More Satellites of Spiral Galaxies

Zaritsky, Dennis; Smith, Rodney; Frenk, Carlos S.; White, Simon D. M.

doi:10.1086/303784

Cited by 205 publications

(234 citation statements)

References 17 publications

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“…The small redshift differences between SFDGs and companions, the distribution of which rises towards smaller values, are comparable to what is found for binary galaxies (Schneider & Salpeter 1992). In particular, a similar behaviour is reported for dwarf satellites of field spirals (Zaritsky et al 1997). This is illustrated in Figs.…”

Section: Frequency Distribution and Properties Of The Companion Candsupporting

confidence: 86%

“…Analogous to spiral companions, there is no evident correlation between ∆cz and s p for the SFDG companions. A plausible explanation of this issue was offered in the framework of a CDM scenario, taking into account a number of further dynamical arguments, by Zaritsky et al (1997). They consider the spiral satellites to be associated with an extended massive DM halo of the mother galaxy, which strongly influences the system's dynamics, so that ∆cz is widely independent of s p .…”

Section: Frequency Distribution and Properties Of The Companion Candmentioning

confidence: 99%

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On faint companions in the close environment of star-forming dwarf galaxies

Noeske

Iglésias-Páramo

Vı́lchez

et al. 2001

A&A

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Abstract.We have searched for companion galaxies in the close environment of 98 star-forming dwarf galaxies (SFDGs) from field and low density environments, using the NASA Extragalactic Database. Most of the companions are dwarf galaxies which due to observational selection effects were previously disregarded in environmental studies of SFDGs. A subsample at low redshift, cz < 2000 km s −1 , was chosen to partially eliminate the observational bias against distant dwarf companions. We find companion candidates for approximately 30% of the objects within a projected linear separation sp < 100 kpc and a redshift difference ∆cz < 500 km s −1 . The limited completeness of the available data sets, together with the non-negligible frequency of H i clouds in the vicinity of SFDGs indicated by recent radio surveys, suggest that a considerably larger fraction of these galaxies may be accompanied by low-mass systems. This casts doubt on the hypothesis that the majority of them can be considered truly isolated. The velocity differences between companion candidates and sample SFDGs amount typically to < ∼ 250 km s −1 , and show a rising distribution towards lower ∆cz. This is similarly found for dwarf satellites of spiral galaxies, suggesting a physical association between the companion candidates and the sample SFDGs. SFDGs with a close companion do not show significant differences in their Hβ equivalent widths and B −V colours as compared to isolated ones. However, the available data do not allow us to rule out that interactions with close dwarf companions can influence the star formation activity in SFDGs.

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Section: Frequency Distribution and Properties Of The Companion Candsupporting

confidence: 86%

Section: Frequency Distribution and Properties Of The Companion Candmentioning

confidence: 99%

On faint companions in the close environment of star-forming dwarf galaxies

Noeske

Iglésias-Páramo

Vı́lchez

et al. 2001

A&A

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“…Satellites to spiral galaxies appear to have a preference for polar orbits. This was first stated by Holmberg (1969) and has been confirmed for the Milky Way (e.g., Lynden-Bell 1982;Majewski 1994) and for other Milky Way-like spirals (Zaritsky et al 1997). Zaritsky & Gonzalez (1999) looked for a dynamical process that could be responsible for this anisotropy through galaxy formation models which start with a spherically symmetric distribution of matter.…”

Section: Alternative Explanationsmentioning

confidence: 75%

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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“…Occasional serendipitous discoveries have given us tantalizing glimpses of these kinds of phenomena, such as infalling dwarf galaxies surrounding Magellanic irregular galaxies (Wilcots, Lehman, & Miller 1996), and infalling gas clouds in LSB galaxies (de Blok & Walter 2000 ;de Blok, Walter, & Bell 1999). For the systems that are known, the dynamics of the infalling dwarf galaxies are an excellent indicator of the presence and mass of dark matter in the parent galaxy, especially since the dwarfs are found out to much larger radii than the galaxy disk (Zaritsky et al 1997).…”

Section: Introductionmentioning

confidence: 99%

On the Neutral Gas Content and Environment of NGC 3109 and the Antlia Dwarf Galaxy

Barnes

Blok

2001

The Astronomical Journal

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As part of a continuing survey of nearby galaxies, we have mapped the neutral gas content of the low surface brightness Magellanic-type galaxy NGC 3109 and its environment, including the Antlia dwarf galaxy, at unprecedented velocity resolution and brightness sensitivity. The H I mass of NGC 3109 is measured to be 3.8^0.5 ] 108A substantial warp in the disk of NGC 3109 is detected in the H I M _ . emission image in the form of an extended low surface brightness feature. We report a positive detection in H I of the nearby Antlia dwarf galaxy and measure its total neutral gas mass to be 6.8^1.4 ] 105We show the warp in NGC 3109 to lie at exactly the same radial velocity as the gas in the Antlia M _ . dwarf galaxy and speculate that Antlia disturbed the disk of NGC 3109 during a mild encounter D1 Gyr in the past. H I data for a further eight galaxies detected in the background are presented.

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More Satellites of Spiral Galaxies

Cited by 205 publications

References 17 publications

On faint companions in the close environment of star-forming dwarf galaxies

On faint companions in the close environment of star-forming dwarf galaxies

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

On the Neutral Gas Content and Environment of NGC 3109 and the Antlia Dwarf Galaxy

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