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arXiv 0907.5199astro-ph.CO
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COSMOS中的大质量星系:在过去的9个Gyrs中黑洞相对于膨胀质量而不是相对于恒星总质量的演化?

Massive Galaxies in COSMOS: Evolution of Black hole versus bulge mass but not versus total stellar mass over the last 9 Gyrs?

Knud Jahnke, Angela Bongiorno, Marcella Brusa, Peter Capak, Nico Cappelluti, Mauricio Cisternas, Francesca Civano, James Colbert, Andrea Comastri, Martin Elvis,… 展开作者

Knud Jahnke, Angela Bongiorno, Marcella Brusa, Peter Capak, Nico Cappelluti, Mauricio Cisternas, Francesca Civano, James Colbert, Andrea Comastri, Martin Elvis, Günther Hasinger, Chris Impey, Katherine Inskip, Anton M. Koekemoer, Simon Lilly, Christian Maier, Andrea Merloni, Dominik Riechers, Mara Salvato, Eva Schinnerer, Nick Z. Scoville, John Silverman, Yoshi Taniguchi, Jonathan R. Trump, Lin Yan

摘要:

我们将COSMOS巡天中第1类活动星系核的黑洞质量与恒星总质量之比限制在1<z<2。对于平均红移z~1.4的10个活动星系核,利用HST/ACS和HST/NICMOS的成像数据,我们能够根据限制质光比的主星系的紫外-光学颜色的重构框架,计算出恒星的总质量M_(*,total)。所有天体都有可从COSMOS Magellan/IMACS和zCOSMOS巡天获得的维里BH质量估计。我们发现在z~1.4处的M_BH-M_(*,total)-关系与局域宇宙中的M_BH-M_(*,bulge)-关系之间没有差别。我们的解释是:(a)如果我们的对象是纯凸支配的,那么M_BH-M_(*,bulge)-关系自z~1.4以来没有演化。然而,(b)由于我们有证据表明存在大量的盘成分,大质量星系(logM_(*,total)=11.1+-0.25或logM_BH~8.3+-0.2)的膨胀在过去的9个Gyr中主要是通过盘-到膨胀质量的再分配而增长的。由于所有必要的恒星质量都存在于z=1.4的星系中,因此不需要恒星形成或外部恒星物质的增加,只需要重新分配,例如由次要和主要合并或通过盘不稳定性引起的。合并,除了重新分配星系的质量,将增加BH和恒星/球质量,但不改变总的最终M_BH/M_(*,球)比。由于整个宇宙恒星和BH质量的积累随着时间的推移相互紧密跟踪,我们的大质量星系中的膨胀形成的情况是独立于任何强烈的BH反馈,这意味着耦合BH和膨胀质量的机制,直到现在是非常间接的。

英文摘要:

We constrain the ratio of black hole (BH) mass to total stellar mass of type-1 AGN in the COSMOS survey at 1<z<2. For 10 AGN at mean redshift z~1.4 with both HST/ACS and HST/NICMOS imaging data we are able to compute total stellar mass M_(*,total), based on restframe UV-to-optical host galaxy colors which constrain mass-to-light ratios. All objects have virial BH mass-estimates available from the COSMOS Magellan/IMACS and zCOSMOS surveys. We find zero difference between the M_BH--M_(*,total)-relation at z~1.4 and the M_BH--M_(*,bulge)-relation in the local Universe. Our interpretation is: (a) If our objects were purely bulge-dominated, the M_BH--M_(*,bulge)-relation has not evolved since z~1.4. However, (b) since we have evidence for substantial disk components, the bulges of massive galaxies (logM_(*,total)=11.1+-0.25 or logM_BH~8.3+-0.2) must have grown over the last 9 Gyrs predominantly by redistribution of disk- into bulge-mass. Since all necessary stellar mass exists in the galaxy at z=1.4, no star-formation or addition of external stellar material is required, only a redistribution e.g. induced by minor and major merging or through disk instabilities. Merging, in addition to redistributing mass in the galaxy, will add both BH and stellar/bulge mass, but does not change the overall final M_BH/M_(*,bulge) ratio. Since the overall cosmic stellar and BH mass buildup trace each other tightly over time, our scenario of bulge-formation in massive galaxies is independent of any strong BH-feedback and means that the mechanism coupling BH and bulge mass until the present is very indirect.

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