TY - JOUR
T1 - Star formation in nearby early-type galaxies
T2 - the radio continuum perspective
AU - Nyland, Kristina
AU - Young, Lisa M.
AU - Wrobel, Joan M.
AU - Davis, Timothy A.
AU - Bureau, Martin
AU - Alatalo, Katherine
AU - Morganti, Raffaella
AU - Duc, Pierre Alain
AU - Zeeuw, P. T.
AU - McDermid, Richard M.
AU - Crocker, Alison F.
AU - Oosterloo, Tom
PY - 2017/1
Y1 - 2017/1
N2 - We present a 1.4 GHz Karl G. Jansky Very Large Array (VLA) study of a sample of early-type galaxies (ETGs) from the ATLAS(3D) survey. The radio morphologies of these ETGs at a resolution of 0(FWHM) approximate to 5 arcsec include sources that are compact on sub-kpc scales, resolved structures similar to those seen in star-forming spiral galaxies, and kpc-scale radio jets/lobes associated with active nuclei. We compare the radio, CO, and infrared (IR) properties of these ETGs. The most CO-rich ETGs have radio luminosities consistent with extrapolations from II2 mass derived star-formation rates from studies of late-type galaxies. These ETGs also follow the radio-IR correlation. However, ETGs with lower molecular gas masses tend to have less radio emission relative to their CO and IR emission compared to spirals. The fraction of galaxies in our sample with high IR-radio ratios is much higher than in previous studies, and cannot be explained by a systematic underestimation of the radio luminosity due to the presence extended, low-surface-brightness emission that was resolved out in our VLA observations. We find that the high IR-radio ratios tend to occur at low IR luminosities, but are not associated with lowdynamical mass or metallicity. Thus, we have identified a population of ETGs that have a genuine shortfall of radio emission relative to both their IR and CO emission. A number of mechanisms may cause this deficiency, including a bottom-heavy stellar initial mass function, weak magnetic fields, a higher prevalence of environmental effects compared to spirals, and enhanced cosmic ray losses.
AB - We present a 1.4 GHz Karl G. Jansky Very Large Array (VLA) study of a sample of early-type galaxies (ETGs) from the ATLAS(3D) survey. The radio morphologies of these ETGs at a resolution of 0(FWHM) approximate to 5 arcsec include sources that are compact on sub-kpc scales, resolved structures similar to those seen in star-forming spiral galaxies, and kpc-scale radio jets/lobes associated with active nuclei. We compare the radio, CO, and infrared (IR) properties of these ETGs. The most CO-rich ETGs have radio luminosities consistent with extrapolations from II2 mass derived star-formation rates from studies of late-type galaxies. These ETGs also follow the radio-IR correlation. However, ETGs with lower molecular gas masses tend to have less radio emission relative to their CO and IR emission compared to spirals. The fraction of galaxies in our sample with high IR-radio ratios is much higher than in previous studies, and cannot be explained by a systematic underestimation of the radio luminosity due to the presence extended, low-surface-brightness emission that was resolved out in our VLA observations. We find that the high IR-radio ratios tend to occur at low IR luminosities, but are not associated with lowdynamical mass or metallicity. Thus, we have identified a population of ETGs that have a genuine shortfall of radio emission relative to both their IR and CO emission. A number of mechanisms may cause this deficiency, including a bottom-heavy stellar initial mass function, weak magnetic fields, a higher prevalence of environmental effects compared to spirals, and enhanced cosmic ray losses.
KW - galaxies: elliptical and lenticular
KW - cD- galaxies: star formation
KW - radio continuum: galaxies
UR - http://www.scopus.com/inward/record.url?scp=85014771940&partnerID=8YFLogxK
U2 - 10.1093/mnras/stw2385
DO - 10.1093/mnras/stw2385
M3 - Article
SN - 0035-8711
VL - 464
SP - 1029
EP - 1064
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 1
ER -