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arXiv 2006.03080astro-ph.GAastro-ph.SR
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外星系II恒星形成普查：GLIMPSE360场

A Census of Star Formation in the Outer Galaxy II: The GLIMPSE360 Field

Elaine Winston, Joseph Hora, Volker Tolls

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25 pages, 14 figures
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摘要：

我们在GLIMPSE 360计划观测的65 \degr $< l <$ 265 \degr ~区域内进行了外星系恒星形成的研究。这个{ \it Spitzer}暖任务计划用IRAC在3.6和4.5~ $μ$ m处绘制了外银河系平面。我们结合了IRAC、{ \it WISE}和2 MASS目录以及我们之前另一次外银河系调查的结果，在银河经度的$>$ 180 \degr \范围内总共识别了47，338个年轻恒星物体（YSO）。使用组合目录上的$DBSCAN$方法，我们确定了618个具有5个或更多成员的YSO集群或聚合。我们确定了10，476例I类、29，604例II类和7，325例贫血II类/III类YSO。被鉴定为簇成员的YSO的比率为25，528/47，338，或54%。我们发现100个被识别的集群以前在{ \it WISE} \ion{H}{2}调查中测量过距离。我们在这些集群中的YSO的光谱能量分布（SED）拟合中使用了这些距离，其中96个具有PDMATHAMT拟合的YSO。我们用SED模型拟合的质量来估计星系团内外的初始质量函数（IMF）：用星系团的质心距离来划分星系团，对于$R_{Gal} < 11.5$ ~kpc，斜率为$Γ= 1.87 \pm 0.31$大于3~M $_{\odot}$，对于$R_{Gal} > 11.5$ ~ kpc，斜率为$Γ= 1.15 \pm 0.24$大于3~M $_{\odot}$。发现在3~M $_{\odot}$以上，组合IMF的斜率为$Γ= 1.92 \pm 0.42$。这些值是相互一致的不确定性，并与文献值在银河系内部的高质量恒星形成区。斜率也可能与通用Salpeter IMF一致。

英文摘要：

We have conducted a study of star formation in the outer Galaxy from 65\degr$< l <$265\degr~in the region observed by the GLIMPSE360 program. This {\it Spitzer} warm mission program mapped the plane of the outer Milky Way with IRAC at 3.6 and 4.5~$μ$m. We combine the IRAC, {\it WISE}, and 2MASS catalogs and our previous results from another outer Galaxy survey and identify a total of 47,338 Young Stellar Objects (YSOs) across the field spanning $>$180\degr\ in Galactic longitude. Using the $DBSCAN$ method on the combined catalog, we identify 618 clusters or aggregations of YSOs having 5 or more members. We identify 10,476 Class I, 29,604 Class II, and 7,325 anemic Class II/Class III YSOs. The ratio of YSOs identified as members of clusters was 25,528/47,338, or 54\%. We found 100 of the clusters identified have previously measured distances in the {\it WISE} \ion{H}{2} survey. We used these distances in our spectral energy distribution (SED) fitting of the YSOs in these clusters, of which 96 had YSOs with $<3σ$ fits. We used the derived masses from the SED model fits to estimate the initial mass function (IMF) in the inner and outer Galaxy clusters: dividing the clusters by Galactocentric distances, the slopes were $Γ= 1.87 \pm 0.31$ above 3~M$_{\odot}$ for $R_{Gal} < 11.5$~kpc and $Γ= 1.15 \pm 0.24$ above 3~M$_{\odot}$ for $R_{Gal} > 11.5$~kpc. The slope of the combined IMF was found to be $Γ= 1.92 \pm 0.42$ above 3~M$_{\odot}$. These values are consistent with each other within the uncertainties, and with literature values in the inner Galaxy high-mass star formation regions. The slopes are likely also consistent with a universal Salpeter IMF.

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