Diagnostics of irradiated gas in galaxy nuclei. I. A far-ultraviolet and X-ray dominated region code

By R. Meijerink, M. Spaans. 2005

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We present a far-ultraviolet (PDR) and an X-ray dominated region (XDR) code. We include and discuss thermal and chemical processes that pertain to irradiated gas. An elaborate chemical network is used and a careful treatment of PAHs and H(2) formation, destruction and excitation is included. For both codes we calculate four depth-dependent models for different densities and radiation fields, relevant to conditions in starburst galaxies and active galactic nuclei. A detailed comparison between PDR and XDR physics is made for total gas column densities between similar to 10(20) and similar to 10(25) cm(-2). We show cumulative line intensities for a number of fine-structure lines (e.g., [CII], [OI], [CI], [SiII], [FeII]), as well as cumulative column densities and column density ratios for a number of species ( e. g., CO/H(2), CO/C, HCO(+)/HCN, HNC/HCN). The comparison between the results for the PDRs and XDRs shows that column density ratios are almost constant up to N(H) = 1022 cm(-2) for XDRs, unlike those in PDRs. For example, CO/C in PDRs changes over four orders of magnitude from the edge to NH = 10(22) cm(-2). The CO/C and CO/H(2) ratios are lower in XDRs at low column densities and rise at NH > 1023 cm-2. At most column densities NH > 10(21.5) cm-2, HNC/HCN ratios are lower in XDRs too, but they show a more moderate increase at higher N(H).

Subfields: Astronomy and Astrophysics, Atmospheric Science

View Paper: https://www.semanticscholar.org/paper/c3a94f79ca46cd725f4035819b19cdd013e6925e

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Citations in the corpus

A photon dominated region code comparison study (2007, background): “…1985; van Dishoeck & Black 1988; Hollenbach et al. 1991; Fuente et al. 1993; Le Bourlot et al. 1993; Jansen et al. 1995; Sternberg & Dalgarno 1995; Lee et al. 1996; Bakes & Tielens 1998; Walmsley et al. 1999; Savage & Ziurys 2004; Teyssier et al. 2004; Fuente et al. 2005; Meijerink & Spaans 2005).”
FIRE-2 simulations: physics versus numerics in galaxy formation (2017, background): “(vii) Dust Collisional Heating/Cooling: from Meijerink & Spaans (2005): ΛDust =1.12×10−32 (T −Tdust) T 1/2× (B19)( 1−0.8 exp [ −75 T ]) ( Z Z ) 32 Available at http://www.strw.leidenuniv.nl/WSS08 where we take Tdust = 30K here, and the Z/Z term comes from assuming a constant dust-to-metals ratio.”
Diagnostics of irradiated dense gas in galaxy nuclei. II. A grid of XDR and PDR models (2006, background): “In the XDR models, HCO+ is chemically less abundant than HCN for very large HX/n (Meijerink & Spaans 2005).”
Cool Gas in High-Redshift Galaxies (2013, background): “In the XDR phase (further inside the cloud) the [O I], [C II], and [S III] lines are main coolants in the sub–millimeter regime (Meijerink & Spaans 2005).”
Molecular line emission in NGC 1068 imaged with ALMA: I. An AGN-driven outflow in the dense molecular gas (2014, background): “Although theoretical models have tried to explain these differences, the underlying reasons for the apparent AGN specificity are still debated (Lepp & Dalgarno 1996; Maloney et al. 1996; Meijerink & Spaans 2005; Meijerink et al. 2007; Yamada et al. 2007; Harada et al. 2013).”
Modelling CO formation in the turbulent interstellar medium (2009, methodology): “We therefore follow Yan (1997) and Meijerink & Spaans (2005) and replace nH2 in Equation 11 with an effective number density neff .”