arXiv subjects

Montse Villar-Martin

Publications and source records attributed to Montse Villar-Martin.

8 recordsLinked to original sources

arXiv2024

AGN feedback can produce metal enrichment on galaxy scales

Giant (>100 kpc) nebulae associated with active galaxies provide rich information about the circumgalactic medium (CGM) around galaxies, its link with the interstellar medium (ISM) of the hosts and the mechanisms involved in their evolution. We have studied the giant nebula associated with the Teacup (z=0.085) quasar based on VLT MUSE integral field spectroscopy to investigate whether the well known giant (~10 kpc) active galactic nucleus (AGN) induced outflow has an impact on the distribution of heavy elements in and outside the host galaxy. For this, we have mapped the O/H and N/O abundances in two spatial dimensions across the giant nebula and within the galaxy by means of comparing emission line ratios with photoionisation model predictions. We have found that the widely studied AGN driven outflow responsible for the 10 kpc ionised bubble is enhancing the gas metal abundance up to 10 kpc from the AGN. O/H is solar or slightly higher in the bubble edges, in comparison with the subsolar abundances across the rest of the nebula (median O/H~0.63 O/H_sun)). The main conclusion is that AGN feedback can produce metal enrichment at large extranuclear distances in galaxies (>~10 kpc).

astro-ph.GA↗

arXiv2016

Ionized outflows in luminous type 2 AGNs at z<0.6: no evidence for significant impact on the host galaxies

We investigate the presence of extended ionized outflows in 18 luminous type 2 AGNs (11 quasars and 7 high luminosity Seyfert 2s) at 0.3 =severalx100 pc and upper limits R<1-2 kpc. Our results are inconsistent with related studies which suggest that large scale R~several-15 kpc are ubiquitous in QSO2. We study the possible causes of discrepancy and propose that seeing smearing is the cause of the large inferred sizes. The implications in our understanding of the feedback phenomenon are important since the mass M (through the density), mass injection M(dot) and energy injection rates E(dot) of the outflows become highly uncertain. One conclusion seems unavoidable: M, M(dot), E(dot) are modest or low compared with previous estimations. No evidence is found supporting that typical outflows can affect the interstellar medium of the host galaxies accross spatial scales >~1-2 kpc.

astro-ph.GA↗

arXiv2012

The importance of galaxy interactions in triggering type II quasar activity

We present deep Gemini GMOS-S optical broad-band images for a complete sample of 20 SDSS selected type II quasars with redshifts 0.3 < z < 0.41 and [OIII] emission line luminosities greater than 10^8.5 solar luminosities. We use these images to determine the significance of galaxy interactions in triggering nuclear activity, finding that 15 (75%) show evidence for interaction in the form of tails, shells, double nuclei etc. The median surface brightness of the features is 23.4 mag arcsec sq and the range is 20.9-24.7 mag arcsec sq. We find a similar rate of interaction in the type II quasars as in a comparison sample of quiescent early-type galaxies at similar redshift (67 +/- 14%). However the surface brightness of the detected features is up to 2 magnitudes brighter for the type II quasars than for the quiescent early-types, which have surface brightnesses in the range 22.1-26.1 mag arcsec sq and a median surface brightness 24.3 mag arcsec sq. This may indicate that the mergers witnessed in the comparison sample galaxies could have different progenitors, or we may be viewing the interactions at different stages. We also compare our results with a sample of radio-loud AGN and find a higher rate of interaction signatures (95 +/- 21%) than in the type II quasars, but a very similar range of surface brightnesses for the morphological features (20.9-24.8 mag arcsec sq), possibly indicating a similarity in the types of triggering interactions. The range of features detected in the type II quasars suggests that AGN activity can be triggered before, during or after the coalescence of the black holes. Overall, our results are consistent with the idea that galaxy interaction plays an important role in the triggering of quasar activity.

astro-ph.CO↗

arXiv2012

Mergers and interactions in SDSS type 2 quasars at z~0.3-0.4. SDSS J143027.66-005614.8: a case study

We present a compilation of HST images of 58 luminous SDSS type 2 AGNs at 0.3 25/42 or >59%) show clear signatures of morphological disturbance which are in most cases identified with merger/interaction processes. We discuss this in the context of related works on type 2 quasars and powerful radio galaxies. We study in detail the particular case of the radio quiet type 2 quasar SDSS J143027.66-005614.8 at z=0.32 based on VLT, HST and SDSS imaging and spectroscopic data. We discuss the global properties of the object in the context of theoretical and observational studies of galaxy mergers/interactions and their role in the triggering of the nuclear and star formation activities in the most luminous active galaxies.

astro-ph.CO↗

arXiv2008

Emission line activity in type 2 quasars from the Sloan Digital Sky Survey

We have compared the optical emission line ratios of type 2 quasars from Zakamska et al. with standard AGN photoionization model predictions, Seyfert 2s, HII galaxies, and narrow line FRII radio galaxies. Moderate to high ionization narrow line radio galaxies and Seyfert 2s are indistinguishable from type 2 quasars based on their optical line ratios. The standard AGN photoionization models, widely discussed for other type 2 AGNs, can reproduce successfully the loci and trends of type 2 quasars in some of the main diagnostic diagrams. These models are not exempt of problems and the discrepancies with the data are the same encountered for other type 2 AGNs. As for these, realistic models must take into account a range of cloud properties, as widely demonstrated in the literature. We also study the possible impact of stellar photoionization.

astro-ph↗

arXiv2006

Giant Ly-alpha nebulae in the high redshift (z>2) Universe

High redshift radio galaxies (z>2) are believed to be progenitors of the giant ellipticals of today. They are often associated with giant Ly-alpha nebulae (sometimes >100 kpc), which have been for more than two decades valuable sources of information about the evolutionary status of the host galaxy and its chemical enrichment and star formation histories. I present in this paper a summary of the most relevant results about the giant nebulae obtained in the last ~10 years and the implications on our understanding of the early phases of evolution of massive elliptical galaxies.

astro-ph↗

arXiv2005

The giant star forming halo associated with the radio galaxy PKS1932-46

We report the discovery of a giant (~160 kpc) knotty extended emission line nebula associated with the radio galaxy PKS1932-46 at z=0.23. The 2-d long slit spectra, obtained with VLT-FORS2 at a large angle (~63 degr) to the radio source axis, shows that the nebula extends well beyond the radio structure and the ionization cones of the active nucleus. This is one of the largest ionized nebulae yet detected around a radio galaxy at any redshift. The analysis of the ionization, morphological and kinematic properties of the knots suggests that these are star forming objects, probably compact HII galaxies. We propose that the giant structure is a star forming halo associated with the debris of the merger that triggered the activity. This study reinforces the view that radio galaxies are activated by major mergers which also trigger substantial star formation. The star formation activity can extend on the scale of a galaxy group, beyond the old stellar halo of the host galaxy.

astro-ph↗

arXiv2004

Nebular and stellar properties of a metal poor HII galaxy at z=3.36

We have characterized the physical properties (electron temperature, density, metallicity) of the ionized gas and the ionizing population (age, metallicity, presence of WR stars) in the Lynx arc at z=3.36. This is a low metallicity (~10% solar) HII galaxy which is undergoing a burst of star formation of <5 Myr age. One possible scenario that explains the emission line spectrum of the Lynx arc, the large strength of the nitrogen lines and the HeII emission is that the object has experienced a merger event that has triggered a burst of star formation. WR stars have formed that contribute to a fast enrichment of the ISM and its overabundance of nitrogen.

astro-ph↗