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arXiv 2305.04098astro-ph.GA
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高红移 QSO 中的中性外流

Neutral outflows in high-z QSOs

Kirsty M. Butler, Paul P. van der Werf, Alain Omont, Pierre Cox

AI总结:

研究利用 ALMA 观测 5 个 z~2–4 强透镜 QSO 的 OH+、CO(9-8) 与尘埃连续谱,发现中性外流仅见于极端恒星形成星系和两类 QSO,可能对应遮蔽 QSO 前后的高能演化阶段。

摘要:

OH+ 吸收是追踪星系周围以原子为主、弥漫且湍动的星系晕中流入和流出气体的有力示踪物。在这篇快报中,我们利用 ALMA 观测了 5 个强引力透镜、红移 z~2–4 的 QSO 中 OH+(1_1-1_0)、CO(9-8) 以及底层尘埃连续谱,以探测外流中性气体。5 个 QSO 中有 3 个探测到蓝移 OH+ 吸收,第 4 个为暂定探测;还在 1 个 QSO 中探测到系统速度处的吸收。5 个 QSO 中有 3 个在系统速度处观测到 OH+ 发射,并且全部 5 个 QSO 均以高 S/N 探测到 CO(9-8),提供了宿主星系内致密分子气体的信息。我们将样本与文献中高红移远红外(FIR)亮恒星形成星系和活动星系进行比较,发现活动星系与恒星形成星系的 OH+ 吸收线性质没有差异,两个样本遵循相同的光深—尘埃温度关系,表明这些观测量在两类样本中由相同机制驱动。类似地,恒星形成星系和活动星系都遵循相同的 OH+ 发射—FIR 关系。遮蔽型 QSO 的发射线比未遮蔽 QSO 以及除一个之外的所有高红移恒星形成星系更宽(>800 km/s),这可能由遮蔽吸积核的暖分子气体储库造成。遮蔽型 QSO 相比未遮蔽 QSO 具有更宽的 CO(9-8) 发射(>500 km/s),但总体线宽覆盖范围与恒星形成星系相似,并遵循低红移星系中发现的 CO(9-8)—FIR 光度关系。我们发现,由 OH+ 追踪的外流仅在极端恒星形成星系(宽 CO 发射)和两类 QSO 中探测到,而这些 QSO 反过来均未显示红移吸收。这表明星系晕中的弥漫中性外流可能与遮蔽 QSO 阶段之前及之后能量最高的演化阶段相关。

英文摘要:

OH+ absorption is a powerful tracer of inflowing and outflowing gas in the predominantly atomic diffuse and turbulent halo surrounding galaxies. In this letter, we present observations of OH+(1_1-1_0), CO(9-8) and the underlying dust continuum in 5 strongly lensed z~2-4 QSOs, using ALMA to detect outflowing neutral gas. Blue-shifted OH+ absorption is detected in 3/5 QSOs and tentatively detected in a 4th. Absorption at systemic velocities is also detected in one. OH+ emission is observed in 3/5 QSOs at systemic velocities and CO(9-8) is detected in all 5 QSOs at high S/N, providing information on the dense molecular gas within the host galaxy. We compare our sample to high-z far-infrared (FIR) luminous star-forming and active galaxies from the literature. We find no difference in OH+ absorption line properties between active and star-forming galaxies with both samples following the same optical depth-dust temperature relation, suggesting that these observables are driven by the same mechanism in both samples. Similarly, star-forming and active galaxies both follow the same OH+ emission-FIR relation. Obscured QSOs display broader (>800 km/s) emission than the unobscured QSOs and all but one of the high-z star-forming galaxies, likely caused by the warm molecular gas reservoir obscuring the accreting nucleus. Broader CO(9-8) emission (>500 km/s) is found in obscured versus unobscured QSOs, but overall cover a similar range in line widths as the star-forming galaxies and follow the CO(9-8)-FIR luminosity relation found in low-z galaxies. We find that outflows traced by OH+ are only detected in extreme star-forming galaxies (broad CO emission) and in both types of QSOs, which, in turn, display no red-shifted absorption. This suggests that diffuse neutral outflows in galaxy halos may be associated with the most energetic evolutionary phases leading up to and following the obscured QSO phase.

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