Hostname: page-component-78c5997874-mlc7c Total loading time: 0 Render date: 2024-11-01T05:44:42.606Z Has data issue: false hasContentIssue false

Dense Molecular Gas at High Redshift: First Detection of Emission from HCO+

Published online by Cambridge University Press:  01 August 2006

D.A. Riechers
Affiliation:
Max-Planck-Institut für Astronomie, Königstuhl 17, Heidelberg, D-69117, Germany
F. Walter
Affiliation:
Max-Planck-Institut für Astronomie, Königstuhl 17, Heidelberg, D-69117, Germany
C.L. Carilli
Affiliation:
National Radio Astronomy Observatory, PO Box O, Socorro, NM 87801, USA
A. Weiss
Affiliation:
Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, Bonn, D-53121, Germany
F. Bertoldi
Affiliation:
Argelander-Institut für Astronomie, Auf dem Hügel 71, Bonn, D-53121, Germany
K.M. Menten
Affiliation:
Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, Bonn, D-53121, Germany
K.K. Knudsen
Affiliation:
Max-Planck-Institut für Astronomie, Königstuhl 17, Heidelberg, D-69117, Germany
P. Cox
Affiliation:
Institut d.RadioAstronomie Millimétrique, 300 R.d.l.Piscine, 38406 St.Martin d'Héres, France
Rights & Permissions [Opens in a new window]

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

Using the Very Large Array (VLA), we have detected the HCO+(1–0) emission line towards the Cloverleaf quasar (z = 2.56; Riechers et al. 2006). This is the first detection of ionized molecular gas emission at high redshift (z>2). HCO+ emission is a star formation indicator similar to HCN, tracing dense molecular hydrogen gas within star-forming molecular clouds. We find a HCO+/CO luminosity ratio of 0.08 and a HCO+/HCN luminosity ratio of 0.8 for the Cloverleaf. These ratios fall within the scatter of the same relationships found for low–z star–forming galaxies. However, a HCO+/HCN luminosity ratio close to unity would not be expected for the Cloverleaf if the recently suggested relation between this ratio and the far–infrared luminosity (Graciá–Carpio et al. 2006) were to hold. We conclude that a ratio between HCO+ and HCN luminosity close to 1 is likely due to the fact that the emission from both lines is optically thick and thermalized and emerges from dense regions of similar volumes. We conclude that HCO+ is potentially a good tracer for dense molecular gas at high redshift.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2007

References

Graciá-Carpio, J., García-Burillo, S., Planesas, P., & Colina, L. 2006, ApJ 640, L135CrossRefGoogle Scholar
Riechers, D. A., Walter, F., Carilli, C. L. 2006, ApJ 645, L13CrossRefGoogle Scholar