Redshift, metallicity and size of two extended dwarf Irregular galaxies: a link between dwarf Irregulars and ultra diffuse galaxies?
Date Issued
2017
Author(s)
•
Belokurov, V.
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•
Fraternali, F.
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•
Beccari, G.
•
•
Abstract
We present the results of the spectroscopic and photometric follow-up of two field galaxies that were selected as possible stellar counterparts of local high-velocity clouds. Our analysis shows that the two systems are distant (D > 20 Mpc) dwarf irregular galaxies unrelated to the local H I clouds. However, the newly derived distance and structural parameters reveal that the two galaxies have luminosities and effective radii very similar to the recently identified ultra diffuse galaxies (UDGs). At odds with classical UDGs, they are remarkably isolated, having no known giant galaxy within ∼2.0 Mpc. Moreover, one of them has a very high gas content compared to galaxies of similar stellar mass, with a H I to stellar mass ratio M_{H I}/M_{\star }∼ 90, typical of almost-dark dwarfs. Expanding on this finding, we show that extended dwarf irregulars overlap the distribution of UDGs in the MV versus log re plane and that the sequence including dwarf spheroidals, dwarf irregulars and UDGs appears as continuously populated in this plane. This may suggest an evolutionary link between dwarf irregulars and UDGs.
Volume
467
Issue
3
Start page
3751
Issn Identifier
0035-8711
Ads BibCode
2017MNRAS.467.3751B
Rights
open.access
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