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- Title
A low H I column density filament in NGC 2403: signature of interaction or accretion.
- Authors
de Blok, W. J. G.; Keating, K. M.; Pisano, D. J.; Fraternali, F.; Walter, F.; Oosterloo, T.; Brinks, E.; Bigiel, F.; Leroy, A.
- Abstract
Observed Hi accretion around nearby galaxies can only account for a fraction of the gas supply needed to sustain the currently observed star formation rates. It is possible that additional accretion occurs in the form of low column density cold flows, as predicted by numerical simulations of galaxy formation. To constrain the presence and properties of such flows, we present deep Hi observations obtained with the NRAO Green Bank Telescope of an area measuring 4° × 4° around NGC 2403. These observations, with a 5σ detection limit of 2.4 × 1018 cm-2 over a 20 km s-1 linewidth, reveal a low column density, extended cloud outside the main Hi disk, about 17' (∼16 kpc or ∼2 R25) to the NW of the center of the galaxy. The total Hi mass of the cloud is 6.3 × 106 M☉, or 0.15 percent of the total Hi mass of NGC 2403. The cloud is associated with an 8 kpc anomalous-velocity Hi filament in the inner disk, that was previously observed in deep VLA observations. We discuss several scenarios for the origin of the cloud, and conclude that it is either accreting from the intergalactic medium, or is the result of a minor interaction with a neigboring dwarf galaxy.
- Subjects
H I regions (Astrophysics); STAR formation; VERY Long Baseline Array (Telescopes); GALACTIC halos; INTERSTELLAR medium; ACCRETION (Astrophysics)
- Publication
Astronomy & Astrophysics / Astronomie et Astrophysique, 2014, Vol 569, p1
- ISSN
0004-6361
- Publication type
Article
- DOI
10.1051/0004-6361/201423880