Vol 17, No 8

Multi-transition study of the peculiar merger Arp 299

Qian Jiao, Ming Zhu


Abstract We present a multi-transition study to investigate the physical properties of dust and molecular gas in the archetypical merger Arp 299 by using data including James Clerk Maxwell Telescope (JCMT) 850 and 450 μm observations, Herschel 500, 350, 250, 160 and 70 μm continuum maps, as well as the CO(3–2), CO(4–3) low-J CO lines and CO(11–10), CO(13–12), CO(14–13) high-J CO lines. The CO(3–2) and CO(4–3) lines are observed by JCMT, and the CO(11–10), CO(13–12), CO(14–13) lines are available on the Herschel Science Archive. The resolution of the Herschel Spectral and Photometric Imaging Receiver (SPIRE) Fourier transform spectrometer (FTS) CO(11–10) data is similar to that of the JCMT CO(3–2) line, while the resolution of the SPIRE/FTS CO(13–12) and Photodetector Array Camera and Spectrometer (PACS) CO(14–13) data is similar to that of JCMT CO(4–3), allowing us to obtain accurate line ratios of ICO(11−10)/ICO(3−2), ICO(13−12)/ICO(4−3) and ICO(14−13) /ICO(4−3). By modeling the spectral energy distribution of the continuum data, we conclude that two components (cold and warm) exist in the dust, with the warm component occupying a small percent of the total dust mass. We further use a radiative transfer analysis code, RADEX, to calculate the density, temperature and column density of warm gas in the central region, which shows that the kinetic temperature Tkin is in the range 110 to 150 K and hydrogen density n(H2) is in the range 104.7 − 105.5 cm−3. We show that the hot dust is located in the central region of IC 694 with a radius of ∼ 4′′ and estimate that the warm gas mass is in the range 3.8 × 107M⊙ to 7.7 × 107M⊙, which contains 5.0%–15.0% of the total H2 mass for the region of IC 694. We also calculate the star formation rate of the galaxy in particular, which is much higher than that of the Milky Way.


Keywords galaxies: merge — galaxies: Arp 299 — galaxies: dust — galaxies: molecular gas — galaxies: warm center

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