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Date and Time of the Query: 2019-05-19 T01:55:16 PDT
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For refcode 2009AJ....138..338S:
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Copyright by American Astronomical Society. Reproduced by permission
2009AJ....138..338S The Arecibo Legacy Fast Alfa Survey. IX. The Leo Region H I Catalog, Group Membership, and the H I Mass Function for the Leo I Group Stierwalt, Sabrina; Haynes, Martha P.; Giovanelli, Riccardo; Kent, Brian R.; Martin, Ann M.; Saintonge, Amelie; Karachentsev, Igor D.; Karachentseva, Valentina E. Abstract. We present the catalog of H I sources extracted from the ongoing Arecibo Legacy Fast ALFA (ALFALFA) extragalactic H I line survey, found within the sky region bounded by 9^h^36^m^ < {alpha} < 11^h^36^m^ and +08^degree^ < {delta} < +12^degree^. The H I catalog presented here for this 118 deg^2^ region is combined with the ones derived from surrounding regions also covered by the ALFALFA survey to examine the large-scale structure in the complex Leo region. Because of the combination of wide sky coverage and superior sensitivity, spatial and spectral resolution, the ALFALFA H I catalog of the Leo region improves significantly on the numbers of low H I mass sources as compared with those found in previous HI surveys. The H I mass function of the Leo I group presented here is dominated by low-mass objects: 45 of the 65 Leo I members have M_H\,{\scriptscriptstyle I} < 10^{8} M_{sun}_, yielding tight constraints on the low-mass slope of the Leo I H I mass function. The best-fit slope is {alpha} ~= -1.41 + 0.2 - 0.1. A direct comparison between the ALFALFA H I line detections and an optical search of the Leo I region proves the advantage of the ALFALFA strategy in finding low-mass, gas-rich dwarfs. These results suggest the existence of a significant population of low surface brightness, gas-rich, yet still very low H I mass galaxies, and may reflect the same type of morphological segregation as is seen in the Local Group. While the low-mass end slope of the Leo I H I mass function is steeper than that determined for luminosity functions of the group, the slope still falls short of the values predicted by simulations of structure formation in the {lambda} cold dark matter paradigm. Key words: galaxies: distances and redshifts, galaxies: dwarf, galaxies: evolution, galaxies: formation, galaxies: halos, galaxies: luminosity function, mass function, radio lines: galaxies
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