arXiv subjects

A. Monreal-Ibero

Publications and source records attributed to A. Monreal-Ibero.

49 records · Page 3Linked to original sources

arXiv2012

The ionized gas in the CALIFA early-type galaxies I. Mapping two representative cases: NGC 6762 and NGC 5966

As part of the CALIFA survey, we conducted a thorough 2D analysis of the ionized gas in two E/S0 galaxies, NGC6762 and NGC5966, aiming to shed light on the nature of their warm ionized ISM. We present optical IFS obtained with the PMAS/PPAK spectrophotometer. To recover the nebular lines, we subtracted the underlying stellar continuum from the observed spectra using the STARLIGHT code. In NGC6762, the ionized gas and stellar emission display similar morphologies, while the emission line morphology is elongated in NGC5966, spanning ~6 kpc, and is oriented roughly orthogonal to the major axis of the stellar continuum ellipsoid. Whereas gas and stars are kinematically aligned in NGC6762, the gas is kinematically decoupled from the stars in NGC5966. A decoupled rotating disk or an ionization cone are two possible interpretations of the elongated ionized gas structure in NGC5966. The latter would be the first ionization cone of such a dimension detected within a weak emission-line galaxy. Both galaxies have weak emission-lines relative to the continuum [EW(Ha)< 3 A] and have low excitation, log([OIII]5007/Hb) < 0.5. Based on optical diagnostic ratios ([OIII]5007/Hb,[NII]6584/Ha,[SII]6717,6731/Ha,[OI]6300/Ha), both objects contain a LINER nucleus and an extended LINER-like gas emission. The emission line ratios do not vary significantly with radius or aperture, which indicates that the nebular properties are spatially homogeneous. The gas emission in NGC6762 can be best explained by photoionization by pAGB stars without the need of invoking any other excitation mechanism. In the case of NGC5966, the presence of a nuclear ionizing source seems to be required to shape the elongated gas emission feature in the ionization cone scenario, although ionization by pAGB stars cannot be ruled out.(abridged)

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arXiv2011

CALIFA, the Calar Alto Legacy Integral Field Area survey: I. Survey presentation

We present here the Calar Alto Legacy Integral Field Area (CALIFA) survey, which has been designed to provide a first step in this direction.We summarize the survey goals and design, including sample selection and observational strategy.We also showcase the data taken during the first observing runs (June/July 2010) and outline the reduction pipeline, quality control schemes and general characteristics of the reduced data. This survey is obtaining spatially resolved spectroscopic information of a diameter selected sample of $\sim600$ galaxies in the Local Universe (0.005< z <0.03). CALIFA has been designed to allow the building of two-dimensional maps of the following quantities: (a) stellar populations: ages and metallicities; (b) ionized gas: distribution, excitation mechanism and chemical abundances; and (c) kinematic properties: both from stellar and ionized gas components. CALIFA uses the PPAK Integral Field Unit (IFU), with a hexagonal field-of-view of $\sim1.3\sq\arcmin'$, with a 100% covering factor by adopting a three-pointing dithering scheme. The optical wavelength range is covered from 3700 to 7000 Å, using two overlapping setups (V500 and V1200), with different resolutions: R\sim850 and R\sim1650, respectively. CALIFA is a legacy survey, intended for the community. The reduced data will be released, once the quality has been guaranteed. The analyzed data fulfill the expectations of the original observing proposal, on the basis of a set of quality checks and exploratory analysis. We conclude from this first look at the data that CALIFA will be an important resource for archaeological studies of galaxies in the Local Universe.

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arXiv2011

Ionization Conditions in the Central Giant HII Region of NGC 5253

We are carrying out a detailed 2D spectroscopic study of the central 210 pc X 130 pc of the blue compact dwarf (BCD) galaxy NGC5253. This contribution presents the ionization conditions and chemical abundance patterns for the different kinematic components of the ionized gas detected in our previous work. All the kinematic components present an excess in nitrogen abundance. In particular, the broad velocity component has larger excess than the narrow one by a factor of ~1.4+-0.4 which is consistent with a scenario for the Giant HII Region where the broad component of the emission lines traces the material expelled by the two central Super Star Clusters while the narrow one is associated to previously existing ionized gas.

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arXiv2011

A 2D multiwavelength study of the ionized gas and stellar population in the Giant HII Region NGC 588

(ABRIDGED) We present an analysis of NGC588 based on IFS data with PMAS, together with Spitzer images at 8 mi and 24 mi. The extinction distribution in the optical shows complex structure, with maxima correlating in position with those of the emission at 24 mi and 8 mi. The Ha luminosity absorbed by the dust within the GHIIR reproduces the structure observed in the 24 mi image, supporting the use of this band as a tracer of recent star formation. A velocity difference of ~50 km/s was measured between the areas of high and low surface brightness, which would be expected if NGC588 were an evolved GHIIR. Line ratios used in the BPT diagnostic diagrams show a larger range of variation in the low surface brightness areas. The ranges are ~0.5 to 1.2 dex for [NII]/Ha, 0.7 to 1.7 dex for [SII]/Ha, and 0.3 to 0.5 dex for [OIII]/Hb. Ratios corresponding to large ionization parameter (U) are found between the peak of the emission in Hb and the main ionizing source decreasing radially outwards within the region. Differences between the integrated and local values of the U tracers can be as high as ~0.8 dex. [OII]/Hb and [OIII]/[OII] yield similar local values for U and consistent with those expected from the integrated spectrum of an HII region ionized by a single star. The ratio [SII]/Ha departs significantly from the range predicted by this scenario, indicating the complex ionization structure in GHIIRs. There is a significant scatter in derivations of Z using strong line tracers as a function of position, caused by variations in the degree of ionization. The scatter is smaller for N2O3 which points to this tracer as a better Z tracer than N2. The comparison between integrated and local line ratio values indicates that measurements of the line ratios of GHIIR in galaxies at distances >~25 Mpc may be dominated by the ionization conditions in their low surface brightness areas.

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arXiv2010

Extreme Starbursts in the Local Universe

The "Extreme starbursts in the local universe" workshop was held at the Insituto de Astrofisica de Andalucia in Granada, Spain on 21-25 June 2010. Bearing in mind the advent of a new generation of facilities such as JWST, Herschel, ALMA, eVLA and eMerlin, the aim of the workshop was to bring together observers and theorists to review the latest results. The purpose of the workshop was to address the following issues: what are the main modes of triggering extreme starbursts in the local Universe? How efficiently are stars formed in extreme starbursts? What are the star formation histories of local starburst galaxies? How well do the theoretical simulations model the observations? What can we learn about starbursts in the distant Universe through studies of their local counterparts? How important is the role of extreme starbursts in the hierarchical assembly of galaxies? How are extreme starbursts related to the triggering of AGN in the nuclei of galaxies? Overall, 41 talks and 4 posters with their corresponding 10 minutes short talks were presented during the workshop. In addition, the workshop was designed with emphasis on discussions, and therefore, there were 6 discussion sessions of up to one hour during the workshop. Here is presented a summary of the purposes of the workshop as well as a compilation of the abstracts corresponding to each of the presentations. The summary and conclusions of the workshop along with a description of the future prospects by Sylvain Veilleux can be found in the last section of this document. A photo of the assistants is included.

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arXiv2010

A study of the interplay between ionized gas and star clusters in the central region of NGC 5253 with 2D spectroscopy

ABRIDGED: A detailed 2D study of the central region of NGC5253 has been performed to characterize the stellar and ionized gas structure as well as the extinction distribution, physical properties and kinematics of the ionized gas in the central ~210pc x 130pc. We utilized optical integral field spectroscopy (IFS) data obtained with FLAMES. A detailed extinction map for the ionized gas in NGC5253 shows that the largest extinction is associated with the prominent Giant HII region. There is an offset of ~0.5" between the peak of the optical continuum and the extinction peak in agreement with findings in the infrared. We found that stars suffer less extinction than gas by a factor of 0.33. The [SII]l6717/[SII]l6731 map shows an electron density (N_e) gradient declining from the peak of emission in Ha (790cm^-3) outwards, while the argon line ratio traces areas with $N_e~4200 - 6200cm^(-3). The area polluted with extra nitrogen, as deduced from the excess [NII]/Ha, extends up to distances of 3.3" (~60pc) from the maximum pollution, which is offset by ~1.5" from the peak of continuum emission. Wolf-Rayet features are distributed in an irregular pattern over a larger area (~100pc x 100pc) and associated with young stellar clusters. We measured He^+ abundances over most of the field of view and values of He^++/H^+<~0.0005 in localized areas which do not coincide, in general, with the areas presenting W-R emission or extra nitrogen. The line profiles are complex. Up to three emission components were needed to reproduce them. One of them, associated with the giant HII region, presents supersonic widths and [NII] and [SII] emission lines shifted up to 40km/s with respect to Ha. Similarly, one of the narrow components presents offsets in the [NII] line of <~20km/s. This is the first time that maps with such velocity offsets for a starburst galaxy have been presented.

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arXiv2010

p3d: a general data-reduction tool for fiber-fed integral-field spectrographs

The reduction of integral-field spectrograph (IFS) data is demanding work. Many repetitive operations are required in order to convert raw data into, typically a large number of, spectra. This effort can be markedly simplified through the use of a tool or pipeline, which is designed to complete many of the repetitive operations without human interaction. Here we present our semi-automatic data-reduction tool p3d that is designed to be used with fiber-fed IFSs. Important components of p3d include a novel algorithm for automatic finding and tracing of spectra on the detector, and two methods of optimal spectrum extraction in addition to standard aperture extraction. p3d also provides tools to combine several images, perform wavelength calibration and flat field data. p3d is at the moment configured for four IFSs. In order to evaluate its performance we have tested the different components of the tool. For these tests we used both simulated and observational data. We demonstrate that for three of the IFSs a correction for so-called cross-talk due to overlapping spectra on the detector is required. Without such a correction spectra will be inaccurate, in particular if there is a significant intensity gradient across the object. Our tests showed that p3d is able to produce accurate results. p3d is a highly general and freely available tool. It is easily extended to include improved algorithms, new visualization tools and support for additional instruments. The program code can be downloaded from the p3d-project web site http://p3d.sourceforge.net

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arXiv2010

Spatially resolved study of the physical properties of the ionized gas in NGC 595

We present Integral Field Spectroscopy (IFS) of NGC 595, one of the most luminous HII regions in M33. This type of observations allows studying the variation of the principal emission-line ratios across the surface of the nebula. At each position of the field of view, we fit the main emission-line features of the spectrum within the spectral range 3650-6990A, and create maps of the principal emission-line ratios for the total surface of the region. The extinction map derived from the Balmer decrement and the absorbed H-alpha luminosity show good spatial correlation with the 24 micron emission from Spitzer. We also show here the capability of the IFS to study the existence of Wolf-Rayet (WR) stars, identifying the previously catalogued WR stars and detecting a new candidate towards the north of the region. The ionization structure of the region nicely follows the H-alpha shell morphology and is clearly related to the location of the central ionizing stars. The electron density distribution does not show strong variations within the HII region nor any trend with the H-alpha emission distribution. We study the behaviour within the HII region of several classical emission-line ratios proposed as metallicity calibrators: while [NII]/Ha and [NII]/[OIII] show important variations, the R23 index is substantially constant across the surface of the nebula, despite the strong variation of the ionization parameter as a function of the radial distance from the ionizing stars. These results show the reliability in using the R23 index to characterize the metallicity of HII regions even when only a fraction of the total area is covered by the observations.

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arXiv2009

Integral field optical spectroscopy of a representative sample of ULIRGs: I. The Data

We present a project aimed at studying the structure, dust distribution, ionization state, and kinematics of a representative sample of 22 ULIRGs. The galaxies in the sample undergo different merger phases (they are evenly divided between pre- and post-coalescence systems) and ionization stages (27% HII, 32% LINER, 18% Seyfert, and 23% mixed classifications) over a wide infrared luminosity range (11.8<Lir/Lsun<12.6), which also includes some galaxies of low luminosity. The main aims of this paper are to present the sample and discuss the structure of the stellar and ionized gas components. Our results imply that evolution caused by a merger is occurring in the ionized gas structure of ULIRGs. The present study relies on the use of integral field optical spectroscopy data obtained with the INTEGRAL instrument at the 4.2 m William Herschel Telescope.

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arXiv2007

Search for Tidal Dwarf Galaxies Candidates in a Sample of Ultraluminous Infrared Galaxies

(ABRIDGED) Star-forming small galaxies made out of collisional debris have been found in a variety of merging systems. So far only a few of them are known in ULIRGs although they show clear signs of interactions. Whether external star formation may take place in such objects is an open question. The aim of this paper is to identify and characterise the physical and kinematic properties of the external star forming regions in a sample of ULIRGs, including TDG candidates, using optical IFS and high angular resolution HST imaging. We have found that the presence of external star-forming regions is common with 12 objects being identified in 5 ULIRGs. These regions show a large range of dynamical mass up to 1x10^{10} M_sun, with average sizes of ~750 pc. In addition, the line ratios, metallicities and Hαequivalent widths are typical of young bursts of star formation (age ~ 5-8 Myr), and similar to those of other TDG candidates. Their extinction corrected Hαluminosities lead to masses for the young stellar component of ~2x10^6 - 7x10^8 M_sun. The likelihood of survival of these regions as TDGs is discussed based on their structural and kinematic properties. Most of these systems follow the relation between effective radius and velocity dispersion found for globular clusters and Ellipticals, which suggests they are stable against internal motions. The stability against forces from the parent galaxy have been studied and a comparison of the data with the predictions of dynamical evolutionary models is also performed. Five regions out of twelve show High-Medium or High likelihood of survival. Our best candidate, which satisfy all the utilized criteria, is located in the advanced merger IRAS15250+3609 and presents a velocity field decoupled from the relatively distant parent galaxy.

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arXiv2006

New observations of the halo radial temperature structure in NGC7662

We report on our studies of the physical structure of the planetary nebula (PN) NGC7662. Using (3D) Integral Field Spectroscopy we have been able to measure the electron temperature more accurately and at a larger number of radial locations than before. Here we briefly present our method by which we find a strong positive temperature gradient with increasing radius. According to hydrodynamic models a hot halo, when compared to the central star, can be the product of the passage of an ionization front (e.g. Marten 1993). Such a gradient is not found in equilibrium models, and this finding - when confirmed for other objects - strongly advocates the use of hydrodynamic models when modeling PN halos.

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arXiv2005

LINER-like Extended Nebulae in ULIRGs: Shocks Generated by Merger Induced Flows

In this work we studied the two-dimensional ionization structure of the circumnuclear and extranuclear regions in a sample of six low-z Ultraluminous Infrared Galaxies using Integral Field Spectroscopy. The ionization conditions in the extranuclear regions of these galaxies (~5-15 kpc) are typical of LINERs as obtained from the Veilleux-Osterbrock line ratio diagnostic diagrams. The range of observed line ratios is best explained by the presence of fast shocks with velocities of 150 to 500 km s^{-1}, while the ionization by an AGN or nuclear starburst is in general less likely. The comparison of the two-dimensional ionization level and velocity dispersion in the extranuclear regions of these galaxies shows a positive correlation, further supporting the idea that shocks are indeed the main cause of ionization. The origin of these shocks is also investigated. Despite the likely presence of superwinds in the circumnuclear regions of these systems, no evidence for signatures of superwinds such as double velocity components are found in the extended extranuclear regions. We consider a more likely explanation for the presence of shocks, the existence of tidally induced large scale gas flows caused by the merging process itself, as evidenced by the observed velocity fields characterized by peak-to-peak velocities of 400 km s^{-1}, and velocity dispersions of up to 200 km s^{-1}.

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arXiv2005

Integral Field Spectroscopy of Faint Haloes of Planetary Nebulae

We present the first integral field spectroscopy observations of the two planetary nebulae NGC3242 and NGC4361 with the VIMOS instrument attached to VLT-UT3. By co-adding a large number of spaxels we reach an emission line detection limit of 5.E-18 erg cm^{-2} s^{-1} arcsec^{-2}. In the case of NGC3242, we succeed in determining some properties of the halo. The radial surface brightness profile in [OIII] implies increasing mass loss before the formation of the PN. Traces of the mysterious 'rings' are clearly visible. We find for the first time an apparent temperature gradient across a halo: from about 16000 K close to the shell/halo transition to 20000 K at the halo's outer edge. No line emission is seen in the suspected halo region of NGC4361 down to the sensitivity limit.

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