TY - JOUR
T1 - Evidence of different star formation histories for high- and low-luminosity radio galaxies
AU - Herbert, Peter D.
AU - Jarvis, Matt J.
AU - Willott, Chris J.
AU - McLure, Ross J.
AU - Mitchell, Ewan
AU - Rawlings, Steve
AU - Hill, Gary J.
AU - Dunlop, James S.
PY - 2010/8/1
Y1 - 2010/8/1
N2 - We present the results of our investigation into the stellar populations
of 24 radio galaxies at z ~= 0.5 drawn from four complete,
low-frequency-selected radio surveys. We use the strength of the
4000-Å break as an indicator of recent star formation and compare
this with radio luminosity, optical spectral classification and
morphological classification. We find evidence of different star
formation histories for high- and low-luminosity radio sources; our
group of low radio luminosity sources (typically Fanaroff-Riley type I
sources) has systematically older stellar populations than the higher
radio luminosity group. Our sample is also fairly well divided by
optical spectral classification. We find that galaxies classified as
having low excitation spectra (LEGs) possess older stellar populations
than high excitation line objects (HEGs), with the HEGs showing evidence
for recent star formation. We also investigate the link between radio
morphology, as used by Owen and Laing, and the stellar populations. We
find that there is a preference for the `fat-double' sources to have
older stellar populations than the `classical double' sources, although
this is also linked to these sources lying predominantly in the LEG and
HEG categories, respectively. These results are consistent with the
hypothesis that HEGs are powered by accretion of cold gas, which could
be supplied, for example, by recent mergers, secular instabilities or
filamentary cold flows. These processes could also trigger star
formation in the host galaxy. The host galaxies of the LEGs do not show
evidence for recent star formation and an influx of cold gas and are
consistent with being powered by the accretion of the hot phase of the
interstellar medium.
AB - We present the results of our investigation into the stellar populations
of 24 radio galaxies at z ~= 0.5 drawn from four complete,
low-frequency-selected radio surveys. We use the strength of the
4000-Å break as an indicator of recent star formation and compare
this with radio luminosity, optical spectral classification and
morphological classification. We find evidence of different star
formation histories for high- and low-luminosity radio sources; our
group of low radio luminosity sources (typically Fanaroff-Riley type I
sources) has systematically older stellar populations than the higher
radio luminosity group. Our sample is also fairly well divided by
optical spectral classification. We find that galaxies classified as
having low excitation spectra (LEGs) possess older stellar populations
than high excitation line objects (HEGs), with the HEGs showing evidence
for recent star formation. We also investigate the link between radio
morphology, as used by Owen and Laing, and the stellar populations. We
find that there is a preference for the `fat-double' sources to have
older stellar populations than the `classical double' sources, although
this is also linked to these sources lying predominantly in the LEG and
HEG categories, respectively. These results are consistent with the
hypothesis that HEGs are powered by accretion of cold gas, which could
be supplied, for example, by recent mergers, secular instabilities or
filamentary cold flows. These processes could also trigger star
formation in the host galaxy. The host galaxies of the LEGs do not show
evidence for recent star formation and an influx of cold gas and are
consistent with being powered by the accretion of the hot phase of the
interstellar medium.
UR - http://www.scopus.com/inward/record.url?scp=77955260387&partnerID=8YFLogxK
U2 - 10.1111/j.1365-2966.2010.16783.x
DO - 10.1111/j.1365-2966.2010.16783.x
M3 - Article
VL - 406
SP - 1841
EP - 1847
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
SN - 0035-8711
ER -