Eddington Ratio Research Articles

Correlation Between Radio Loudness and the Eddington Ratio in Quasars

ABSTRACTQuasars can be categorized into radio‐loud and radio‐quiet populations based on radio properties. The physical mechanisms underlying this dichotomy have long been an active area of investigation. In this work, we analyze multi‐wavelength data from 851 quasars matched between the SDSS DR14 and FIRST catalogs, requiring emission line measurements with signal‐to‐noise ratios > 3, we fit quasar optical continuum spectra and compute the radio loudness, luminosities, and Eddington ratios. We classify quasars as radio‐loud or radio‐quiet using a dividing line of . We find that the distribution of the Eddington ratio and radio luminosity is different between the radio‐loud and radio‐quiet quasars, and the correlation between the Eddington ratio and radio loudness is disparate as well. The Eddington ratio shows a weakly positive correlation with radio loudness in both the whole sample and radio‐loud quasars, which imply that the Eddington ratio contributes to the radio loudness but it is not the dominant factor and that additional factors influence relativistic jet production in radio‐loud quasars. However, the Eddington ratio is anti‐correlated with radio loudness in radio‐quiet quasars, potentially related to the properties of the accretion disk.

Discovery of Six Low-z, High-luminosity, and High-mass Quasars

This study presents the discovery of six low-redshift quasars, identified through spectral observations conducted with the RTT-150 telescope. These quasars, with redshifts ranging from 0.3 to 0.6, were selected incorporating their placement in the color–color diagrams and detection by ROSAT 2RXS, focusing on those resembling the spectral energy distribution of a quasar. Our analysis includes detailed modeling of their continuum and emission line properties, which allowed us to estimate their bolometric luminosities, central black hole masses, and Eddington ratios. The findings reveal that these quasars exhibit exceptionally high luminosities and high masses for their redshift values, making them rare examples in the low-redshift quasar population. The results contribute to our understanding of quasar characteristics and their role in probing the structure and evolution of the nearby universe. This research underscores the importance of continued exploration of low-redshift quasars to enhance our knowledge of cosmic evolution and the dynamics of supermassive black holes in the early universe.

The M•–σe relation for local type 1 AGNs and quasars

We analyzed Multi Unit Spectroscopic Explorer observations of 42 local z ≲ 0.1 type 1 active galactic nucleus (AGN) host galaxies taken from the Palomar-Green quasar sample and the close AGN reference survey. Our goal was to study the relation between the black hole mass (M•) and bulge stellar velocity dispersion (σe) for type 1 active galaxies. The sample spans black hole masses of 106.0 − 109.2 M⊙, bolometric luminosities of 1042.9 − 1046.0 erg s−1, and Eddington ratios of 0.006 − 1.2. We avoided AGN emission by extracting the spectra over annular apertures. We modeled the calcium triplet stellar features and measured stellar velocity dispersions of σ* = 60 − 230 km s−1 for the host galaxies. We find stellar velocity dispersion values in agreement with previous measurements for local (z ≲ 0.1) AGN host galaxies, but slightly lower compared with those reported for nearby X-ray-selected type 2 quasars. Using a novel annular aperture correction recipe to estimate σe from σ* that considers the bulge morphology and observation beam-smearing, we estimate flux-weighted σe = 60 − 250 km s−1. If we consider the bulge type when estimating M•, we find no statistical difference between the distributions of AGN hosts and the inactive galaxies on the M•–σe plane for M• ≲ 108 M⊙. Conversely, if we do not consider the bulge type when computing M•, we find that both distributions disagree. We find no correlation between the degree of offset from the M•–σe relation and Eddington ratio for M• ≲ 108 M⊙. The current statistics preclude firm conclusions from being drawn for the high-mass range. We argue these observations support notions that a significant fraction of the local type 1 AGNs and quasars have undermassive black holes compared with their host galaxy bulge properties.

BASS

We present one of the largest multiwavelength studies of simultaneous optical-to-X-ray spectral energy distributions (SEDs) of unobscured (NH < 1022 cm−2) active galactic nuclei (AGN) in the local Universe. Using a representative sample of hard-X-ray-selected AGN from the 70-month Swift/BAT catalog, with optical/UV photometric data from Swift/UVOT and X-ray spectral data from Swift/XRT, we constructed broadband SEDs of 236 nearby AGN (0.001 < z < 0.3). We employed GALFIT to estimate host galaxy contamination in the optical/UV and determine the intrinsic AGN fluxes. We used an absorbed power law with a reflection component to model the X-ray spectra and a dust-reddened multi-temperature blackbody to fit the optical/UV SED. We calculated intrinsic luminosities at multiple wavelengths, total bolometric luminosities (Lbol), optical-to-X-ray spectral indices (αox), and multiple bolometric corrections (κλ) in the optical, UV, and X-rays. We used black hole masses obtained by reverberation mapping and the virial method to estimate Eddington ratios (λEdd) for all our AGN. We confirm the tight correlation (scatter = 0.45 dex) between UV (2500 Å) and X-ray (2 keV) luminosity for our sample. We observe a significant decrease in αox with Lbol and λEdd, suggesting that brighter sources emit more UV photons per X-rays. We report a second-order regression relation (scatter = 0.15 dex) between the 2–10 keV bolometric correction (κ2 − 10) and αox, which is useful to compute Lbol in the absence of multiband SEDs. We also investigate the dependence of optical/UV bolometric corrections on the physical properties of AGN and obtain a significant increase in the UV bolometric corrections (κW2 and κM2) with Lbol and λEdd, unlike those in the optical (κV and κB), which are constant across five orders of Lbol and λEdd. We obtain significant dispersions (∼0.1–1 dex) in all bolometric corrections, and hence recommend using appropriate relations with observed quantities while including the reported scatter, instead of their median values.

Spectrophotometric Reverberation Mapping of Intermediate-mass Black Hole NGC 4395

Understanding the origins of massive black hole seeds and their coevolution with their host galaxy requires studying intermediate-mass black holes (IMBHs) and estimating their mass. However, measuring the masses of these IMBHs is challenging, due to the high-spatial-resolution requirement. Spectrophotometric reverberation monitoring is performed for a low-luminosity Seyfert 1 galaxy, NGC 4395, to measure the size of the broad-line region and black hole mass. The data were collected using the 1.3 m Devasthal fast optical telescope and 3.6 m Devasthal optical telescope at ARIES, Nainital, over two consecutive days in 2022 March. The analysis revealed strong emission lines in the spectra and light curves of the merged 5100 Å spectroscopic continuum flux (f 5100) with the photometric continuum V band and Hα, with fractional variabilities of 6.38% and 6.31% respectively. In comparison to several previous studies with lag estimation <90 minutes, our calculated Hα lag supersedes them by 125.0−6.1+6.2 minutes, using the ICCF and JAVELIN methods. The velocity dispersion (σ line) of the broad-line clouds is measured to be 544.7−25.1+22.4 km s−1, yielding a black hole mass of ∼ 2.2−0.2+0.2×104M⊙ and an Eddington ratio of 0.06.

Windy or Not: Radio Parsec-scale Evidence for a Broad-line Region Wind in Radio-quiet Quasars

Does a broad-line region (BLR) wind in radio-quiet (RQ) active galactic nuclei (AGN) extend to parsec scales and produce radio emission? We explore the correlations between a parsec-scale radio wind and the BLR wind in a sample of 19 RQ Palomar–Green quasars. The radio wind is defined based on the spectral slope and the compactness of the emission at 1.5–5 GHz, and the BLR wind is defined by the excess blue wing in the C iv emission line profile. The five objects with both radio and BLR wind indicators are found at high Eddington ratios, L/L Edd (≥0.66), and eight of the nine objects with neither radio nor BLR winds reside at low L/L Edd (≤0.28). This suggests that the BLR wind and the radio wind in RQ AGN are related to a radiation-pressure-driven wind. Evidence for free–free absorption by AGN photoionized gas, which flattens the spectral slope, is found in two objects. Radio outflows in three low-L/L Edd (0.05–0.12) objects are likely from a low-power jet, as suggested by additional evidence. The presence of a mild equatorial BLR wind in four intermediate-L/L Edd (0.2–0.4) objects can be tested with future spectropolarimetry.

The eROSITA Final Equatorial Depth Survey (eFEDS). The hard X-ray selected sample

During its calibration and performance verification phase, the eROSITA instrument aboard the Spectrum-RG satellite performed a uniform wide-area X-ray survey of approximately 140 deg2, known as the eROSITA Final Equatorial Depth Survey (eFEDS). The primary aim of eFEDS is to demonstrate the scientific performance to be expected at the end of the eight--pass eROSITA all--sky survey. This survey will provide the first focussed image of the whole sky in the hard X-ray ($&gt;2$ keV) bandpass. The expected source population in this energy range is thus of great interest, particularly for AGN studies. We used a 2.3--5 keV selection to construct a sample of 246 point-like hard X-ray sources for further study and characterisation. These sources are classified as either extragalactic ($ 90$ &lt;!PCT!&gt;) or Galactic ($ 10$ &lt;!PCT!&gt;), with the former consisting overwhelmingly of AGN and the latter active stars. We concentrated our further analysis on the extragalactic AGN sample, describing their X-ray and multi-wavelength properties and comparing them to the eFEDS main AGN sample selected in the softer 0.2--2.3 keV band. The eROSITA hard band selects a subsample of sources that is a factor of more than ten brighter than the eFEDS main sample. The AGN within the hard population reach up to $z=3.2$ but on the whole, they are relatively nearby, with median $z$=0.34 compared to $z$=0.94 for the main sample. The hard survey probes typical luminosities in the range $ X = 43-46$. The X-ray spectral analysis shows significant intrinsic absorption (with $ H &gt;21$) in $ 20$ &lt;!PCT!&gt; of the sources, with a hard X-ray power law continuum with mean $&lt; which is typical of AGN, but slightly harder than the soft-selected eROSITA sample. Around $10$ &lt;!PCT!&gt; of the hard sample show a significant `soft excess' component. The sampled black hole mass distribution in the eFEDS broad-line AGN population is consistent with that of the deeper COSMOS survey that probes a higher redshift population. On the other hand, the Eddington ratios appear systematically lower, which is consistent with the idea that the decline in SMBH activity since $z 1$ is due to a reduction in the typical accretion rate, rather than a shift towards activity in lower-mass black holes. The eFEDS hard sample provides a preview of what can be expected from the eRASS final survey in terms of data quality. This pilot survey indicates the power of eROSITA to shed new light on the demographics and evolution of AGN, and the potential for discovery of new and rare populations.

Accretion mediated spin-eccentricity correlations in LISA massive black hole binaries

Abstract We examine expected effective spin (χeff, 1yr) and orbital eccentricity ($e_{1\rm yr}$) correlations for a population of observable equal-mass massive black hole binaries (MBHBs) with total redshifted mass Mz ∼ [104.5, 107.5] M⊙ embedded in a circumbinary disc (CBD) at redshifts z = 1 and z = 2, one-year before merging in the LISA band. We find a strong correlation between measurable eccentricity and negative effective spin for MBHBs that are carried to merger by retrograde accretion. This is due to the well-established eccentricity pumping of retrograde accretion and less-well-established formation of retrograde minidiscs coupled with a stable retrograde CBD throughout the binary evolution from the self-gravitating radius. Conversely, prograde accretion channels result in positive $\chi _{{\rm eff},1\rm yr}$ and non-measurable $e_{1\rm yr}$ except for almost unity Eddington ratio and Mz ≲ 105 M⊙ MBHBs at z = 1. This clear contrast between the two CBD orientations – and particularly the unique signature of retrograde configurations – provides a promising way to unlock the mysteries of MBHB formation channels in the LISA era.

Spatially–resolved gas-phase metallicity in Seyfert galaxies

Abstract We explore the relations between the gas-phase metallicity radial profiles (few hundred inner parsec) and multiple galaxy properties for 15 Seyfert galaxies from the AGNIFS (Active Galactic Nuclei Integral Field Spectroscopy) sample using optical Integral Field Unit (IFU) observations from Gemini Multi-Object Spectrographs (GMOS) and Multi Unit Spectroscopic Explorer (MUSE) processed archival data. The data were selected at z ≲ 0.013 within black hole mass range [6 &amp;lt; log (MBH/M⊙) &amp;lt; 9] with moderate 14–150 keV X-ray luminosities $\left[42\, \lesssim \, \log L_X (\rm erg\, s^{-1})\, \lesssim \, 44\right]$. We estimated the gas-phase metallicity using the strong-line methods and found mean values for the oxygen dependent (Z ∼ 0.75 Z⊙) and nitrogen dependent (Z ∼ 1.14 Z⊙) calibrations. These estimates show excellent agreement with ΔZ ≈ 0.19 dex and ΔZ ≈ 0.18 dex between the mean values from the two strong-line calibrations for GMOS and MUSE respectively, consistent with the order of metallicity uncertainty via the strong-line methods. We contend that our findings align with a scenario wherein local Seyferts have undergone seamless gas accretion histories, resulting in positive metallicity profile over an extended period of time, thereby providing insights into galaxy evolution and the chemical enrichment or depletion of the universe. Additionally, we argue that metal-poor gas inflow from the local interstellar medium (ISM) and accreted through the circumgalactic medium (CGM) onto the galaxy systems regulates the star formation processes by diluting their central metallicity and inverting their metallicity gradients, producing a more prominent anti-correlation between gas-phase metallicity and Eddington ratio.

Radio Scrutiny of the X-Ray-weak Tail of Low-mass Active Galactic Nuclei: A Novel Signature of High-Eddington Accretion?

The supermassive black holes (M BH ∼ 106–1010 M ⊙) that power luminous active galactic nuclei (AGNs), i.e., quasars, generally show a correlation between thermal disk emission in the ultraviolet (UV) and coronal emission in hard X-rays. In contrast, some “massive” black holes (mBHs; M BH ∼ 105–106 M ⊙) in low-mass galaxies present curious X-ray properties with coronal radiative output up to 100× weaker than expected. To examine this issue, we present a pilot study incorporating Very Large Array radio observations of a sample of 18 high-accretion-rate (Eddington ratios L bol/L Edd > 0.1), mBH-powered AGNs (M BH ∼ 106 M ⊙) with Chandra X-ray coverage. Empirical correlations previously revealed in samples of radio-quiet, high-Eddington AGNs indicate that the radio–X-ray luminosity ratio, L R/L X, is approximately constant. Through multiwavelength analysis, we instead find that the X-ray-weaker mBHs in our sample tend toward larger values of L R/L X even though they remain radio-quiet per their optical–UV properties. This trend results in a tentative but highly intriguing correlation between L R/L X and X-ray weakness, which we argue is consistent with a scenario in which X-rays may be preferentially obscured from our line of sight by a “slim” accretion disk. We compare this observation to weak emission-line quasars (AGNs with exceptionally weak broad-line emission and a significant X-ray-weak fraction) and conclude by suggesting that our results may offer a new observational signature for finding high-accretion-rate AGNs.

A Deeper Look into eFEDS AGN Candidates in Dwarf Galaxies with Chandra

The ability to accurately discern active massive black holes (BHs) in nearby dwarf galaxies is paramount to understanding the origins and processes of “seed” BHs in the early Universe. We present Chandra X-ray Observatory observations of a sample of three local dwarf galaxies (M * ≤ 3 × 109 M ⊙, z ≤ 0.15) previously identified as candidates for hosting active galactic nuclei (AGN). The galaxies were selected from the NASA-Sloan Atlas with spatially coincident X-ray detections in the eROSITA Final Equatorial Depth Survey. Our new Chandra data reveal three X-ray point sources in two of the target galaxies with luminosities between log(L 2−10 keV [erg s−1]) = 39.1 and 40.4. Our results support the presence of an AGN in these two galaxies and an ultraluminous X-ray source (ULX) in one of them. For the AGNs, we estimate BH masses of M BH ∼ 105−6 M ⊙ and Eddington ratios on the order of ∼10−3.

A SPectroscopic Survey of Biased Halos In the Reionization Era (ASPIRE): Broad-line AGN at z = 4−5 Revealed by JWST/NIRCam WFSS

Low-luminosity active galactic nuclei (AGNs) with low-mass black holes (BHs) in the early universe are fundamental to understanding the BH growth and their coevolution with the host galaxies. Utilizing JWST NIRCam Wide Field Slitless Spectroscopy, we perform a systematic search for broad-line Hα emitters (BHAEs) at z ≈ 4–5 in 25 fields of the A SPectroscopic survey of biased halos In the Reionization Era (ASPIRE) project, covering a total area of 275 arcmin2. We identify 16 BHAEs with FWHM of the broad components spanning from ∼1000 to 3000 km s−1. Assuming that the broad line widths arise as a result of Doppler broadening around BHs, the implied BH masses range from 107 to 108 M ⊙, with broad Hα-converted bolometric luminosities of 1044.5–1045.5 erg s−1 and Eddington ratios of 0.07–0.47. The spatially extended structure of the F200W stacked image may trace the stellar light from the host galaxies. The Hα luminosity function indicates an increasing AGN fraction toward the higher Hα luminosities. We find possible evidence for clustering of BHAEs: two sources are at the same redshift with a projected separation of 519 kpc; one BHAE appears as a composite system residing in an overdense region with three close companion Hα emitters. Three BHAEs exhibit blueshifted absorption troughs indicative of the presence of high column density gas. We find that the broad-line-selected and photometrically selected BHAE samples exhibit different distributions in the optical continuum slopes, which can be attributed to their different selection methods. The ASPIRE broad-line Hα sample provides a good database for future studies of faint AGN populations at high redshift.

Eddington ratios of dust-obscured quasars at z ≲ 1: Evidence supporting dust-obscured quasars as young quasars

Eddington ratios of dust-obscured quasars at <i>z</i> ≲ 1: Evidence supporting dust-obscured quasars as young quasars

Red Quasars: Estimation of SMBH Spin, Mass, and Accretion Disk Inclination Angle

ABSTRACTWe estimated values of spin, mass, and inclination angle for sample of 42 red quasars. Our estimations show that two objects: F2MS J1113+1244 and F2MS J1434+0935 with the highest Eddington ratios may have geometrically thick disk. Six objects: SDSS J0036‐0113, S82X 0040+0058, S82X 0118+0018, S82X 0303‐0115, FBQS J1227+3214, S82X 2328‐0028 may have “retrograde” rotation. Analysis of estimated spin values shows that red quasar population may contain Seyfert galaxies and NLS1.

Stripe 82X Data Release 3: Multiwavelength Catalog with New Spectroscopic Redshifts and Black Hole Masses

We present the third catalog release of the wide-area (31.3 deg2) Stripe 82 X-ray survey. This catalog combines previously published X-ray source properties with multiwavelength counterparts and photometric redshifts, presents 343 new spectroscopic redshifts, and provides black hole masses for 1297 Type 1 active galactic nuclei (AGN). With spectroscopic redshifts for 3457 out of 6181 Stripe 82X sources, the survey has a spectroscopic completeness of 56%. This completeness rises to 90% when considering the contiguous portions of the Stripe 82X survey with homogeneous X-ray coverage at an optical magnitude limit of r < 22. Within that portion of the survey, 23% of AGN can be considered obscured by being either a Type 2 AGN, reddened (R − K > 4, Vega), or X-ray obscured with a column density of N H > 1022 cm−2. Unlike other surveys, there is only an 18% overlap between Type 2 and X-ray obscured AGN. We calculated black hole masses for Type 1 AGN that have Sloan Digital Sky Survey spectra using virial mass estimators calibrated on the Hβ, Mg ii, Hα, and C iv emission lines. We find wide scatter in these black hole mass estimates, indicating that statistical analyses should use black hole masses calculated from the same formula to minimize bias. We find that the AGN with the highest X-ray luminosities are accreting at the highest Eddington ratios, consistent with the picture that most black hole mass accretion happens in the phase when the AGN is luminous (L 2−10keV > 1045 erg s−1).

Origin of the Very High Energy Gamma Rays in the Low-luminosity Active Galactic Nucleus NGC 4278

NGC 4278, a low-luminosity active galactic nucleus, is generally classified as a low-ionization nuclear emission-line region (LINER). Recently, it has been reported to be associated with a very high energy γ-ray source 1LHAASO J1219+2915 in the first Large High Altitude Air Shower Observatory source catalog. However, no associated counterpart has been detected by analyzing the data collected by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. By analyzing its X-ray observation data from Swift-XRT, we find that NGC 4278 is in a high-flux state on MJD 59546, with the X-ray flux more than one order of magnitude higher than that observed ∼11.7 yr earlier by Chandra. Interestingly, this Swift-XRT observation was conducted during the active phase of the γ-ray source 1LHAASO J1219+2915. We propose that the detection of very high energy γ-rays from NGC 4278 may be attributed to the presence of an active nucleus in its center. To reproduce the spectral energy distribution (SED) of NGC 4278, we employ a one-zone leptonic model, typically used for fitting broadband SEDs of BL Lacs, and find that a smaller magnetic field strength is required than that of typical TeV BL Lacs. Furthermore, NGC 4278 exhibits significantly lower luminosity in both radio and TeV bands when compared with typical TeV BL Lacs. In the radio luminosity versus Eddington ratio plane, NGC 4278 shows greater similarity to Seyfert galaxies and LINERs than to BL Lacs; however, it still roughly follows the extension toward lower luminosity seen in BL Lacs.

Constraining Wind-driven Accretion onto Gaia BH3 with Chandra

Gaia BH3 is the most massive known stellar-origin black hole in the Milky Way, with a mass M • ≈ 33 M ⊙. Detected from Gaia’s astrometry, this black hole is in the mass range of those observed via gravitational waves, whose nature is still highly debated. Hosted in a binary system with a companion giant star that is too far away for Roche-lobe mass transfer, this black hole could nonetheless accrete at low levels due to wind-driven mass loss from its companion star, thus accreting in advection-dominated accretion flow, or ADAF, mode. Using stellar wind models, we constrain its Eddington ratio in the range 10−9 < f Edd < 10−7, corresponding to radiative efficiencies 5 × 10−5 < ϵ < 10−3, compatible with radiatively inefficient accretion modes. Chandra ACIS-S observed this object and obtained the most sensitive upper bound of its [2–10] keV flux: F X < 3.25 × 10−15 erg s−1 cm−2 at 90% confidence level corresponding to L [2–10] < 2.10 × 1029 erg s−1. Using ADAF emission models, we constrained its accretion rate to f Edd < 4.91 × 10−7 at the apastron, in agreement with our theoretical estimate. At the periastron, we expect fluxes ∼50 times larger. Because of the inferred low rates, accretion did not significantly contribute to black hole growth over the system’s lifetime. Detecting the electromagnetic emission from Gaia BH3 will be fundamental to informing stellar wind and accretion disk models.

Discovery of a hyperluminous quasar at z = 1.62 with Eddington ratio &amp;gt;3 in the eFEDS field confirmed by KOOLS-IFU on Seimei Telescope

Abstract We report the discovery of a hyperluminous type 1 quasar (eFEDS J082826.9-013911; eFEDS J0828-0139) at $z_{\rm spec} = 1.622$ with a super-Eddington ratio ($\lambda _{\rm Edd}$). We perform the optical spectroscopic observations with KOOLS-IFU (the Kyoto Okayama Optical Low-dispersion Spectrograph with optical fiber) on the Seimei Telescope. The black hole mass ($M_{\rm BH}$) based on the single-epoch method with Mg ii $\lambda$2798 is estimated to be $M_{\rm BH} = {(6.2 \pm 1.2) }\times 10^8\, M_{\odot }$. To measure the precise infrared luminosity ($L_{\rm IR}$), we obtain submillimeter data taken by SCUBA-2 on the James Clerk Maxwell Telescope and conduct the spectral energy distribution analysis with X-ray to submillimeter data. We find that $L_{\rm IR}$ of eFEDS J0828-0139 is $L_{\rm IR} = {(6.8 \pm 1.8)} \times 10^{13}\, L_{\odot }$, confirming the existence of a hypeluminous infrared galaxy. $\lambda _{\rm Edd}$ is estimated to be $\lambda _{\rm Edd} = {3.6 \pm 0.7}$, making it a quasar with one of the highest BH mass accretion rates at cosmic noon.

UVIT Survey of the Host Galaxies of Active Galactic Nuclei. I. Star Formation Scenarios

Circumnuclear star formation (SF) is generally seen in galaxies hosting active galactic nuclei (AGN); however, the connection between the AGN activity and SF in them is less well understood. To explore this connection on scales of a few tens of parsecs to a few tens of kiloparsecs and larger, we carried out an investigation of SF in seven Seyfert-type AGN and one low-ionization nuclear emission-line region galaxy, using observations with the Ultraviolet Imaging Telescope on board AstroSat in the near-ultraviolet (2000–3000 Å) and far-ultraviolet (1300−1800 Å) bands. A total of 1742 star-forming regions were identified, having size scales of 0.010–63.642 kpc2. Considering all the galaxies, we found a positive correlation between their total surface density of SF (ΣSFR) and extinction. For five galaxies, namely NGC 1365, NGC 4051, NGC 4321, NGC 5033, and NGC 6814, we found a gradual decrease of both extinction and ΣSFR from the centre to the outer regions. Four sources are found to lie in the main sequence of star-forming galaxies, and the other four lie away from it. We found the ratio of the star formation rate (SFR) in the nuclear region to the total SFR to be positively correlated with the Eddington ratio. This points to the influence of AGN in enhancing the SF characteristics of the hosts. However, the impact is dominant only in the central nuclear region and has no significant effect on the larger scales probed in this work.

QSOFEED: Relationship between star formation and active galactic nuclei feedback

Context. Large-scale cosmological simulations suggest that feedback from active galactic nuclei (AGN) plays a crucial role in galaxy evolution. More specifically, outflows are one of the mechanisms by which the accretion energy of the AGN is transferred to the interstellar medium (ISM), heating and driving out gas and impacting star formation (SF). Aims. The purpose of this study is to directly test this hypothesis utilising SDSS spectra of a well-defined sample of 48 low-redshift (z &lt; 0.14) type 2 quasars (QSO2s). Methods. By exploiting these data, we were able to characterise the kinematics of the warm ionised gas by performing a non-parametric analysis of the [OIII]λ5007 emission line. We also constrained the properties of the young stellar populations (YSP; tysp &lt; 100 Myr) of their host galaxies via spectral synthesis modelling. Results. These analyses revealed that 85% of the QSO2s display velocity dispersions in the warm ionised gas phase greater than that of the stellar component of their host galaxies, indicating the presence of AGN-driven outflows. We compared the gas kinematics with the intrinsic properties of the AGN and found that there is a positive correlation between gas velocity dispersion and 1.4 GHz radio luminosity – but not with the AGN bolometric luminosity or Eddington ratio. This either suggests that the radio luminosity is the key factor driving outflows or that the outflows themselves are shocking the ISM and producing synchrotron emission. We found that 98% of the sample host YSPs to varying degrees, with star formation rates (SFRs) of 0 ≤ SFR ≤ 92 M⊙ yr−1, averaged over 100 Myr. We compared the gas kinematics and outflow properties to the SFRs to establish possible correlations that could suggest that the presence of the outflowing gas could be impacting SF, but we found that no such correlation exists. This leads us to the conclusion that on the scales probed by the SDSS fibre (between 2 and 7 kpc diameters), AGN-driven outflows do not impact SF on the timescales probed in this study. However, we find a positive correlation between the light-weighted stellar ages of the QSO2s and the black hole mass, which might indicate that successive AGN episodes lead to the suppression of SF over the course of galaxy evolution.