ΛCDM Satellites and H I Companions—the Arecibo ALFA Survey of NGC 2903

Judith A. Irwin, G. Lyle Hoffman, Kristine Spekkens, Martha P. Haynes, Riccardo Giovanelli, Suzanne M. Linder, Barbara Catinella, Emmanuel Momjian, Bärbel S. Koribalski, Jonathan Davies, Elias Brinks, W.J.G. J.G. De Blok, Mary E. Putman, Wim van Driel

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Abstract

We have conducted a deep, completeH I survey, using Arecibo/Arecibo L-band Feed Array (ALFA), of a field centered on the nearby, isolated galaxy, NGC 2903, which is similar to the Milky Way in its properties. The field size was 150 kpc × 260 kpc and the final velocity range spanned from 100 to 1133 km s –1 . The ALFA beams have been mapped as a function of azimuth and cleaned from each azimuth-specific cube prior to forming final cubes. The finalH I data are sensitive down to anH I mass of 2 × 10 5 M ☉ and column density of 2 × 10 17 cm –2 at the 3 σ 2 δ V level, where σ is the rms noise level and δ V is the velocity resolution. NGC 2903 is found to have anH I envelope that is larger than previously known, extending to at least three times the optical diameter of the galaxy. Our search for companions yields one new discovery with anH I mass of 2.6 × 10 6 M ☉ . The companion is 64 kpc from NGC 2903 in projection, is likely associated with a small optical galaxy of similar total stellar mass, and is dark matter dominated, with a total mass >10 8 M ☉ . In the region surveyed, there are now two known companions: our new discovery and a previously known system that is likely a dwarf spheroidal, lackingH I content. IfH I constitutes 1% of the total mass in all possible companions, then we should have detected 230 companions, according to Λ cold dark matter (ΛCDM) predictions. Consequently, if this number of dark-matter clumps are indeed present, then they contain less than 1%H I content, possibly existing as very faint dwarf spheroidals or as starless, gasless dark-matter clumps.
Original languageUndefined/Unknown
Pages (from-to)1447
Number of pages1
JournalThe Astrophysical Journal
Volume692
Issue number2
Publication statusPublished - 2009

Cite this

Irwin, J. A., Hoffman, G. L., Spekkens, K., Haynes, M. P., Giovanelli, R., Linder, S. M., Catinella, B., Momjian, E., Koribalski, B. S., Davies, J., Brinks, E., De Blok, W. J. G. J. G., Putman, M. E., & Driel, W. V. (2009). ΛCDM Satellites and H I Companions—the Arecibo ALFA Survey of NGC 2903. The Astrophysical Journal, 692(2), 1447. http://stacks.iop.org/0004-637X/692/i=2/a=1447