Astronomy and Astrophysics – Astrophysics – Galaxy Astrophysics
Scientific paper
2011-06-03
Astronomy and Astrophysics
Astrophysics
Galaxy Astrophysics
Accepted for publication in the Astrophysical Journal Letters
Scientific paper
We produce a stacked 20 cm radio image with FIRST survey data of 763 K+A galaxies selected from DR7 of the SDSS on the basis of their Balmer line and [OII] equivalent widths. We find a mean flux density of 0.4 $\mu$Jy in an aperture equivalent to the FIRST beam around the center of the stacked radio image. Monte Carlo simulations were carried out by stacking equivalent numbers of images of radio quiet targets (white dwarfs) for a total of 10,000 samples. The mean flux from these objects is zero, but from these data we determined a $5\sigma$ noise limit (for detection) of 0.4 $\mu$Jy. Our analysis yields a barely significant detection of 20 cm radio flux from K+A galaxies and an upper limit to current star formation of $< 0.2$ M$_{\odot}$ yr$^{-1}$. We split the sample according to age (derived from the Balmer line strength) and find that even for galaxies whose starburst age is less than 250 Myr, there is no significant 20 cm signal. K+A galaxies appear to have ceased any star formation since the past several hundred Myr.
de Propris Roberto
Goto Tomotsugu
Nielsen Danielle
Ridgway Susan E.
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