The LOFAR view of giant, early-type galaxies: Radio emission from active nuclei and star formation
The LOFAR view of giant, early-type galaxies: Radio emission from active nuclei and star formation
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巨型早期型星系的 LOFAR 视图：来自活动核和恒星形成的无线电发射
DOI：
10.1051/0004-6361/202142911
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发表时间：
2022
影响因子：
6.5
通讯作者：
Capetti A
中科院分区：
文献类型：
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作者：
Capetti A
我们研究了附近宇宙中最明亮的早期星系（etg） （MK≤- 25，衰退速度≤7500 km s - 1）的性质和射电发射的起源，这些射电发射是由150 MHz低频阵列（LOFAR）观测到的。这些巨型ETGs （gETGs）中有188个可获得LOFAR图像，其中146个（78%）在典型亮度为~ 1021W Hz−1以上被检测到。它们显示出很大的功率分布，可达~ 1026W Hz−1。我们证实了getg的恒星亮度与它们的中位射电功率、探测率和扩展源的比例之间存在正相关。在探测到的getg中，约有三分之二（91个）是未解析的，它们的大小都小于4 kpc，这证实了紧凑射电源在局部源中的普遍存在。46个getg在4 ~ 340 kpc的尺度上表现出扩展的排放，其中至少80%具有FR I级形态。根据扩展源的形态和光谱指数，其中约30%可能是残余或重新启动的源，但需要进一步的研究来证实这一点。光学光谱（可用于44个getg）表明，7个getg的核气体被年轻恒星电离，这表明它们来自恒星形成区域的射电辐射有贡献。它们的射电亮度对应于恒星形成速率（SFR）在0.1−8M⊙yr−1范围内，中位数特定SFR为0.8 × 10−12yr−1。流向gETGs中心的气体可以吸积到超大质量黑洞上，但也会在更大的半径处停滞并形成新的恒星，这表明反馈并没有完全抑制恒星的形成。最明亮的getg（25个mk < - 25.8的星系）都是在150 MHz被探测到的；然而，它们目前并没有全部开启：其中至少有四个是残余源，至少有一个可能是由恒星形成提供动力的。
We studied the properties and the origin of the radio emission in the most luminous, early-type galaxies (ETGs) in the nearby Universe (MK≤ −25, recession velocity ≤7500 km s−1), as seen by the 150 MHz Low-Frequency ARray (LOFAR) observations. LOFAR images are available for 188 of these giant ETGs (gETGs), and 146 (78%) of them are detected above a typical luminosity of ∼1021W Hz−1. They show a large spread in power, reaching up to ∼1026W Hz−1. We confirm a positive link between the stellar luminosity of gETGs and their median radio power, the detection rate, and the fraction of extended sources. About two-thirds (91) of the detected gETGs are unresolved, with sizes ≲4 kpc, confirming the prevalence of compact radio sources in local sources. Forty-six gETGs show extended emission on scales ranging from 4 to 340 kpc, at least 80% of which have a FR I class morphology. Based on the morphology and spectral index of the extended sources, ∼30% of them might be remnant or restarted sources, but further studies are needed to confirm this. Optical spectroscopy (available for 44 gETGs) indicates that for seven gETGs the nuclear gas is ionized by young stars suggesting a contribution to their radio emission from star forming regions. Their radio luminosities correspond to a star formation rate (SFR) in the range 0.1−8M⊙yr−1and a median specific SFR of 0.8 × 10−12yr−1. The gas flowing toward the center of gETGs can accrete onto the supermassive black hole but also stall at larger radii and form new stars, an indication that feedback does not completely quench star formation. The most luminous gETGs (25 galaxies withMK< −25.8) are all detected at 150 MHz; however, they are not all currently turned on: at least four of them are remnant sources and at least one is likely powered by star formation.