Astronomy and Astrophysics – Astrophysics
Scientific paper
2001-07-03
Astronomy and Astrophysics
Astrophysics
15 pages with 20 figures. A&A, in press
Scientific paper
10.1051/0004-6361:20010800
We study the molecular gas content and distribution in the Coma cluster spiral galaxy NGC 4848. Plateau de Bure interferometric CO(1-0) observations reveal a lopsided H_2 distribution with an off-center secondary maximum coincident with the inner part of the HI. NGC 4848 is not at all deficient in molecular gas as it contains M_H_2~4x10^9 M_solar. At the interface between the CO and HI emission regions, about 8 kpc NW of the center, however, strong star formation is present as witnessed by Halpha and radio continuum emission. This is the region in which earlier Fabry-Perot observations revealed a double-peaked Halpha line, indicating gas at two different velocities at the same sky position. In order to understand these observations, we present the results of numerical simulations of the ISM-ICM interaction. We suggest that NGC 4848 already passed through the center of the cluster about 4x10^8 years ago. At the observed stage ram pressure has no more direct dynamical influence on the galaxy's ISM. We observe the galaxy when a fraction of the stripped gas is falling back onto the galaxy. Ram pressure is thus a short-lived event with longer-lasting consequences. The combination of ram-pressure and rotation results in gas at different velocities colliding where the double-peaked Halpha line is observed. Ram-pressure can thus result, after re-accretion, in displaced molecular gas without the H_2 itself being pushed efficiently by the ICM. A scenario where two interactions take place simultaneously is also consistent with the available data but less probable on the basis of our numerical simulations.
Balkowski Ch.
Braine Jonathan
Cayatte Veronique
Duschl Wolfgang J.
Vollmer Bernd
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