发表机构
Thüringer Landessternwarte; Homi Bhabha Centre for Science Education (HBCSE-TIFR); Indian Institute of Technology Indore; Deutsches Zentrum für Astrophysik; Max-Planck-Institut für Radioastronomie; Manipal Centre for Natural Sciences, Centre of Excellence, Manipal Academy of Higher Education（图林根州立天文台; 霍米·巴巴科学教育中心（TIFR）; 印度印度理工学院印多尔分校; 德国天体物理中心; 马克斯·普朗克射电天文研究所; 马尼拉卓越自然科学中心，马尼拉高等教育学院）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过宽带射电观测和谱建模，揭示了极端倒转谱射电源的物理性质，表明其磁场与电子密度类似峰值谱源，且宿主多为尘埃星暴或遮蔽AGN，支持其年轻或受限射电AGN的起源。
AI 中文摘要
我们给出了10个极端倒转谱河外射电源（EISERS）样本在0.15-8 GHz范围内的宽带射电连续谱，这些源选自1.4 GHz以下的窄带低频巡天。在这些巡天中，EISERS显示出异常陡峭的低频谱指数，接近或超过均匀同步加速源预期的同步加速自吸收（SSA）极限α=+2.5。我们使用uGMRT（0.150-1.4 GHz）和VLA（1.0-8.0 GHz）对这些源进行了后续准同时射电观测。新观测提供了改进的频率覆盖，并在光学厚和光学薄谱区均实现了一致的流量定标。我们发现，EISERS在光学厚区的谱斜率比使用TGSS和WENSS得到的双频谱指数更平缓，范围在+1.6到+3之间，这表明异构巡天数据可能通过流量尺度偏移、这些致密源的内在变化性以及巡天之间不同的角分辨率引入偏差。我们将宽带射电谱建模为受同步加速自吸收影响的同步加速辐射，并随后在外部电离介质中经自由-自由吸收的修正。基于最佳拟合估计的物理参数表明，磁场和热电子密度与一般峰值谱源类别相似，其中B_SSA跨越从20 mG到8 G的较大范围，n_e约为29-128 cm^{-3}。光学和红外观测进一步表明，EISERS优先与尘埃星暴星系、星暴-活动星系核复合系统或嵌入致密环核环境中的遮蔽活动星系核相关联，支持了这些源中至少一部分代表年轻或环境受限的射电活动星系核的图景。
英文摘要
We present broadband radio continuum spectra spanning 0.15-8 GHz for a sample of ten Extremely Inverted Spectrum Extragalactic Radio Sources (EISERS), selected from narrowband, low-frequency surveys below 1.4 GHz. In these surveys, EISERS show unusually steep low-frequency spectral indices, approaching or exceeding the synchrotron self-absorption (SSA) limit of $α$= +2.5, expected for homogeneous synchrotron sources. We have performed follow-up quasi-simultaneous radio observations of these sources using uGMRT (0.150-1.4 GHz) and VLA (1.0-8.0 GHz). The new observations provide improved frequency coverage and consistent flux calibration across both the optically thick and optically thin spectral regimes. We find that the spectral slopes of EISERS in optically thick regime are flatter than the two frequency spectral indices obtained using TGSS and WENSS and lie in the range +1.6 to +3, suggesting that heterogeneous survey data can introduce biases through flux-scale offsets, intrinsic variability of these compact sources and diverse angular resolutions between surveys. We modelled the broadband radio spectra as synchrotron emission affected by synchrotron self-absorption and subsequently modified by free-free absorption in an external ionised medium. The estimated physical parameters based on the best-fits indicate that the magnetic fields and thermal electron densities are similar to the general class of peak spectrum sources, with $B_{SSA}$ spanning over a large range of values from 20 mG to 8 G and $n_{e} \sim 29-128{cm}^{-3}$. Optical and infrared analysis further indicates that the EISERS are preferentially associated with dusty starburst galaxies, composite starburst-AGN systems, or obscured AGN embedded in dense circumnuclear environments, supporting a scenario in which at least a fraction of these sources represent young or environmentally confined radio AGN.
CommentsAccepted for publication in Astronomy and Astrophysics
