We present integral field unit (IFU) observations covering the [O III]λλ4959, 5007 and Hβ emission lines of sixteen z < 0.2 type 2 active galactic nuclei (AGN). Our targets are selected from a well-constrained parent sample of ≈ 24, 000 AGN so that we can place our observations into the context of the overall AGN population. Our targets are radio-quiet with star formation rates ( [10-100] M ⊙ yr −1 ) that are consistent with normal star-forming galaxies. We decouple the kinematics of galaxy dynamics and mergers from outflows. We find high-velocity ionised gas (velocity widths ≈ 600-1500 km s −1 ; maximum velocities 1700 km s −1 ) with observed spatial extents of (6-16) kpc in all targets and observe signatures of spherical outflows and bi-polar superbubbles. We show that our targets are representative of z < 0.2, luminous (i.e., L [O III] > 10 41.7 erg s −1 ) type 2 AGN and that ionised outflows are not only common but also in 70% (3σ confidence) of cases, they are extended over kiloparsec scales. Our study demonstrates that galaxy-wide energetic outflows are not confined to the most extreme star-forming galaxies or radio-luminous AGN; however, there may be a higher incidence of the most extreme outflow velocities in quasars hosted in ultra-luminous infrared galaxies. Both star formation and AGN activity appear to be energetically viable to drive the outflows and we find no definitive evidence that favours one process over the other. Although highly uncertain, we derive mass outflow rates (typically ≈10× the SFRs), kinetic energies (≈ 0.5-10% of L AGN ) and momentum rates (typically 10-20 × L AGN /c) consistent with theoretical models that predict AGN-driven outflows play a significant role in shaping the evolution of galaxies.
Using a sample of 24264 optically selected AGNs from the SDSS DR7 database, we characterise how the profile of the [O III]λ5007 emission line relates to bolometric luminosity (L AGN ), Eddington ratio, radio loudness, radio luminosity (L 1.4 GHz ) and optical class (i.e., broad/narrow line Seyfert 1, Type 2) to determine what drives the kinematics of this kpcscale line emitting gas. Firstly, we use spectral stacking to characterise how the average [O III]λ5007 profile changes as function of these five variables. After accounting for the known correlation between L AGN and L 1.4 GHz , we report that L 1.4 GHz has the strongest influence on the [O III]λ5007 profile, with AGNs of moderate radio luminosity (L 1.4 GHz = 10 23 − 10 25 W Hz −1 ) having the broadest [O III]λ5007 profiles. Conversely, we find only a modest change in the [O III]λ5007 profile with increasing radio loudness and find no significant difference between the [O III]λ5007 profiles of broad and narrow-line Seyfert 1s. Similarly, only the very highest Eddington ratio AGNs (i.e., > 0.3) show any signs of having broadened [O III]λ5007 profiles, although the small numbers of such extreme AGNs in our sample mean we cannot rule out that other processes (e.g., radio jets) are responsible for this broadening. The [O III]λ5007 profiles of Type 1 and Type 2 AGNs show the same trends in terms of line width, but Type 1 AGNs display a much stronger "blue-wing", which we interpret as evidence of outflowing ionised gas. We perform multi-component fitting to the Hβ, [O III]λλ4959, 5007, [N II]λλ6548, 6584 and Hα lines for all the AGNs in our sample to calculate the proportions of AGNs with broad [O III]λ5007 profiles. The individual fits confirm the results from our stacked spectra; AGNs with L 1.4 GHz > 10 23 W Hz −1 are roughly 5 times more likely to have extremely broad [O III]λ5007 lines (FWHM Avg > 1000 km s −1 ) compared to lower L 1.4 GHz AGNs and the width of the [O III]λ5007 line peaks in moderate radio luminosity AGNs (L 1.4 GHz ∼ 10 24 W Hz −1 ). Our results are consistent with the most disturbed gas kinematics being induced by compact radio cores (rather than powerful radio jets), although broadened [O III]λ5007 lines are also present, but much rarer, in low L 1.4 GHz systems. Our catalogue of multi-component fits is freely available as an online resource for statistical studies of the kinematics and luminosities of the narrow and broad line AGN regions and the identification of potential targets for follow-up observations.
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We exploit ALMA 870-µm (345 GHz) observations of sub-millimetre sources in the Extended Chandra Deep Field South to investigate the far-infrared properties of highredshift sub-millimetre galaxies (SMGs). Using the precisely located 870 µm ALMA positions of 99 SMGs, together with 24µm and radio imaging of this field, we deblend the Herschel / SPIRE imaging of this region to extract their far-infrared fluxes and colours. The median redshifts for ALMA LESS (ALESS) SMGs which are detected in at least two SPIRE bands increases as expected with wavelength of the peak in their SEDs, with z = 2.3 ± 0.2, 2.5 ± 0.3 and 3.5 ± 0.5 for the 250, 350 and 500-µm peakers respectively. We find that 34 ALESS SMGs do not have a >3 σ counterpart at 250, 350 or 500µm. These galaxies have a median photometric redshift derived from the rest-frame UV-mid-infrared SEDs of z = 3.3 ± 0.5, which is higher than the full ALESS SMG sample; z = 2.5 ± 0.2. Using the photometric redshifts together with the 250-870µm photometry, we estimate the far-infrared luminosities and characteristic dust temperature of each SMG. The median infrared luminosity and characteristic dust temperature of the S 870µm > 2 mJy SMGs is L IR = (3.0 ± 0.3) × 10 12 L ⊙ (star formation rate of SFR = 300 ± 30 M ⊙ yr −1 ) and T d = 32 ± 1 K (λ peak = 93 ± 4 µm). At a fixed luminosity, the characteristic dust temperature of these high-redshift SMGs is ∆T d = 3-5 K lower than comparably luminous galaxies at z = 0, reflecting the more extended star formation occurring in these systems. By extrapolating the 870µm number counts to S 870 = 1 mJy, we show that the contribution of S 870µm ≥ 1 mJy SMGs to the cosmic star formation budget is 20% of the total over the redshift range z ∼ 1-4. We derive a median dust mass for these galaxies of M d = (3.6 ± 0.3) × 10 8 M ⊙ and by adopting an appropriate gas-to-dust ratio, we estimate that the typical molecular mass of the ALESS SMGs in our sample is M H2 = (4.2 ± 0.4) × 10 10 M ⊙ . Together with the average stellar masses of SMGs, M ⋆ = (8 ± 1) × 10 10 M ⊙ , this suggests an average molecular gas fraction of ∼ 40%. Finally, we use our estimates of the H 2 masses to show that SMGs with S 870µm > 1 mJy (L IR > ∼ 10 12 L ⊙ ) contain ∼ 10% of the z ∼ 2 volume-averaged H 2 mass density at this epoch.
We present 1-7 GHz high-resolution radio imaging (VLA and e-MERLIN) and spatially-resolved ionized gas kinematics for ten z < 0.2 type 2 'obscured' quasars (log[L AGN /erg s −1 ] 45) with moderate radio luminosities (log[L 1.4 GHz /W Hz −1 ]=23.3-24.4). These targets were selected to have known ionized outflows based on broad [O iii] emission-line components (FWHM≈800-1800 km s −1 ). Although 'radio-quiet' and not 'radio AGN' by many traditional criteria, we show that for nine of the targets, star formation likely accounts for 10 per cent of the radio emission. We find that ∼80-90 per cent of these nine targets exhibit extended radio structures on 1-25 kpc scales. The quasars' radio morphologies, spectral indices and position on the radio size-luminosity relationship reveals that these sources are consistent with being low power compact radio galaxies. Therefore, we favour radio jets as dominating the radio emission in the majority of these quasars. The radio jets we observe are associated with morphologically and kinematically distinct features in the ionized gas, such as increased turbulence and outflowing bubbles, revealing jetgas interaction on galactic scales. Importantly, such conclusions could not have been drawn from current low-resolution radio surveys such as FIRST. Our observations support a scenario where compact radio jets, with modest radio luminosities, are a crucial feedback mechanism for massive galaxies during a quasar phase.
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