The Close AGN Reference Survey (CARS)

Abstract

Context. Active galactic nuclei (AGN) are thought to be responsible for the suppression of star formation in massive ∼1010 M⊙ galaxies. While this process is a key feature in numerical simulations of galaxy formation, it has not been unambiguously confirmed in observational studies yet. Aims. The characterization of the star formation rate (SFR) in AGN host galaxies is challenging as AGN light contaminates most SFR tracers. Furthermore, the various SFR tracers are sensitive to different timescales of star formation from approximately a few to 100 Myr. We aim to obtain and compare SFR estimates from different tracers for AGN host galaxies in the Close AGN Reference Survey (CARS) to provide new observational insights into the recent SFR history of those systems. Methods. We constructed integrated panchromatic spectral energy distributions to measure the far infrared (FIR) luminosity as a tracer for the recent (< 100 Myr) SFR. In addition we used the integral-field unit observation of the CARS targets to employ the Hα luminosity decontaminated by AGN excitation as a proxy for the current (< 5 Myr) SFR. Results. We find that significant differences in specific SFR of the AGN host galaxies as compared with the larger galaxy population disappear once cold gas mass, in addition to stellar mass, is used to predict the SFR for a specific AGN host. Only a tentative trend with the inclination of the host galaxy remains, such that SFR appears slightly lower than expected when the galaxies of unobscured AGN appear more edge-on along our line-of-sight, particular for dust-insensitive FIR-based SFRs. We identify individual galaxies with a significant difference in their SFR which can be related to a recent enhancement or decline in their SFR history that might be related to various processes including interactions, gas consumption, outflows, and AGN feedback. Conclusions. AGN can be present in various stages of galaxy evolution which makes it difficult to relate the SFR solely to the impact of the AGN. Our study shows that stellar mass alone is an insufficient parameter to estimate the expected SFR of an AGN host galaxy compared to the underlying non-AGN galaxy population. We do not find any strong evidence for a global positive or negative AGN feedback in the CARS sample. However, there is tentative evidence that (1) the relative orientation of the AGN engine with respect to the host galaxies might alter the efficiency of AGN feedback and that (2) the recent SFH is an additional tool to identify rapid changes in galaxy growth driven by the AGN or other processes.

The Collisional and Photoionized Plasma in the Polarized NLS1 galaxy Mrk 1239

“…Using a relationship between the 𝐿 2−10 keV of the CIE and star formation rate (SFR) (Franceschini et al 2003), the SFR of Mrk 1239 was found to be 4 − 6 M yr −1 . This is comparable with the SFR of < 7.5 M yr −1 measured using PAH signatures (Ruschel-Dutra et al 2016), ∼ 3.5 M yr −1 found using SED fitting (Gruppioni et al 2016), and ∼ 2.1 M yr −1 found using IR measurements (Smirnova-Pinchukova et al 2022). To fully probe the soft band of this galaxy and determine the origin of the 0.91 keV feature conclusively deeper observations of Mrk 1239 were needed.…”

The Close AGN Reference Survey (CARS)

“…Together with the LOS projection, different ionization conditions are inevitably captured within one spaxel. Furthermore, different ISM metallicities and densities lead to the star-forming cloud occupying a large area in the BPT diagram (e.g., Smirnova-Pinchukova et al 2022). Nonetheless, the vast majority of spaxels in the MUSE NFM FOV is consistent with excitation through SF.…”

The Star-forming Main Sequence of the Host Galaxies of Low-redshift Quasars

“…Nearby, low-luminosity AGNs mainly lie in the green valley (e.g., Salim et al 2007;Leslie et al 2016), the sparsely populated region with reduced SFR below the MS, or are altogether quiescent (Ho et al 2003). By contrast, their more luminous counterparts, the quasars, can be found below (e.g., Shimizu et al 2015;Stemo et al 2020), on (e.g., Husemann et al 2014;Woo et al 2017;Smirnova-Pinchukova et al 2022), or even above (e.g., Jarvis et al 2020;Shangguan et al 2020b;Xie et al 2021;Koutoulidis et al 2022) the starforming galaxy MS. Several factors contribute to this confusing status of affairs, including the wavelength used for sample selection (X-ray, optical, infrared, or radio), the methodology and uncertainties associated with SFR and stellar mass determination, and even the very shape and normalization of the MS used for reference comparison. Recent works suggest that the position of an AGN relative to the MS is correlated with the Eddington ratio (e.g., Shimizu et al 2015;Ellison et al 2016;Woo et al 2020;Torbaniuk et al 2021), with higher SFRs found in hosts of AGNs with higher Eddington ratio.…”