How Typical Are the Local Group Dwarf Galaxies?

Weisz, Daniel R.; Dolphin, Andrew E.; Dalcanton, Julianne J.; Skillman, Evan D.; Holtzman, Jon A.; Williams, Benjamin F.; Gilbert, Karoline M.; Seth, Anil; Cole, A. A.; Gogarten, Stephanie M.; Rosema, K. D.; Караченцев, И. Д.; McQuinn, Kristen B. W.; Zaritsky, Dennis

doi:10.1088/0004-637x/743/1/8

Cited by 77 publications

(101 citation statements)

References 50 publications

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“…It is known that star-forming dwarf galaxies reside in low density environments, with a majority having no massive galaxy in the close vicinity (Weisz et al 2011). The star formation triggering in dwarf galaxies is believed to both internal such as stochastic self propagating star formation mechanism (Gerola et al 1980) or external such as tidal interactions.…”

Section: Galaxy Environment and Tidal Interactionsmentioning

confidence: 99%

Tidal interaction, star formation and chemical evolution in blue compact dwarf galaxy Mrk 22

Paswan¹,

Omar²,

Jaiswal³

2017

Monthly Notices of the Royal Astronomical Society

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The optical spectroscopic and radio interferometric HI 21 cm-line observations of the blue compact dwarf galaxy Mrk 22 are presented. The Wolf-Rayet (WR) emission line features corresponding to high ionization lines of HeII λ4686 and CIV λ5808 from young massive stars are detected. The ages of two prominent star forming regions in the galaxy are estimated as ∼10 Myr and ∼ 4 Myr. The galaxy has non-thermal radio deficiency, which also indicates a young star-burst and lack of supernovae events from the current star formation activities, consistent with the detection of WR emission lines features. A significant N/O enrichment is seen in the fainter star forming region. The gas-phase metallicities [12 + log(O/H)] for the bright and faint regions are estimated as 7.98±0.07 and 7.46±0.09 respectively. The galaxy has a large diffuse HI envelop. The HI images reveal disturbed gas kinematics and HI clouds outside the optical extent of the galaxy, indicating recent tidal interaction or merger in the system. The results strongly indicate that Mrk 22 is undergoing a chemical and morphological evolution due to ongoing star formation, most likely triggered by a merger.

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Section: Galaxy Environment and Tidal Interactionsmentioning

confidence: 99%

Tidal interaction, star formation and chemical evolution in blue compact dwarf galaxy Mrk 22

Paswan¹,

Omar²,

Jaiswal³

2017

Monthly Notices of the Royal Astronomical Society

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“…Likewise, Weisz et al (2011b) find a pronounced morphology-distance relation. Outliers to the morphologydistance relation for LG dwarfs do exist, as the cases of the isolated Cetus and Tucana dwarf spheroidals (dSphs) demonstrate (e.g., Lewis et al 2007;Fraternali et al 2009;Monelli et al 2010a,b, and references therein).…”

Section: Confirm Thatmentioning

confidence: 90%

Population gradients and photometric metallicities in early- and transition-type dwarf galaxies: Clues from the Sculptor group

Lianou¹,

Grebel²,

Costa³

et al. 2013

A&A

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Aims. We focus on the resolved stellar populations of one early-type and four transition-type dwarf galaxies in the Sculptor group, with the aim to examine the potential presence of population gradients and place constraints on their mean metallicities. Methods. We use deep Hubble Space Telescope images to construct color-magnitude diagrams, from which we select stellar populations that trace different evolutionary phases in order to constrain their range of ages and metallicities, as well as to examine their spatial distribution. In addition, we use the resolved stars in the red giant branch in order to derive photometric metallicities. Results. All studied dwarfs contain intermediate-age stars with ages of ∼1 Gyr and older as traced by the luminous asymptotic giant branch and red clump stars, while the transition-type dwarfs contain also stars younger than ∼1 Gyr as traced by a young main sequence and vertical red clump stars. Moreover, the spatial distribution of the stars that trace different evolutionary phases shows a population gradient in all transition-type dwarfs. The derived error-weighted mean metallicities, assuming purely old stellar populations, range from −1.5 dex for ESO294-G010 to −1.9 dex for Scl-dE1, and should be considered as lower limits to their true metallicities. Assuming intermediate-age stellar populations to dominate the dwarfs, we derive upper limits for the metallicities that are 0.3 to 0.2 dex higher than the metallicities derived assuming purely old populations. We discuss how photometric metallicity gradients are affected by the age-metallicity degeneracy, which prevents strong conclusions regarding their actual presence. Finally, the transition-type dwarfs lie beyond the virial radius of their closest bright galaxy, as also observed for the Local Group transition-type dwarfs. Scl-dE1 is the only dwarf spheroidal in our sample and is an outlier in a potential morphology-distance relation, similar as the two isolated dwarf spheroidals of the Local Group, Tucana, and Cetus.

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“…Called dwarf transitionals, such galaxies have little ongoing star formation and often have detectable reservoirs of H I. The star-formation history of such galaxies was very similar to irregulars and spheroidals until roughly 1 Gyr ago (Weisz et al 2011a(Weisz et al , 2011b. The general interpretation is that dwarf transitionals are either between major episodes of star formation, or have simply permanently stopped forming stars (Grebel et al 2003;Skillman et al 2003).…”

Section: Between Bursts Of Star Formationmentioning

confidence: 99%

H i in Virgo’s “Red and Dead” Dwarf Ellipticals—A Tidal Tail and Central Star Formation

Hallenbeck

Koopmann

Giovanelli

et al. 2017

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We investigate a sample of three dwarf elliptical galaxies in the Virgo Cluster that have significant reservoirs of H I. We present deep optical imaging (from CFHT and KPNO), H I spectra (Arecibo), and resolved H I imaging (VLA) of this sample. These observations confirm their H I content and optical morphologies, and indicate that the gas is unlikely to be recently accreted. The sample has more in common with dwarf transitionals, though dwarf transitionals are generally lower in stellar mass and gas fraction. VCC 190 has an H I tidal tail from a recent encounter with the massive spiral galaxy NGC 4224. In VCC 611, blue star-forming features are observed that were not seen by shallower SDSS imaging.

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How Typical Are the Local Group Dwarf Galaxies?

Cited by 77 publications

References 50 publications

Tidal interaction, star formation and chemical evolution in blue compact dwarf galaxy Mrk 22

Tidal interaction, star formation and chemical evolution in blue compact dwarf galaxy Mrk 22

Population gradients and photometric metallicities in early- and transition-type dwarf galaxies: Clues from the Sculptor group

H i in Virgo’s “Red and Dead” Dwarf Ellipticals—A Tidal Tail and Central Star Formation

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