Close-up view of a luminous star-forming galaxy at z = 2.95-猫眼课题宝

DOI：

10.1051/0004-6361/202039743

发表时间：

2020-12

期刊：

Astronomy & Astrophysics

影响因子：

6.5

通讯作者：

中科院分区：

物理与天体物理2区

文献类型：

作者：

S. Berta;A. Young;P. Cox;R. Neri;B. M. Jones;A. Baker;A. Omont;L. Dunne;A. Rosell;L. Marchetti;M. Negrello;C. Yang;D. Riechers;H. Dannerbauer;I. Pérez-Fournon;P. Werf;T. Bakx;R. Ivison;A. Beelen;V. Buat;A. Cooray;I. Cortzen;S. Dye;S. Eales;R. Gavazzi;A. Harris;C. Herrera;D. Hughes;S. Jin;M. Krips;G. Lagache;M. Lehnert;H. Messias;S. Serjeant;F. Stanley;S. Urquhart;C. Vlahakis;A. Weiss

利用IRAM北向扩展毫米波阵列的灵敏度和处理大瞬时带宽的能力，我们研究了恒星形成星系H-ATLAS J131611.5+281219(HASSERS-89a)在z=2.95时分子气体和尘埃的形态和其他性质。高角分辨率(0.“3)图像显示，尘埃连续谱发射和12Co(9−8)和H2O(2 0 2−111)分子发射线中有一个直径为1.0的部分爱因斯坦环。连同较低的角分辨率(0.“6)图像，我们报告了一系列分子谱线的探测，包括分子离子OH+的三个基本跃迁，即在吸收中看到的(11−01)、(12−01)和(10−01)；在吸收中看到的分子离子CH+(1−0)，并暂时在发射中；在发射中看到的酰胺(NH)的两个跃迁，即(202−111)和(220−211)；以及在吸收中看到的HCN(11−10)和/或NH(12−01)。NOEMA数据与追踪12CO(1−0)发射线的非常大的阵列数据相辅相成，该数据提供了分子气体总质量的测量和CO激发分析的锚。此外，我们还给出了哈勃太空望远镜成像，它显示了近红外(1.15μm)的前景透镜星系。结合来自Gran Telescope io Canarias的测光数据，我们得到前景透镜星系的测光红移为ZPot=0.9ZPot=0.9ZPot 0.5+0.3。模拟草药-89a的透镜，我们重建了源平面上的尘埃连续谱(放大因子μ≃5.0)和分子发射线(放大μ∼4−5)，探测∼0.“1(或800pC)的尺度。12Co(9−8)和H2O(202−111)的发射线具有类似的空间和运动分布；源面重建没有明确区分单成分和双成分的情况，但后者显示了两个大小为≈1kpc的紧凑旋转成分可能正在合并，这更自然地解释了在Herrus-89a中观察到的宽线宽。在草药-89a的核心，由NH_2发射线和可能的∼(11−10)吸收线揭示出具有NH_2−_(107)和9 cm−_3的非常稠密的气体。草药-89a是一个强大的恒星形成星系，其分子气体质量为⊙=(2.1±0.4)×10~11M⊙，红外光度为LIR=(4.6±0.4)×10~(12)L⊙，尘埃质量为(2.6±0.2)×10~9M⊙，产生尘气比δGdR≈80。得到了恒星形成率Sfr=6 14±5 9M⊙yr−1和耗竭时间标度τDepl=(3 4±1 0)×10 8年。示踪低密度(∼10 0 cm−3)分子气的OH+和CH+吸收谱线的主要速度分量均被ΔV∼10 0 km S−1相对于全球CO储集层红移。我们认为，这些吸收线追踪了一个罕见的气体流入星系中心的例子，表明草药-89a正在从其周围吸积气体。

Exploiting the sensitivity of the IRAM NOrthern Extended Millimeter Array (NOEMA) and its ability to process large instantaneous bandwidths, we have studied the morphology and other properties of the molecular gas and dust in the star forming galaxy, H-ATLAS J131611.5+281219 (HerBS-89a), at z = 2.95. High angular resolution (0.″3) images reveal a partial 1.″0 diameter Einstein ring in the dust continuum emission and the molecular emission lines of 12CO(9−8) and H2O(202 − 111). Together with lower angular resolution (0.″6) images, we report the detection of a series of molecular lines including the three fundamental transitions of the molecular ion OH+, namely (11 − 01), (12 − 01), and (10 − 01), seen in absorption; the molecular ion CH+(1 − 0) seen in absorption, and tentatively in emission; two transitions of amidogen (NH2), namely (202 − 111) and (220 − 211) seen in emission; and HCN(11 − 10) and/or NH(12 − 01) seen in absorption. The NOEMA data are complemented with Very Large Array data tracing the 12CO(1 − 0) emission line, which provides a measurement of the total mass of molecular gas and an anchor for a CO excitation analysis. In addition, we present Hubble Space Telescope imaging that reveals the foreground lensing galaxy in the near-infrared (1.15 μm). Together with photometric data from the Gran Telescopio Canarias, we derive a photometric redshift of zphot = 0.9−0.5+0.3 for the foreground lensing galaxy. Modeling the lensing of HerBS-89a, we reconstruct the dust continuum (magnified by a factor μ ≃ 5.0) and molecular emission lines (magnified by μ ∼ 4 − 5) in the source plane, which probe scales of ∼0.″1 (or 800 pc). The 12CO(9 − 8) and H2O(202 − 111) emission lines have comparable spatial and kinematic distributions; the source-plane reconstructions do not clearly distinguish between a one-component and a two-component scenario, but the latter, which reveals two compact rotating components with sizes of ≈1 kpc that are likely merging, more naturally accounts for the broad line widths observed in HerBS-89a. In the core of HerBS-89a, very dense gas with nH2 ∼ 107 − 9 cm−3 is revealed by the NH2 emission lines and the possible HCN(11 − 10) absorption line. HerBS-89a is a powerful star forming galaxy with a molecular gas mass of Mmol = (2.1 ± 0.4) × 1011 M⊙, an infrared luminosity of LIR = (4.6 ± 0.4) × 1012 L⊙, and a dust mass of Mdust = (2.6 ± 0.2) × 109 M⊙, yielding a dust-to-gas ratio δGDR ≈ 80. We derive a star formation rate SFR = 614 ± 59 M⊙ yr−1 and a depletion timescale τdepl = (3.4 ± 1.0) × 108 years. The OH+ and CH+ absorption lines, which trace low (∼100 cm−3) density molecular gas, all have their main velocity component red-shifted by ΔV ∼ 100 km s−1 relative to the global CO reservoir. We argue that these absorption lines trace a rare example of gas inflow toward the center of a galaxy, indicating that HerBS-89a is accreting gas from its surroundings.

Close-up view of a luminous star-forming galaxy at z = 2.95

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