分类： 天文学 >> 天文学 提交时间： 2023-02-19
Zhijie Qu
Hsiao-Wen Chen
Gwen C. Rudie
Fakhri S. Zahedy
Sean D. Johnson
Erin Boettcher
Sebastiano Cantalupo
Mandy C. Chen
Kathy L. Cooksey
David DePalma
Claude-André Faucher-Giguère
Michael Rauch
Joop Schaye
Robert A. Simcoe
摘要： This paper presents a systematic study of the photoionization and thermodynamic properties of the cool circumgalactic medium (CGM) as traced by rest-frame ultraviolet absorption lines around 26 galaxies at redshift $z\lesssim1$. The study utilizes both high-quality far-ultraviolet and optical spectra of background QSOs and deep galaxy redshift surveys to characterize the gas density, temperature, and pressure of individual absorbing components and to resolve their internal non-thermal motions. The derived gas density spans more than three decades, from $\log (n_{\rm H}/{\rm cm^{-3}}) \approx -4$ to $-1$, while the temperature of the gas is confined in a narrow range of $\log (T/{\rm K})\approx 4.3\pm 0.3$. In addition, a weak anti-correlation between gas density and temperature is observed, consistent with the expectation of the gas being in photoionization equilibrium. Furthermore, decomposing the observed line widths into thermal and non-thermal contributions reveals that more than 30% of the components at $z\lesssim 1$ exhibit line widths driven by non-thermal motions, in comparison to $<20$% found at $z\approx 2$-3. Attributing the observed non-thermal line widths to intra-clump turbulence, we find that massive quenched galaxies on average exhibit higher non-thermal broadening/turbulent energy in their CGM compared to star-forming galaxies at $z\lesssim 1$. Finally, strong absorption features from multiple ions covering a wide range of ionization energy (e.g., from Mg II to O IV) can be present simultaneously in a single absorption system with kinematically aligned component structure, but the inferred pressure in different phases may differ by a factor of $\approx 10$.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Mandy C. Chen
Hsiao-Wen Chen
Michael Rauch
Zhijie Qu
Sean D. Johnson
Jennifer I-Hsiu Li
Joop Schaye
Gwen C. Rudie
Fakhri S. Zahedy
Erin Boettcher
Kathy L. Cooksey
Sebastiano Cantalupo
摘要： We present the first empirical constraints on the turbulent velocity field of the diffuse circumgalactic medium around four luminous QSOs at $z\!\approx\!0.5$--1.1. Spatially extended nebulae of $\approx\!50$--100 physical kpc in diameter centered on the QSOs are revealed in [OII]$\lambda\lambda\,3727,3729$ and/or [OIII]$\lambda\,5008$ emission lines in integral field spectroscopic observations obtained using MUSE on the VLT. We measure the second- and third-order velocity structure functions (VSFs) over a range of scales, from $\lesssim\!5$ kpc to $\approx\!20$--50 kpc, to quantify the turbulent energy transfer between different scales in these nebulae. While no constraints on the energy injection and dissipation scales can be obtained from the current data, we show that robust constraints on the power-law slope of the VSFs can be determined after accounting for the effects of atmospheric seeing, spatial smoothing, and large-scale bulk flows. Out of the four QSO nebulae studied, one exhibits VSFs in spectacular agreement with the Kolmogorov law, expected for isotropic, homogeneous, and incompressible turbulent flows. The other three fields exhibit a shallower decline in the VSFs from large to small scales. However, with a limited dynamic range in the spatial scales in seeing-limited data, no constraints can be obtained for the VSF slopes of these three nebulae. For the QSO nebula consistent with the Kolmogorov law, we determine a turbulence energy cascade rate of $\approx\!0.2$ cm$^{2}$ s$^{-3}$. We discuss the implication of the observed VSFs in the context of QSO feeding and feedback in the circumgalactic medium.
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