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Post Info TOPIC: NGC 4016


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Arp 305
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Title: HI, star formation and tidal dwarf candidate in the Arp 305 system
Author: C. Sengupta, T. C. Scott, S. Paudel, K. S. Dwarakanath, D. J. Saikia, B. W. Sohn

We present results from our Giant Metrewave Radio Telescope (GMRT) HI observations of the Arp 305 system. The system consists of two interacting spiral galaxies NGC 4016 and NGC 4017, a large amount of resultant tidal debris and a prominent tidal dwarf galaxy (TDG) candidate projected within the tidal bridge between the two principal galaxies. Our higher resolution GMRT HI mapping, compared to previous observations, allowed detailed study of smaller scale features. Our HI analysis supports the conclusion in Hanc÷ck et al. (2009) that the most recent encounter between the pair occurred ~ 4 x 10^8 yrs ago. The GMRT observations also show HI features near NGC 4017 which may be remnants of an earlier encounter between the two galaxies. The HI properties of the Bridge TDG candidate include: M(HI) ~ 6.6 x 10^8 msolar and V(HI) = 3500▒ 7 km/s, which is in good agreement with the velocities of the parent galaxies. Additionally the TDG's HI linewidth of 30 km/s and a modest velocity gradient together with its SFR of 0.2 msolar/yr add to the evidence favouring the bridge candidate being a genuine TDG. The Bridge TDG's Spitzer 3.6 Ám and 4.5 Ám counterparts with a [3.6]--[4.5] colour ~ -0.2 mag suggests stellar debris may have seeded its formation. Future spectroscopic observations could confirm this formation scenario and provide the metallicity which is a key criteria for the validation for TDG candidates.á

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Posts: 131433
Date:
NGC 4016
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NGC 4016 (also Arp 305, MCG 5-28-63, UGC 6954 and PGC 37687) is a magnitude +13.8 barred spiral galaxy located 158 million light-years away in the constellation Coma Berenices.á
The galaxy is gravitationally interacting with the neighbouring galaxy NGC 4017: these two galaxies are listed as Arp 305 in the Atlas of peculiar galaxies by Halton Arp.

The galaxy was discovered by British astronomer R. J. Mitchell (Lord Rosse staff astronomer 1852-55) using a 182.88 cm (72 inch) speculum reflector at Birr Castle on the 30th March 1854.

Right Ascension 11h 58m 29.0s, Declination +27░ 31? 44"



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