光解区附近的恒星形成：探测到Ced 201附近的一颗特殊原恒星
Star Formation Near Photodissociation Regions: Detection of a Peculiar Protostar Near Ced 201
摘要：
我们提出了一个特殊的低质量原恒星（IRAS 22129+7000）的检测和表征，距离Ced 201光解区（PDR）约0.4 pc，距离HH 450喷流约0.2 pc。围绕该物体的冷拱星包层已通过IRAM-30 m/MAMBO的1.2 mm尘埃连续辐射绘制。Spitzer/MIPS（70 μ m）、IRS（20-35 μ m）和IRAC（4.5、5.8和8 μ m）都能清楚地探测到深埋的原恒星，K_s波段（2.15 μ m）也能探测到。由于它的光谱能量分布中有大量的“近红外和中红外过剩”，但它的亚毫米光度与辐射热光度之比很大（~2%），IRAS 22129+7000必须是一个过渡0/I类源和/或一个多恒星系统。对CO、~（13）CO、C ~（18）O、HCO ~+和DCO ~+等分子谱线进行了有针对性的观测。CSO望远镜在CO J=3-2线绘制的准直分子外流的存在表明，原恒星/盘系统仍然是吸积材料从其出生的信封。事实上，从高密度示踪剂，如HCO+ J=1-0的光学粗线轮廓显示红移吸收不对称性，让人想起向内运动。我们构建了一个初步的物理模型的拱星信封（包括径向密度和温度梯度，速度场和湍流），再现所观察到的线的轮廓和估计的电离分数。机械和（非电离）FUV辐射输入的存在下，使该地区一个有趣的情况下，研究触发恒星形成。
英文摘要：
We present the detection and characterization of a peculiar low-mass protostar (IRAS 22129+7000) located ~0.4 pc from Ced 201 Photodissociation Region (PDR) and ~0.2 pc from the HH450 jet. The cold circumstellar envelope surrounding the object has been mapped through its 1.2 mm dust continuum emission with IRAM-30m/MAMBO. The deeply embedded protostar is clearly detected with Spitzer/MIPS (70 um), IRS (20-35 um) and IRAC (4.5, 5.8, and 8 um) but also in the K_s band (2.15 um). Given the large "near- and mid-IR excess" in its spectral energy distribution, but large submillimeter-to-bolometric luminosity ratio (~2%), IRAS 22129+7000 must be a transition Class 0/I source and/or a multiple stellar system. Targeted observations of several molecular lines from CO, 13CO, C18O, HCO+ and DCO+ have been obtained. The presence of a collimated molecular outflow mapped with the CSO telescope in the CO J=3-2 line suggests that the protostar/disk system is still accreting material from its natal envelope. Indeed, optically thick line profiles from high density tracers such as HCO+ J=1-0 show a red-shifted-absorption asymmetry reminiscent of inward motions. We construct a preliminary physical model of the circumstellar envelope (including radial density and temperature gradients, velocity field and turbulence) that reproduces the observed line profiles and estimates the ionization fraction. The presence of both mechanical and (non-ionizing) FUV-radiative input makes the region an interesting case to study triggered star formation.
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