Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userKiloparsec-scale jet-driven feedback in AGN probed by highly ionized gas: a MUSE/VLT perspective
83
0
0.0
(
0
)
Added by
Alberto Rodriguez-Ardila
Publication date
2020
fields
Physics
and research's language is
English
Ask ChatGPT about the research
No Arabic abstract
We employ optical spectroscopy from the Multi Unit Spectroscopic Explorer (MUSE) combined with X-ray and radio data to study the highly-ionized gas (HIG) phase of the feedback in a sample of five local nearby Active Galactic Nuclei (AGN). Thanks to the superb field of view and sensitivity of MUSE, we found that the HIG, traced by the coronal line [FeVII] $lambda$6089, extends to scales not seen before, from 700 pc in Circinus and up to ~2 kpc in NGC5728 and NGC3393. The gas morphology is complex, following closely the radio jet and the X-ray emission. Emission line ratios suggest gas excitation by shocks produced by the passage of the radio jet. This scenario is further supported by the physical conditions derived for the HIG, stressing the importance of the mechanical feedback in AGN with low-power radio jets.
rate research
Read More
Recent observations and simulations have challenged the long-held paradigm that mergers are the dominant mechanism driving the growth of both galaxies and supermassive black holes (SMBH), in favour of non-merger (secular) processes. In this pilot study of merger-free SMBH and galaxy growth, we use Keck Cosmic Web Imager spectral observations to examine four low-redshift ($0.043 < z < 0.073$) disk-dominated `bulgeless galaxies hosting luminous AGN, assumed to be merger-free. We detect blueshifted broadened [OIII] emission from outflows in all four sources, which the oiii/hbeta~ratios reveal are ionised by the AGN. We calculate outflow rates in the range $0.12-0.7~rm{M}_{odot}~rm{yr}^{-1}$, with velocities of $675-1710~rm{km}~rm{s}^{-1}$, large radial extents of $0.6-2.4~rm{kpc}$, and SMBH accretion rates of $0.02-0.07~rm{M}_{odot}~rm{yr}^{-1}$. We find that the outflow rates, kinematics, and energy injection rates are typical of the wider population of low-redshift AGN, and have velocities exceeding the galaxy escape velocity by a factor of $sim30$, suggesting that these outflows will have a substantial impact through AGN feedback. Therefore, if both merger-driven and non-merger-driven SMBH growth lead to co-evolution, this suggests that co-evolution is regulated by feedback in both scenarios. Simulations find that bars and spiral arms can drive inflows to galactic centres at rates an order of magnitude larger than the combined SMBH accretion and outflow rates of our four targets. This work therefore provides further evidence that non-merger processes are sufficient to fuel SMBH growth and AGN outflows in disk galaxies.
IC 1459 is an early-type galaxy (ETG) with a rapidly counter-rotating stellar core, and is the central galaxy in a gas-rich group of spirals. In this work, we investigate the abundant ionized gas in IC 1459 and present new stellar orbital models to connect its complex array of observed properties and build a more complete picture of its evolution. Using the Multi-Unit Spectroscopic Explorer (MUSE), the optical integral field unit (IFU) on the Very Large Telescope (VLT), we examine the gas and stellar properties of IC 1459 to decipher the origin and powering mechanism of the galaxys ionized gas. We detect ionized gas in a non-disk-like structure rotating in the opposite sense to the central stars. Using emission-line flux ratios and velocity dispersion from full-spectral fitting, we find two kinematically distinct regions of shocked emission-line gas in IC 1459, which we distinguished using narrow ($sigma$ $leq$ 155 km s$^{-1}$) and broad ($sigma$ $>$ 155 km s$^{-1}$) profiles. Our results imply that the emission-line gas in IC 1459 has a different origin than that of its counter-rotating stellar component. We propose that the ionized gas is from late-stage accretion of gas from the group environment, which occurred long after the formation of the central stellar component. We find that shock heating and AGN activity are both ionizing mechanisms in IC 1459 but that the dominant excitation mechanism is by post-asymptotic giant branch stars from its old stellar population.
We report observations of the radio galaxy 3C317 (at z=0.0345) located at the center of the Abell cluster A2052, obtained with the VLT/MUSE integral field spectrograph. The Chandra images of this cluster show cavities in the X-ray emitting gas, which were produced by the expansion of the radio lobes inflated by the active galactic nucleus (AGN). Our exquisite MUSE data show with unprecedented detail the complex network of line emitting filaments enshrouding the northern X-ray cavity. We do not detect any emission lines from the southern cavity, with a luminosity asymmetry between the two regions higher than about 75. The emission lines produced by the warm phase of the interstellar medium (WIM) enable us to obtain unique information on the properties of the emitting gas. We find dense gas (up to 270 cm-3) that makes up part of a global quasi spherical outflow that is driven by the radio source, and obtain a direct estimate of the expansion velocity of the cavities (265 km s-1). The emission lines diagnostic rules out ionization from the AGN or from star-forming regions, suggesting instead ionization from slow shocks or from cosmic rays. The striking asymmetric line emission observed between the two cavities contrasts with the less pronounced differences between the north and south sides in the hot gas; this represents a significant new ingredient for our understanding of the process of the exchange of energy between the relativistic plasma and the external medium. We conclude that the expanding radio lobes displace the hot tenuous phase of the interstellar medium (ISM), but also impact the colder and denser ISM phases. These results show the effects of the AGN on its host and the importance of radio mode feedback.
We characterize the ionized gas outflows in 15 low-redshift star-forming galaxies, a Valparaiso ALMA Line Emission Survey (VALES) subsample, using MUSE integral field spectroscopy and GAMA photometric broadband data. We measure the emission-line spectra by fitting a double-component profile, with the second and broader component being related to the outflowing gas. This interpretation is in agreement with the correlation between the observed star-formation rate surface density ($Sigma_{mathrm{SFR}}$) and the second-component velocity dispersion ($sigma_{mathrm{2nd}}$), expected when tracing the feedback component. By modelling the broadband spectra with spectra energy distribution (SED) fitting and obtaining the star-formation histories of the sample, we observe a small decrease in SFR between 100 and 10 Myr in galaxies when the outflow H$alpha$ luminosity contribution is increased, indicating that the feedback somewhat inhibits the star formation within these timescales. The observed emission-line ratios are best reproduced by photoionization models when compared to shock-ionization, indicating that radiation from young stellar population is dominant, and seems to be a consequence of a continuous star-formation activity instead of a bursty event. The outflow properties such as mass outflow rate ($sim 0.1,$M$_odot$ yr$^{-1}$), outflow kinetic power ($sim 5.2 times 10^{-4}% L_{mathrm{bol}}$) and mass loading factor ($sim 0.12$) point towards a scenario where the measured feedback is not strong and has a low impact on the evolution of galaxies in general.
Observation shows that nebular emission, molecular gas, and young stars in giant galaxies are associated with rising X-ray bubbles inflated by radio jets launched from nuclear black holes. We propose a model where molecular clouds condense from low entropy gas caught in the updraft of rising X-ray bubbles. The low entropy gas becomes thermally unstable when it is lifted to an altitude where its cooling time is shorter than the time required to fall to its equilibrium location in the galaxy i.e., t_c/t_I < 1. The infall speed of a cloud is bounded by the lesser of its free-fall and terminal speeds, so that the infall time here can exceed the the free-fall time by a significant factor. This mechanism is motivated by ALMA observations revealing molecular clouds lying in the wakes of rising X-ray bubbles with velocities well below their free-fall speeds. Our mechanism would provide cold gas needed to fuel a feedback loop while stabilizing the atmosphere on larger scales. The observed cooling time threshold of ~ 5x 10^8 yr --- the clear-cut signature of thermal instability and the onset of nebular emission and star formation--- may result from the limited ability of radio bubbles to lift low entropy gas to altitudes where thermal instabilities can ensue. Outflowing molecular clouds are unlikely to escape, but instead return to the central galaxy in a circulating flow. We contrast our mechanism to precipitation models where the minimum value of t_c/t_ff < 10 triggers thermal instability, which we find to be inconsistent with observation.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
