ISM MASSES AND THE STAR FORMATION LAW AT Z = 1 TO 6: ALMA OBSERVATIONS OF DUST CONTINUUM IN 145 GALAXIES IN THE COSMOS SURVEY FIELD
ISM MASSES AND THE STAR FORMATION LAW AT Z = 1 TO 6: ALMA OBSERVATIONS OF DUST CONTINUUM IN 145 GALAXIES IN THE COSMOS SURVEY FIELD
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DOI：
10.3847/0004-637x/820/2/83
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发表时间：
2015-11
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通讯作者：
N. Scoville;K. Sheth;H. Aussel;P. V. Bout;P. Capak;A. Bongiorno;C. Casey;L. Murchikova;J. Koda-J
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作者：
N. Scoville;K. Sheth;H. Aussel;P. V. Bout;P. Capak;A. Bongiorno;C. Casey;L. Murchikova;J. Koda-J
利用阿尔马第2周期对145个恒星形成星系的长波长尘埃辐射观测，探讨了恒星形成星际介质（ISM）的演化。我们还开发了一个物理基础和经验校准（与72低z和z 2星系）使用的尘埃连续ISM质量的定量探针。银河系中最高的星星形成率（SFR）在2000年？> = 2.2和4.4的气体质量高达银河系的100倍，气体质量分数达到50%-80%，即，气体质量是恒星质量的1-4倍我们发现了一个高z星星的形成规律：SFR = 35 M mol 0.89 ×（1 + z）z = 2 0.95 ×（sSFR）MS 0.23？M？> yr−1-与ISM质量近似线性相关，在较高的红移下，每单位气体质量的星星形成效率增加。位于主序层（MS）之上的星系团有较大的气体质量，但它们将ISM转化为恒星的时间尺度只比MS上的略短;因此，这些“星爆”主要是气体质量大大增加的结果，而不是气体转化为恒星的效率增加的结果。在z > 1时，整个恒星形成星系的气体耗尽时间比低z星系短2.2 -5倍。这些较短的耗尽时间表明了宇宙早期星星形成的不同模式最有可能是由压缩的、高色散的气体运动驱动的这是高气体吸积率的自然结果。
ALMA Cycle 2 observations of long-wavelength dust emission in 145 star-forming galaxies are used to probe the evolution of the star-forming interstellar medium (ISM). We also develop a physical basis and empirical calibration (with 72 low-z and z ∼ 2 galaxies) for using the dust continuum as a quantitative probe of ISM masses. The galaxies with the highest star formation rates (SFRs) at ⟨ z ⟩ ?> = 2.2 and 4.4 have gas masses up to 100 times that of the Milky Way and gas mass fractions reaching 50%–80%, i.e., gas masses 1-4× their stellar masses. We find a single high-z star formation law: SFR = 35 M mol 0.89 × ( 1 + z ) z = 2 0.95 × ( sSFR ) MS 0.23 ?> M ⊙ ?> yr−1—an approximately linear dependence on the ISM mass and an increased star formation efficiency per unit gas mass at higher redshift. Galaxies above the main sequence (MS) have larger gas masses but are converting their ISM into stars on a timescale only slightly shorter than those on the MS; thus, these “starbursts” are largely the result of having greatly increased gas masses rather than an increased efficiency of converting gas to stars. At z > 1, the entire population of star-forming galaxies has ∼2–5 times shorter gas depletion times than low-z galaxies. These shorter depletion times indicate a different mode of star formation in the early universe—most likely dynamically driven by compressive, high-dispersion gas motions—a natural consequence of the high gas accretion rates.