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arXiv 1712.04540astro-ph.GA
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大质量大小选择星系团的Herschel和ALMA观测

Herschel and ALMA Observations of Massive SZE-selected Clusters

John F. Wu, Paula Aguirre, Andrew J. Baker, Mark J. Devlin, Matt Hilton, John P. Hughes, Leopoldo Infante, Robert R. Lindner, Cristóbal Sifón

摘要:

我们在$0.3 \leq z \leq 1.1$上对四个大质量的Sunyaev-Zel'dovich效应(SZE)选择的星系团进行了新的赫歇尔观测,其中两个也是用ALMA观测到的。我们检测到19个Herschel/PACS对应的光谱确认的集群成员,其中五个具有红移通过CO($4-3$)和[CI](${}^3P_1 - {}^3P_0$)线确定。平均[CI]/CO线比为亮温单位的$0.19 \pm 0.07$,与现场样品的先前结果一致。我们没有检测到显着的堆叠ALMA尘埃连续谱或谱线发射,意味着平均星际介质(H $_2$ + HI)和分子气体质量的上限。$L_{IR}$与星团中心半径之间的明显关系是由恒星形成速率与恒星质量之间的紧密关系驱动的。我们发现,平均特定的恒星形成率log(sSFR/yr $^{-1}$)=-10.36,这是低于SFR $-M_*$相关测量场星系在类似的红移。每个星系团中红外亮星系(IRBG; $\log (L_{IR}/L_\odot) > 10.6$)的比例和平均sSFR随红移显著上升。对于CO的检测,我们发现$f_{gas} \sim 0.2$,相当于场星系,和气体耗尽的时间尺度约2 Gyr。我们利用射电观测来区分活动星系核(AGN)和恒星形成星系。在我们的19个赫歇尔星团成员中,至少有4个具有$q_{IR} < 1.8$,这意味着我们的PACS选择的样本中存在活动星系核部分$f_{AGN} \gtrsim 0.2$。

英文摘要:

We present new Herschel observations of four massive, Sunyaev-Zel'dovich Effect (SZE)-selected clusters at $0.3 \leq z \leq 1.1$, two of which have also been observed with ALMA. We detect 19 Herschel/PACS counterparts to spectroscopically confirmed cluster members, five of which have redshifts determined via CO($4-3$) and [CI](${}^3P_1 - {}^3P_0$) lines. The mean [CI]/CO line ratio is $0.19 \pm 0.07$ in brightness temperature units, consistent with previous results for field samples. We do not detect significant stacked ALMA dust continuum or spectral line emission, implying upper limits on mean interstellar medium (H$_2$ + HI) and molecular gas masses. An apparent anticorrelation of $L_{IR}$ with clustercentric radius is driven by the tight relation between star formation rate and stellar mass. We find average specific star formation rate log(sSFR/yr$^{-1}$) = -10.36, which is below the SFR$-M_*$ correlation measured for field galaxies at similar redshifts. The fraction of infrared-bright galaxies (IRBGs; $\log (L_{IR}/L_\odot) > 10.6$) per cluster and average sSFR rise significantly with redshift. For CO detections, we find $f_{gas} \sim 0.2$, comparable to those of field galaxies, and gas depletion timescales of about 2 Gyr. We use radio observations to distinguish active galactic nuclei (AGNs) from star-forming galaxies. At least four of our 19 Herschel cluster members have $q_{IR} < 1.8$, implying an AGN fraction $f_{AGN} \gtrsim 0.2$ for our PACS-selected sample.

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