arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2002.02968astro-ph.GA
收藏

解释7 <z <9星系的Spitzer/IRAC色:用ALMA区分线发射和星光

Interpreting the Spitzer/IRAC Colours of 7<z<9 Galaxies: Distinguishing Between Line Emission and Starlight Using ALMA

Guido Roberts-Borsani, Richard S. Ellis, Nicolas Laporte

摘要:

在JWST发射之前,斯皮策/IRAC测光提供了研究z> 7星系静止坐标系光学特性的唯一方法。许多这样的高红移星系显示红色[3.6]-[4.5]微米的颜色,通常被称为“IRAC过量”,这通常被解释为在[4.5]微米带通内强烈的[OIII]+ H β发射。这种解释的一个吸引人的方面是在较低红移的恒星形成星系中看到的类似的强烈线发射,以及在z~7以上的IRAC颜色的红移依赖行为,模拟为各种星云线通过两个带通。在本文中,我们证明,鉴于光度的不确定性,建立恒星星族与巴耳末(4000埃,休息框架)的突破,如那些推断在z> 9的线发射不污染的IRAC带,可以同样很好地解释红移依赖的行为的IRAC颜色在7 <z <9星系。我们讨论了可能的方式来区分这两种假设使用ALMA措施[OIII] 88微米和灰尘连续通量。在与JWST进一步研究之前,我们表明,区别是重要的,在第一个5亿年的星系的组装历史。

英文摘要:

Prior to the launch of JWST, Spitzer/IRAC photometry offers the only means of studying the rest-frame optical properties of z>7 galaxies. Many such high redshift galaxies display a red [3.6] - [4.5] micron colour, often referred to as the "IRAC excess", which has conventionally been interpreted as arising from intense [OIII]+Hbeta emission within the [4.5] micron bandpass. An appealing aspect of this interpretation is similarly intense line emission seen in star-forming galaxies at lower redshift as well as the redshift-dependent behaviour of the IRAC colours beyond z~7 modelled as the various nebular lines move through the two bandpasses. In this paper we demonstrate that, given the photometric uncertainties, established stellar populations with Balmer (4000 A, rest-frame) breaks, such as those inferred at z>9 where line emission does not contaminate the IRAC bands, can equally well explain the redshift-dependent behaviour of the IRAC colours in 7<z<9 galaxies. We discuss possible ways of distinguishing between the two hypotheses using ALMA measures of [OIII] 88 micron and dust continuum fluxes. Prior to further studies with JWST, we show that the distinction is important in determining the assembly history of galaxies in the first 500 Myr.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑