The Diversity of Extremely Red Objects Smail, Ian; Owen, F. N; Morrison, G. E ...
Astrophysical journal/The Astrophysical journal,
12/2002, Letnik:
581, Številka:
2
Journal Article
Context.
The
z
∼ 0.1 type-2 QSO J1430+1339, known as the “
Teacup
”, is a complex galaxy showing a loop of ionised gas ∼10 kpc in diameter, co-spatial radio bubbles, a compact (∼1 kpc) jet, and ...outflow activity. Its closeness offers the opportunity to study in detail the intricate interplay between the central supermassive black hole (SMBH) and the material in and around the galaxy, both the interstellar medium (ISM) and circumgalactic medium (CGM).
Aims.
We characterise the spatially resolved properties and effects of the galactic ionised gas outflow and compare them with those of the radio jet and with theoretical predictions to infer its acceleration mechanism.
Methods.
We used VLT/MUSE optical integral field spectroscopic observations to obtain flux, kinematic, and excitation maps of the extended (up to ∼100 kpc) ionised gas and to characterise the properties of stellar populations. We built radial profiles of the outflow properties as a function of distance from the active nucleus, from kiloparsec up to tens of kiloparsec scales, at ∼1 kpc resolution.
Results.
We detect a velocity dispersion enhancement (≳300 km s
−1
) elongated over several kiloparsecs perpendicular to the radio jet, the active galactic nucleus (AGN) ionisation lobes, and the fast outflow, similar to what is found in other galaxies hosting compact, low-power jets, indicating that the jet strongly perturbs the host ISM during its passage. We observe a decreasing trend with distance from the nucleus for the outflow properties (mass outflow rate, kinetic rate, momentum rate). The mass outflow rate drops from around 100
M
⊙
yr
−1
in the inner 1–2 kpc to ≲0.1
M
⊙
yr
−1
at 30 kpc. The mass outflow rate of the ionised outflow is significantly higher (∼1–8 times) than the molecular one, in contrast with what is often quoted in AGN. Based on energetic and morphological arguments, the driver of the multi-phase outflow is likely a combination of AGN radiation and the jet, or AGN radiation pressure on dust alone. The outflow mass-loading factor is ∼5–10 and the molecular gas depletion time due to the multi-phase outflow is ≲10
8
yr, indicating that the outflow can significantly affect the star formation and the gas reservoir in the galaxy. However, the fraction of the ionised outflow that is able to escape the dark matter halo potential is likely negligible. We detect blue-coloured continuum emission co-spatial with the ionised gas loop. Here, stellar populations are younger (≲100–150 Myr) than in the rest of the galaxy (∼0.5–1 Gyr). This constitutes possible evidence for star formation triggered at the edge of the bubble due to the compressing action of the jet and outflow (“positive feedback”), as predicted by theory. All in all, the Teacup constitutes a rich system in which AGN feedback from outflows and jets, in both its negative and positive flavours, co-exist.
Abstract
We present integral field spectroscopic observations of NGC 5972 obtained with the Multi-Unit Spectroscopic Explorer at the Very Large Telescope. NGC 5972 is a nearby galaxy containing both ...an active galactic nucleus (AGN) and an extended emission-line region (EELR) reaching out to ∼17 kpc from the nucleus. We analyze the physical conditions of the EELR using spatially resolved spectra, focusing on the radial dependence of ionization state together with the light-travel time distance to probe the variability of the AGN on ≳10
4
yr timescales. The kinematic analysis suggests multiple components: (a) a faint component following the rotation of the large-scale disk, (b) a component associated with the EELR suggestive of extraplanar gas connected to tidal tails, and (c) a kinematically decoupled nuclear disk. Both the kinematics and the observed tidal tails suggest a major past interaction event. Emission-line diagnostics along the EELR arms typically evidence Seyfert-like emission, implying that the EELR was primarily ionized by the AGN. We generate a set of photoionization models and fit these to different regions along the EELR. This allows us to estimate the bolometric luminosity required at different radii to excite the gas to the observed state. Our results suggest that NGC 5972 is a fading quasar, showing a steady gradual decrease in intrinsic AGN luminosity, and hence the accretion rate onto the SMBH, by a factor ∼100 over the past 5 × 10
4
yr.
The emission spectra of 29 spiral galaxies with low-ionization emission have been studied in detail, using synthetic galaxy spectra to correct the observed spectra for the contribution of starlight. ...The resulting emission-line intensities and ratios have been compared to published models of shock-heated and power-law photoionized plasmas. The observed spectra are best described by models in which a weak flat-spectrum (power-law) radiation field photoionizes the gas; this nonthermal continuum is generally too weak to be seen directly in the optical. Broad H-alpha emission, extending over a total velocity range as great as 4000 km/s, is identified in several 'normal' nuclei with strong low-ionization emission. The inferred nonthermal continuum and observed broad permitted lines indicate the presence of low-luminosity active nuclei in most, if not all, spiral galaxies.
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