Abstract:We present a comparative analysis of the properties of AGN emitting at radio and X-ray wavelengths. The study is performed on 907 X-ray AGN and 100 radio AGN selected on the CDFS and UDS fields and makes use of new and ancillary data available to the VANDELS collaboration. Our results indicate that the mass of the host galaxy is a fundamental quantity which determines the level of AGN activity at the various wavelengths. Indeed large stellar masses are found to be connected with AGN radio emission, as virtuall… Show more
“…These results demonstrate that vigorous SF activity is coeval with the growth of the SMBHs residing in the nuclei of the RLQs host galaxies. This agrees with previous works that found evidence for high SFRs in radio AGN (e.g., Seymour et al 2011;Magliocchetti et al 2014;Podigachoski et al 2015;Magliocchetti et al 2016Magliocchetti et al , 2020. Moreover, bright RDQs have been associated with higher SFRs in comparison to their radio-quiet counterparts (e.g., Kalfountzou et al 2014Kalfountzou et al , 2017 The enhancement in the star formation in radio AGN could be explained considering the formation of bow shocks caused by radio jets that compress the interstellar medium in the host galaxy.…”
Section: Positive and Negative Agn Feedbacksupporting
Radio emission in the brightest radio quasars can be attributed to processes inherent to active galactic nuclei (AGN) powered by super massive black holes (SMBHs), while the physical origins of the radio fluxes in quasars without radio detections have not been established with full certainly. Deep radio surveys carried out with the Low Frequency ARray (LOFAR) are at least one order of magnitude more sensitive for objects with typical synchrotron spectra than previous wide-area high-frequency surveys (> 1.0 GHz). With the enhanced sensitivity that LOFAR offers, we investigate the radio-infrared continuum of LOFAR radio-detected quasars (RDQs) and LOFAR radio-undetected quasars (RUQs) in the 9.3 deg 2 NOAO Deep Wide-field survey (NDWFS) of the Boötes field; RUQs are quasars that are individually undetected at a level of ≥ 5σ in the LOFAR observations. To probe the nature of the radio and infrared emission, where direct detection is not possible due to the flux density limits, we used a median image stacking procedure. This was done in the radio frequencies of 150 MHz, 325 MHz, 1.4 GHz and 3.0 GHz, and in nine infrared bands between 8 and 500 µm. The stacking analysis allows us to probe the radio-luminosity for quasars that are up to one order of magnitude fainter than the ones detected directly. The radio and infrared photometry allow us to derive the median spectral energy distributions of RDQs and RUQs in four contiguous redshift bins between 0 < z < 6.15. The infrared photometry is used to derive the infrared star-formation rate (SFR) through SED fitting, and is compared with two independent radio-based star-formation (SF) tracers using the far-infrared radio correlation (FIRC) of star-forming galaxies. We find a good agreement between our radio and infrared SFR measurements and the predictions of the FIRC. Moreover, we use the FIRC predictions to establish the level of the contribution due to SMBH accretion to the total radio-luminosity. We show that SMBH accretion can account for ∼ 5 − 41% of the total radio-luminosity in median RUQs, while for median RDQs the contribution is ∼ 50 − 84%. This implies that vigorous SF activity is coeval with SMBH growth in our median stacked quasars. We find that median RDQs have higher SFRs that agree well with those of massive star-forming main sequence galaxies, while median RUQs present lower SFRs than RDQs. Furthermore, the behavior of the radio-loudness parameter (R = log 10 (L rad /LAGN)) is investigated. For quasars with R ≥ −4.5, the radio-emission is consistent with being dominated by SMBH accretion, while for low radio luminosity quasars with R < −4.5 the relative contribution of SF to the radio fluxes increases as the SMBH component becomes weaker. We also find signatures of SF suppression due to negative AGN feedback in the brightest median RDQs at 150 MHz. Finally, taking advantage of our broad spectral coverage, we studied the radio spectra of median RDQs and RUQs. The spectral indices of RUQs and RDQs do not evolve significantly with redshift, but they become fl...
“…These results demonstrate that vigorous SF activity is coeval with the growth of the SMBHs residing in the nuclei of the RLQs host galaxies. This agrees with previous works that found evidence for high SFRs in radio AGN (e.g., Seymour et al 2011;Magliocchetti et al 2014;Podigachoski et al 2015;Magliocchetti et al 2016Magliocchetti et al , 2020. Moreover, bright RDQs have been associated with higher SFRs in comparison to their radio-quiet counterparts (e.g., Kalfountzou et al 2014Kalfountzou et al , 2017 The enhancement in the star formation in radio AGN could be explained considering the formation of bow shocks caused by radio jets that compress the interstellar medium in the host galaxy.…”
Section: Positive and Negative Agn Feedbacksupporting
Radio emission in the brightest radio quasars can be attributed to processes inherent to active galactic nuclei (AGN) powered by super massive black holes (SMBHs), while the physical origins of the radio fluxes in quasars without radio detections have not been established with full certainly. Deep radio surveys carried out with the Low Frequency ARray (LOFAR) are at least one order of magnitude more sensitive for objects with typical synchrotron spectra than previous wide-area high-frequency surveys (> 1.0 GHz). With the enhanced sensitivity that LOFAR offers, we investigate the radio-infrared continuum of LOFAR radio-detected quasars (RDQs) and LOFAR radio-undetected quasars (RUQs) in the 9.3 deg 2 NOAO Deep Wide-field survey (NDWFS) of the Boötes field; RUQs are quasars that are individually undetected at a level of ≥ 5σ in the LOFAR observations. To probe the nature of the radio and infrared emission, where direct detection is not possible due to the flux density limits, we used a median image stacking procedure. This was done in the radio frequencies of 150 MHz, 325 MHz, 1.4 GHz and 3.0 GHz, and in nine infrared bands between 8 and 500 µm. The stacking analysis allows us to probe the radio-luminosity for quasars that are up to one order of magnitude fainter than the ones detected directly. The radio and infrared photometry allow us to derive the median spectral energy distributions of RDQs and RUQs in four contiguous redshift bins between 0 < z < 6.15. The infrared photometry is used to derive the infrared star-formation rate (SFR) through SED fitting, and is compared with two independent radio-based star-formation (SF) tracers using the far-infrared radio correlation (FIRC) of star-forming galaxies. We find a good agreement between our radio and infrared SFR measurements and the predictions of the FIRC. Moreover, we use the FIRC predictions to establish the level of the contribution due to SMBH accretion to the total radio-luminosity. We show that SMBH accretion can account for ∼ 5 − 41% of the total radio-luminosity in median RUQs, while for median RDQs the contribution is ∼ 50 − 84%. This implies that vigorous SF activity is coeval with SMBH growth in our median stacked quasars. We find that median RDQs have higher SFRs that agree well with those of massive star-forming main sequence galaxies, while median RUQs present lower SFRs than RDQs. Furthermore, the behavior of the radio-loudness parameter (R = log 10 (L rad /LAGN)) is investigated. For quasars with R ≥ −4.5, the radio-emission is consistent with being dominated by SMBH accretion, while for low radio luminosity quasars with R < −4.5 the relative contribution of SF to the radio fluxes increases as the SMBH component becomes weaker. We also find signatures of SF suppression due to negative AGN feedback in the brightest median RDQs at 150 MHz. Finally, taking advantage of our broad spectral coverage, we studied the radio spectra of median RDQs and RUQs. The spectral indices of RUQs and RDQs do not evolve significantly with redshift, but they become fl...
“…The sources detected in the Luo et al ( 2017) catalogue at 𝑧 3 are very likely to be AGN, owing to X-ray luminosities of > 10 42 erg s −1 at these redshifts (e.g. Magliocchetti et al 2020;Saxena et al 2020aSaxena et al , 2021. We identify and remove two sources with counterparts in the X-ray catalogue that are also classified as AGN in the catalogue and therefore, the total number of sources in our final sample comes to 183.…”
We present Lyman continuum (LyC) radiation escape fraction ( 𝑓 esc ) measurements for 183 spectroscopically confirmed starforming galaxies in the redshift range 3.11 < 𝑧 < 3.53 in the Chandra Deep Field South. We use ground-based imaging to measure 𝑓 esc , and use ground-and space-based photometry to derive galaxy physical properties using spectral energy distribution (SED) fitting. We additionally derive [O ] + H𝛽 equivalent widths (that fall in the observed 𝐾 band) by including nebular emission in the SED fitting. After removing foreground contaminants, we report the discovery of 11 new candidate LyC leakers, with absolute LyC escape fractions, 𝑓 esc in the range 0.07 − 0.52. Most galaxies in our sample (≈ 94%) do not show any LyC leakage, and we place 1𝜎 upper limits of 𝑓 esc < 0.07 through weighted averaging, where the Lyman-break selected galaxies have 𝑓 esc < 0.07 and 'blindly' discovered galaxies with no prior photometric selection have 𝑓 esc < 0.10. We additionally measure 𝑓 esc < 0.09 for extreme emission line galaxies in our sample with rest-frame [O ] + H𝛽 equivalent widths > 300 Å. For the candidate LyC leakers, we do not find a strong dependence of 𝑓 esc on their stellar masses and/or specific star-formation rates, and no correlation between 𝑓 esc and EW 0 ([O ] + H𝛽). We suggest that this lack of correlations may be explained by viewing angle and/or non-coincident timescales of starburst activity and periods of high 𝑓 esc . Alternatively, escaping radiation may predominantly occur in highly localised star-forming regions, thereby obscuring any global trends with galaxy properties. Both hypotheses have important consequences for models of reionisation.
“…VANDELS, proposed as an ESO public spectroscopic survey in 2014, aims to shed new light on these aspects, not limiting itself to finding a redshift, but also providing midresolution, high signal-to-noise ratio (S/N) spectra that allow us to study the physical characteristics of the high-redshift galaxies in detail and with statistically meaningful numbers (McLure et al 2018). Since the first data release of VANDELS (Pentericci et al 2018b), a number of different studies have already been published: from dust attenuation and stellar metallicities of star forming (Cullen et al 2018(Cullen et al , 2019Calabrò et al 2021) and quiescent galaxies (Carnall et al 2019(Carnall et al , 2020, to Lyα and He II λ1640 emitters (Marchi et al 2019;Hoag et al 2019;Cullen et al 2020;Saxena et al 2020a,b;Guaita et al 2020), intergalactic-medium properties (Thomas et al 2020) and active galactic nuclei (AGNs) (Magliocchetti et al 2020). All these works were based on only a subset of the data.…”
VANDELS is an ESO Public Spectroscopic Survey designed to build a sample of high-signal-to-noise ratio, medium-resolution spectra of galaxies at redshifts between 1 and 6.5. Here we present the final Public Data Release of the VANDELS Survey, comprising 2087 redshift measurements. We provide a detailed description of sample selection, observations, and data reduction procedures. The final catalogue reaches a target selection completeness of 40% at iAB = 25. The high signal-to-noise ratio of the spectra (above 7 in 80% of the spectra) and the dispersion of 2.5 Å allowed us to measure redshifts with high precision, the redshift measurement success rate reaching almost 100%. Together with the redshift catalogue and the reduced spectra, we also provide optical mid-infrared photometry and physical parameters derived through fitting the spectral energy distribution. The observed galaxy sample comprises both passive and star forming galaxies covering a stellar mass range of 8.3 < Log(M*/M⊙) < 11.7.
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