TY - JOUR
T1 - Alfalfa discovery of the nearby gas-rich dwarf galaxy Leo P. I. HI observations
AU - Giovanelli, Riccardo
AU - Haynes, Martha P.
AU - Adams, Elizabeth A.K.
AU - Cannon, John M.
AU - Rhode, Katherine L.
AU - Salzer, John J.
AU - Skillman, Evan D.
AU - Bernstein-Cooper, Elijah Z.
AU - McQuinn, Kristen B.W.
PY - 2013/7
Y1 - 2013/7
N2 - The discovery of a previously unknown 21 cm H I line source identified as an ultra-compact high velocity cloud in the ALFALFA survey is reported. The H I detection is barely resolved by the Arecibo 305 m telescope ∼4′ beam and has a narrow H I linewidth (half-power full width of 24 km s-1). Further H I observations at Arecibo and with the Very Large Array corroborate the ALFALFA H I detection, provide an estimate of the H I radius, ∼1′ at the 5 × 1019 cm-2 isophote, and show the cloud to exhibit a velocity field which, if interpreted as disk rotation, has an amplitude of ≃9.0 ± 1.5 km s-1. In other papers, Rhode et al. show the H I source to have a resolved stellar counterpart and ongoing star forming activity, while Skillman et al. reveal it as having extremely low metallicity: 12 + log (O/H) = 7.16 ± 0.04. The H I mass to stellar mass ratio of the object is found to be 2.6. We use the Tully-Fisher template relation in its baryonic form to obtain a distance estimate . Additional constraints on the distance are also provided by the optical data of Rhode et al. and McQuinn et al., both indicating a distance in the range of 1.5 to 2.0 Mpc. The three estimates are compatible within their errors. The object appears to be located beyond the dynamical boundaries of, but still in close proximity to the Local Group. Its pristine properties are consistent with the sedate environment of its location. At a nominal distance of 1.75 Mpc, it would have an H I mass of ≃ 1.0 × 106 M⊙, a stellar mass of ≃ 3.6 × 105 M⊙, and a dynamical mass within the H I radius of ≃ 1.5 × 107 M ⊙. This discovery supports the idea that optically faint - or altogether dark - low mass halos may be detectable through their non-stellar baryons.
AB - The discovery of a previously unknown 21 cm H I line source identified as an ultra-compact high velocity cloud in the ALFALFA survey is reported. The H I detection is barely resolved by the Arecibo 305 m telescope ∼4′ beam and has a narrow H I linewidth (half-power full width of 24 km s-1). Further H I observations at Arecibo and with the Very Large Array corroborate the ALFALFA H I detection, provide an estimate of the H I radius, ∼1′ at the 5 × 1019 cm-2 isophote, and show the cloud to exhibit a velocity field which, if interpreted as disk rotation, has an amplitude of ≃9.0 ± 1.5 km s-1. In other papers, Rhode et al. show the H I source to have a resolved stellar counterpart and ongoing star forming activity, while Skillman et al. reveal it as having extremely low metallicity: 12 + log (O/H) = 7.16 ± 0.04. The H I mass to stellar mass ratio of the object is found to be 2.6. We use the Tully-Fisher template relation in its baryonic form to obtain a distance estimate . Additional constraints on the distance are also provided by the optical data of Rhode et al. and McQuinn et al., both indicating a distance in the range of 1.5 to 2.0 Mpc. The three estimates are compatible within their errors. The object appears to be located beyond the dynamical boundaries of, but still in close proximity to the Local Group. Its pristine properties are consistent with the sedate environment of its location. At a nominal distance of 1.75 Mpc, it would have an H I mass of ≃ 1.0 × 106 M⊙, a stellar mass of ≃ 3.6 × 105 M⊙, and a dynamical mass within the H I radius of ≃ 1.5 × 107 M ⊙. This discovery supports the idea that optically faint - or altogether dark - low mass halos may be detectable through their non-stellar baryons.
KW - galaxies: distances and redshifts
KW - galaxies: halos
KW - galaxies: luminosity function, mass function
KW - galaxies: photometry
KW - galaxies: spiral
KW - radio lines: galaxies
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U2 - 10.1088/0004-6256/146/1/15
DO - 10.1088/0004-6256/146/1/15
M3 - Article
AN - SCOPUS:84879077623
SN - 0004-6256
VL - 146
JO - Astronomical Journal
JF - Astronomical Journal
IS - 1
M1 - 15
ER -