Astrophys. J., 541, 624-643 (2000/October-1)
Interstellar gas in the NGC 4410 galaxy group.
Abstract (from CDS):
We present new radio continuum, 21 cm H I, and 2.6 mm CO data for the peculiar radio galaxy NGC 4410A and its companion NGC 4410B and compare with available optical and X-ray maps. Our radio continuum maps show an asymmetric double-lobed structure, with a high surface brightness lobe extending 3'.6 (∼100 kpc) to the southeast and a 6'.2 (∼180 kpc) low surface brightness feature in the northwest. Molecular gas is abundant in NGC 4410A, with MH2∼4x109 M☉ (using the standard Galactic conversion factor) but is undetected in NGC 4410B. H I is less abundant, with M_HI_∼109 M☉ for the pair. Our H I map shows a 3x108 M☉ H I tail extending 1'.7 (50 kpc) to the southeast of the pair, coincident with a faint optical tail and partially overlapping with the southeastern radio lobe. The H I tail is anticoincident with a 2' (56 kpc) long X-ray structure aligned with a stellar bridge that connects the pair to a third galaxy. If this X-ray emission is associated with the group, we infer (3-8)x108 M☉ of hot gas in this feature. This may be either intracluster gas or shocked gas associated with the bridge. Our detection of abundant interstellar gas in this pair, including an H I-rich tidal tail near the southeastern radio lobe, suggests that the observed distortions in this lobe may have been caused by the interstellar medium in this system. The gravitational interaction of the two galaxies and the subsequent motion of the interstellar medium in the system relative to the jet may have produced sufficient ram pressure to bend and distort the radio jet. An alternative hypothesis is that the jet was distorted by ram pressure due to an intracluster medium, although the small radial velocity of NGC 4410A relative to the group and the lack of diffuse X-ray emission in the group makes this less likely unless the group is not virialized or is in the process of merging with another group. Using our VLA data, we also searched for H I counterparts to the other 10 known members of the NGC 4410 group and CO from three other galaxies in the inner group. In our velocity range of 6690-7850 km.s–1, we detected six other galaxies above our H I sensitivity limits of 2x108 M☉ for the inner group and 4x108 M☉ for the outer group. The total H I in the group is 1.4x1010 M☉, 80% of which arises from four galaxies in the outer group. Three of these galaxies (VCC 822, VCC 831, and VCC 847) are spirals with M_HI/LB_ ratios typical of field galaxies, while FGC 170A appears to be a gas-rich dwarf galaxy (MB~-18, M_HI_∼3x109 M☉). In the inner group, the SBa galaxy NGC 4410D (VCC 934) was detected in H I and CO (M_HI_∼5x108 M☉ and MH2∼8x108 M☉) and has a 1' (28 kpc) long H I tail that points toward the nearby disk galaxy NGC 4410F. NGC 4410F was also detected in H I (M_HI_∼4x108 M☉). The galaxies in the inner group appear to be somewhat deficient in H I compared to their blue luminosities, suggesting phase changes driven by galaxy-galaxy or galaxy-intracluster medium encounters.
galaxies: individual (NGC 4410) - Galaxies: Interactions - Galaxies: ISM
Table 1: [S2000g] Anon N (Nos 1-4).
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