword(s):  
Spiral Galaxy ◽  
Surface Brightness ◽  
Elliptical Galaxy ◽  
Position Angle ◽  
Sloan Digital Sky Survey ◽  
Surface Photometry ◽  
Contour Maps ◽  
Sky Survey ◽  
Flat Field ◽  
The Galaxy

Two galaxies have been chosen, spiral galaxy NGC 5005 and elliptical galaxy NGC 4278 to study their photometric properties by using surface photometric techniques with griz-Filters. Observations are obtained from the Sloan Digital Sky Survey (SDSS). The data reduction of all images have done, like bias and flat field, by SDSS pipeline. The overall structure of the two galaxies (a bulge, a disk), together with isophotal contour maps, surface brightness profiles and a bulge/disk decomposition of the galaxy images were performed, although the disk position angle, ellipticity and inclination of the galaxies have been estimated.

scholarly journals Surveys of Low Surface Brightness Galaxies by 4415 Films

1994 ◽  
Vol 161 ◽  
pp. 541-544
Author(s):  
S. Phillipps ◽  
Q.A. Parker
Keyword(s):  
Surface Brightness ◽  
Signal To Noise ◽  
The Past ◽  
Cluster Area ◽  
Sky Survey ◽  
Low Surface Brightness ◽  
Low Surface Brightness Galaxies

During the past few years there have been a number of surveys for low surface brightness galaxies (LSBGs). Searches using both photographic and CCD data have shown that LSBGs are actually very numerous (Impey, Bothun & Malin 1987; Irwin et al. 1990). However, they are seriously biased against in any random sky survey, and even in a cluster area there are inherent size and signal-to-noise problems. The number of objects we can detect are therefore limited in two ways.

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