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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 729998.0, MPI für Astronomie / Publikationen_mpia
ALMA imaging of HCN, CS, and dust in Arp 220 and NGC 6240
Authors:Scoville, N.; Sheth, K.; Walter, F.; Manohar, S.; Zschaechner, L.; Yun, M.; Koda, J.; Sanders, D.; Murchikova, L.; Thompson, T.; Robertson, B.; Genzel, R.; Hernquist, L.; Tacconi, L.; Brown, R.; Narayanan, D.; Hayward, C. C.; Barnes, J.; Kartaltepe, J.; Davies, R.; van der Werf, P.; Fomalont, E.
Date of Publication (YYYY-MM-DD):2015
Title of Journal:The Astrophysical Journal
Issue / Number:1
Start Page:id. 70 (17 pp)
Audience:Not Specified
Abstract / Description:We report ALMA Band 7 (350 GHz) imaging at 0.''4-0.''6 resolution and Band 9 (696 GHz) at ~0.''25 resolution of the luminous IR galaxies Arp 220 and NGC 6240. The long wavelength dust continuum is used to estimate interstellar medium masses for Arp 220 east and west and NGC 6240 of 1.9, 4.2, and 1.6 × 109 M within radii of 69, 65, and 190 pc. The HCN emission was modeled to derive the emissivity distribution as a function of radius and the kinematics of each nuclear disk, yielding dynamical masses consistent with the masses and sizes derived from the dust emission. In Arp 220, the major dust and gas concentrations are at radii less than 50 pc in both counter-rotating nuclear disks. The thickness of the disks in Arp 220 estimated from the velocity dispersion and rotation velocities are 10-20 pc and the mean gas densities are nH_2 ˜ 10^5 cm-3 at R <50 pc. We develop an analytic treatment for the molecular excitation (including photon trapping), yielding volume densities for both the HCN and CS emission with n H2 ~ 2 × 105 cm-3. The agreement of the mean density from the total mass and size with that required for excitation suggests that the volume is essentially filled with dense gas, i.e., it is not cloudy or like swiss cheese.
Free Keywords:galaxies: individual: Arp 220 NGC 6240; galaxies: starburst
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
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