Astronomy and Astrophysics, volume 534A, 15-15 (2011/10-1)
GOODS-Herschel: a population of 24µm dropout sources at z < 2.
MAGDIS G.E., ELBAZ D., DICKINSON M., HWANG H.S., CHARMANDARIS V., ARMUS L., DADDI E., LE FLOC'H E., AUSSEL H., DANNERBAUER H., RIGOPOULOU D., BUAT V., MORRISON G., MULLANEY J., LUTZ D., SCOTT D., COIA D., POPE A., PANNELLA M., ALTIERI B., BURGARELLA D., BETHERMIN M., DASYRA K., KARTALTEPE J., LEITON R., MAGNELLI B., POPESSO P. and VALTCHANOV I.
Abstract (from CDS):
Using extremely deep PACS 100- and 160µm Herschel data from the GOODS-Herschel program, we identify 21 infrared bright galaxies previously missed in the deepest 24µm surveys performed by Spitzer/MIPS. These MIPS dropouts are predominantly found in two redshift bins, centred at z∼0.4 and ∼1.3. Their S100/S24 flux density ratios are similar to those of local (ultra-) luminous infrared galaxies (LIRGs and ULIRGs), whose silicate absorption features at 18µm (at z∼0.4) and 9.7µm (at z∼1.3) are shifted into the 24µm MIPS band at these redshifts. The high-z sub-sample consists of 11 infrared luminous sources, accounting for ∼2% of the whole GOODS-Herschel sample and putting strong upper limits on the fraction of LIRGs/ULIRGs at 1.0<z<1.7 that are missed by the 24µm surveys. We find that a S100/S24>43 colour cut selects galaxies with a redshift distribution similar to that of the MIPS dropouts and when combined with a second colour cut, S16/S8 > 4, isolates sources at 1.0<z<1.7. We show that these sources have elevated specific star formation rates (sSFR) compared to main sequence galaxies at these redshifts and are likely to be compact starbursts with moderate/strong 9.7µm silicate absorption features in their mid-IR spectra. Herschel data reveal that their infrared luminosities extrapolated from the 24µm flux density are underestimated, on average, by a factor of ∼3. These silicate break galaxies account for 16% (8%) of the ULIRG (LIRG) population in the GOODS fields, indicating a lower limit in their space density of 2.0x10–5/Mpc3. Finally, we provide estimates of the fraction of z<2 MIPS dropout sources as a function of the 24-, 100-, 160-, 250- and 350µm sensitivity limits, and conclude that previous predictions of a population of silicate break galaxies missed by the major 24µm extragalactic surveys have been overestimated.
galaxies: active - galaxies: evolution - galaxies: formation - galaxies: groups: general - infrared: galaxies
Paragraph 3.2 NGC 22491 is a probable misprint for IRAS 22491-1808, IRAS 17128 a probable misprint for IRAS 17208-0014.
View the reference in ADS
To bookmark this query, right click on this link: simbad:2011A&A...534A..15M and select 'bookmark this link' or equivalent in the popup menu