arXiv subjects

R. Azzollini

Publications and source records attributed to R. Azzollini.

21 records · Page 2Linked to original sources

arXiv2010

Wavelength calibration of the JWST-MIRI medium resolution spectrometer

We present the wavelength and spectral resolution characterisation of the Integral Field Unit (IFU) Medium Resolution Spectrometer for the Mid-InfraRed Instrument (MIRI), to fly onboard the James Webb Space Telescope in 2014. We use data collected using the Verification Model of the instrument and develop an empirical method to calibrate properties such as wavelength range and resolving power in a portion of the spectrometer's full spectral range (5-28 microns). We test our results against optical models to verify the system requirements and combine them with a study of the fringing pattern in the instrument's detector to provide a more accurate calibration. We show that MIRI's IFU spectrometer will be able to produce spectra with a resolving power above R=2800 in the wavelength range 6.46-7.70 microns, and that the unresolved spectral lines are well fitted by a Gaussian profile.

astro-ph.IM↗

arXiv2010

Outskirts of spiral galaxies: result of a secular evolution process?

We present our recent results on the properties of the outskirts of disk galaxies. In particular, we focus on spiral galaxies with stellar disk truncations in their radial surface brightness profiles. Using SDSS, UDF and GOODS data we show how the position of the break (i.e., a direct estimator of the size of the stellar disk) evolves with time since z~1. Our findings agree with an evolution on the radial position of the break by a factor of 1.3+/-0.1 in the last 8 Gyr for galaxies with similar stellar masses. We also present radial color gradients and how they evolve with time. At all redshift we find a radial inside-out bluing reaching a minimum at the position of the break radius, this minimum is followed by a reddening outwards. Our results constrain several galaxy disk formation models and favour a scenario where stars are formed inside the break radius and are relocated in the outskirts of galaxies through secular processes.

astro-ph.GA↗

arXiv2009

Radial Distribution of Near-UV Flux in Disc Galaxies in the range 0<z<1

(Abridged) The goal of this paper is to quantify the changes on the SF distribution within the disc galaxies in the last ~8 Gyr. We use as a proxy for the SF radial profile the Near-UV surface brightness distributions, allowing suitably for extinction. We compare the effective radii (R_eff) and concentration of the flux distribution in the rest-frame Near-UV for a sample of 270 galaxies in the range 0<z<1. This radial distribution is compared to that measured in the rest-frame B-band, which traces older stellar populations. The analysis is performed using deep, high resolution, multi-band images from GALEX, SDSS, and HST/ACS - GOODS-South. The relation R_eff(NUV)- M* suffers a moderate change between z~1 and z~0: at a fixed stellar mass of 1E10 M_sun, galaxies increase their effective radii by a factor 1.18+/-0.06. Median profiles in NUV show signs of truncation at R~R_eff, and median colour profiles (NUV-B) show a minimum (a "bluest" point) also around R~1-1.5 R_eff. The distributions of NUV flux are more compact at z~1 than nowadays, in terms of the fraction of flux enclosed in a specific radius (in kpc). Our results indicate that the SF surface density has decreased dramatically in discs since z~1, and this decline has been more intense in the central parts (<~R_eff) of the galaxies. In addition, our data suggest that the bulges/pseudo-bulges have grown in surface brightness with regard to the discs since z~1.

astro-ph.CO↗