论文标题

无线电调查中的星形形成:附近星系核和核周外形成区域的3-33 GHz成像

The Star Formation in Radio Survey: 3 - 33 GHz Imaging of Nearby Galaxy Nuclei and Extranuclear Star-forming Regions

论文作者

Linden, S. T., Murphy, E. J., Dong, D., Momjian, E., Kennicutt Jr., R. C., Meier, D. S., Schinnerer, E., Turner, J. L.

论文摘要

我们使用karl G. jansky非常大的阵列作为恒星构造的一部分,向星系核和核周外形成区域提出了3、15和33 GHz成像。凭借$ 3-33 $ GHz的无线电光谱,我们测量了光谱指数和相应的热(免费(免费)发射分数,用于在至少两个无线电带中具有显着检测的335个离散区域的样本。在删除了14个可能的背景星系后,我们发现,当采用两种组分的幂律模型以适合无线电光谱时,中位绝对偏差为$ 11 \%$,中位数绝对偏差为$ 112 \ pm 0.8 \%$。将样品限制在238个来源中,这些来源自信地识别为星形区域,并且不受潜在的AGN污染的影响(即具有半乳突半径$ r _ {\ rm G} \ geq 250 $ PC),导致中位数热量分数为$ 93 \ pm pm 0.8 \%$ 0.8 \%$ $ $ 10 $ $ 10 $ 10 $ 10 $ 10 $ 10 $ $ 10 $ 10 $ 10 $ 10 $ 10 $ 10 $ 10 $ 10 $ 10 $ 10 $ 10 $ 10 $ 10 $ 10 $ 10 $ 10 $ 10 $ 10 $ 10 $ 10 $ 10 $ 10 $ 10 $ 10 $ 10 $ 10 $ 10 $ 10. We further measure the thermal fraction at 33 GHz for 163 regions identified at 7" resolution to be $94 \pm 0.8 \%$ with a median absolute deviation of $8\%$. Together, these results confirm that free-free emission dominates the radio spectra of star-forming regions on scales up to $\sim$500 pc in normal star-forming galaxies. We additionally find a factor of $\sim$1.6 increase in测得的光谱指数和热分子分布的散射是减小星乳半radius的函数。

We present 3, 15, and 33 GHz imaging towards galaxy nuclei and extranuclear star-forming regions using the Karl G. Jansky Very Large Array as part of the Star Formation in Radio Survey. With $3-33$ GHz radio spectra, we measured the spectral indices and corresponding thermal (free-free) emission fractions for a sample of 335 discrete regions having significant detections in at least two radio bands. After removing 14 likely background galaxies, we find that the median thermal fraction at 33 GHz is $92 \pm 0.8\%$ with a median absolute deviation of $11\%$, when a two-component power-law model is adopted to fit the radio spectrum. Limiting the sample to 238 sources that are confidently identified as star-forming regions, and not affected by potential AGN contamination (i.e., having galactocentric radii $r_{\rm G} \geq 250$ pc), results in a median thermal fraction of $93 \pm 0.8 \%$ with a median absolute deviation of $10\%$. We further measure the thermal fraction at 33 GHz for 163 regions identified at 7" resolution to be $94 \pm 0.8 \%$ with a median absolute deviation of $8\%$. Together, these results confirm that free-free emission dominates the radio spectra of star-forming regions on scales up to $\sim$500 pc in normal star-forming galaxies. We additionally find a factor of $\sim$1.6 increase in the scatter of the measured spectral index and thermal fraction distributions as a function of decreasing galactocentric radius. This trend is likely reflective of the continuous star-formation activity occurring in the galaxy centers, resulting a larger contribution of diffuse nonthermal emission relative to star-forming regions in the disk.

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