TY - JOUR
T1 - A low H I column density filament in NGC 2403
T2 - signature of interaction or accretion
AU - de Blok, W.J.G.
AU - Keating, K.M.
AU - Pisano, D.J.
AU - Fraternali, F.
AU - Walter, F.
AU - Oosterloo, T.
AU - Brinks, E.
AU - Bigiel, F.
AU - Leroy, A.
N1 - Date of acceptance: 12/07/2014
PY - 2014/9/25
Y1 - 2014/9/25
N2 - Observed H i 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 H i 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 H i disk, about 17′ (~ 16 kpc or ~ 2 R25) to the NW of the center of the galaxy. The total H i mass of the cloud is 6.3 × 106 M⊙, or 0.15 percent of the total H i mass of NGC 2403. The cloud is associated with an 8 kpc anomalous-velocity H i 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
AB - Observed H i 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 H i 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 H i disk, about 17′ (~ 16 kpc or ~ 2 R25) to the NW of the center of the galaxy. The total H i mass of the cloud is 6.3 × 106 M⊙, or 0.15 percent of the total H i mass of NGC 2403. The cloud is associated with an 8 kpc anomalous-velocity H i 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
KW - galaxies: ISM, galaxies: kinematics and dynamics, galaxies: halos, galaxies: individual: NGC 2403, galaxies: structure
U2 - 10.1051/0004-6361/201423880
DO - 10.1051/0004-6361/201423880
M3 - Article
SN - 0004-6361
VL - 569
JO - Astronomy & Astrophysics
JF - Astronomy & Astrophysics
M1 - A68
ER -