A New Local Group Galaxy in Cetus

Whiting, Alan B.; Hau, G. K. T.; Irwin, M. J.

doi:10.1086/301142

Cited by 79 publications

(76 citation statements)

References 28 publications

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“…Absolute magnitudes and half-light radii are taken from from Walker et al (2010) and from Kalirai et al (2010); when lacking in these sources they have been drawn from Mateo (1998). Surface brightness estimates have been taken from Mateo (1998), McConnachie & Irwin (2006), Martin et al (2009, Irwin et al (2008), and Whiting et al (1999), with this priority. All the values of surface brightness are corrected for extinction.…”

Section: Summary and Discussionmentioning

confidence: 99%

An optical and H i study of the dwarf Local Group galaxy VV124 = UGC4879

Bellazzini

Beccari

Oosterloo

et al. 2011

A&A

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We present a detailed study of the dwarf galaxy VV124 (UGC4879), recently recognized as a remarkably isolated member of the Local Group. We have obtained deep (r 26.5) wide-field (23 × 23 ) g,r photometry of individual stars with the LBC camera at the Large Binocular Telescope under sub-arcsec seeing conditions. The color-magnitude diagram suggests that the stellar content of the galaxy is dominated by an old, metal-poor population, with a significant metallicity spread. A very clean detection of the RGB tip allows us to derive an accurate distance of D = 1.3 ± 0.1 Mpc. Combining surface photometry with star counts, we are able to trace the surface brightness profile of VV124 out to ∼5 1.9 kpc radius (where μ r 30 mag/arcsec 2 ), showing that it is much more extended than previously believed. Moreover, the surface density map reveals the presence of two symmetric flattened wings emanating from the central elongated spheroid and aligned with its major axis, resembling a stellar disk seen nearly edge-on. We also present H i observations obtained with the Westerbork Synthesis Radio Telescope (WSRT), the first ever of this object. A total amount of 10 6 M of H i gas is detected in VV124. Compared to the total luminosity, this gives a value of M HI /L V = 0.11, which is particularly low for isolated Local Group dwarfs. The spatial distribution of the gas does not correlate with the observed stellar wings. The systemic velocity of the H i in the region superposed to the stellar main body of the galaxy is V h = −25 km s −1 . The velocity field shows substructures typical of galaxies of this size but no sign of rotation. The H i spectra indicates the presence of a two-phase interstellar medium, again typical of many dwarf galaxies.

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Section: Summary and Discussionmentioning

confidence: 99%

An optical and H i study of the dwarf Local Group galaxy VV124 = UGC4879

Bellazzini

Beccari

Oosterloo

et al. 2011

A&A

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“…In the Local Group, ''latetype'' dwarf galaxies (spiral or irregular galaxies) tend to be blue, although a large fraction ($50%) of the known dwarf galaxies (M V > À14) are ''early types'' (dwarf spheroidal and elliptical galaxies) and have red colors typical of high-luminosity galaxies. In the past few years, there have been several new detections of low-luminosity objects in the Local Group (Ibata et al 1995;Armandroff et al 1998Armandroff et al , 1999Whiting et al 1999;Zucker et al 2004;Willman et al 2005).…”

Section: Motivationmentioning

confidence: 99%

The Properties and Luminosity Function of Extremely Low Luminosity Galaxies

Blanton

Lupton

Schlegel

et al. 2005

ApJ

416

662

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We examine a sample of low-redshift (10 h À1 Mpc < d < 150 h À1 Mpc) field galaxies including galaxies with luminosities as low as M r À 5 log h $ À12:5, selected from the Sloan Digital Sky Survey Data Release 2 (SDSS DR2). The sample is unique in containing galaxies of extremely low luminosities in a wide range of environments, selected with uniform and well-understood criteria. We present the luminosity function, as well as the broadband properties, of low-luminosity galaxies in this sample. A Schechter function is an insufficient parameterization of the r-band luminosity function; there is an upturn in the slope for M r À 5 log h > À18. The resulting slope at low luminosities in this sample is 2 $ À1:3. However, we almost certainly miss a large number of galaxies at very low luminosities due to low surface brightness selection effects, and we estimate that the true low-luminosity slope may be as steep as or steeper than 2 $ À1:5. The results here are consistent with previous SDSS results and, in the g band, roughly consistent with the results of the Two Degree Field Galaxy Redshift Survey. Extremely low luminosity galaxies are predominantly low surface brightness, exponential disks, the majority of which are red.

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“…In that context it is interesting to note that the latest discoveries of new faint LG members with M V −9 mag (e.g. Armandroff et al 1999;Whiting et al 1999;Zucker et al 2004) are restricted to rather small scale sizes. This may indicate that the LG dE sample is more incomplete at smaller than at larger galaxy sizes.…”

Section: Magnitude-surface Brightness Relationmentioning

confidence: 99%

The early-type dwarf galaxy population of the Fornax cluster

Mieske¹,

Hilker²,

Infante³

et al. 2006

A&A

147

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Aims. We analyse the photometric properties of the early-type Fornax cluster dwarf-galaxy population (M V > −17 mag), based on a wide-field imaging study of the central cluster area in V and I bandpasses. We used the instrument/telescope combination IMACS/Magellan at Las Campanas Observatory, providing much larger light-collecting area and better image resolution than previous wide-field imaging surveys. Methods. We created a fiducial sample of Fornax cluster dwarf ellipticals (dEs) in the following three steps. (1) To verify cluster membership, we measured I-band surface brightness fluctuations (SBF) distances to candidate dEs known from previous surveys.(2) We re-assessed morphological classifications for those candidate dEs that are too faint for SBF detection. (3) We searched for new candidate dEs in the size-luminosity regime close to the resolution limit of previous surveys. Results.(1) We confirm cluster membership for 28 candidate dEs in the range −16.6 < M V < −10.1 mag by means of SBF measurement. We find no SBF background galaxy. (2) Of 51 other candidate dEs in the range −13.2 < M V < −8.6 mag, 2/3 are confirmed as probable cluster members by morphological re-assessment, while 1/3 are re-classified as probable background objects. (3) We find 12 new dE candidates in the range −12.3 < M V < −8.8 mag, two of which are directly confirmed via SBF measurement. The resulting fiducial dE sample follows a well-defined surface brightness-magnitude relation, showing that Fornax dEs are about 40% larger than Local Group dEs. The sample also defines a colour-magnitude relation that appears slightly shallower than that of Local Group dEs. The early-type dwarf galaxy luminosity function in Fornax has a very flat faint end slope α −1.1 ± 0.1. We discuss these findings in the context of structure-formation theories. Conclusions. The SBF method is a very powerful tool to help constrain the faint end of the galaxy luminosity function in nearby galaxy clusters. For the Fornax cluster, morphological cluster memberships -if performed at sufficient resolution -are very reliable.

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A New Local Group Galaxy in Cetus

Cited by 79 publications

References 28 publications

An optical and H i study of the dwarf Local Group galaxy VV124 = UGC4879

An optical and H i study of the dwarf Local Group galaxy VV124 = UGC4879

The Properties and Luminosity Function of Extremely Low Luminosity Galaxies

The early-type dwarf galaxy population of the Fornax cluster

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