Cosmic Rays: Gas Phase Astrophysics and Astrochemistry Marco Spaans (Groningen) Rowin Meijerink (Leiden), Edo Loenen (Leiden), Paul van der Werf (Leiden), Padelis Papadopoulos (Bonn) Rowin Meijerink (Leiden), Edo Loenen (Leiden), Paul van der Werf (Leiden), Padelis Papadopoulos (Bonn)

n CRDRs (CRs/SNe) n MDRs (shocks) n PDRs (UV/SBs) n XDRs (X-ray/AGN)

Multi-Phase Medium; heating by CRs or dust (Wolfire et al. 2003; Spaans & Norman 1997; Field et al. 1969)

Metallicity & Multi-Phase ISM : n Lower metallicity yields smaller molecular clouds n X-factor: CO/H 2 Mihos et al. (1999), Bolatto et al. (1999), Roellig et al. (2006)

CR protons upto 100 MeV listed: H 2 ionization, while 1-20 GeV CRs responsible for bulk of π 0 mesons → 2γ and, e.g., pp→pnπ +

n Effects of CRs? n One often has a UV irradiated cloud edge n PDR model with CR rate = 5x s -1 ; so SN rate for ~100 M 0 /yr n Note small changes in C, OH and H 2 O

n CR ionization acts deep in molecular clouds (similar to XDRs)

PDRs: 6 < E < 13.6 eV n Heating: Photo-electric emission from grains and cosmic rays n Cooling: Fine-structure lines like [OI] 63, 145; [CII] 158 μm and emission by H 2, CO, H 2 O n 10 eV photon penetrates 0.5 mag of dust n Heating efficiency ~ 0.1 – 1.0 %

XDRs: E > 1 keV n Heating: X-ray photo-ionization --> fast electrons - Coulomb heating H and H 2 vib excitation - UV n Cooling: [FeII] 1.26, 1.64; [OI] 63; [CII] 158; [SiII] 35 μm; thermal H 2 vib; gas-dust n 1 keV photon penetrates cm -2 of N H n Heating efficiency ~ 10 – 50 %

n PDR (left) with n=10 5 cm -3 and G= n XDR with n=10 5 cm -3 and F X = 5.1 erg s -1 cm -3 n Note N H dependence H 2, C +, C, CO, OH, etc.

CR heating: ~8 eV per H 2 ionization (H, He slightly different Cravens & Dalgarno 1978)

CRs can dominate gas heating for SFR > 100 Mo/yr; think of Arp220 and IMF through M Jeans (Papadopoulos 2010)

CRs drive ionization and shift C + -C-CO transition

CRs drive ionization, form molecular ions

Particularly oxygen bearing ones!

BUT: CRs ≠ X-rays; only very high CR rates boost OH + and H 2 O + (fine- structure lines little affected by CRs)

Mrk 231 SPIRE data van der Werf et al. (2010) Mrk 231 SPIRE data van der Werf et al. (2010)

How about shocks? M82, shock tracer SiO GHz radio (García-Burillo et al. 2001, IRAM PdB)

M82, CO 6-5 (116K; Ward et al. 2003, CSO)

Jump Conditions

J-Shocks of > 50 km/s lead to high compression, molecule dissociation and reformation in the shock wake

J-shock structure

J-shock chemistry

Summary n CRs (strongly) affect cloud chemistry (in SBs) and can be distinguished from XDRs and shocks through OH, H 2 O, OH +, H 2 O +, H 3 O + and high-J CO; not through fine-structure and low-J CO lines if UV irradiation acts n For the future, ALMA will be crucial to provide spatial information on CR exposed molecular clouds

Maloney et al. (1996)

Energetics G 0 = 1.6x10 -3 erg cm -2 s -1 is the Habing flux over eV G 0 = 1.6x10 -3 erg cm -2 s -1 is the Habing flux over eV Orion Bar has 10 5 G 0 Orion Bar has 10 5 G 0 F X = 84 L 44 r 2 -2 erg cm -2 s -1 F X = 84 L 44 r 2 -2 erg cm -2 s -1 is the X-ray flux over keV with a power law E -0.9 is the X-ray flux over keV with a power law E -0.9 Think of Seyfert nucleus at 100 pc or TTauri star with erg/s at 20 AU Think of Seyfert nucleus at 100 pc or TTauri star with erg/s at 20 AU