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Titolo:
Radial velocity of the Phoenix dwarf galaxy: Linking stars and H Iota gas
Autore:
Gallart, C; Martinez-Delgado, D; Gomez-Flechoso, MA; Mateo, M;
Indirizzi:
Univ Chile, Dept Astron, Santiago, Chile Univ Chile Santiago ChileUniv Chile, Dept Astron, Santiago, Chile Yale Univ, Dept Astron, New Haven, CT 06520 USA Yale Univ New Haven CT USA 06520 iv, Dept Astron, New Haven, CT 06520 USA Inst Astrofis Canarias, E-38200 La Laguna, Spain Inst Astrofis Canarias La Laguna Spain E-38200 E-38200 La Laguna, Spain Observ Geneva, CH-1290 Sauverny, Switzerland Observ Geneva Sauverny Switzerland CH-1290 CH-1290 Sauverny, Switzerland Univ Michigan, Dept Astron, Ann Arbor, MI 48109 USA Univ Michigan Ann Arbor MI USA 48109 Dept Astron, Ann Arbor, MI 48109 USA
Titolo Testata:
ASTRONOMICAL JOURNAL
fascicolo: 5, volume: 121, anno: 2001,
pagine: 2572 - 2583
SICI:
0004-6256(200105)121:5<2572:RVOTPD>2.0.ZU;2-6
Fonte:
ISI
Lingua:
ENG
Soggetto:
LOCAL GROUP; SPHEROIDAL GALAXY; GALACTIC HALO; LEO-I; MASS; EVOLUTION; MATTER; CLUSTERS; HISTORY; ORIGIN;
Keywords:
galaxies : dwarf; galaxies : evolution; galaxies : individual (Phoenix Dwarf); ISM : H Iota; Local Group;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
50
Recensione:
Indirizzi per estratti:
Indirizzo: Gallart, C Univ Chile, Dept Astron, Casilla 36-D, Santiago, Chile Univ Chile Casilla 36-D Santiago Chile 36-D, Santiago, Chile
Citazione:
C. Gallart et al., "Radial velocity of the Phoenix dwarf galaxy: Linking stars and H Iota gas", ASTRONOM J, 121(5), 2001, pp. 2572-2583

Abstract

We present the first radial velocity measurement of the stellar component of the Local Group dwarf galaxy Phoenix, using the FORS1 instrument at the VLT's Unit Telescope 1 (Antu). From the spectra of 31 red giant branch stars, we derive a heliocentric optical radial velocity for Phoenix of V. = -52+/- 6 km s(-1). On the basis of this velocity, and taking into account theresults of a series of semianalytical and numerical simulations, we discuss the possible association of the H I clouds observed in the Phoenix vicinity. We conclude that the characteristics of the H I cloud with heliocentricvelocity -23 km s(-1) are consistent with this gas having been associated with Phoenix in the past and being lost by the galaxy after the last event of star formation in the galaxy, about 100 Myr ago. Two possible scenarios are discussed : the ejection of the gas by the energy released by the supernovae (SNe) produced in that last event of star formation and a ram pressure stripping scenario. We derive that the kinetic energy necessary to eject the gas is E-SNe similar to 2 x 10(51) ergs and that the number of SNe necessary to transfer this amount of kinetic energy to the gas cloud is similarto 20. This is consistent with the number of SNe expected for the last event of star formation in Phoenix, according to the star formation history derived by Gallart, & Aparicio. The drawback of this scenario is the regular appearance of the Martinez-Delgado, H I cloud and its anisotropic distribution with respect to the stellar component. Another possibility is that the H I gas was stripped as a consequence of ram pressure by the intergalactic medium. In our simulations, the structure of the gas remains quite smooth as it is stripped from Phoenix, keeping a distribution similar to that of the observed H I cloud. Both in the SNe ejection case and in the ram pressuresweeping scenario, the distances and relative velocities imply that the H I cloud is not gravitationally bound to Phoenix, since this would require aPhoenix total mass about an order of magnitude larger than its total estimated mass. Finally, we discuss the possibility that Phoenix may be a bound Milky Way satellite. The minimum required mass of the Milky Way for Phoenixto be bound is M-MW (<450 kpc) <greater than or equal to> 1.2 x 10(12) M.,which comfortably fits within most current estimates.

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Documento generato il 19/01/20 alle ore 20:52:20