The coevolution of supermassive black holes and galaxies in luminous AGN over a wide range of redshift

It is well known that supermassive black holes (SMBHs) and their host galaxies co-evolve. A manifestation of this co-evolution is the correlation that has been found between the SMBH mass, M$_{BH}$, and the galaxy bulge or stellar mass, M$_*$. The cosmic evolution of this relation, though, is still a matter of debate. In this work, we examine the M$_{BH}-$M$_*$ relation, using 687 X-ray luminous (median $\rm log\,[L_{X,2-10keV}(ergs^{-1})]=44.3$), broad line AGN, at $\rm 0.2<z<4.0$ (median $\rm z\approx 1.4$) that lie in the XMM-{\it{XXL}} field. Their M$_{BH}$ and M$_*$ range from $\rm 7.5<log\,[M_{BH}\,(M_\odot)]<9.5$ and $\rm 10<log\,[M_*(M_\odot)]<12$, respectively. Most of the AGN live in star-forming galaxies and their Eddington ratios range from 0.01 to 1, with a median value of 0.06. Our results show that M$_{BH}$ and M$_*$ are correlated ($\rm r=0.47\pm0.21$, averaged over different redshift intervals). Our analysis also shows that the mean ratio of the M$_{BH}$ and M$_*$ does not evolve with redshift, at least up to $\rm z=2$ and has a value of $\rm log($M$_{BH}/$M$_*)=-2.44$. The majority of the AGN ($75\%$) are in a SMBH mass growth dominant phase. In these systems, the M$_{BH}-$M$_*$ correlation is weaker and their M$_*$ tends to be lower (for the same M$_{BH}$) compared to systems that are in a galaxy mass growth phase. Our findings suggest that the growth of black hole mass occurs first, while the early stellar mass assembly may not be so efficient.Comment: Accepted for publication in A&A. 8 pages, 7 figure

XMMPZCAT: A catalogue of photometric redshifts for X-ray sources

The third version of the XMM-Newton serendipitous catalogue (3XMM), containing almost half million sources, is now the largest X-ray catalogue. However, its full scientific potential remains untapped due to the lack of distance information (i.e. redshifts) for the majority of its sources. Here we present XMMPZCAT, a catalogue of photometric redshifts (photo-z) for 3XMM sources. We searched for optical counterparts of 3XMM-DR6 sources outside the Galactic plane in the SDSS and Pan-STARRS surveys, with the addition of near- (NIR) and mid-infrared (MIR) data whenever possible (2MASS, UKIDSS, VISTA-VHS, and AllWISE). We used this photometry data set in combination with a training sample of 5157 X-ray selected sources and the MLZ-TPZ package, a supervised machine learning algorithm based on decision trees and random forests for the calculation of photo-z. We have estimated photo-z for 100,178 X-ray sources, about 50% of the total number of 3XMM sources (205,380) in the XMM-Newton fields selected to build this catalogue (4208 out of 9159). The accuracy of our results highly depends on the available photometric data, with a rate of outliers ranging from 4% for sources with data in the optical+NIR+MIR, up to $\sim$40% for sources with only optical data. We also addressed the reliability level of our results by studying the shape of the photo-z probability density distributions.Comment: 16 pages, 14 figures, A&A accepte

QSOs and galaxies: lensing, clustering and redshift-space distortions

The aim of this thesis is to analyze statistically the available QSO, LRG, galaxy and cluster samples in order to estimate the QSO-galaxy lensing anti-correlation signal and measure the mass of foreground galaxies and clusters and to estimate the QSO-LRG clustering amplitude, the QSO bias and their dependence on QSO luminosity. We also investigate the behaviour of the group-galaxy infall parameter and their rms velocity dispersions for different group memberships. The aim here is to make dynamical estimates of the group masses to check the QSO lensing results. We first cross-correlate the SDSS photo-z, g < 21, 1.0 < Z(_p) < 2.2 QSOs with g < 21 galaxies and clusters in the same areas. The anti-correlation found is somewhat less than the results of Myers et al. based on 2QZ QSOs. But contamination of the QSOs by low redshift NELGs and QSOs can cause underestimation of the anticorrelation lensing signal. Correcting for such low redshift contamination at the levels indicated by our spectroscopic checks suggests that the effect is generally small for QSO cross-correlations with g < 21 galaxies but may be an issue for fainter galaxy samples. Thus when this correction is applied to the photo-z QSO sample of Scranton et al. the anti-correlation increases and the agreement with the 2QZ results of Myers et al. is improved. When we also take into account the fainter r < 21 galaxy limit of Scranton et al. as opposed to g < 21 for Myers et al., the two observational results appear to be in very good agreement. We then measure the bias of QSOs as a function of QSO luminosity at fixed redshift (z < 1) by cross-correlating them with Luminous Red Galaxies (LRGs) in the same spatial volume, hence breaking the degeneracy between QSO luminosity and redshift. We use three QSO samples from 2SLAQ, 2QZ and SDSS covering a QSO absolute magnitude range -24.5 < M(_bj) < -21.5, and cross-correlate them with 2SLAQ (z ≈ 0.5) and AAOmega (z ≈ 0.7) photometric and spectroscopic LRGs in the same redshift ranges. The 2-D and 3-D cross-clustering measurements are generally in good agreement. Our (2SLAQ) QSO-LRG clustering amplitude (r(_0) = 6.8 (^+0.1_-0.3)h(^-1)Mpc) as measured from the semi-projected cross-correlation function appears similar to the (2SLAQ) LRG-LRG auto-correlation amplitude (r(_0) = 7.45 ± 0.35h(^-1)Mpc) and both are higher than the (2QZ-t-2SLAQ) QSO-QSO amplitude (r(_0) ≈ 5.0h(^-1)Mpc). Our measurements show remarkably little QSO-LRG cross- clustering dependence on QSO luminosity. Assuming a standard ACDM model and values for b(_LRG) measured from LRG autocorrelation analyses, we find b(_Q) = 1.45 ± 0.11 at M(_bj) ≈ -24 and b(_Q) = 1.90 ± 0.16 at M(_bj) ≈ -22. We also find consistent results for the QSO bias from a z-space distortion analysis of the QSO-LRG cross-clustering at z ≈ 0.55. The velocity dispersions fitted to QSO-LRG cross-correlation, ع (σ,π), at 680 kms(^-1) are intermediate between those for QSO-QSO and LRG-LRG clustering, as expected given the larger QSO redshift errors. The dynamical infall results give ẞ(_Q) = 0.55 ± 0.10, implying b(_Q) = 1.4 ± 0.2. Thus both the z-space distortion and the amplitude analyses yield b(_Q) ≈ 1.5 at M(_bj) ≈ -23. The implied dark matter halo mass inhabited by QSOs at z ≈ 0.55 is ~ 10(^13)h(^-1)M(_ʘ), again approximately independent of QSO luminosity. Prompted by the indications from QSO lensing that there may be more mass associated with galaxy groups than expected from virial analyses, we make new dynamical infall estimates of the masses associated with 2PIGG groups and clusters. We analyse the redshift distortions in the cluster-galaxy cross-correlation function as a function of cluster membership, cross-correlating z < 0.12 2PIGG clusters and groups with the full 2dF galaxy catalogue. We make estimates of the dynamical infall parameter, ẞ, and new estimates of the group velocity dispersions for group membership classes out to z < 0.12. We first find that, out to 30-40h(^-1)Mpc, the amplitude of the full 3-D redshift space cross-correlation function, ع (_cg), rises monotonically with group membership. We use a simple linear-theory infall model to fit ع (σ,π), in the range 5 < s < 40h(^-1) Mpc. We find that the ẞ versus membership relation for the data shows a minimum at intermediate group membership n ≈ 20 or L ≈ 2 x l0(^11)h(^-2)L(_ʘ), implying that the bias and hence M/L ratios rise by a significant factor (≈ 5x) both for small groups and rich clusters. The minimum for the mocks is at a 2 - 3x lower luminosity than for the data. However, the mocks also show a systematic shift between the location of the ẞ minimum and the M/L minimum at L ≈ l0(^11)h(^-2)L(_ʘ), given by direct calculation using the known DM distribution. Our overall conclusion is that bias estimates from dynamical infall appear to support the minimum in star-formation efficiency at intermediate halo masses. Nevertheless, there may still be significant systematic problems arising from measuring ẞ x (^1/_b) ∂P(_mass) /∂P(_gaiaxies) using large-scale infall rather than M/L using small-scale velocity dispersion

Amphiphilic block copolymers by a combination of anionic polymerization and selective post-polymerization functionalization

AbstractAnionic polymerization is the oldest known living/controlled polymerization methodology that leads to well defined macromolecules. It has been also used, with considerable success, for the synthesis of amphiphilic block copolymers (AmBC), a class of functional copolymers having interesting self-assembling properties and high potential for applications in various technological fields. The use of mild and effective post-polymerization functionalization/chemical modification reactions on block copolymers has substantially increased the synthetic capabilities of anionic polymerization methodologies, toward the creation of a variety of AmBC. In this feature article we review work done on these directions in the last ten years. Some perspectives and future work on this particular field of polymer science are also discussed

Testing the evolutionary pathways of galaxies and their supermassive black holes and the impact of feedback from Active Galactic Nuclei via large multiwavelength datasets

It is still a matter of intense debate how supermassive black holes (SMBH) grow, and the role played by feedback from active galactic nuclei (AGN) in the co-evolution of SMBHs and galaxies. To test the coevolution proposed by theoretical models, we compile a large AGN sample of 5639 X-ray detected AGN, over a wide redshift range, spanning nearly three orders of magnitude in X-ray luminosity. The AGN have been detected in the {\it{COSMOS-Legacy}}, the Bo$\rm \ddot{o}$tes, the XMM-{\it{XXL}} and the eFEDS fields. Using the specific star formation rate estimates, we split the AGN host galaxies into star forming (SF), starburst (SB) and quiescent (Q). Our results show that the AGN accretion is increased in SB systems compared to SF and Q. Our analysis reveals a mild increase of L$_X$ with M$_*$. The L$_X$/SFR ratio has a weak dependence on M$_*$, and at fixed M$_*$ it is highest in Q systems. The latter trend is mostly driven by the significant drop in SFR in the Q state. The measured strong variations in SFR from the SB/SF to Q mirror those predicted in merger models with AGN feedback. However, the observed mild variations in L$_X$ are at variance with the same models. We also study the evolution of SFR for a galaxy control sample and found that it is very similar to that of X-ray AGN. This suggests that either AGN play a minor role in the star formation quenching, or the relative timescales of the two processes are different.Comment: MNRAS, accepted, 15 pages, 12 Figure

An obscured AGN population hidden in the VIPERS galaxies: identification through spectral energy distribution decomposition

The detection of X-ray emission constitutes a reliable and efficient tool for the selection of Active Galactic Nuclei (AGNs), although it may be biased against the most heavily absorbed AGNs. Simple mid-IR broad-band selection criteria identify a large number of luminous and absorbed AGNs, yet again host contamination could lead to non-uniform and incomplete samples. Spectral Energy Distribution (SED) decomposition is able to decouple the emission from the AGN versus that from star-forming regions, revealing weaker AGN components. We aim to identify the obscured AGN population in the VIPERS survey in the CFHTLS W1 field through SED modelling. We construct SEDs for 6,860 sources and identify 160 AGNs at a high confidence level using a Bayesian approach. Using optical spectroscopy, we confirm the nature of ~85% of the AGNs. Our AGN sample is highly complete (~92%) compared to mid-IR colour selected AGNs, including a significant number of galaxy-dominated systems with lower luminosities. In addition to the lack of X-ray emission (80%), the SED fitting results suggest that the majority of the sources are obscured. We use a number of diagnostic criteria in the optical, infrared and X-ray regime to verify these results. Interestingly, only 35% of the most luminous mid-IR selected AGNs have X-ray counterparts suggesting strong absorption. Our work emphasizes the importance of using SED decomposition techniques to select a population of type II AGNs, which may remain undetected by either X-ray or IR colour surveys.Comment: Accepted for publication in MNRAS in May 4, 2020. 18 figures, 3 tables

Estimating Photometric Redshifts for X-ray sources in the X-ATLAS field, using machine-learning techniques

We present photometric redshifts for 1,031 X-ray sources in the X-ATLAS field, using the machine learning technique TPZ (Carrasco Kind & Brunner 2013). X-ATLAS covers 7.1 deg2 observed with the XMM-Newton within the Science Demonstration Phase (SDP) of the H-ATLAS field, making it one of the largest contiguous areas of the sky with both XMMNewton and Herschel coverage. All of the sources have available SDSS photometry while 810 have additionally mid-IR and/or near-IR photometry. A spectroscopic sample of 5,157 sources primarily in the XMM/XXL field, but also from several X-ray surveys and the SDSS DR13 redshift catalogue, is used for the training of the algorithm. Our analysis reveals that the algorithm performs best when the sources are split, based on their optical morphology, into point-like and extended sources. Optical photometry alone is not enough for the estimation of accurate photometric redshifts, but the results greatly improve when, at least, mid-IR photometry is added in the training process. In particular, our measurements show that the estimated photometric redshifts for the X-ray sources of the training sample, have a normalized absolute median deviation, n_mad=0.06, and the percentage of outliers, eta=10-14 percent, depending on whether the sources are extended or point-like. Our final catalogue contains photometric redshifts for 933 out of the 1,031 X-ray sources with a median redshift of 0.9.Comment: 10 pages, 13 figures, A&A accepte

Obscuration properties of mid-IR selected AGN

The goal of this work is to study the obscuration properties of mid-infrared (mid-IR) selected AGN. For that purpose, we use {\it{WISE}} sources in the Stripe 82-XMM area to identify mid-IR AGN candidates, applying the Assef et al. criteria. Stripe 82 has optical photometry $\approx$\,2 times deeper than any single-epoch SDSS region. XMM-Newton observations cover $\sim$26\,deg$^2$. Applying the aforementioned criteria, 1946 IR AGN are selected. $\sim 78\%$ have SDSS detection, while 1/3 of them is detected in X-rays, at a flux limit of $\rm \sim 5 \times 10^{-15}\,erg\,s^{-1}\,cm^{-2}$. Our final sample consists of 507 IR AGN with X-ray detection and optical spectra. Applying a $\rm r-W2>6$ colour criterion, we find that the fraction of optically red AGN drops from 43\% for those sources with SDSS detection to $23\%$ for sources that also have X-ray detection. X-ray spectral fitting reveals 40 ($\sim8\%$) X-ray absorbed AGN ($\rm N_H>10^{22}~cm^{-2}$). Among the X-ray unabsorbed AGN, there are 70 red systems. To further investigate the absorption of these sources, we construct Spectral Energy Distributions (SEDs) for the total IR AGN sample. SED fitting reveals that $\sim20\%$ of the optically red sources have such colours because the galaxy emission is a primary component in the optical part of the SED, even though the AGN emission is not absorbed at these wavelengths. SED fitting also confirms that $12\%$ of the X-ray unabsorbed, IR AGN are optically obscured.Comment: MNRAS accepted, 10 pages, 8 figure