We present a new integral-field spectroscopic dataset of the central part of the Orion Nebula (M 42), observed with the MUSE instrument at the ESO VLT. We reduced the data with the public MUSE pipeline. The output products are two FITS cubes with a s
patial size of ~5.9x4.9 (corresponding to ~0.76 pc x 0.63 pc) and a contiguous wavelength coverage of 4595...9366 Angstrom, spatially sampled at 0.2. We provide t
Diffuse Interstellar Bands (DIBs) are non-stellar weak absorption features of unknown origin found in the spectra of stars viewed through one or several clouds of Interstellar Medium (ISM). Research of DIBs outside the Milky Way is currently very lim
ited. Specifically spatially resolved investigations of DIBs outside of the Local Group is, to our knowledge, inexistent. Here, we explore the capability of the high sensitivity Integral Field Spectrograph, MUSE, as a tool to map diffuse interstellar bands at distances larger than 100 Mpc. We use MUSE commissioning data for AM 1353-272 B, the member with highest extinction of the The Dentists Chair, an interacting system of two spiral galaxies. High signal-to-noise spectra were created by co-adding the signal of many spatial elements distributed in a geometry of concentric elliptical half-rings. We derived decreasing radial profiles for the equivalent width of the $lambda$5780.5 DIB both in the receding and approaching side of the companion galaxy up to distances of $sim$4.6 kpc from the center of the galaxy. Likewise, interstellar extinction, as derived from the Halpha/Hbeta line ratio displays a similar trend, with decreasing values towards the external parts. This translates into an intrinsic correlation between the strength of the DIB and the extinction within AM 1353-272 B consistent with the current existing global trend between these quantities when using measurements for both Galactic and extragalactic sight lines. Mapping of DIB strength in the Local Universe as up to now only done for the Milky Way seems feasible. This offers a new approach to study the relationship between DIBs and other characteristics and species of the ISM in different conditions as those found in our Galaxy to the use of galaxies in the Local Group and/or single sightlines towards supernovae, quasars and galaxies outside the Local Group.
We use optical integral field spectroscopy and 8 and 24 micron mid-IR observations of the giant HII region NGC 588 in the disc of M33 as input and constraints for two-dimensional tailor-made photoionisation models. Two different geometrical approache
s are followed for the modelling structure: i) Each spatial element of the emitting gas is studied individually using models which assume that the ionisation structure is complete in each element to look for azimuthal variations across gas and dust. ii) A single model is considered, and the two-dimensional structure of the gas and the dust are assumed to be due to the projection of an emitting sphere onto the sky. The models in both assumptions reproduce the radial profiles of Hbeta surface brightness, the observed number of ionising photons, and the strong optical emission-line relative intensities. The first approach produces a constant-density matter-bounded thin shell of variable thickness and dust-to-gas ratio, while the second gives place to a radiation-bounded thick shell sphere of decreasing particle density. However, the radial profile of the 8/24 microns IR ratio, depending on the gas and dust geometry, only fits well when the thick-shell model is used. The resulting dust-to-gas mass ratio, which was obtained empirically from the derived dust mass using data from Spitzer, also has a better fit using the thick-shell solution. In both approaches, models support the chemical homogeneity, and the ionisation-parameter radial decrease, These results must be taken with care in view of the very low extinction values that are derived from the IR, as compared to that derived from the Balmer decrement. Besides, the IR can be possibly contaminated with the emission from a cloud of diffuse gas and dust above the plane of the galaxy detected at 250 micron Herschel image.
ABRIDGED: NGC5253 was previously studied by our group with the aim to elucidate in detail the starburst interaction processes. Some open issues regarding the 2D structure of the main properties of the ionized gas remain to be addressed. Using IFS dat
a obtained with FLAMES, we derived 2D maps for different tracers of electron density (n_e), electron temperature (T_e) and ionization degree. The maps for n_e as traced by several line ratios are compatible with a 3D stratified view of the nebula with the highest n_e in the innermost layers and a decrease of n_e outwards. To our knowledge, this is the first time that a T_e map based on [SII] lines for an extragalactic object is presented. The joint interpretation of our two T_e maps is consistent with a T_e structure in 3D with higher temperatures close to the main ionizing source surrounded by a colder and more diffuse component. The highest ionization degree is found at the peak of emission for the gas with relatively high ionization in the main GHIIR and lower ionization degree delineating the more extended diffuse component. Abundances for O, Ne and Ar are constant over the mapped area within <0.1 dex. The mean 12+log(O/H) is 8.26 while the relative abundances of log(N/O), log(Ne/O) and log(Ar/O) were sim-1.32, -0.65 and -2.33, respectively. There are two locations with enhanced N/O. The first (log(N/O)sim-0.95) is associated to two super star clusters. The second (log(N/O)sim-1.17), reported here for the first time, is associated to two moderately massive (2-4x10^4 M_sun) and relatively old (sim10 Myr) clusters. A comparison of the N/O map with those produced by strong line methods supports the use of N2O2 over N2S2 in the search for chemical inhomogeneities within a galaxy. The results on the localized nitrogen enhancement were used to compile and discuss the factors that affect the complex relationship between Wolf-Rayet stars and N/O excess.
LIRGs and ULIRGs are much more numerous at higher redshifts than locally, dominating the star-formation rate density at redshifts ~1 - 2. Therefore, they are important objects in order to understand how galaxies form and evolve through cosmic time. W
e aim to characterize the morphologies of the stellar continuum and the ionized gas (H_alpha) emissions from local sources, and investigate how they relate with the dynamical status and IR-luminosity of the sources. We use optical (5250 -- 7450 AA) integral field spectroscopic (IFS) data for a sample of 38 sources, taken with the VIMOS instrument, on the VLT. We present an atlas of IFS images of continuum emission, H_alpha emission, and H_alpha equivalent widths for the sample. The H_alpha images frequently reveal extended structures that are not visible in the continuum, such as HII regions in spiral arms, tidal tails, rings, of up to few kpc from the nuclear regions. The morphologies of the continuum and H_alpha images are studied on the basis of the C_{2kpc} parameter, which measures the concentration of the emission within the central 2 kpc. The C_{2kpc} values found for the H_alpha images are higher than those of the continuum for the majority (85%) of the objects in our sample. On the other hand, most of the objects in our sample (~62%) have more than half of their H_alpha emission outside the central 2 kpc. No clear trends are found between the values of C_{2kpc} and the IR-luminosity of the sources. On the other hand, our results suggest that the star formation in advance mergers and early-stage interactions is more concentrated than in isolated objects. We compared the H_alpha and infrared emissions as tracers of the star-formation activity. We find that the star-formation rates derived using the H_alpha luminosities generally underpredict those derived using the IR luminosities, even after accounting for reddening effects.
