Volume 558, October 2013
|Number of page(s)||7|
|Published online||03 October 2013|
The Lockman Hole project: gas and galaxy properties from a stacking experiment
Netherlands Institute for Radio Astronomy (ASTRON),
PO Box 2,
2 Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700 AV Groningen, The Netherlands
3 Istituto di Radioastronomia, Bologna (INAF), via Gobetti 101, 40129 Bologna, Italy
4 University of Bologna, Dept of Astronomy, Via Ranzani 2, Bologna, Italy
Received: 20 June 2013
Accepted: 13 August 2013
We perform an H I stacking analysis to study the relation between H I content and optical/radio/IR properties of galaxies located in the Lockman Hole area. In the redshift range covered by the observations (up to z = 0.09), we use the SDSS to separate galaxies with different optical characteristics, and we exploit the deep L-band radio continuum image (with noise 11 μJy beam-1) to identify galaxies with radio continuum emission. Infrared properties are extracted from the Spitzer catalog. We detect H I in blue galaxies, but H I is also detected in the group of red galaxies – albeit with smaller amounts than for the blue sample. We identify a group of optically inactive galaxies with early-type morphology that does not reveal any H I and ionized gas. These inactive galaxies likely represent the genuine red and dead galaxies depleted of all gas. Unlike inactive galaxies, H I is detected in red LINER-like objects. Galaxies with radio continuum counterparts mostly belong to the sub-mJy population, whose objects are thought to be a mixture of star-forming galaxies and low-power AGNs. After using several AGN diagnostics, we conclude that the radio emission in the majority of our sub-mJy radio sources stems from star formation. LINERs appear to separate into two groups based on IR properties and H I content. LINERs with a 24 μm detection show relatively large amounts of H I and are also often detected in radio continuum as a result of ongoing star formation. The LINER galaxies which are not detected at 24 μm are more like the optically inactive galaxies by being depleted of H I gas and having no sign of star formation. Radio LINERs in the latter group are the best candidates for hosting low-luminosity radio AGN.
Key words: radio continuum: galaxies / galaxies: star formation / galaxies: evolution / radio lines: galaxies
© ESO, 2013
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.