The oxygen abundance in the IFU era

Spatially-resolved information of gas-phase emission provided by integral field units (IFUs) are allowing us to perform a new generation of emission-line surveys, based on large samples of HII regions and full two-dimensional coverage. Here we present two highlights of our current studies employing this technique: 1) A statistical approach to the abundance gradients of spiral galaxies, which indicates an -universal- radial gradient for oxygen abundance; and 2) The discovery of a new scaling relation of HII regions in spiral galaxies, the "local" mass-metallicity relation of star-forming galaxies.Comment: 6 pages, to appear in Highlights of Spanish Astrophysics VII, Proceedings of the X Scientific Meeting of the Spanish Astronomical Society held on July 9-13, 2012, in Valencia, Spai

Inner and outer star forming regions over the disks of spiral galaxies. I. Sample characterization

Context. The knowledge of abundance distributions is central to understanding the formation and evolution of galaxies. Most of the relations employed for the derivation of gas abundances have so far been derived from observations of outer disk HII regions, despite the known differences between inner and outer regions. Aims. Using integral field spectroscopy (IFS) observations we aim to perform a systematic study and comparison of two inner and outer HII regions samples. The spatial resolution of the IFS, the number of objects and the homogeneity and coherence of the observations allow a complete characterization of the main observational properties and differences of the regions. Methods. We analyzed a sample of 725 inner HII regions and a sample of 671 outer HII regions, all of them detected and extracted from the observations of a sample of 263 nearby, isolated, spiral galaxies observed by the CALIFA survey. Results. We find that inner HII regions show smaller equivalent widths, greater extinction and luminosities, along with greater values of [NII]{\lambda}6583/H{\alpha} and [OII]{\lambda}3727/[OIII]{\lambda}5007 emission-line ratios, indicating higher metallicites and lower ionization parameters. Inner regions have also redder colors and higher photometric and ionizing masses, although Mion/Mphot is slighty higher for the outer regions. Conclusions. This work shows important observational differences between inner and outer HII regions in star forming galaxies not previously studied in detail. These differences indicate that inner regions have more evolved stellar populations and are in a later evolution state with respect to outer regions, which goes in line with the inside-out galaxy formation paradigm.Comment: 16 page

PPAK Wide-field Integral Field Spectroscopy of NGC 628: II. Emission line abundance analysis

In this second paper of the series, we present the 2-dimensional (2D) emission line abundance analysis of NGC 628, the largest object within the PPAK Integral Field Spectroscopy (IFS) Nearby Galaxies Survey: PINGS. We introduce the methodology applied to the 2D IFS data in order to extract and deal with large spectral samples, from which a 2D abundance analysis can be later performed. We obtain the most complete and reliable abundance gradient of the galaxy up-to-date, by using the largest number of spectroscopic points sampled in the galaxy, and by comparing the statistical significance of different strong-line metallicity indicators. We find features not previously reported for this galaxy that imply a multi-modality of the abundance gradient consistent with a nearly flat-distribution in the innermost regions of the galaxy, a steep negative gradient along the disc and a shallow gradient or nearly-constant metallicity beyond the optical edge of the galaxy. The N/O ratio seems to follow the same radial behaviour. We demonstrate that the observed dispersion in metallicity shows no systematic dependence with the spatial position, signal-to-noise or ionization conditions, implying that the scatter in abundance for a given radius is reflecting a true spatial physical variation of the oxygen content. Furthermore, by exploiting the 2D IFS data, we were able to construct the 2D metallicity structure of the galaxy, detecting regions of metal enhancement, and showing that they vary depending on the choice of the metallicity estimator. The analysis of axisymmetric variations in the disc of NGC 628 suggest that the physical conditions and the star formation history of different-symmetric regions of the galaxy have evolved in a different manner.Comment: Accepted for publication in MNRAS, 40 pages, 22 figures, online data: http://www.ast.cam.ac.uk/ioa/research/ping

Associations between physical activity and comorbidities in people with COPD residing in Spain: A cross-sectional analysis

There is a high prevalence of comorbidities among patients with chronic obstructive pulmonary disease (COPD). Comorbidities are likely common in patients with any COPD degree and are associated with increased mortality. The aim of this study was to determine the prevalence of thirty-one different COPD comorbidities and to evaluate the association between physical activity (PA) levels in people with COPD residing in Spain. Cross-sectional data from the Spanish National Health Survey 2017 were analysed. A total of 601 adults (52.2% females) with COPD aged 15 to 69 participated in this study. PA (exposure) was measured with the International Physical Activity Questionnaire (IPAQ) short form and comorbidities (outcomes) were self-reported in response to the question “Have you ever been diagnosed with…?” Multivariable logistic regression, in three different models, was used to assess this association. Results showed a high prevalence of comorbidities (94%), these being chronic lumbar back pain (38.9%), chronic allergy (34.8%), arthrosis (34.1%), chronic cervical back pain (33.3%), asthma (32.9%) and hypertension (32.8%) the most prevalent. Low PA level was significantly associated with urinary incontinence (2.115[1.213–3.689]), chronic constipation (1.970[1.119–3.459]), cataracts (1.840[1.074–3.153]), chronic anxiety (1.508[1.002–2.269]) and chronic lumbar back pain (1.489[1.044–2.125]). Therefore, people with COPD should increase their PA levels in order to reduce their risk of comorbidities and increase their quality of life

Census of HII regions in NGC 6754 derived with MUSE: Constraints on the metal mixing scale

We present a study of the HII regions in the galaxy NGC 6754 from a two pointing mosaic comprising 197,637 individual spectra, using Integral Field Spectrocopy (IFS) recently acquired with the MUSE instrument during its Science Verification program. The data cover the entire galaxy out to ~2 effective radii (re ), sampling its morphological structures with unprecedented spatial resolution for a wide-field IFU. A complete census of the H ii regions limited by the atmospheric seeing conditions was derived, comprising 396 individual ionized sources. This is one of the largest and most complete catalogue of H ii regions with spectroscopic information in a single galaxy. We use this catalogue to derive the radial abundance gradient in this SBb galaxy, finding a negative gradient with a slope consistent with the characteristic value for disk galaxies recently reported. The large number of H ii regions allow us to estimate the typical mixing scale-length (rmix ~0.4 re ), which sets strong constraints on the proposed mechanisms for metal mixing in disk galaxies, like radial movements associated with bars and spiral arms, when comparing with simulations. We found evidence for an azimuthal variation of the oxygen abundance, that may be related with the radial migration. These results illustrate the unique capabilities of MUSE for the study of the enrichment mechanisms in Local Universe galaxies.Comment: 13 pages, 7 Figurs, accepted for publishing in A&

Wannier-Stark ladders in one-dimensional elastic systems

The optical analogues of Bloch oscillations and their associated Wannier-Stark ladders have been recently analyzed. In this paper we propose an elastic realization of these ladders, employing for this purpose the torsional vibrations of specially designed one-dimensional elastic systems. We have measured, for the first time, the ladder wave amplitudes, which are not directly accessible either in the quantum mechanical or optical cases. The wave amplitudes are spatially localized and coincide rather well with theoretically predicted amplitudes. The rods we analyze can be used to localize different frequencies in different parts of the elastic systems and viceversa.Comment: 10 pages, 6 figures, accepted in Phys. Rev. Let