8-12 juin, 2014


Staring into the Whirlpool with Herschel: SPIRE-FTS Observations of Warm Molecular Gas in M51

Maximilien Schirm (McMaster University)

Christine D. Wilson, McMaster University

The Whirlpool galaxy (M51, NGC 5194) is a nearby (~9.9 Mpc), grand-design spiral galaxy, and is a unique system in which to study star formation along with molecular gas heating and cooling. Its Seyfert-2 nucleus provides a perfect comparison for the star formation molecular gas located in the spiral arms. Furthermore, the ongoing interaction with the nearby irregular galaxy NGC 5195 likely contributes to an increased star formation rate throughout the system. We will present observations of M51 from the Herschel Space Observatory, using the SPIRE Fourier Transform Spectrometer, of CO and [CI], both of which trace a combination of cold and warm molecular gas throughout the system. We supplement these observations with ground based observations of CO and perform a radiative transfer analysis of the molecular gas in the galaxy, highlighting the nucleus along with several bright star forming regions. Assuming a single component to the molecular gas, the CO and [CI] spectral line energy distributions suggest that the emission is dominated by warm (~ 100 - 200 K), diffuse (~a few hundred cm^-3) molecular gas. We will discuss the possible sources of heating to this warm molecular gas, including mechanical heating, heating due to the central active galactic nucleus, and heating from massive stars which result in photon dominated regions. Finally, we will compare the physical state of the molecular gas along with the sources of heating and cooling in M51 to other star formation dominated galaxies in our sample, including M82, M83, Arp220 and NGC 4038/39.
(doit être confirmé par le SOC)