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Probing GLIMPSE Extended Green Objects (EGOs) with hydroxyl masers
Monthly Notices of the Royal Astronomical Society ( IF 4.8 ) Pub Date : 2020-09-21 , DOI: 10.1093/mnras/staa2885
O S Bayandina 1, 2 , P Colom 3 , S E Kurtz 4 , G M Rudnitskij , N N Shakhvorostova 2 , I E Val’tts 2
Affiliation  

ABSTRACT
We present a study of 18 cm OH maser emission toward 20 high-mass young stellar object outflow candidates (Extended Green Objects, EGOs) identified from the Spitzer Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE). All four OH ground state lines at 1612, 1665, 1667, and 1720 MHz, together with 20-cm continuum emission, were observed with the Karl G. Jansky Very Large Array C-configuration. Follow-up polarimetric single-dish observations with the Nançay radio telescope were performed for the same OH transitions, except 1612 MHz. OH maser emission is found to be an uncommon feature of the sample, with a 50 per cent detection rate for the entire sample and a ∼44 per cent detection rate for the ‘likely’ EGOs. No 20-cm continuum emission is detected toward any of the sources. In most cases, the detected OH maser emission arises in vicinity to compact central sources; OH masers coexist with the 6.7 GHz methanol masers, but are found in more diffuse and extended halo-shaped regions of several thousand astronomical units in size. Comparing EGO samples with OH maser detection and non-detection, EGOs showing OH maser emission tend to have lower dust clump masses, but higher 24 and 4.5 μm flux densities. Thus, OH maser emission might be an indicator of more evolved EGOs, since strong compact mid-infrared emission in the absence of compact radio continuum emission is thought to be associated with the later stage of massive star formation.


中文翻译:

用羟基物质探测GLIMPSE扩展绿色物体(EGO)

摘要
我们提出了一项针对从Spitzer Galactic Legacy红外中平面特别调查(GLIMPSE)确定的20个高质量年轻恒星物体流出候选物(扩展绿色物体,EGO)的18 cm OH maser发射的研究。使用Karl G.Jansky超大型阵列C构型可以观察到1612、1665、1667和1720 MHz的所有四个OH基态线,以及20 cm的连续发射。使用Nançay射电望远镜对除1612 MHz以外的相同OH跃迁进行了后续的偏振单碟观测。发现OH maser排放是样品的一个罕见特征,整个样品的检出率为50%,“可能的” EGO的检出率为〜44%。未向任何源探测到20厘米连续发射。在多数情况下,探测到的OH maser发射出现在紧凑的中央源附近;OH masers与6.7 GHz甲醇masers共存,但在几千个天文单位大小的更弥散和扩展的晕圈形区域中发现。将EGO样品与OH maser检测和未检测相比较,显示OH maser排放的EGO倾向于具有较低的粉尘团块质量,但较高的24和4.5 μ中号磁通密度。因此,OH maser发射可能是EGO进一步发展的指示,因为在没有紧凑的连续无线电发射的情况下,强烈的紧凑型中红外发射被认为与大规模恒星形成的后期有关。
更新日期:2020-11-02
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