arXiv subjects

M. Singha

Publications and source records attributed to M. Singha.

11 recordsLinked to original sources

arXiv2025

The JWST View of Cygnus A: Jet-Driven Coronal Outflow with a Twist

We present first results from James Webb Space Telescope (JWST) Near-Infrared Spectrograph (NIRSpec), Mid-Infrared Instrument (MIRI), and Keck Cosmic Webb Imager (KCWI) integral field spectroscopy of the powerful but highly obscured host-galaxy of the jetted radio source Cygnus A. We detect 169 infrared emission lines at 1.7--27 micron and explore the kinematics and physical properties of the extended narrow-line region (NLR) in unprecedented detail. The density-stratified NLR appears to be shaped by the initial blow-out and ongoing interaction of the radio jet with the interstellar medium, creating a multi-phase bicone with a layered structure composed of molecular and ionized gas. The NLR spectrum, with strong coronal emission at kpc-scale, is well-modeled by AGN photoionization. We find evidence that the NLR is rotating around the radio axis, perhaps mediated by magnetic fields and driven by angular momentum transfer from the radio jet. The overall velocity field of the NLR is well described by 250 km/s outflow along biconical spiral flow lines, combining both rotation and outflow signatures. There is particularly bright [Fe II] 1.644 micron emission from a dense, high-velocity dispersion, photoionized clump of clouds found near the projected radio axis. Outflows of 600--2000 km/s are found in bullets and streamers of ionized gas that may be ablated by the radio jet from these clouds, driving a local outflow rate of 40 Msun/yr.

astro-ph.GA↗

arXiv2024

Cocoon shock, X-ray cavities and extended Inverse Compton emission in Hercules A: clues from Chandra observations

We present a detailed analysis of jet activity in the radio galaxy 3C348 at the center of the galaxy cluster Hercules A. We use archival Chandra data to investigate the jet-driven shock front, the radio-faint X-ray cavities, the eastern jet, and the presence of extended Inverse Compton (IC) X-ray emission from the radio lobes. We detect two pairs of shocks: one in the north-south direction at 150 kpc from the center, and another in the east-west direction at 280 kpc. These shocks have Mach numbers of $\mathcal{M} = 1.65\pm0.05$ and $\mathcal{M} = 1.9\pm0.3$, respectively. Together, they form a complete cocoon around the large radio lobes. Based on the distance of the shocks from the center, we estimate that the corresponding jet outburst is 90-150 Myr old. We confirm the presence of two radio-faint cavities within the cocoon, misaligned from the lobes, each $\sim$100 kpc wide and 40-60 Myr old. A backflow from the radio lobes might explain why the cavities are dynamically younger than the cocoon shock front. We also detect non-thermal X-ray emission from the eastern jet and from the large radio lobes. The X-ray emission from the jet is visible at 80 kpc from the AGN and can be accounted for by an IC model with a mild Doppler boosting ($\delta\sim2.7$). A synchrotron model could explain the radio-to-X-ray spectrum only for very high Lorentz factors $\gamma\geq10^{8}$ of the electrons in the jet. For the large radio lobes, we argue that the X-ray emission has an IC origin, with a 1 keV flux density of $21.7\pm1.4\text{(statistical)}\pm1.3\text{(systematic)}$ nJy. A thermal model is unlikely, as it would require unrealistically high gas temperature, density, and pressure, along with a strong depolarization of the radio lobes, which are instead highly polarized. The IC detection, combined with the synchrotron flux density, suggests a magnetic field of $12\pm3\mu$G in the lobes.

astro-ph.HE↗

arXiv2023

The Close AGN Reference Survey (CARS): An interplay between radio jets and AGN radiation in the radio-quiet AGN HE 0040-1105

We present a case study of HE 0040-1105, an unobscured radio-quiet AGN at a high accretion rate (Eddington ratio = 0.19+/-0.04). This particular AGN hosts an ionized gas outflow with the largest spatial offset from its nucleus compared to all other AGNs in the Close AGN Reference Survey (CARS). By combining multi-wavelength observations from VLT/MUSE, HST/WFC3, VLA, and EVN we probe the ionization conditions, gas kinematics, and radio emission from host galaxy scales to the central few pc. We detect four kinematically distinct components, one of which is a spatially unresolved AGN-driven outflow located within the central 500 pc, where it locally dominates the ISM conditions. Its velocity is too low to escape the host galaxy's gravitational potential, and maybe re-accreted onto the central black hole via chaotic cold accretion. We detect compact radio emission in HE 0040-1105,within the region covered by the outflow, varying on ~20 yr timescale. We show that neither AGN coronal emission nor star formation processes wholly explain the radio morphology/spectrum. The spatial alignment between the outflowing ionized gas and the radio continuum emission on 100 pc, scales is consistent with a weak jet morphology rather than diffuse radio emission produced by AGN winds. > 90% of the outflowing ionized gas emission originates from the central 100 pc, within which the ionizing luminosity of the outflow is comparable to the mechanical power of the radio jet. Although radio jets might primarily drive the outflow in HE 0040-1105,, radiation pressure from the AGN may contribute in this process.

astro-ph.GA↗

arXiv2023

Still alive and kicking: A significant outburst in changing-look AGN Mrk 1018

Changing-look active galactic nuclei (CL-AGN) have been observed to change optical spectral type. Mrk 1018 is unique: first classified as a type 1.9 Seyfert galaxy, it transitioned to a type 1 before returning to its initial classification after approximately 30 years. We present a high-cadence monitoring programme that caught a major outburst in 2020. Due to sunblock, only the decline could be observed. We studied X-ray, UV, optical, and IR before and after the outburst to investigate the responses of the AGN structures. We derived a u'-band light curve of the AGN contribution alone. The flux increased by a factor of the order of 13. We confirmed this in other optical bands and determined the shape and speed of the decline in each waveband. The shapes of H beta and H alpha were analysed before and after the event. Two XMM-Newton observations from before and after the outburst were also exploited. The outburst is asymmetric, with a swifter rise than decline. The decline is best fit by a linear function, ruling out a tidal disruption event. The optical spectrum shows no change approximately 8 months before and 17 months after. The UV flux increased slightly after the outburst but the X-ray primary flux is unchanged. However, the 6.4 keV Iron line has doubled in strength. IR data taken 13 days after the observed optical peak show an increased emission level. Calculating the distance of the broad-line region and inner edge of the torus from the supermassive black hole can explain the multi-wavelength response to the outburst, in particular: i) the unchanged H beta and H alpha lines, ii) the unchanged primary X-ray spectral components, iii) the rapid and extended infrared response, as well as iv) the enhanced emission of the reflected 6.4 keV line. The outburst was due to a dramatic and short-lasting change in the intrinsic accretion rate. We discuss different models as potential causes.

astro-ph.HE↗

arXiv2022

The Close AGN Reference Survey (CARS): Tracing the circumnuclear star formation in the super-Eddington NLS1 Mrk 1044

The host galaxy conditions for rapid supermassive black hole growth are poorly understood. Narrow-line Seyfert 1 (NLS1) galaxies often exhibit high accretion rates and are hypothesized to be prototypes of active galactic nuclei (AGN) at an early stage of their evolution. We present VLT MUSE NFM-AO observations of Mrk 1044, the nearest super-Eddington accreting NLS1. Together with archival MUSE WFM data we aim to understand the host galaxy processes that drive Mrk 1044's black hole accretion. We extract the faint stellar continuum emission from the AGN-deblended host and perform spatially resolved emission line diagnostics with an unprecedented resolution. Combining both MUSE WFM and NFM-AO observations, we use a kinematic model of a thin rotating disk to trace the stellar and ionized gas motion from 10$\,$kpc down to 30$\,$pc around the nucleus. Mrk 1044's stellar kinematics follow circular rotation, whereas the ionized gas shows tenuous spiral features in the center. We resolve a compact star forming circumnuclear ellipse (CNE) that has a semi-minor axis of 306$\,$pc. Within this CNE, the gas is metal rich and its line ratios are entirely consistent with excitation by star formation. With an integrated SFR of $0.19 \pm 0.05 \,{\rm M}_\odot\,{\rm yr}^{-1}$ the CNE contributes 27% of the galaxy-wide star formation. We conclude that Mrk 1044's nuclear activity has not yet affected the circumnuclear star formation. Thus, Mrk 1044 is consistent with the idea that NLS1s are young AGN. A simple mass budget consideration suggests that the circumnuclear star formation and AGN phase are connected and the patterns in the ionized gas velocity field are a signature of the ongoing AGN feeding.

astro-ph.GA↗

arXiv2021

The Close AGN Reference Survey (CARS): IFU survey data and the BH mass dependence of long-term AGN variability

[Abridged] AGN are thought to be intimately connected with their host galaxies through feeding and feedback processes. A spatially resolved multiwavelength survey is required to map the interaction of AGN with their host galaxies on different spatial scales and different phases of the ISM. The goal of CARS is to obtain the necessary spatially resolved multiwavelength observations for an unbiased sample of local unobscured luminous AGN. We present the overall CARS survey design and the associated wide-field optical IFU spectroscopy for all 41 CARS targets at z<0.06 randomly selected from the Hamburg/ESO survey of luminous unobscured AGN. This data set provides the backbone of CARS and allows us to characterize host galaxy morphologies, AGN parameters, precise systemic redshifts, and ionized gas distributions including excitation conditions, kinematics, and metallicities in unprecedented detail. We focus our study on the size of the ENLR which has been traditionally connected to AGN luminosity. Given the large scatter in the ENLR size-luminosity relation, we performed a large parameter search to identify potentially more fundamental relations. Remarkably, we identified the strongest correlation between the maximum projected ENLR size and the black hole mass, consistent with an $R_\mathrm{ENLR,max}\sim M_\mathrm{BH}^{0.5}$ relationship. We interpret the maximum ENLR size as a timescale indicator of a single BH radiative-efficient accretion episode for which we inferred log(t_AGN) = (0.45+- 0.08)log(M_BH)+1.78 using forward modeling. The extrapolation of our inferred relation toward higher BH masses is consistent with an independent lifetime estimate from the HeII proximity zones around luminous AGN at z~3. While our proposed link between the BH mass and AGN lifetime might be a secondary correlation itself or impacted by unknown biases, it has a few relevant implications if confirmed.

astro-ph.GA↗

arXiv2021

The Close AGN Reference Survey (CARS): Locating the [O III] wing component in luminous local Type 1 AGN

[Abridged]The strong asymmetry in the optical [O III]$λ$5007 emission line is one of the best signatures of AGN-driven warm (~10$^4$ K) ionized gas outflows on host galaxy scales. While large spectroscopic surveys like SDSS have characterized the kinematics of [O III] for large samples of AGN, estimating the associated energetics requires spatially resolving these outflows with, for example, IFU studies. As part of CARS we obtained spatially-resolved IFU spectroscopy for a representative sample of 39 luminous type 1 AGN at 0.01 80 % of the flux associated with a point-like source. We measure <100 pc offsets in the spatial location of the outflow from the AGN nucleus using the spectro-astrometry technique for these sources. For the other 13 AGN, the [O III] wing emission is resolved and possibly extended on kpc scale. We conclude that [O III] wing emission can be compact or extended in an unbiased luminous AGN sample, where both cases are likely to appear. Electron density in the compact [O III] wing regions (median $n_e$~1900 cm$^{-3}$) is nearly a magnitude higher than in the extended ones (median $n_e$~500 cm$^{-3}$). The presence of spatially extended and compact [O III] wing emission is unrelated to the AGN bolometric luminosity and to inclination effects, which means other features such as time delays, or mechanical feedback/radio jets may shape the ionized gas outflow properties.

astro-ph.GA↗

arXiv2021

The Close AGN Reference Survey (CARS): No obvious signature of AGN feedback on star formation, but subtle trends

[Abridged] Active Galactic Nuclei (AGN) are thought to be responsible for the suppression of star formation in massive ~10$^{10}$ M$_\odot$ galaxies. While this process is a key feature in numerical simulations, it is not yet unambiguously confirmed in observational studies. Characterization of the star formation rate (SFR) in AGN host galaxies is challenging as AGN light contaminates most SFR tracers. 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. We construct integrated panchromatic spectral energy distributions (SED) to measure the FIR luminosity as a tracer for the recent (< 100 Myr) SFR. In addition, we use integral-field unit observation of the CARS targets to employ the H$α$ luminosity decontaminated by AGN excitation as a proxy for the current (< 5 Myr) SFR. 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. 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. AGN can occur in various stages of galaxy evolution which makes it difficult to relate the SFR solely to the impact of the AGN. We do not find any strong evidence for 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 2) the recent SFH is an additional tool to identify rapid changes in galaxy growth driven by the AGN or other processes.

astro-ph.GA↗

arXiv2019

The Close AGN Reference Survey (CARS). A massive multi-phase outflow impacting the edge-on galaxy HE1353-1917

[Abridged] We combine extensive spatially-resolved multi-wavelength observations, taken as part of the Close AGN Reference Survey (CARS), for the edge-on disc galaxy HE1353-1917 to characterize the impact of the AGN on its host galaxy via outflows and radiation. Multi-color broad-band photometry is combined with spatially-resolved optical, NIR and sub-mm and radio observations taken with VLT/MUSE, Gemini-N/NIFS, ALMA and the VLA to map the physical properties and kinematics of the multi-phase inter-stellar medium (ISM). We detect a biconical extended narrow-line region (ENLR) ionized by the luminous AGN oriented nearly parallel to the galaxy disc, extending out to at least 25kpc. The extra-planar gas originates from galactic fountains initiated by star formation processes in the disc, rather than an AGN outflow, as shown by the kinematics and the metallicity of the gas. Nevertheless, a fast multi-phase AGN-driven outflow with speeds up to 1000km/s is detected close to the nucleus at 1kpc distance. A radio jet, in connection with the AGN radiation field, is likely responsible for driving the outflow as confirmed by the energetics and the spatial alignment of the jet and multi-phase outflow. Evidence for negative AGN feedback suppressing the star formation rate (SFR) is mild and restricted to the central kpc. But while any SFR suppression must have happened recently, the outflow has the potential to greatly impact the future evolution of the galaxy disc due to its geometrical orientation. Our observations reveal that low-power radio jets can play a major role in driving fast multi-phase galaxy-scale outflows even in radio-quiet AGN. Since the outflow energetics for HE1353-1917 are consistent with literature scaling relations of AGN-driven outflows the contribution of radio jets as the driving mechanisms still needs to be systematically explored.

astro-ph.GA↗

arXiv2019

The Close AGN Reference Survey (CARS). Discovery of a global [CII] 158 $μ$m line excess in AGN HE1353-1917

The [CII]158$μ$m line is one of the strongest far-infrared (FIR) lines and an important coolant in the interstellar medium of galaxies that is accessible out to high redshifts. The excitation of [CII] is complex and can best be studied in detail at low redshifts. Here we report the discovery of the highest global [CII] excess with respect to the FIR luminosity in the nearby AGN host galaxy HE1353-1917. This galaxy is exceptional among a sample of five targets because the AGN ionization cone and radio jet directly intercept the cold galactic disk. As a consequence, a massive multiphase gas outflow on kiloparsec scales is embedded in an extended narrow-line region. Because HE1353-1917 is distinguished by these special properties from our four bright AGN, we propose that a global [CII] excess in AGN host galaxies could be a direct signature of a multiphase AGN-driven outflow with a high mass-loading factor.

astro-ph.GA↗

arXiv2012

Fuzzy sequential topological spaces(FSTS)

In this paper we define fuzzy sequential topology on a non empty set X which is a collection of fuzzy sequential sets satisfying certain conditions given in its definition and many pleasant properties of a countable number of fuzzy topologies on X associated as components of a FST are investigated.

math.GN↗