%0 Generic %1 munoz2015deficit %A Muñoz, Joseph A. %A Oh, S. Peng %D 2015 %K [CII] galaxy gas high-z molecular pdr %T The CII Deficit in LIRGs and ULIRGs is Due to High-Temperature Saturation %U http://arxiv.org/abs/1510.00397 %X Current predictions for the line ratios from photo-dissociative regions (PDRs) in galaxies adopt theoretical models that consider only individual parcels of PDR gas each characterized by the local density and far-UV radiation field. However, these quantities are not measured directly from unresolved galaxies, making the connection between theory and observation ambiguous. We develop a model that uses galaxy-averaged, observable inputs to explain and predict measurements of the CII fine structure line in luminous and ultra-luminous infrared galaxies. We find that the CII deficit observed in the highest IR surface-brightness systems is a natural consequence of saturating the upper fine-structure transition state at gas temperatures above 91 K. To reproduce the measured amplitude of the CII/FIR ratio in deficit galaxies, we require that CII trace approximately 10-17% of all gas in these systems, roughly independent of IR surface brightness and consistent with observed CII to CO(1--0) line ratios. Calculating the value of this fraction is a challenge for theoretical models. The difficulty may reside in properly treating the topology of molecular and dissociated gas, different descriptions for which may be observationally distinguished by the OI63 micron line in yet-to-be-probed regions of parameter space, allowing PDR emission lines from to probe not only the effects of star formation but also the state and configuration of interstellar gas.

@misc{munoz2015deficit, abstract = {Current predictions for the line ratios from photo-dissociative regions (PDRs) in galaxies adopt theoretical models that consider only individual parcels of PDR gas each characterized by the local density and far-UV radiation field. However, these quantities are not measured directly from unresolved galaxies, making the connection between theory and observation ambiguous. We develop a model that uses galaxy-averaged, observable inputs to explain and predict measurements of the [CII] fine structure line in luminous and ultra-luminous infrared galaxies. We find that the [CII] deficit observed in the highest IR surface-brightness systems is a natural consequence of saturating the upper fine-structure transition state at gas temperatures above 91 K. To reproduce the measured amplitude of the [CII]/FIR ratio in deficit galaxies, we require that [CII] trace approximately 10-17% of all gas in these systems, roughly independent of IR surface brightness and consistent with observed [CII] to CO(1--0) line ratios. Calculating the value of this fraction is a challenge for theoretical models. The difficulty may reside in properly treating the topology of molecular and dissociated gas, different descriptions for which may be observationally distinguished by the [OI]63 micron line in yet-to-be-probed regions of parameter space, allowing PDR emission lines from to probe not only the effects of star formation but also the state and configuration of interstellar gas.}, added-at = {2015-10-05T10:21:28.000+0200}, author = {Muñoz, Joseph A. and Oh, S. Peng}, biburl = {https://www.bibsonomy.org/bibtex/2f499c129b58c7d7e3bcaba611ae7c5b4/miki}, description = {[1510.00397] The [CII] Deficit in LIRGs and ULIRGs is Due to High-Temperature Saturation}, interhash = {42f2a287079abea86c21a9acee6cc341}, intrahash = {f499c129b58c7d7e3bcaba611ae7c5b4}, keywords = {[CII] galaxy gas high-z molecular pdr}, note = {cite arxiv:1510.00397Comment: 7 pages, 2 figures, submitted to MNRAS}, timestamp = {2015-10-05T10:21:28.000+0200}, title = {The [CII] Deficit in LIRGs and ULIRGs is Due to High-Temperature Saturation}, url = {http://arxiv.org/abs/1510.00397}, year = 2015 }