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arXiv 1201.3792astro-ph.CO
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z~0.3时LINER宿主星系中的恒星形成

Star formation in LINER host galaxies at z~0.3

Silvia Tommasin, Hagai Netzer, Amiel Sternberg, Raanan Nordon, Dieter Lutz, Angela Bongiorno, Stefano Berta, Benjamin Magnelli, Emeric Le Floc'h, Laurie Riguccini, Francesca Pozzi

摘要:

我们提出了从zCOSMOS调查中选择的97个红移z \sim 0.3的LINER样本的Herschel-PACS研究结果。在这些源中,34个在至少一个PACS波段中被检测到,从而能够可靠地估计远红外L(FIR)光度,并与当地LINER的FIR光度进行比较。我们的许多PACS检测的LINER也是Galex检测的UV源。假设FIR产生于年轻的尘埃恒星形成区,我们样本中宿主星系的典型恒星形成率(SFR)为\sim 10 M_Sun yr-1,比许多局部LINER大1-2个数量级。鉴于恒星质量推断光学/近红外测光的(无遮挡)演变的恒星星族,我们发现,整个样本位于靠近恒星形成的“主序列”的星系在红移0.3。对于年轻的恒星形成区,即使假设所有的Hα辐射都是由O星电离而不是活动星系核产生的,基于Hα和UV的SFR估计值也要比基于FIR的估计值小\sim 30倍。这些差异可能是由于对年轻恒星系统的大(和不确定的)干扰。或者,Hα和紫外线辐射可能是在一个较老的恒星形成过程中,在恒星形成过程中,恒星形成过程的衰减。我们还比较了L(SF)和L(AGN)在当地LINERS和我们的样品和评论的问题使用几个线诊断图的情况下,类似的样本进行研究。

英文摘要:

We present the results of a Herschel-PACS study of a sample of 97 LINERs at redshift z\sim 0.3 selected from the zCOSMOS survey. Of these sources, 34 are detected in a least one PACS band, enabling reliable estimates of the far-infrared L(FIR) luminosities, and a comparison to the FIR luminosities of local LINERs. Many of our PACS-detected LINERs are also UV sources detected by Galex. Assuming that the FIR is produced in young dusty star-forming regions, the typical star-formation rates (SFRs) for the host galaxies in our sample is \sim 10 M_Sun yr-1, 1-2 orders of magnitude larger than in many local LINERs. Given stellar masses inferred from optical/NIR photometry of the (unobscured) evolved stellar populations, we find that the entire sample lies close to the star-forming "main sequence" for galaxies at redshift 0.3. For young star-forming regions, the Hα- and UV-based estimates of the SFRs are much smaller than the FIR-based estimates, by factors \sim 30, even assuming that all of the Hα emission is produced by O-star ionization rather than by the AGNs. These discrepancies may be due to large (and uncertain) extinctions towards the young stellar systems. Alternatively, the Hα and UV emissions could be tracing residual star-formation in an older less obscured population with decaying star formation. We also compare L(SF) and L(AGN) in local LINERs and in our sample and comment on the problematic use of several line diagnostic diagrams in cases similar to the sample under study.

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