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arXiv 1005.1089astro-ph.CO
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高z星系中质量-SFR联系的第一个Herschel视图

The first Herschel view of the mass-SFR link in high-z galaxies

G. Rodighiero, A. Cimatti, C. Gruppioni, P. Popesso, P. Andreani, B. Altieri, H. Aussel, S. Berta, A. Bongiovanni, D. Brisbin, A. Cava, J. Cepa, E. Daddi, H. Do… 展开作者

G. Rodighiero, A. Cimatti, C. Gruppioni, P. Popesso, P. Andreani, B. Altieri, H. Aussel, S. Berta, A. Bongiovanni, D. Brisbin, A. Cava, J. Cepa, E. Daddi, H. Dominguez-Sanchez, D. Elbaz, A. Fontana, N. Forster Schreiber, A. Franceschini, R. Genzel, A. Grazian, D. Lutz, G. Magdis, M. Magliocchetti, B. Magnelli, R. Maiolino, C. Mancini, R. Nordon, A. M. Perez Garcia, A. Poglitsch, P. Santini, M. Sanchez-Portal, F. Pozzi, L. Riguccini, A. Saintonge, L. Shao, E. Sturm, L. Tacconi, I. Valtchanov, M. Wetzstein, E. Wieprecht

摘要:

我们利用在Herschel上的PACS对GOODS-N场进行的深度观测,作为PEP保证时间的一部分,来研究z~2星系中恒星形成和恒星质量之间的联系。从一个恒星质量选择的样本~4500星系与mag[4.5 mu]<23(AB),我们确定了~350对象与PACS检测在100或160 mu和~1500只有斯皮策24 mu对应。恒星质量和总红外光度(LIR)的估计通过拟合的SED。与其他Herschel结果一致,我们发现仅基于24 mu数据的LIR在z~2处被高估了约1.8的中值因子,而在0.5<z<1.0处被低估了约1.6的因子。然后,我们利用这种校准来校正基于MIPS通量的LIR。这些结果清楚地表明,赫歇尔是如何基本上限制LIR,因此SFR,高红移星系。利用PACS(和/或MIPS)探测到的星系,研究了恒星形成率(SFR)、比恒星形成率(SSFR=SFR/质量)与恒星质量之间关系的存在和演化。此外,为了避免选择效应,我们还重复这项研究,通过堆叠分析的PACS图像,充分利用远红外信息也为赫歇尔和斯皮策未检测到的子样本。我们发现SSFR-质量关系随着红移的增加而变陡,在z<1.0处几乎是平坦的,在z~2处达到α =-0.50 ^(+0.13)_(-0.16)的斜率,这与最近基于相同红移的射电堆积分析的结果不一致。星系的平均SSFR随红移而增加,对于质量大于10^(11)(M_sun)的星系,从z=0到z=2的范围内增加了约15倍,在这个质量范围内,似乎在z>1.5时变平。此外,质量最大的星系在任何z上都有最低的SSFR,这意味着它们比低质量的星系更早更快地形成恒星。

英文摘要:

We exploit deep observations of the GOODS-N field taken with PACS, on board of Herschel, as part of the PEP guaranteed time, to study the link between star formation and stellar mass in galaxies to z~2. Starting from a stellar mass-selected sample of ~4500 galaxies with mag[4.5mu]<23 (AB), we identify ~350 objects with a PACS detection at 100 or 160mu and ~1500 with only Spitzer 24 mu counterpart. Stellar masses and total IR luminosities (LIR) are estimated by fitting the SEDs. Consistently with other Herschel results, we find that LIR based only on 24 mu data is overestimated by a median factor ~1.8 at z~2, whereas it is underestimated (with our approach) up to a factor ~1.6 at 0.5<z<1.0. We then exploit this calibration to correct LIR based on the MIPS fluxes. These results clearly show how Herschel is fundamental to constrain LIR, and hence the SFR, of high redshift galaxies. Using the galaxies detected with PACS (and/or MIPS), we investigate the existence and evolution of the relations between the star formation rate (SFR), the specific star formation rate (SSFR=SFR/mass) and the stellar mass. Moreover, in order to avoid selection effects, we also repeat this study through a stacking analysis on the PACS images to fully exploit the far-IR information also for the Herschel and Spitzer undetected subsamples. We find that the SSFR-mass relation steepens with redshift, being almost flat at z<1.0 and reaching a slope of alpha=-0.50^(+0.13)_(-0.16) at z~2, at odds with recent works based on radio-stacking analysis at the same redshift. The mean SSFR of galaxies increases with redshift, by a factor ~15 for massive M>10^(11) (M_sun) galaxies from z=0 to z=2, and seems to flatten at z>1.5 in this mass range. Moreover, the most massive galaxies have the lowest SSFR at any z, implying that they have formed their stars earlier and more rapidly than their low mass counterparts.

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