Submillimeter H 2 O and H 2 O + emission in lensed ultra- and hyper-luminous infrared galaxies at z ~ 2-4
Artikel i vetenskaplig tidskrift, 2016

We report rest-frame submillimeter H2O emission line observations of 11 ultra- or hyper-luminous infrared galaxies (ULIRGs or HyLIRGs) at z ∼ 2-4 selected among the brightest lensed galaxies discovered in the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS). Using the IRAM NOrthern Extended Millimeter Array (NOEMA), we have detected 14 new H2O emission lines. These include five 321-312 ortho-H2O lines (Eup/k = 305 K) and nine J = 2 para-H2O lines, either 202-111 (Eup/k = 101 K) or 211-202 (Eup/k = 137 K). The apparent luminosities of the H2O emission lines are μLH2O ∼ 6-21 × 108 L⊙ (3 > μ > 15, where μ is the lens magnification factor), with velocity-integrated line fluxes ranging from 4-15 Jy km s-1. We have also observed CO emission lines using EMIR on the IRAM 30 m telescope in seven sources (most of those have not yet had their CO emission lines observed). The velocity widths for CO and H2O lines are found to be similar, generally within 1σ errors in the same source. With almost comparable integrated flux densities to those of the high-J CO line (ratios range from 0.4 to 1.1), H2O is found to be among the strongest molecular emitters in high-redshift Hy/ULIRGs. We also confirm our previously found correlation between luminosity of H2O(LH2O) and infrared (LIR) that LH2O ∼ LIR1:1-1:2, with our new detections. This correlation could be explained by a dominant role of far-infrared pumping in the H2O excitation. Modelling reveals that the far-infrared radiation fields have warm dust temperature Twarm ∼ 45-75 K, H2O column density per unit velocity interval NH2O/ΔV ≳ 0:3 × 1015 cm-2 km-1 s and 100 μm continuum opacity τ100 1 (optically thick), indicating that H2O is likely to trace highly obscured warm dense gas. However, further observations of J ≥ 4 H2O lines are needed to better constrain the continuum optical depth and other physical conditions of the molecular gas and dust. We have also detected H2O+ emission in three sources. A tight correlation between LH2O and LH2O+ has been found in galaxies from low to high redshift. The velocity-integrated flux density ratio between H2O+ and H2O suggests that cosmic rays generated by strong star formation are possibly driving the H2O+ formation. © 2016 ESO.

Radio lines: ISM

ISM: molecules

Galaxies: ISM

Submillimeter: galaxies

Infrared: galaxies

Galaxies: high-redshift


C. Yang

Université Paris-Sud

Université Pierre et Marie Curie (UPMC)

Chinese Academy of Sciences

Centre national de la recherche scientifique (CNRS)

A.A. Omont

Centre national de la recherche scientifique (CNRS)

Université Pierre et Marie Curie (UPMC)

A. Beelen

Université Paris-Sud

E. Gonzalez-Alfonso

Universidad de Alcala

R. Neri

Institut de Radioastronomie Millimétrique (IRAM)

Y. Gao

Chinese Academy of Sciences

P. van der Werf

Universiteit Leiden

A. Weiß


R. Gavazzi

Université Pierre et Marie Curie (UPMC)

Centre national de la recherche scientifique (CNRS)

Niklas Falstad

Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik

A. J. Baker

Rutgers University

R. S. Bussmann

Cornell University

A. Cooray

University of California at Irvine (UCI)

P. Cox

Atacama Large Millimeter-submillimeter Array (ALMA)

H. Dannerbauer

Universität Wien

S. Dye

University of Nottingham

M. Guélin

Institut de Radioastronomie Millimétrique (IRAM)

R. J. Ivison

European Southern Observatory (ESO)

University of Edinburgh

M. Krips

Institut de Radioastronomie Millimétrique (IRAM)

M. Lehnert

Université Pierre et Marie Curie (UPMC)

Centre national de la recherche scientifique (CNRS)

M. J. Michalowski

University of Edinburgh

D. A. Riechers

Cornell University

M. Spaans

Rijksuniversiteit Groningen

E. Valiante

Cardiff University

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 595 Art no A80- A80


Astronomi, astrofysik och kosmologi


Grundläggande vetenskaper


Onsala rymdobservatorium



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