An $\ion{H}{i}$
 survey of the Centaurus and Sculptor groups

Blok, W. J. G. de; Dijkstra, Mark; Briggs, F.; Freeman, K. C.

doi:10.1051/0004-6361:20011553

Cited by 41 publications

(42 citation statements)

References 24 publications

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“…Prior evidence for preprocessing of the gas content in the group environment comes from estimates of the H I mass function (HIMF) which historically have been derived from individual groups or small group samples (e.g. Verheijen et al 2000;de Blok et al 2002;Kovac et al 2005;Freeland et al 2009;Kilborn et al 2009;Pisano et al 2011;Hess 2011). Despite the small number statistics, calculations of the group HIMF reliably suggest a flatter slope at the low mass end than the field or global HIMF.…”

Section: Halo Occupation Distributionmentioning

confidence: 99%

“…In any case, population studies derived from small samples of groups consistently show that the group H I mass function (HIMF) is flatter than the global HIMF, revealing either a paucity of low gas-mass galaxies or simply hinting that denser environments are harsh on low gas-mass galaxies (Verheijen et al 2000;de Blok et al 2002;Kovac et al 2005;Freeland et al 2009;Kilborn et al 2009;Pisano et al 2011;Hess 2011). While Freeland et al (2009) found that groups with a mix of morphological types exhibit more signs of recent tidal interactions than groups dominated by one morphological type.…”

Section: Introductionmentioning

confidence: 99%

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Evolution in the H I Gas Content of Galaxy Groups: Pre-Processing and Mass Assembly in the Current Epoch

2013

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We present an analysis of the neutral hydrogen (H I) content and distribution of galaxies in groups as a function of their parent dark matter halo mass. The Arecibo Legacy Fast ALFA survey α.40 data release allows us, for the first time, to study the H I properties of over 740 galaxy groups in the volume of sky common to the Sloan Digital Sky Survey and ALFALFA surveys. We assigned ALFALFA H I detections a group membership based on an existing magnitude/volume-limited SDSS DR7 group/cluster catalog. Additionally, we assigned group "proximity" membership to H I detected objects whose optical counterpart falls below the limiting optical magnitude-thereby not contributing substantially to the estimate of the group stellar mass, but significantly to the total group H I mass. We find that only 25% of the H I detected galaxies reside in groups or clusters, in contrast to approximately half of all optically detected galaxies. Further, we plot the relative positions of optical and H I detections in groups as a function of parent dark matter halo mass to reveal strong evidence that H I is being processed in galaxies as a result of the group environment: as optical membership increases, groups become increasingly deficient of H I rich galaxies at their center and the H I distribution of galaxies in the most massive groups starts to resemble the distribution observed in comparatively more extreme cluster environments. We find that the lowest H I mass objects lose their gas first as they are processed in the group environment, and it is evident that the infall of gas rich objects is important to the continuing growth of large scale structure at the present epoch, replenishing the neutral gas supply of groups. Finally, we compare our results to those of cosmological simulations and find that current models cannot simultaneously predict the H I selected halo occupation distribution for both low and high mass halos.

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Section: Halo Occupation Distributionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Evolution in the H I Gas Content of Galaxy Groups: Pre-Processing and Mass Assembly in the Current Epoch

2013

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“…However, since the Local Group and the Sculptor Group appear to form a filament of galaxies, rather than two unique groups (e.g., Jerjen et al 1998), the bias in the clouds distribution toward the southern and closest part of the group could actually be an extension of a population of Local Group intergalactic H i clouds in the direction of the closest group to the Local. This explanation places the detected clouds closer and makes them less massive (generally under 6 Â 10 6 M at 1 Mpc), leaving the nondetection in the northern half of the Sculptor Group and other groups open to further speculation (e.g., de Blok et al 2002;Zwaan 2001;Banks et al 1999). Although the diffuse connections between the clouds was used to argue for a closer origin above, extended H i at lower column densities might also be expected if the clouds are the equivalent of the Ly absorbers along filaments of galaxies.…”

Section: Relationship To the Sculptor Group Galaxies?mentioning

confidence: 99%

The Magellanic Stream, High‐Velocity Clouds, and the Sculptor Group

Putman

Staveley‐Smith

Freeman

et al. 2003

ApJ

291

401

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The Magellanic Stream is a 100 Â 10 filament of gas that lies within the Galactic halo and contains $2 Â 10 8 M of neutral hydrogen. In this paper we present data from the H i Parkes All Sky Survey (HIPASS) in the first complete survey of the entire Magellanic Stream and its surroundings. We also present a summary of the reprocessing techniques used to recover large-scale structure in the Stream. The substantial improvement in spatial resolution and angular coverage compared to previous surveys reveals a variety of prominent features, including bifurcation along the main Stream filament; dense, isolated clouds that follow the entire length of the Stream; head-tail structures; and a complex filamentary web at the head of the Stream where gas is being freshly stripped away from the Small Magellanic Cloud and the Bridge. Debris that appears to be of Magellanic origin extends out to 20 from the main Stream filaments. The Magellanic Stream has a velocity gradient of 700 km s À1 from the Clouds to the tail of the Stream, $390 km s À1 greater than that due to Galactic rotation alone, therefore implying a noncircular orbit. The dual filaments comprising the Stream are likely to be relics from gas stripped separately from the Magellanic Bridge and the SMC. This implies that (1) the Bridge is somewhat older than conventionally assumed; and (2) the Clouds have been bound together for at least one or two orbits. The transverse velocity gradient of the Stream also appears to support long-term binary motion of the Clouds. A significant number of the most elongated cataloged Stream clouds (containing $1% of the Stream mass) have position angles aligned along the Stream. This suggests the presence of shearing motions within the Stream, arising from tidal forces or interaction with the tenuous Galactic halo. As previously noted, clouds within one region of the Stream, along the sight line to the less distant half (southern half on the sky) of the Sculptor Group, show anomalous properties. There are more clouds along this sight line than any other part of the Stream, and their velocity distribution significantly deviates from the gradient along the Stream. We argue that this deviation could be due to a combination of halo material, and not to distant Sculptor clouds, based on a spatial and kinematic comparison between the Sculptor Group galaxies and the anomalous clouds and the lack of cloud detection in the northern half of the group. This result has significant implications for the hypothesis that there might exist distant, massive high-velocity clouds within the Local Group. Cataloged clouds within the Magellanic Stream do not have a preferred scale size. Their mass spectrum f ðM H i Þ / M À2:0 H i and column density spectrum f ðN H i Þ / N À2:8 H i are steep compared with Ly absorbers and galaxies, and similar to the anomalous clouds along the Sculptor Group sight line.

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“…Zwaan (2001) andde Blok (2002) made incomplete samplings of several galaxy groups to limits of a few × 10 6 M . Minchin et al (2003) surveyed the Cen A group to a limit of 2 × 10 6 M , and Pisano et al (2004Pisano et al ( , 2007 observed six Local Group analogs to (2-5) ×10…”

Section: Previous H I Surveys and Comparison With Ngc 2903mentioning

confidence: 99%

Λcdm Satellites and H I Companions—the Arecibo Alfa Survey of NGC 2903

Irwin¹,

Hoffman²,

Spekkens³

et al. 2009

ApJ

Self Cite

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We have conducted a deep, complete H i survey, using Arecibo/Arecibo L-band Feed Array (ALFA), of a field centered on the nearby, isolated galaxy, NGC 2903, which is similar to the Milky Way in its properties. The field size was 150 kpc × 260 kpc and the final velocity range spanned from 100 to 1133 km s −1 . The ALFA beams have been mapped as a function of azimuth and cleaned from each azimuth-specific cube prior to forming final cubes. The final H i data are sensitive down to an H i mass of 2 × 10 5 M and column density of 2 × 10 17 cm −2 at the 3 σ 2 δ V level, where σ is the rms noise level and δ V is the velocity resolution. NGC 2903 is found to have an H i envelope that is larger than previously known, extending to at least three times the optical diameter of the galaxy. Our search for companions yields one new discovery with an H i mass of 2.6×10 6 M . The companion is 64 kpc from NGC 2903 in projection, is likely associated with a small optical galaxy of similar total stellar mass, and is dark matter dominated, with a total mass >10 8 M . In the region surveyed, there are now two known companions: our new discovery and a previously known system that is likely a dwarf spheroidal, lacking H i content. If H i constitutes 1% of the total mass in all possible companions, then we should have detected 230 companions, according to Λ cold dark matter (ΛCDM) predictions. Consequently, if this number of dark-matter clumps are indeed present, then they contain less than 1% H i content, possibly existing as very faint dwarf spheroidals or as starless, gasless dark-matter clumps.

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An $\ion{H}{i}$ survey of the Centaurus and Sculptor groups

Cited by 41 publications

References 24 publications

Evolution in the H I Gas Content of Galaxy Groups: Pre-Processing and Mass Assembly in the Current Epoch

Evolution in the H I Gas Content of Galaxy Groups: Pre-Processing and Mass Assembly in the Current Epoch

The Magellanic Stream, High‐Velocity Clouds, and the Sculptor Group

Λcdm Satellites and H I Companions—the Arecibo Alfa Survey of NGC 2903

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