3月29日 H2O and other molecules in Herschel high-z galaxies, a new diagnosis of their dense cores
题目：H2O and other molecules in Herschel high-z galaxies, a new diagnosis of their dense cores
报告人：Alain Omont (IAP, UPMC)
摘要：As confirmed by Herschel, submillimeter lines of H2Oare, just after CO, among the strongestsubmillimeter molecular lines in local and high-z ultra-luminous infrared galaxies (ULIRGs). They provide a diagnosis of their dense, warm cores complementary to CO because of the large electric dipole of H2O, the high water abundance and their sensitivity to infrared excitation.
I will report on the progress of our program, led by Chentao Yang, of high-z studies of multi-line H2O and other molecules in strongly lensed high-z Herschel galaxies from the H-ATLAS survey. High-z H2O detections with IRAM/PdBI will be recalled in 15 objects, as well as its comparison with Herschel detections in local ULIRGs. We have shown that H2O is easily detectable at all redshifts. The H2O line luminosity increases as LIR~1.2, high-excitation lines (Eup/k ~ 300K) remain strong in the majority of the sources, but not in all and at higher excitation. H2O lines provide thus an important diagnosis in extreme starbust (and possibly AGN) conditions of warm, dense cores/clumps of these galaxies, which are often more extreme than local equivalents. Modeling H2O rotational excitation allows us to constrain physical parameters there such as warm dust opacity and temperature and H2O abundance.
Extensions and work in progress will be presented in various directions: H2O+ lines are easy to detect and provide important constraints on the H2O chemistry. We have just got the first IRAM/NOEMA map at high angular resolution of two H2O lines plus CO(10-9) and H2O+ in one source; it displays striking differences in the spatial distribution of the FIR continuum and various lines. Multi-line CO detections at IRAM/30m provides a complementary view of their excitation in many of our H2O galaxies. Observations of lines connected to the ground state, mostly in absorption, of various molecules (H2O, H2O+, CH+, OH) present exciting prospects for probing the external layers of the galaxy and of its core and their dynamics. High-J detections of HCN, HCO+ and HNC provide a complementary diagnostic of their low-J lines for the dense, star-forming gas.
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