IRAS 07251-0248 E 的 CON-类星体阶段
The CON-quasar stage of IRAS 07251-0248 E
AI总结：
IRAS 07251-0248 E 的观测揭示了一个被遮蔽的紧凑核，其隐藏的AGN正在以类星体亮度发射，同时存在由高浓度气体排出形成的热气泡。
摘要：
ALMA在667微米处对本地ULIRG IRAS 07251-0248 E的连续性测量揭示了一个极其紧凑（R < 27 pc）且明亮（T_B > 200 K）的核区，具有前方吸收的包层和周围（R ~ 75 pc）的盘或环，几乎面朝上观察。明亮且未解析的核发射表明存在大的光学深度（τ_{667μm} > 0.5，对应N_H > 10^{25} cm^-2）的热尘埃，温度大于500 K。此外，JWST观测显示该源在H2O nu_2=1-0（5-7 μm）的罗-振动带及其他物种（包括CO、HCN、C2H2、CH4和CO2）的中红外区有强吸收，并且Herschel/PACS观测显示由于OH、H2O、CH^+和CH的强吸收导致的饱和吸收。我们提出一个模型，其中未解析的ALMA亚毫米波和JWST中红外连续谱追踪同一个核源，前者深入核区，后者探测核光球。该连续谱模型，包括光子的捕获（温室效应），表明核区（R_h ~ 13 pc）的光度和光度表面密度约为10^{12} Lsun和Σ_{bol} ~ 5e8 Lsun pc^-2，起源于一个被埋得如此深的活动星系核（AGN），以至于高电离线完全被遮蔽。观测到的中红外气体相分子带探测出流速约为160 km/s的外流气体，并且与预测的T_{dust}分布一致，而远红外分子吸收线则在周围的厚盘或环中生成，τ_{100 μm} ~10。我们得出结论，IRAS 07251-0248拥有一个紧凑的遮蔽核（CON），隐藏着当前以类星体亮度发射的AGN。虽然观测到的外流可能由辐射压力驱动，但我们倾向于一个场景，即一个（部分）能量守恒的热气泡处于非常早期的高浓度气体在银河核处被排出的阶段。
英文摘要：
ALMA continuum measurements of the local ULIRG IRAS 07251-0248 E at 667$μ$m reveal an extremely compact (R < 27 pc) and bright ($T_B$ >200 K) nucleus with an absorbing foreground envelope and a surrounding (R ~ 75 pc) disk or torus seen nearly face-on. The bright and unresolved nuclear emission implies large optical depths ($τ_{667μm}$ >0.5, corresponding to $N_H > 10^{25}$ cm^-2) of hot dust at >500 K. In addition, JWST observations of the source show strong mid-infrared (mid-IR) absorption in the ro-vibrational bands of H2O nu_2=1-0 (5-7 $μ$m) and of other species including CO, HCN, C2H2, CH4, and CO2, and Herschel/PACS observations exhibit strong and saturated absorption due to OH, H2O, CH^+, and CH. We propose a model in which the unresolved ALMA submillimeter and JWST mid-IR continua trace the same nuclear source, the former penetrating deep into the nucleus and the latter probing the nuclear photosphere. The continuum model, which includes trapping of photons (the "greenhouse" effect), indicates that the nuclear ($R_h$ ~ 13 pc) luminosity and luminosity surface density are ~10$^{12}$ Lsun and $Σ_{bol}$~ 5e8 Lsun pc^-2, arising from an active galactic nucleus (AGN) so buried that high-ionization lines are completely obscured. The observed mid-IR gas-phase molecular bands probe outflowing gas with velocities of ~160 km s^-1 and are reproduced with the predicted $T_{dust}$ profile, while the far-IR molecular absorption lines are generated in the surrounding thick disk or torus with $τ_{100 μm}$~10. We conclude that IRAS 07251-0248 harbors a compact obscured nucleus (CON) that hides an AGN currently emitting at quasar luminosity. While the observed outflow could be driven by radiation pressure, we favor the scenario of a (partially) energy-conserving hot bubble caught in a very early phase of the expulsion of the highly concentrated gas at the galactic nucleus.
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