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Register a new userMultiwavelength morphological study of active galaxies
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Studying the morphology of a large sample of active galaxies at different wavelengths and comparing it with active galactic nuclei (AGN) properties, such as black hole mass ($M_{BH}$) and Eddington ratio ($lambda_{Edd}$), can help us in understanding better the connection between AGN and their host galaxies and the role of nuclear activity in galaxy formation and evolution. By using the BAT-SWIFT hard X-ray public data and by extracting those parameters measured for AGN and by using other public catalogues for parameters such as stellar mass ($M_*$), star formation rate (SFR), bolometric luminosity ($L_{bol}$), etc., we studied the multiwavelength morphological properties of host galaxies of ultra-hard X-ray detected AGN and their correlation with other AGN properties. We found that ultra hard X-ray detected AGN can be hosted by all morphological types, but in larger fractions (42%) they seem to be hosted by spirals in optical, to be quiet in radio, and to have compact morphologies in X-rays. When comparing morphologies with other galaxy properties, we found that ultra hard X-ray detected AGN follow previously obtained relations. On the SFR vs. stellar mass diagram, we found that although the majority of sources are located below the main sequence (MS) of star formation (SF), still non-negligible number of sources, with diverse morphologies, is located on and/or above the MS, suggesting that AGN feedback might have more complex influence on the SF in galaxies than simply quenching it, as it was suggested in some of previous studies.
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We tested how the AGN contribution (5% - 75% of the total flux) may affect different morphological parameters commonly used in galaxy classification. We carried out all analysis at $z$,$sim$,0 and at higher redshifts that correspond to the COSMOS field. Using a local training sample of $>$,2000 visually classified galaxies, we carried out all measurements with and without the central source and quantified how the contribution of a bright nuclear point source could affect different morphological parameters, such as: Abraham and Concelice-Bershady indices, Gini, Asymmetry, $M20$ moment of light, and Smoothness. We found that concentration indexes are less sensitive to both redshift and brightness in comparison to the other parameters. We also found that all parameters change significantly with AGN contribution. At $z$$sim$0, up to a 10% of AGN contribution the morphological classification will not be significantly affect, but for $ge$25% of AGN contribution late-type spirals follow the range of parameters of elliptical galaxies and can therefore be misclassified early types.
Star-forming regions are usually studied in the context of Galactic surveys, but dedicated observations are sometimes needed when the study reaches beyond the survey area. Here, we studied the G345.5+1.5 region, which is located slightly above the Galactic plane, to understand its star formation properties. We combined the LABOCA and $^{12}$CO(4$-$3) transition line observations complemented with the Hi-GAL and $it{Spitzer}$-GLIMPSE surveys to study the star formation toward this region. We used the Clumpfind algorithm to extract the clumps from the 870$mu$m and $^{12}$CO(4$-$3) data. Radio emission at 36cm was used to estimate the number of HII regions and to remove the contamination from the free-free emission at 870$mu$m. We employed color-color diagrams and spectral energy distribution slopes to distinguish between prestellar and protostellar clumps. We studied the boundedness of the clumps through the virial parameter. Finally, we estimated the star formation efficiency and star formation rate of the region and used the Schmidt-Kennicutt diagram to compare its ability to form stars. Of the 13 radio sources that we found using the MGPS-2 catalog, 7 are found to be associated with HII regions corresponding to late-B or early-O stars. We found 45 870$mu$m clumps, and 107 $^{12}$CO clumps. More than 50% of the clumps are protostellar and bounded and are able to host star formation. High SFR and SFR density values are associated with the region, with an SFE of a few percent. With submillimeter, CO transition, and short-wavelength infrared observations, our study reveals a population of massive stars, protostellar and bound starless clumps, toward G345.5+1.5. This region is therefore actively forming stars, and its location in the starburst quadrant of the Schmidt-Kennicutt diagram is comparable to other star-forming regions found within the Galactic plane.
We present a multiwavelength analysis of 20 EUV jets which occurred at the periphery of active regions close to sunspots. We discuss the physical parameters of the jets and their relation with other phenomena such as H alpha surges, nonthermal type III radio bursts and hard X-ray emission. Using AIA wavelength channels sensitive to coronal temperatures, we studied the temperature distribution in the jets using the line-of-sight Differential Emission Measure technique. We also investigated the role of the photospheric magnetic field using the LOS magnetogram data from the HMI. The lifetime of jets range from 5 to 39 minutes with an average of 18 minutes and their velocities range from 87 to 532 km/s with an average of 271 km/s. Most of the jets are co-temporal with nonthermal type III radio bursts observed by the Wind/WAVES spacecraft. We confirm the source region of these bursts using the Potential Field Source Surface technique. 10 out of 20 events showed that the jets originated in a region of flux cancellation and 6 jets in a region of flux emergence. 4 events showed flux emergence and then cancellation during the jet evolution. DEM analyses showed that for most of the spires of the jets, the DEM peaked at around log T [K] = 6.2/6.3. In addition, we derived an emission measure and a lower limit of electron density at the location of the spire and the footpoint. These results are in agreement with those obtained earlier by studying individual active region jets. The observation of flux cancellation, the association with HXR emission and emission of nonthermal type III radio bursts, suggest that the initiation and therefore, heating is taking place at the base of the jet. This is also supported by the high temperature plasma revealed by the DEM analysis in the jet footpoint. Our results provide substantial constraints for theoretical modeling of the jets and their thermodynamic nature.
We perform a systematic X-ray spectroscopic analysis of 57 local ultra/luminous infrared galaxy systems (containing 84 individual galaxies) observed with Nuclear Spectroscopic Telescope Array and/or Swift/BAT. Combining soft X-ray data obtained with Chandra, XMM-Newton, Suzaku and/or Swift/XRT, we identify 40 hard ($>$10 keV) X-ray detected active galactic nuclei (AGNs) and constrain their torus parameters with the X-ray clumpy torus model XCLUMPY (Tanimoto et al. 2019). Among the AGNs at $z < 0.03$, for which sample biases are minimized, the fraction of Compton-thick ($N_{rm H} geq 10^{24}$ cm$^{-2}$) AGNs reaches 64$^{+14}_{-15}$% (6/9 sources) in late mergers, while 24$^{+12}_{-10}$% (3/14 sources) in early mergers, consistent with the tendency reported by Ricci et al. (2017). We find that the bolometric AGN luminosities derived from the infrared data increase, but the X-ray to bolometric luminosity ratios decrease, with merger stage. The X-ray weak AGNs in late mergers ubiquitously show massive outflows at sub-pc to kpc scales. Among them, the most luminous AGNs ($L_{rm bol,AGN} sim 10^{46}$ erg s$^{-1}$) have relatively small column densities of $lesssim$10$^{23}$ cm$^{-2}$ and almost super-Eddington ratios ($lambda_{rm Edd} sim$ 1.0). Their torus covering factors ($C_{rm T}^{rm (22)} sim 0.6$) are larger than those of Swift/BAT selected AGNs with similarly high Eddington ratios. These results suggest a scenario that, in the final stage of mergers, multiphase strong outflows are produced due to chaotic quasi-spherical inflows and the AGN becomes extremely X-ray weak and deeply buried due to obscuration by inflowing and/or outflowing material.
We study the morphological transformation from late types to early types and the quenching of galaxies with the seventh Data Release (DR7) of the Sloan Digital Sky Survey (SDSS). Both early type galaxies and late type galaxies are found to have bimodal distributions on the star formation rate versus stellar mass diagram ($lg SFR - lg M_*$). We therefore classify them into four types: the star-forming early types (sEs), the quenched early types (qEs), the star-forming late types (sLs) and the quenched late types (qLs). We checked many parameters on various environmental scales for their potential effects on the quenching rates of late types and early types, as well as the early type fractions among star-forming galaxies and those among quenched galaxies. These parameters include: the stellar mass $M_*$, and the halo mass $M_{halo}$; the small-scale environmental parameters, such as the halo centric radius $R_p/r_{180}$ and the third nearest neighbor distances ($d_{3nn}$); the large-scale environmental parameters, specifically whether they are located in clusters, filaments, sheets, or voids. We found that the morphological transformation is mainly regulated by the stellar mass. Quenching is mainly driven by the stellar mass for more massive galaxies and by the halo mass for galaxies with smaller stellar masses. In addition, we see an overall stronger halo quenching effect in early type galaxies, which might be attributed to their lacking of cold gas or earlier accretion into the massive host halos.
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