论文标题
解释7 <z <9星系的Spitzer/IRAC颜色：使用Alma区分线排放和星光
Interpreting the Spitzer/IRAC Colours of 7<z<9 Galaxies: Distinguishing Between Line Emission and Starlight Using ALMA
论文作者
论文摘要
在发布JWST之前，Spitzer/IRAC光度法提供了研究Z> 7星系的剩余光学特性的唯一手段。许多这样的高红移星系显示出红色[3.6] - [4.5]微米的颜色，通常称为“ IRAC多余”，通常将其解释为由[4.5] Micron Bandpass中强烈的[OIII]+HBETA发射引起的。这种解释的一个吸引人的方面类似地是在较低的红移的星形星系中观察到的强烈线条发射，以及随着Z〜7超过Z〜7的红移依赖性行为，随着各种静脉线穿过两个带通道的移动。在本文中，我们证明，鉴于光度不确定性，建立了具有Balmer（4000 A，REST-FRAME）断裂的恒星种群，例如在Z> 9中推断的恒星种群，在线发射不会污染IRAC频段，同样可以很好地解释7 <z <9 Galaxies中IRAC颜色的红移依赖性行为。我们讨论了使用[OIII] 88微米和尘埃连续通量的ALMA测量方法区分这两个假设的可能方法。在与JWST进行进一步研究之前，我们表明，这种区别对于确定第500 MYR中星系的组装历史很重要。
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.
