Galaxy evolution explorer ultraviolet color-magnitude relations and evidence of recent star formation in early-type galaxies

Yi, S.K.; Yoon, S.-J.; Lee, Y.-W.; Ree, C.H.; Sohn, Y.-J.; Rey, S.-C.; Rhee, J.; Byun, Y.-I.; Kim, S.-W.; Kaviraj, S.; Deharveng, J.-M.; Boselli, A.; Donas, J.; Malina, R.; Milliard, B.; Rich, R.M.; Salim, S.; Friedman, P.G.; Martin, D.C.; Morrissey, P.; Small, T.; Barlow, T.; Forster, K.; Wyder, T.K.; Lee, J.-W.; Bianchi, L.; Heckman, T.M.; Szalay, A.S.; Jee, M.J.; Jelinsky, P.; Siegmund, O.; Welsh, B.; Madore, B.F.; Neff, S.; Schiminovich, D.

Author

Yi, S.K.

Yoon, S.-J.

Lee, Y.-W.

Ree, C.H.

Sohn, Y.-J.

Rey, S.-C.

Rhee, J.

Byun, Y.-I.

Kim, S.-W.

Kaviraj, S.

Deharveng, J.-M.

Boselli, A.

Donas, J.

Malina, R.

Milliard, B.

Rich, R.M.

Salim, S.

Friedman, P.G.

Martin, D.C.

Morrissey, P.

Small, T.

Barlow, T.

Forster, K.

Wyder, T.K.

Lee, J.-W.

Bianchi, L.

Heckman, T.M.

Szalay, A.S.

Jee, M.J.

Jelinsky, P.

Siegmund, O.

Welsh, B.

Madore, B.F.

Neff, S.

Schiminovich, D.

Abstract

We have used the Galaxy Evolution Explorer UV photometric data to construct a first near-UV (NUV) color-magnitude relation (CMR) for the galaxies preclassified as early-type by Sloan Digital Sky Survey studies. The NUV CMR is a powerful tool for tracking the recent star formation history in early-type galaxies, owing to its high sensitivity to the presence of young stellar populations. Our NUV CMR for UV-weak galaxies shows a well-defined slope and thus will be useful for interpreting the rest-frame NUV data of distant galaxies and studying their star formation history. Compared to optical CMRs, the NUV CMR shows a substantially larger scatter, which we interpret as evidence of recent star formation activities. Roughly 15% of the recent epoch (z <0.13) bright [M(r) <-22] early-type galaxies show a sign of recent ≤1 Gyr) star formation at the 1%-2% level (lower limit) in mass compared to the total stellar mass. This implies that low-level residual star formation was common during the last few billion years even in bright early-type galaxies.