HST-ACS photometry of the isolated dwarf galaxy VV124=UGC 4879

Bellazzini, M.; Perina, S.; Galleti, S.; Oosterloo, Thomas

doi:10.1051/0004-6361/201117275

Cited by 11 publications

(8 citation statements)

References 45 publications

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“…We measured a mean metallicity of [Fe/H] = −1.58± 0.06. This number agrees with previous photometric estimates: [Fe/H] = −1.37 (Kopylov et al 2008;Tikhonov et al 2010), [Fe/H] = −1.79 (Jacobs et al 2011), [M/H] = −1.5 (in the outskirts, B11a), and [M/H] = −1.4 (in the region 0.5 ′ < R ǫ < 1.0 ′ , where R ǫ is the elliptical radius, Bellazzini et al 2011b). The metallicities measured by Jacobs et al (2011) and Bellazzini et al (2011a,b) and Bellazzini et al (2011a,b) also noted that the great majority of old RGB stars have [Fe/H] ≤ −1.…”

Section: Metallicity Distributionsupporting

confidence: 92%

“…The rest are younger than 1 Gyr. Bellazzini et al (2011b) used the same HST images as Jacobs et al to show that the oldest, most metalpoor population is significantly more extended than the younger stars. The galaxy-averaged star formation rates that Jacobs et al derived were (3.0±0.2)×10 −4 M ⊙ yr −1 over the last 0.5 Gyr and (8.0 ± 0.5) × 10 −4 M ⊙ yr −1 over the last 1 Gyr.…”

Section: Introductionmentioning

confidence: 99%

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The Dynamics and Metallicity Distribution of the Distant Dwarf Galaxy Vv124

Kirby

Cohen

Bellazzini

2012

ApJ

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VV124 (UGC 4879) is an isolated, dwarf irregular/dwarf spheroidal (dIrr/dSph) transition-type galaxy at a distance of 1.36 Mpc. Previous low-resolution spectroscopy yielded inconsistent radial velocities for different components of the galaxy, and photometry hinted at the presence of a stellar disk. In order to quantify the stellar dynamics, we observed individual red giants in VV124 with the Keck/DEIMOS spectrograph. We validated members based on their positions in the color-magnitude diagram, radial velocities, and spectral features. Our sample contains 67 members. The average radial velocity is v r = −29.1 ± 1.3 km s −1 , in agreement with the previous radio measurements of H I gas. The velocity distribution is Gaussian, indicating that VV124 is supported primarily by velocity dispersion inside a radius of 1.5 kpc. Outside that radius, our measurements provide only an upper limit of 8.6 km s −1 on any rotation in the photometric disk-like feature. The velocity dispersion is σ v = 9.4 ± 1.0 km s −1 , from which we inferred a mass of M 1/2 = (2.1 ± 0.2) × 10 7 M ⊙ and a massto-light ratio of (M/L V ) 1/2 = 5.2 ± 1.1 M ⊙ /L ⊙ , both measured within the half-light radius. Thus, VV124 contains dark matter. We also measured the metallicity distribution from neutral iron lines. The average metallicity, [Fe/H] = −1.58 ± 0.06, is consistent with the mass-metallicity relation defined by dwarf spheroidal galaxies. The dynamics and metallicity distribution of VV124 appear similar to dSphs of similar stellar mass.

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Section: Metallicity Distributionsupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

The Dynamics and Metallicity Distribution of the Distant Dwarf Galaxy Vv124

Kirby

Cohen

Bellazzini

2012

ApJ

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“…We reduced and analysed independently the S17 dataset to have a deeper insight on the stellar populations in SECCO 1 by combining the HST-ACS and MUSE data. Positions and photometry of individual stars were obtained with the ACS module of the point spread function (PSF) fitting package DOLPHOT v.2.0 Dolphin (2000), as described, for example, in Bellazzini et al (2011b). We adopted a threshold of 2.5σ above the background for the source detection.…”

Section: Discussionmentioning

confidence: 99%

Alone on a wide wide sea. The origin of SECCO 1, an isolated star-forming gas cloud in the Virgo cluster*†‡

Bellazzini¹,

Armillotta

Perina

et al. 2018

Monthly Notices of the Royal Astronomical Society

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SECCO 1 is an extremely dark, low-mass (M 10 5 M ), star-forming stellar system lying in the Low Velocity Cloud (LVC) substructure of the Virgo cluster of galaxies, and hosting several Hii regions. Here we review our knowledge of this remarkable system, and present the results of (a) additional analysis of our panoramic spectroscopic observations with MUSE, (b) the combined analysis of Hubble Space Telescope and MUSE data, and (c) new narrow-band observations obtained with OSIRIS@GTC to search for additional Hii regions in the surroundings of the system. We provide new evidence supporting an age as young as < ∼ 4 Myr for the stars that are currently ionising the gas in SECCO 1. We identify only one new promising candidate Hii region possibly associated with SECCO 1, thus confirming the extreme isolation of the system. We also identify three additional candidate pressure-supported dark clouds in Virgo among the targets of the SECCO survey. Various possible hypotheses for the nature and origin of SECCO 1 are considered and discussed, also with the help of dedicated hydrodynamical simulations showing that a hydrogen cloud with the characteristics of SECCO 1 can likely survive for > ∼ 1 Gyr while traveling within the LVC Intra Cluster Medium.

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“…In Fig. 5 the CMDs for two large radial ranges of the IN6 sample is presented as a greyscale Hess diagram (as in Bellazzini et al 2011b). Some features are more clearly seen in this diagram, such as the density peak of the RC and a weak overdensity above the RGB Tip that may trace the AGB population identified by M05 and Gullieuszik et al (2007).…”

Section: The Colour−magnitude Diagramsmentioning

confidence: 93%

The extended structure of the dwarf irregular galaxy Sagittarius

Beccari¹,

Bellazzini²,

Fraternali³

et al. 2014

A&A

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We present a detailed study of the stellar and H  structure of the dwarf irregular galaxy Sagittarius. We use new deep and wide field photometry to trace the surface brightness profile of the galaxy out to 5.0 (corresponding to 1600 pc) and down to µ V 30.0 mag/arcsec 2 , thus showing that the stellar body of the galaxy is much more extended than previously believed, and it is similarly (or more) extended than the overall H  distribution. The whole major-axis profile is consistent with a pure exponential, with a scale radius of 340 pc. The surface density maps reveal that the distribution of old and intermediate-age stars is smooth and remarkably flattened out to its edges, while the associated H  has a much rounder shape, is off-centred and presents multiple density maxima and a significant hole. No clear sign of systemic rotation is detectable in the complex H  velocity field. No metallicity gradient is detected in the old and intermediate age population of the galaxy, and we confirm that this population has a much more extended distribution than young stars (age < ∼ 1 Gyr).

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HST-ACS photometry of the isolated dwarf galaxy VV124=UGC 4879

Cited by 11 publications

References 45 publications

The Dynamics and Metallicity Distribution of the Distant Dwarf Galaxy Vv124

The Dynamics and Metallicity Distribution of the Distant Dwarf Galaxy Vv124

Alone on a wide wide sea. The origin of SECCO 1, an isolated star-forming gas cloud in the Virgo cluster*†‡

The extended structure of the dwarf irregular galaxy Sagittarius

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