Searcharxiv⌕ Search

arXiv subjects

Cristina Ramos Almeida

Publications and source records attributed to Cristina Ramos Almeida.

At least 73 records · Page 4Linked to original sources
arXiv2022

The complex infrared dust continuum emission of NGC1068: ground-based N- and Q-band spectroscopy and new radiative transfer models

Thanks to ground-based infrared and sub-mm observations the study of the dusty torus of nearby AGN has greatly advanced in the last years. With the aim of further investigating the nuclear mid-infrared emission of the archetypal Seyfert 2 galaxy NGC1068, here we present a fitting to the N- and Q-band Michelle/Gemini spectra. We initially test several available SED libraries, including a smooth, clumpy and two phase torus models, and a clumpy disk plus wind model. Although, the smooth torus model describe the spectra of NGC1068 if we allow to vary some model parameters among the two spectral bands. Motivated by this result, we produced new SEDs using the radiative transfer code SKIRT. We use two concentric tori that allow us to test a more complex geometry. We test different values for the inner and outer radii, half opening angle, radial and polar exponent of the power-law density profile, opacity, and viewing angle. Furthermore, we also test the dust grains size and different optical and calorimetric properties of silicate grains. The best fitting model consists of two concentric components with outer radii of 1.8 and 28 pc, respectively. We find that the size and the optical and calorimetric properties of graphite and silicate grains in the dust structure are key to reproduce the spectra of NGC1068. We conclude that the dust in NGC1068 reaches different scales, where the highest contribution to the mid-infrared is given by a central and compact component. A less dense and extended component is present, which can be either part of the same torus (conforming a flared disk) or can represent the emission of a polar dust component, as already suggested from interferometric observations.

astro-ph.GA↗
arXiv2021

HARMONI view of the host galaxies of active galactic nuclei around cosmic noon: Resolved stellar morpho-kinematics and the M$_{BH}$-$σ_{\star}$ relation

Context. The formation and evolution of galaxies appear linked to the growth of supermassive black holes, as evidenced by empirical scaling relations in nearby galaxies. Understanding this co-evolution over cosmic time requires the revelation of the dynamical state of galaxies and the measurement of the mass of their central black holes (MBH) at a range of cosmic distances. Bright active galactic nuclei (AGNs) are ideal for this purpose. Aims. The High Angular Resolution Monolithic Optical and Near-infrared Integral field spectrograph (HARMONI), the first light integral-field spectrograph for the Extremely Large Telescope (ELT), will transform visible and near-infrared ground-based astrophysics thanks to its advances in sensitivity and angular resolution. We aim to analyse the capabilities of HARMONI to reveal the stellar morpho-kinematic properties of the host galaxies of AGNs at about cosmic noon. Methods. We made use of the simulation pipeline for HARMONI (HSIM) to create mock observations of representative AGN host galaxies at redshifts around cosmic noon. We used observations taken with the Multi-Unit Spectroscopic Explorer (MUSE) of nearby galaxies showing different morphologies and dynamical stages combined with theoretical AGN spectra to create the target inputs for HSIM. Results. According to our simulations, an on-source integration time of three hours should be enough to measure the MBH and to trace the morphology and stellar kinematics of the brightest host galaxies of AGNs beyond cosmic noon. For host galaxies with stellar masses $<$10$^{11}$ solar masses, longer exposure times are mandatory to spatially resolve the stellar kinematics.

astro-ph.GA↗
arXiv2021

Capturing dual AGN activity and kiloparsec-scale outflows in IRAS 20210+1121

The most accepted scenario for the evolution of massive galaxies across cosmic time predicts a regulation based on the interplay between AGN feedback, which injects large amounts of energy in the host environment, and galaxy mergers, being able to trigger massive star formation events and accretion onto the supermassive black holes. Interacting systems hosting AGN are useful laboratories to get key insights into both phenomena. In this context, we present the analysis of the optical spectral properties of IRAS 20210+1121 (I20210), a merging system at $z = 0.056$. According to X-ray data, this object comprises two interacting galaxies, each hosting an obscured AGN. The optical spectra confirm the presence of AGN features in both galaxies. In particular, we are able to provide a Seyfert classification for I20210 North. The spectrum of I20120 South shows broad blueshifted components associated with the most intense emission lines that indicate the presence of an ionized outflow, for which we derive a maximum velocity of $\sim$2000 km s$^{-1}$, an extension of $\sim$2 kpc and a mass rate of $\sim$0.6 M$_\odot$ yr$^{-1}$. We also report the existence of an ionized nebular component with $v \sim 1000$ km s$^{-1}$ at $\sim$6.5 kpc Southwards of I20210 South, that can be interpreted as disrupted gas ejected from the host galaxy by the action of the outflow. I20120 therefore exhibits a double obscured AGN, with one of them showing evidence of ongoing events for AGN-powered outflows. Future spatially-resolved spectroscopy will allow to accurately map on the gas kinematics in this AGN pair and evaluate the impact of the outflow on both the interstellar medium and galaxy environment.

astro-ph.GA↗
arXiv2021

The dust-gas AGN torus as constrained from X-ray and mid-infrared observations

In the last decades, several multiwavelength studies have been dedicated to exploring the properties of the obscuring material in active galactic nuclei (AGN). Various models have been developed to describe the structure and distribution of this material and constrain its physical and geometrical parameters through spectral fitting techniques. However, questions, including how the torus mid-infrared (mid-IR) and X-ray emission are related remain unanswered. In this work, we study whether the dust continuum at mid-IR and gas reflection at X-rays have the same distribution in a sample of AGN. We carefully selected a sample of 36 nearby AGN with NuSTAR and Spitzer spectra available in both archives. We derived the properties of the nuclear dust and gas through a spectral fitting, using models developed for mid-IR and X-ray wavelengths assuming smooth and clumpy distributions for this structure. We found that a combination of smooth and clumpy distributions of gas and dust, respectively, is preferred for ~80% of sources with good spectral fits according to the Akaike criterion. However, considering extra information about each individual source, such as the absorption variability, we found that ~50% of our sources are best described by a clumpy distribution of both dust and gas. The remaining ~50% of our sources can still be explained with a smooth distribution of gas and a clumpy distribution of dust. The results presented in this paper suggest that the distribution of the gas and dust in AGN is complex. We find at least six scenarios to explain the observed properties of our sample. In these scenarios, three gas-dust distribution combinations are possible: clumpy-clumpy, smooth-smooth, and smooth-clumpy. Most of them are in agreement with the notion that gas could also be located in the dust-free region, which is consistent with the dust-to-gas ratio found.

astro-ph.GA↗
arXiv2019

A near-infrared study of the multi-phase outflow in the type-2 quasar J1509+0434

Based on new near-infrared spectroscopic data from the instrument EMIR on the 10.4 m Gran Telescopio Canarias (GTC) we report the presence of an ionized and warm molecular outflow in the luminous type-2 quasar J150904.22+043441.8 (z = 0.1118). The ionized outflow is faster than its molecular counterpart, although the outflow sizes that we derive for them are consistent within the errors (1.34$\pm$0.18 kpc and 1.46$\pm$0.20 kpc respectively). We use these radii, the broad emission-line luminosities and in the case of the ionized outflow, the density calculated from the trans-auroral [OII] and [SII] lines, to derive mass outflow rates and kinetic coupling efficiencies. Whilst the ionized and warm molecular outflows represent a small fraction of the AGN power ($\leq$0.033% and 0.0001% of L$_{bol}$ respectively), the total molecular outflow, whose mass is estimated from an assumed warm-to-cold gas mass ratio of 6$\times10^{-5}$, has a kinetic coupling efficiency of $\sim$1.7%L$_{bol}$. Despite the large uncertainty, this molecular outflow represents a significant fraction of L$_{bol}$ and it could potentially have a significant impact on the host galaxy. In addition, the quasar spectrum reveals bright and patchy narrow Pa$α$ emission extending out to 4 arcsec (8 kpc) South-East and North-West from the active nucleus.

astro-ph.GA↗
arXiv2019

Do AGN triggering mechanisms vary with radio power? I.Optical morphologies of radio-intermediate HERGs

Radio AGNs with intermediate radio powers are capable of driving multi-phase outflows in galaxy bulges, and are also more common than their high-radio-power counterparts. In-depth characterisation of the typical host galaxies and likely triggering mechanisms for this population is therefore required in order to better understand the role of radio AGN feedback in galaxy evolution. Here, we use deep optical imaging data to study the detailed host morphologies of a complete sample of 30 local radio AGNs with high-excitation optical emission (HERG) spectra and intermediate radio powers (z $<$ 0.1; 22.5 $<$ log(L$_{\rm 1.4GHz}$) $<$ 24.0 WHz$^{-1}$). The fraction of hosts with morphological signatures of mergers and interactions is greatly reduced compared to the 2 Jy radio-powerful galaxies (log(L$_{\rm 1.4GHz}$) $>$ 25.0 WHz$^{-1}$) with strong optical emission lines: 53 $\pm$ 9 per cent and 94 $\pm$ 4 per cent, respectively. In addition, the most radio-powerful half of the sample has a higher frequency of morphological disturbance than the least radio-powerful half (67 $\pm$ 12 per cent and 40 $\pm$ 13 per cent, respectively), including the eight most highly-disturbed galaxies. This suggests that the importance of triggering nuclear activity in HERGs through mergers and interactions reduces with radio power. Both visual inspection and detailed light profile modelling reveal a mixed population of early-type and late-type morphologies, contrary to the massive elliptical galaxy hosts of radio-powerful AGNs. The prevalence of late-type hosts could suggest that triggering via secular, disk-based processes has increased importance for HERGs with lower radio powers (e.g. disk instabilities, large scale bars).

astro-ph.GA↗
arXiv2018

The host galaxy of the gamma-ray-emitting narrow-line Seyfert 1 galaxy PKS 1502+036

The detection of gamma-ray emission from narrow-line Seyfert 1 galaxies (NLSy1) has challenged the idea that large black hole (BH) masses ($\ge$10$^8$ M$_{\odot}$) are needed to launch relativistic jets. We present near-infrared imaging data of the gamma-ray-emitting NLSy1 PKS 1502+036 obtained with the Very Large Telescope. Its surface brightness profile, extending to $\sim$ 20 kpc, is well described by the combination of a nuclear component and a bulge with a Sersic index $n$ = 3.5, which is indicative of an elliptical galaxy. A circumnuclear structure observed near PKS 1502+036 may be the result of galaxy interactions. A BH mass of about $\sim 7 \times 10^{8}$ M$_{\odot}$ has been estimated by the bulge luminosity. The presence of an additional faint disc component cannot be ruled out with the present data, but this would reduce the BH mass estimate by only $\sim$ 30%. These results, together with analogous findings obtained for FBQS J1644+2619, indicate that the relativistic jets in gamma-ray-emitting NLSy1 are likely produced by massive black holes at the center of elliptical galaxies.

astro-ph.GA↗
arXiv2018

Circumnuclear star-formation and AGN activity: Clues from surface brightness radial profile of PAHs and [SIV]

We studied the circumnuclear MIR emission in a sample of 19 local active galactic nuclei (AGN) with high spatial resolution spectra using T-ReCS (Gemini) and CanariCam (GTC), together with IRS/Spitzer observations. We measured the flux and the equivalent width for the 11.3 micron PAH feature and the [SIV] line emission as a function of galactocentric distance. This allowed to study the star formation (SF) at sub-kpc scales from the nucleus for a large sample of nearby AGN. The [SIV] line emission could be tracing the AGN radiation field within a few thousand times the sublimation radius (R_sub), but it often peaks at distances greater than 1000 R_sub. One possibility is that the SF is contributing to the [SIV] total flux. We found an 11.3 micron PAH emission deficit within the inner few tens of parsecs from the AGN. This deficit might be due to the destruction of the molecules responsible for this feature or the lack of SF at these distances. We found a sensible agreement in the expected shift of the relation of the AGN bolometric luminosity and the SF rate. This indicates that numerical models attributing the link between AGN activity and host galaxy growth to mergers are in agreement with our data, for most inner galaxy parts.

astro-ph.GA↗
arXiv2018

The emission and distribution of dust of the torus of NGC 1068

We present observations of NGC 1068 covering the $19.7-53.0$ $μ$m wavelength range using FORCAST and HAWC+ onboard SOFIA. Using these observations, high-angular resolution infrared (IR) and sub-mm observations, we find an observational turn-over of the torus emission in the $30-40$ $μ$m wavelength range with a characteristic temperature of $70-100$ K. This component is clearly different from the diffuse extended emission in the narrow line and star formation regions at 10-100 $μ$m within the central 700 pc. We compute $2.2-432$ $μ$m 2D images using the best inferred \textsc{clumpy} torus model based on several nuclear spectral energy distribution (SED) coverages. We find that when $1-20$ $μ$m SED is used, the inferred result gives a small torus size ($<4$ pc radius) and a steep radial dust distribution. The computed torus using the $1-432$ $μ$m SED provides comparable torus sizes, $5.1^{+0.4}_{-0.4}$ pc radius, and morphology to the recently resolved 432 $μ$m ALMA observations. This result indicates that the $1-20$ $μ$m wavelength range is not able to probe the full extent of the torus. The characterization of the turn-over emission of the torus using the $30-60$ $μ$m wavelength range is sensitive to the detection of cold dust in the torus. The morphology of the dust emission in our 2D image at 432 $μ$m is spatially coincident with the cloud distribution, while the morphology of the emission in the $1-20$ $μ$m wavelength range shows an elongated morphology perpendicular to the cloud distribution. We find that our 2D \textsc{clumpy} torus image at 12 $μ$m can produce comparable results to those observed using IR interferometry.

astro-ph.GA↗
arXiv2017

A 100 kpc nebula associated with the "Teacup" fading quasar

We report the discovery of a ~100 kpc ionized nebula associated with the radio quiet type 2 quasar (QSO2) nicknamed the "Teacup" (z=0.085). The giant nebula is among the largest known around active galaxies at any z. We propose that it is part of the circumgalactic medium (CGM) of the QSO2 host, which has been populated with tidal debris by galactic interactions. This rich gaseous medium has been rendered visible due to the illumination by the powerful active nucleus (AGN). Subsolar abundances (~0.5Z(sun)) are tentatively favored by AGN photoionization models. We also report the detection of coronal emission (Fe+6) from the NE bubble, at ~9 kpc from the AGN. The detection of coronal lines at such large distances from the AGN and the [NII]/Halpha, [SII]/Halpha, [OI]/Halpha optical emission line ratios of the giant nebula are consistent with the fading quasar scenario proposed by Gagne et al. (2014). The fading rate appears to have been faster in the last ~46,000 yr. Deep wide field integral field spectroscopy of giant nebulae around powerful AGN such as the "Teacup's" with instruments such as MUSE on VLT opens up a way to detect and study the elusive material from the CGM around massive active galaxies thanks to the illumination by the luminous AGN.

astro-ph.GA↗
arXiv2017

Quantifying the AGN-driven outflows in ULIRGs (QUADROS) I: VLT/Xshooter observations of 9 nearby objects

Although now routinely incorporated into hydrodynamic simulations of galaxy evolution, the true importance of the feedback effect of the outflows driven by active galactic nuclei (AGN) remains uncertain from an observational perspective. This is due to a lack of accurate information on the densities, radial scales and level of dust extinction of the outflow regions. Here we use the unique capabilities of VLT/Xshooter to investigate the warm outflows in a representative sample of 9 local (0.06 $<$ z $<$ 0.15) ULIRGs with AGN nuclei and, for the first time, accurately quantify the key outflow properties. We find that the outflows are compact (0.05 $<$ R$_{[OIII]}$ $<$ 1.2 kpc), significantly reddened (median E(B-V)$\sim$0.5 magnitudes), and have relatively high electron densities (3.4 $<$ log$_{10}$ n$_e$ (cm$^{-3}$) $<$ 4.8). It is notable that the latter densities -- obtained using trans-auroral [SII] and [OII] emission-line ratios -- exceed those typically assumed for the warm, emission-line outflows in active galaxies, but are similar to those estimated for broad and narrow absorption line outflow systems detected in some type 1 AGN. Even if we make the most optimistic assumptions about the true (deprojected) outflow velocities, we find relatively modest mass outflow rates ($0.07 < \dot{M} < 11$ M$_{sol}$ yr$^{-1}$) and kinetic powers measured as a fraction of the AGN bolometric luminosities ($4\times10^{-4} < \dot{E}/L_{BOL} <1$%). Therefore, although warm, AGN-driven outflows have the potential to strongly affect the star formation histories in the inner bulge regions ($r \sim$ 1kpc) of nearby ULIRGs, we lack evidence that they have a significant impact on the evolution of these rapidly evolving systems on larger scales.

astro-ph.GA↗
arXiv2017

Nuclear obscuration in active galactic nuclei

The material surrounding accreting supermassive black holes connects the active galactic nucleus (AGN) with its host galaxy and, besides being responsible for feeding the black hole, provides important information on the feedback that nuclear activity produces on the galaxy. In this review we summarize our current understanding of the close environment of accreting supermassive black holes obtained from studies of local AGN carried out in the infrared and X-ray band. The structure of this circumnuclear material is complex, clumpy and dynamical, and its covering factor depends on the accretion properties of the AGN. From the infrared point of view, this obscuring material is a transition zone between the broad- and narrow-line region, and at least in some galaxies, it consists of two structures: an equatorial disk/torus and a polar component. In the X-ray regime, the obscuration is produced by multiple absorbers on various spatial scales, mostly associated with the torus and the broad-line region. In the next decade the new generation of infrared and X-ray facilities will greatly contribute to our understanding of the structure and physical properties of nuclear obscuration in AGN.

astro-ph.GA↗
arXiv2017

Galaxy wide radio induced feedback in a radio quiet quasar

We report the discovery of a radio quiet type 2 quasar (SDSS J165315.06+234943.0 nicknamed the "Beetle" at z=0.103) with unambiguous evidence for active galactic nucleus (AGN) radio induced feedback acting across a total extension of ~46 kpc and up to ~26 kpc from the AGN. To the best of our knowledge, this is the first radio quiet system where radio induced feedback has been securely identified at >>several kpc from the AGN. Turbulent gas is also found far from the radio axis, ~25 kpc in the perpendicular direction. We propose a scenario in which the radio structures have perforated the interstellar medium of the galaxy and escaped into the circumgalactic medium. While advancing, they have interacted with in-situ gas modifying its properties. Our results show that jets of modest power can be the dominant feedback mechanism acting across huge volumes in radio quiet systems, including highly accreting luminous AGN, where radiative mode feedback may be expected.

astro-ph.GA↗
arXiv2017

An infrared view of AGN feedback in a type-2 quasar: the case of the Teacup galaxy

We present near-infrared integral field spectroscopy data obtained with VLT/SINFONI of "the Teacup galaxy". The nuclear K-band (1.95-2.45 micron) spectrum of this radio-quiet type-2 quasar reveals a blueshifted broad component of FWHM~1600-1800 km/s in the hydrogen recombination lines (Pa$α$, Br$δ$, and Br$γ$) and also in the coronal line [Si VI]$λ$1.963 micron. Thus the data confirm the presence of the nuclear ionized outflow previously detected in the optical and reveal its coronal counterpart. Both the ionized and coronal nuclear outflows are resolved, with seeing-deconvolved full widths at half maximum of 1.1$\pm$0.1 and 0.9$\pm$0.1 kpc along PA$\sim$72-74 deg. This orientation is almost coincident with the radio axis (PA=77 deg), suggesting that the radio jet could have triggered the nuclear outflow. In the case of the H$_2$ lines we do not require a broad component to reproduce the profiles, but the narrow lines are blueshifted by ~50 km/s on average from the galaxy systemic velocity. This could be an indication of the presence of a nuclear molecular outflow, although the bulk of the H$_2$ emission in the inner ~2 arcsec (~3 kpc) of the galaxy follows a rotation pattern. We find evidence for kinematically disrupted gas (FWHM>250 km/s) at up to 5.6 kpc from the AGN, which can be naturally explained by the action of the outflow. The narrow component of [Si VI] is redshifted with respect to the systemic velocity, unlike any other emission line in the K-band spectrum. This indicates that the region where the coronal lines are produced is not co-spatial with the narrow line region.

astro-ph.GA↗
arXiv2017

Uncovering the host galaxy of the $γ$-ray-emitting narrow-line Seyfert 1 galaxy FBQS J1644+2619

The discovery of $γ$-ray emission from radio-loud narrow-line Seyfert 1 (NLSy1) galaxies has questioned the need for large black hole masses (> 10$^8$ M$_{\odot}$) to launch relativistic jets. We present near-infrared data of the $γ$-ray-emitting NLSy1 FBQS J1644+2619 that were collected using the camera CIRCE (Canarias InfraRed Camera Experiment) at the 10.4-m Gran Telescopio Canarias to investigate the structural properties of its host galaxy and to infer the black hole mass. The 2D surface brightness profile is modelled by the combination of a nuclear and a bulge component with a Sérsic profile with index $n$ = 3.7, indicative of an elliptical galaxy. The structural parameters of the host are consistent with the correlations of effective radius and surface brightness against absolute magnitude measured for elliptical galaxies. From the bulge luminosity, we estimated a black hole mass of (2.1$\pm$0.2) $\times$10$^8$ M$_{\odot}$, consistent with the values characterizing radio-loud active galactic nuclei.

astro-ph.GA↗
arXiv2017

A comparison between the soft X-ray and [O III] morphologies of active galactic nuclei

Several studies of nearby active galactic nuclei (AGN) have shown that the soft X-ray emission presents a size and morphology that resembles that of the narrow-line region (NLR) traced by [O III]. Since the NLR is mainly constituted by gas photoionised by the AGN, it seems logical to assume that this is also the primary source of the soft X-ray emission. However, these results are based on individual sources or small samples, particularly focused on type-2 Seyfert galaxies. Very little has been said concerning other types of AGN. The purpose of this work is to compare the circumnuclear morphologies of soft X-ray and [O III] images to test whether they match in different optical classes of AGN. Our sample is composed of 27 AGN: nine type-1 Seyferts, 10 type-2 Seyferts, and eight low ionisation nuclear emission-line regions (LINERs). We find a good match in 100% of the type-2 Seyferts in our sample. This correspondence is less frequent in type-1 Seyferts (22%) and it is not seen in LINERs. The good resemblance in type-2 Seyferts constitutes an evidence for a common physical origin. We argue that the lack of correspondence in type-1 Seyferts might be due to the line of sight perpendicular to the accretion disk. Based on the morphologies of the eight LINERs in our sample, we discard a common origin for the soft X-ray and [O III] emissions in these objects. Regarding the X-ray properties, both high column density and hard X-ray luminosity are associated with matched morphologies.

astro-ph.GA↗
arXiv2016

Young stellar populations in type II quasars: timing the onset of star formation and nuclear activity

Despite the emerging morphological evidence that luminous quasar-like AGN are triggered in galaxy mergers, the natures of the triggering mergers and the order of events in the triggering sequence remain uncertain. In this work, we present a detailed study of the stellar populations of the host galaxies of 21 type II quasars, with the aim of understanding the sequence of events between the onset of the merger, the triggering of the associated starburst and the initiation of the quasar activity. To this end, we model high quality, wide spectral coverage, intermediate resolution optical spectra of the type II quasars. We find that of the 21 objects, the higher-order Balmer absorption lines, characteristic of young stellar populations (YSP) , are directly detected in ~62% of the sample. We also fit these spectra using a number of combinations of stellar and/or power-law components, representative of viable formation histories, as well as including the possibility of scattered AGN light. We find that 90 % of the type II quasar host galaxies require the inclusion of a YSP to adequately model their spectra, whilst 71 % of the sample require the inclusion of a YSP with age < 100 Myr. Since the ages of the YSP in most type II quasar host galaxies are comparable with the expected lifetimes of the AGN activity, these results provide strong evidence that the quasars are triggered close to the peaks of the merger-induced starbursts.

astro-ph.GA↗