The first blazar observed at z > 6 Belladitta, S.; Moretti, A.; Caccianiga, A. ...
Astronomy and astrophysics (Berlin),
03/2020, Volume:
635
Journal Article
Peer reviewed
Open access
We present the discovery of PSO J030947.49+271757.31, the radio brightest (23.7 mJy at 1.4 GHz) active galactic nucleus (AGN) at
z
> 6.0. It was selected by cross-matching the NRAO VLA Sky Survey ...and the Panoramic Survey Telescope and Rapid Response System PS1 databases and its high-
z
nature was confirmed by a dedicated spectroscopic observation at the Large Binocular Telescope. A pointed
Neil Gehrels Swift
Observatory XRT observation allowed us to measure a flux of ∼3.4 × 10
−14
erg s
−1
cm
−2
in the 0.5–10 keV energy band, which also makes this object the X-ray brightest AGN ever observed at
z
> 6.0. Its flat radio spectrum (
α
νr
< 0.5), very high radio loudness (
R
> 10
3
), and strong X-ray emission, compared to the optical, support the hypothesis of the blazar nature of this source. Assuming that this is the only blazar at this redshift in the surveyed area of sky, we derive a space density of blazars at
z
∼ 6 and with
M
1450 Å
< −25.1 of 5.5
+11.2
−4.6
× 10
−3
Gpc
−3
. From this number, and assuming a reasonable value of the bulk velocity of the jet (Γ = 10), we can also infer a space density of the entire radio-loud AGN population at
z
∼ 6 with the same optical/UV absolute magnitude of 1.10
+2.53
−0.91
Gpc
−3
. Larger samples of blazars will be necessary to better constrain these estimates.
We present the final data release of the APEX low-redshift legacy survey for molecular gas (ALLSMOG), comprising CO(2–1) emission line observations of 88 nearby, low-mass (108.5<M∗ M⊙ < 1010) ...star-forming galaxies carried out with the 230 GHz APEX-1 receiver on the APEX telescope. The main goal of ALLSMOG is to probe the molecular gas content of more typical and lower stellar mass galaxies than have been studied by previous CO surveys. We also present IRAM 30 m observations of the CO(1–0) and CO(2–1) emission lines in nine galaxies aimed at increasing the M∗< 109M⊙ sample size. In this paper we describe the observations, data reduction and analysis methods and we present the final CO spectra together with archival Hi 21 cm line observations for the entire sample of 97 galaxies. At the sensitivity limit of ALLSMOG, we register a total CO detection rate of 47%. Galaxies with higher M∗, SFR, nebular extinction (AV), gas-phase metallicity (O/H), and Hi gas mass have systematically higher CO detection rates. In particular, the parameter according to which CO detections and non-detections show the strongest statistical differences is the gas-phase metallicity, for any of the five metallicity calibrations examined in this work. We investigate scaling relations between the CO(1–0) line luminosity (L'CO(1-0)) and galaxy-averaged properties using ALLSMOG and a sub-sample of COLD GASS for a total of 185 sources that probe the local main sequence (MS) of star-forming galaxies and its ± 0.3 dex intrinsic scatter from M∗ = 108.5M⊙ to M∗ = 1011M⊙. L'CO(1-0) is most strongly correlated with the SFR, but the correlation with M∗ is closer to linear and almost comparably tight. The relation between L'CO(1-0) and metallicity is the steepest one, although deeper CO observations of galaxies with AV< 0.5 mag may reveal an as much steep correlation with AV. Our results suggest that star-forming galaxies across more than two orders of magnitude in M∗ obey similar scaling relations between CO luminosity and the galaxy properties examined in this work. Besides SFR, the CO luminosity is likely most fundamentally linked to M∗, although we note that stellar mass alone cannot explain all of the variation in CO emission observed as a function of O/H and MHI.
ABSTRACT
We present a highly complete and reliable mid‐infrared (MIR) colour selection of luminous active galactic nucleus (AGN) candidates using the 3.4, 4.6 and 12 μm bands of the Wide‐field ...Infrared Survey Explorer (WISE) survey. The MIR colour wedge was defined using the wide‐angle Bright Ultrahard XMM–Newton survey (BUXS), one of the largest complete flux‐limited samples of bright (f4.5--10 keV >6×10−14 erg s−1 cm −2) ‘ultrahard’ (4.5–10 keV) X‐ray‐selected AGN to date. The BUXS includes 258 objects detected over a total sky area of 44.43 deg2 of which 251 are spectroscopically identified and classified, with 145 being type 1 AGN and 106 type 2 AGN. Our technique is designed to select objects with red MIR power‐law spectral energy distributions (SEDs) in the three shortest bands of WISE and properly accounts for the errors in the photometry and deviations of the MIR SEDs from a pure power‐law. The completeness of the MIR selection is a strong function of luminosity. At L2–10 keV >1044 erg s‐1, where the AGN is expected to dominate the MIR emission, 97.1−4.8+2.2 and 76.5−18.4+13.3 per cent of the BUXS type 1 and type 2 AGN, respectively, meet the selection. Our technique shows one of the highest reliability and efficiency of detection of the X‐ray‐selected luminous AGN population with WISE amongst those in the literature. In the area covered by BUXS our selection identifies 2755 AGN candidates detected with signal‐to‐noise ratio ≥5 in the three shorter wavelength bands of WISE with 38.5 per cent having a detection at 2–10 keV X‐ray energies. We also analysed the possibility of including the 22 μm WISE band to select AGN candidates, but neither the completeness nor the reliability of the selection improves. This is likely due to both the significantly shallower depth at 22 μm compared with the first three bands of WISE and star formation contributing to the 22 μm emission at the WISE 22 μm sensitivity.
Abstract
We report the first Atacama large millimeter/submillimeter array observations of MCG-03-58-007, a local (z = 0.03236 ± 0.00002, this work) AGN ($L_{\mathrm{ AGN}\mathrm{ }}\sim 10^{45}~\rm ...erg~s^{-1}$), hosting a powerful X-ray ultrafast (v = 0.1c) outflow (UFO). The CO(1-0) line emission is observed across ∼18 kpc scales with a resolution of $\sim 1\, \rm kpc$. About 78 per cent of the CO(1-0) luminosity traces a galaxy-size rotating disc. However, after subtracting the emission due to such rotating disc, we detect with a S/N = 20 a residual emission in the central ∼4 kpc. Such residuals may trace a low velocity (vLOS = 170 km s−1) outflow. We compare the momentum rate ($\dot{P}$) and kinetic power ($\dot{E}$) of such putative molecular outflow with that of the X-ray UFO and find $\dot{P}_{\mathrm{ mol}}/\dot{P}_{\mathrm{ UFO}}\sim 0.4$ and $\dot{E}_{\mathrm{ mol}}/\dot{E}_{\mathrm{ UFO}}\sim 4\times 10^{-3}$. This result is at odds with the energy-conserving scenario suggested by the large momentum boosts measured in some other molecular outflows. An alternative interpretation of the residual CO emission would be a compact rotating structure, distinct from the main disc, which would be a factor of ∼10–100 more extended and massive than typical circumnuclear discs revealed in Seyferts. In conclusion, in both scenarios, our results rule out the hypothesis of a momentum-boosted molecular outflow in this AGN, despite the presence of a powerful X-ray UFO.
Abstract
Past X-ray observations of the nearby Seyfert 2 MCG-03-58-007 revealed the presence of a powerful and highly variable disk wind, where two possible phases outflowing with
v
out1
/
c
∼ −0.07 ...and
v
out2
/
c
∼ −0.2 were observed. Multi-epoch X-ray observations, covering the period from 2010 to 2018, showed that the lower-velocity component is persistent, as it was detected in all the observations, while the faster phase outflowing with
v
out2
/
c
∼ −0.2 appeared to be more sporadic. Here we present the analysis of a new monitoring campaign of MCG-03-58-007 performed in 2019 May–June and consisting of four simultaneous XMM-Newton and NuSTAR observations. We confirm that the disk wind in MCG-03-58-007 is persistent, as it is detected in all the observations, and powerful, having a kinetic power that ranges between 0.5% and 10% of the Eddington luminosity. The highly ionized wind (log(
ξ
/erg cm s
−1
) ∼ 5) is variable in both the opacity and, remarkably in its velocity. This is the first time where we have observed a substantial variability of the outflowing velocity in a disk wind, which dropped from
v
out
/
c
∼ −0.2 (as measured in the first three observations) to
v
out
/
c
∼ −0.074 in just 16 days. We conclude that such a dramatic and fast variability of the outflowing velocity could be due to the acceleration of the wind, as recently proposed by Mizumoto et al. Here, the faster wind, seen in the first three observations, is already accelerated to
v
out
/
c
∼ −0.2, while in the last observation our line of sight intercepts only the slower, pre-accelerated streamline.
We investigate the mid-infrared (mid-IR) properties of the largest (42 objects) sample of radio-loud narrow-line Seyfert 1 (RL NLS1) collected to date, using data from the Wide-field Infrared Survey ...Explorer. We analyse the mid-IR colours of these objects and compare them to what is expected from different combinations of AGN and galaxy templates. We find that, in general, the host galaxy emission gives an important contribution to the observed mid-IR flux in particular at the longest wavelengths (W3, at 12 μm, and W4, at 22 μm). In about half of the sources (22 objects), we observe a very red mid-IR colour (W4 − W3 > 2.5) that can be explained only using a starburst galaxy template (M82). Using the 22 μm luminosities, corrected for the AGN contribution, we have then estimated the star formation rate (SFR) for 20 of these ‘red’ RL NLS1, finding values ranging from 10 to 500 M⊙ yr−1. For the RL NLS1 showing bluer colours, instead, we cannot exclude the presence of a star-forming (SF) host galaxy although, on average, we expect a lower SFR. Studying the radio (1.4 GHz) to mid-IR (22 μm) flux ratios of the RL NLS1 in the sample, we found that in ∼10 objects the SF activity could represent the most important component also at radio frequencies, in addition (or in alternative) to the relativistic jet. We conclude that both the mid-IR and the radio emission of RL NLS1 are a mixture of different components, including the relativistic jet, the dusty torus and an intense SF activity.
We have determined the relation between the AGN luminosities at rest-frame 6 μm associated with the dusty torus emission and at 2–10 keV energies using a complete, X-ray-flux-limited sample of 232 ...AGN drawn from the Bright Ultra-hard XMM-Newton Survey. The objects have intrinsic X-ray luminosities between 1042 and 1046 erg s−1 and redshifts from 0.05 to 2.8. The rest-frame 6 μm luminosities were computed using data from the Wide-field Infrared Survey Explorer and are based on a spectral energy distribution decomposition into AGN and galaxy emission. The best-fitting relationship for the full sample is consistent with being linear, L
6 μm ∝
$L_{\rm 2{\rm -}10\,keV}^{0.99\pm 0.03}$
, with intrinsic scatter, Δ log L
6 μm ∼ 0.35 dex. The
$L_{\rm 6\,\mu m}/L_{\rm 2{\rm -}10\,keV}$
luminosity ratio is largely independent of the line-of-sight X-ray absorption. Assuming a constant X-ray bolometric correction, the fraction of AGN bolometric luminosity reprocessed in the mid-IR decreases weakly, if at all, with the AGN luminosity, a finding at odds with simple receding torus models. Type 2 AGN have redder mid-IR continua at rest-frame wavelengths <12 μm and are overall ∼1.3–2 times fainter at 6 μm than type 1 AGN at a given X-ray luminosity. Regardless of whether type 1 and type 2 AGN have the same or different nuclear dusty toroidal structures, our results imply that the AGN emission at rest-frame 6 μm is not isotropic due to self-absorption in the dusty torus, as predicted by AGN torus models. Thus, AGN surveys at rest-frame ∼6 μm are subject to modest dust obscuration biases.
Uncovering obscured luminous AGN with WISE Mateos, S; Alonso-Herrero, A; Carrera, F. J ...
Monthly notices of the Royal Astronomical Society,
09/2013, Volume:
434, Issue:
2
Journal Article
Peer reviewed
Open access
Mateos et al. presented a highly reliable and efficient mid-infrared (MIR) colour-based selection technique for luminous active galactic nuclei (AGN) using the Wide-field Infrared Survey Explorer ...(WISE) survey. Here, we evaluate the effectiveness of this technique to identify obscured AGN missed in X-ray surveys. To do so we study the WISE properties of AGN independently selected in hard X-ray and optical surveys. We use the largest catalogue of 887 Oiii λ5007-selected type 2 quasars (QSO2s) at z ≤ 0.83 in the literature from the Sloan Digital Sky Survey (SDSS), and the 258 hard (>4.5 keV) X-ray-selected AGN from the Bright Ultrahard XMM-Newton Survey (BUXS). The fraction of SDSS QSO2s in our infrared AGN selection region (wedge) increases with the AGN luminosity, reaching
per cent at the highest Oiii luminosities in the sample. This fraction is substantially lower than for the BUXS type 1 AGN (
per cent), but consistent, within the uncertainties, with that for the BUXS type 2 AGN (
per cent) with the same luminosity. The SDSS QSO2s appear to reside in more luminous (massive) hosts than the BUXS AGN, due to the tight magnitude limits applied in the SDSS spectroscopic target selection. Since host galaxy dilution can reduce substantially the effectiveness of MIR-based techniques, this may explain the lower fraction of SDSS QSO2s in the WISE AGN wedge. The fraction of SDSS QSO2s identified as Compton-thick candidates that fall in the wedge is consistent with the fraction of all SDSS QSO2s in that zone. At the AGN luminosities involved in the comparison, Compton-thick and Compton-thin SDSS QSO2s have similar WISE colour distributions. We conclude that at high luminosities and z ≤ 1 our MIR technique is very effective at identifying both Compton-thin and Compton-thick AGN.
We study the link between the X-ray emission in radio-quiet active galactic nuclei (AGN) and the accretion rate on the central supermassive black hole using a statistically well-defined and ...representative sample of 71 type 1 AGN extracted from the XMM-Newton Bright Serendipitous Survey. We search and quantify the statistical correlations between some fundamental parameters that characterize the X-ray emission, i.e. the X-ray spectral slope, Γ, and the X-ray 'loudness', and the accretion rate, both absolute (Ṁ) and normalized to the Eddington luminosity (Eddington ratio, λ). We parametrize the X-ray loudness using three different quantities: the bolometric correction K
bol, the two-point spectral index αOX and the disc/corona luminosity ratio. We find that the X-ray spectral index depends on the normalized accretion rate while the 'X-ray loudness' depends on both the normalized and the absolute accretion rate. The dependence on the Eddington ratio, in particular, is probably induced by the Γ - λ correlation. The two proxies usually adopted in the literature to quantify the X-ray loudness of an AGN, i.e. K
bol and αOX, behave differently, with K
bol being more sensitive to the Eddington ratio and αOX having a stronger dependence with the absolute accretion. The explanation of this result is likely related to the different sensitivity of the two parameters to the X-ray spectral index.
Aims. We present a new efficient diagnostic method, based on mid-infrared and X-ray data, to select local (z < 0.1) Compton-thick AGN with the aim of estimating their surface and space density. ...Methods. We define a region in the X-ray-to-mid-IR F(2−12 keV)/F25ν25 vs. X-ray color (HR) plane associated to Compton-thick AGN, i.e. F(2−12 keV)/F25ν25 < 0.02 and HR > − 0.2. On the basis of this selection method we build up a sample of 43 Compton-thick AGN candidates using data from IRAS Point Source and 2XMM-Newton catalogues. In order to test the efficiency of the proposed method in selecting Compton-thick AGN we use the results of the X-ray spectral analysis performed on all the sources of our sample (presented in a parallel work). After taking into account the different selection effects, we have estimated the number of Compton-thick in the local Universe and their density down to the IRAS flux limit of F25 = 0.5 Jy. Results. We find that the diagnostic plot proposed here is an efficient method to select Compton-thick AGN in the nearby Universe since ~84% of the sources populating the proposed Compton-thick region are actually Compton-thick AGN. Twenty percent are newly-discovered Compton-thick AGN. We then estimate the surface density of Compton-thick AGN down to the IRAS PSC catalogue flux limit (F25 = 0.5 Jy) that turns out to be ρCT ~ 3 × 10-3 src deg-2. After estimating an equivalent IR-to-hard-X-ray limiting flux, we compare our result with those found with Swift-BAT. We find that the surface density derived here is a factor 4 above the density computed in the hard X-ray surveys. This difference is ascribed, at least in part, to a significant contribution (~60−90%) of the star-forming activity to the total 25 μm emission for the sources in our sample. By considering only the 25 μm AGN emission, we estimate a surface density of Compton-thick AGN which is consistent with the results found by hard X-ray surveys. Finally, we estimated the co-moving space density of Compton-thick AGN with intrinsic LX > 1043 erg s-1 (0.004 < z < 0.06): ΦC-thick ~ (3.5-0.5+4.5)×10-6 Mpc-3. The prediction for Compton-thick AGN based on the synthesis model of X-ray background in Gilli et al. (2007) is consistent with this value.
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