arXiv subjects

George Mountrichas

Publications and source records attributed to George Mountrichas.

6 recordsLinked to original sources

arXiv2024

The miniJPAS Survey: The radial distribution of star formation rates in faint X-ray active galactic nuclei

We study the impact of black hole nuclear activity on both the global and radial star formation rate (SFR) profiles in X-ray-selected active galactic nuclei (AGN) in the field of miniJPAS, the precursor of the much wider J-PAS project. Our sample includes 32 AGN with z < 0.3 detected via the XMM-Newton and Chandra surveys. For comparison, we assembled a control sample of 71 star-forming (SF) galaxies with similar magnitudes, sizes, and redshifts. To derive the global properties of both the AGN and the control SF sample, we used CIGALE to fit the spectral energy distributions derived from the 56 narrowband and 4 broadband filters from miniJPAS. We find that AGN tend to reside in more massive galaxies than their SF counterparts. After matching samples based on stellar mass and comparing their SFRs and specific SFRs (sSFRs), no significant differences appear. This suggests that the presence of AGN does not strongly influence overall star formation. However, when we used miniJPAS as an integral field unit (IFU) to dissect galaxies along their position angle, a different picture emerges. We find that AGN tend to be more centrally concentrated in mass with respect to SF galaxies. Moreover, we find a suppression of the sSFR up to 1Re and then an enhancement beyond 1Re , strongly contrasting with the decreasing radial profile of sSFRs in SF galaxies. This could point to an inside-out quenching of AGN host galaxies. These findings suggest that the reason we do not see differences on a global scale is because star formation is suppressed in the central regions and enhanced in the outer regions of AGN host galaxies. While limited in terms of sample size, this work highlights the potential of the upcoming J-PAS as a wide-field low-resolution IFU for thousands of nearby galaxies and AGN.

astro-ph.GA↗

arXiv2023

The link between star-formation and supermassive black hole properties

It is well known that supermassive black holes (SMBHs) and their host galaxies co-evolve. AGN feedback plays an important role on this symbiosis. To study the effect of the AGN feedback on the host galaxy, a popular method is to study the star-formation rate (SFR) as a function of the X-ray luminosity (L$_X$). However, hydrodynamical simulations suggest that the cumulative impact of AGN feedback on a galaxy is encapsulated in the mass of the SMBH, M$_{BH}$, rather than the L$_X$. In this study, we compare the SFR of AGN and non-AGN galaxies as a function of L$_X$, M$_{BH}$, Eddington ratio (n$_{Edd}$) and specific black hole accretion rate ($λ_{sBHAR}$). For that purpose, we use 122 X-ray AGN in the XMM-XXL field and 3371 galaxies from the VIPERS survey and calculate the SFR$_{norm}$ parameter, defined as the ratio of the SFR of AGN to the SFR of non-AGN galaxies with similar stellar mass, M$_*$, and redshift. Our datasets span a redshift range of $\rm 0.5\leq z\leq 1.2$. The results show that the correlation between SFR$_{norm}$ and M$_{BH}$ is stronger compared to that between SFR$_{norm}$ and L$_X$. A weaker correlation is found between SFR$_{norm}$ and $λ_{sBHAR}$. No correlation is detected between SFR$_{norm}$ and n$_{Edd}$. These results corroborate the idea that the M$_{BH}$ is a more robust tracer of the cumulative impact of the AGN feedback compared to the instantaneous accretion rate (L$_X$) and, thus, a better predictive parameter of the changes of the SFR of the host galaxy.

astro-ph.GA↗

arXiv2023

Star formation in the dwarf Seyfert galaxy NGC 4395: Evidence for both AGN and SNe feedback?

We present a detailed multi-wavelength study of star formation in the dwarf galaxy NGC 4395 which hosts an active galactic nucleus (AGN). From our observations with the Ultra-Violet Imaging Telescope, we have compiled a catalogue of 284 star forming (SF) regions, out of which we could detect 120 SF regions in H$α$ observations. Across the entire galaxy, we found the extinction corrected star formation rate (SFR) in the far ultra-violet (FUV) to range from 2.0 $\times$ 10$^{-5}$ M$_\odot$yr$^{-1}$ to 1.5 $\times$ 10$^{-2}$ M$_\odot$yr$^{-1}$ with a median of 3.0 $\times$ 10$^{-4}$ M$_\odot$yr$^{-1}$ and age to lie in the range of $\sim$ 1 to 98 Myr with a median of 14 Myr. In H$α$ we found the SFR to range from 7.2 $\times$ 10$^{-6}$ M$_\odot$yr$^{-1}$ to 2.7 $\times$ 10$^{-2}$ M$_\odot$yr$^{-1}$ with a median of 1.7 $\times$ 10$^{-4}$ M$_\odot$yr$^{-1}$ and age to lie between 3 to 6 Myr with a median of 5 Myr. The stellar ages derived from H$α$ show a gradual decline with galactocentric distance. We found three SF regions close to the center of NGC~4395 with high SFR both from H$α$ and UV which could be attributed to feedback effects from the AGN. We also found six other SF regions in one of the spiral arms having higher SFR. These are very close to supernovae remnants which could have enhanced the SFR locally. We obtained a specific SFR (SFR per unit mass) for the whole galaxy 4.64 $\times$ 10$^{-10}$ yr$^{-1}$.

astro-ph.GA↗

arXiv2023

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.

astro-ph.GA↗

arXiv2022

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.

astro-ph.GA↗

arXiv2022

Fitting AGN/galaxy X-ray-to-radio SEDs with CIGALE and improvement of the code

Modern and future surveys effectively provide a panchromatic view for large numbers of extragalactic objects. Consistently modeling these multiwavelength survey data is a critical but challenging task for extragalactic studies. The Code Investigating GALaxy Emission (CIGALE) is an efficient PYTHON code for spectral energy distribution (SED) fitting of galaxies and active galactic nuclei (AGNs). Recently, a major extension of CIGALE (named X-CIGALE) has been developed to account for AGN/galaxy X-ray emission and improve AGN modeling at UV-to-IR wavelengths. Here, we apply X-CIGALE to different samples, including COSMOS spectroscopic type 2 AGNs, CDF-S X-ray detected normal galaxies, SDSS quasars, and COSMOS radio objects. From these tests, we identify several weaknesses of X-CIGALE and improve the code accordingly. These improvements are mainly related to AGN intrinsic X-ray anisotropy, X-ray binary emission, AGN accretion-disk SED shape, and AGN radio emission. These updates improve the fit quality and allow new interpretation of the results, based on which we discuss physical implications. For example, we find that AGN intrinsic X-ray anisotropy is moderate, and can be modeled as $L_X(θ) \propto 1+\cos θ$, where $θ$ is the viewing angle measured from the AGN axis. We merge the new code into the major branch of CIGALE, and publicly release this new version as CIGALE v2022.0 on https://cigale.lam.fr

astro-ph.GA↗