SPECTRAL ENERGY DISTRIBUTION MAPPING OF TWO ELLIPTICAL GALAXIES ON SUB-kpc SCALES

Abstract

We use high-resolution Herschel-PACS data of 2 nearby elliptical galaxies, IC1459 & NGC2768 to characterize their dust and stellar content. IC1459 & NGC2768 have an unusually large amount of dust for elliptical galaxies (1 to 3×10 5 M ), this dust is also not distributed along the stellar content. Using data from GALEX (ultra-violet) to PACS (far-infrared), we analyze the spectral energy distribution (SED) of these galaxies with CIGALEMC as a function of the projected position, binning images in 7.2" pixels. From this analysis, we derive maps of SED parameters, such as the metallicity, the stellar mass, the fraction of young star and the dust mass. The larger amount of dust in FIR maps seems related in our model to a larger fraction of young stars which can reach up to 4% in the dustier area. The young stellar population is fitted as a recent (∼ 0.5 Gyr) short burst of star formation for both galaxies. The metallicities, which are fairly large at the center of both galaxies, decrease with the radial distance with fairly steep gradient for elliptical galaxies.

Unravelling the origin of the counter-rotating core in IC 1459 with KMOS and MUSE

“…However, we do not detect the low-metal populations towards the centre (top and middle panels of Figure 10), so if it was purely a problem with the fit then perhaps this should be seen in every radial bin. Previous studies of IC 1459 also measure this negative metallicity gradient (Carollo, Danziger & Buson 1993;Amblard et al 2017). This radial trend in metallicity has also been reported for several other KDCs (e.g., Efstathiou & Gorgas 1985;Franx & Illingworth 1988;Gorgas, Efstathiou & Aragon Salamanca 1990;Bender & Surma 1992;Mehlert et al 1998;Davies et al 2001;Emsellem et al 2004;Kuntschner et al 2010).…”

“…We measured a relatively constant metallicity gradient in IC 1459 with PyStaff but a negative gradient with ppxf (as determined in previous studies of IC 1459 e.g., Carollo, Danziger & Buson 1993;Amblard et al 2017). This radial trend in metallicity has also been reported for several other KDCs (e.g., Efstathiou & Gorgas 1985;FI88;Gorgas, Efstathiou & Aragon Salamanca 1990;Bender & Surma 1992;Mehlert et al 1998;Davies et al 2001;Emsellem et al 2004;Kuntschner et al 2010).…”

Panchromatic SED modelling of spatially resolved galaxies

“…Other works have found tentative evidence for similar resolution-dependent bias in dust masses derived for the Large Magellanic Cloud (Galliano et al 2011), and for NGC 628 and NGC 6946 (Aniano et al 2012). Elsewhere, Amblard et al (2017) attempted a spatially-resolved SED decomposition of two local early type galaxies (IC1459 and NGC2768) on sub-kpc scales from rest-frame UV to the far-infrared (including wavelengths up to 160 µm). Most recently, Jung et al (2017) studied the difference in stellar mass, SFR, UV dust obscuration, and mass-weighted age recovered whether the integrated or resolved UV to near-IR photometry is used for parameter estimation (using a Monte-Carlo Markov Chain sampler based on CB07 models), in order to investigate the radial dependence of the specific star formation rate in high-redshift galaxies.…”

“…That MAGPHYS is able to at least qualitatively recover the metallicity gradient in the simulated galaxy is particularly interesting, despite the bias towards lower values and scatter of around δZ ≈ 0.2 in the recovered values. With Amblard et al (2017), for example, finding evidence for radial dependence in the Figure 13. Recovery of mass-weighted age for camera 0.…”

“…The views which we have used for the MAGPHYS analysis (cameras 0, 3 & 5) are outlined. Sanders et al 2013;Acquaviva 2016, though see also Amblard et al 2017). It is generally recognised that the best metallicity and age estimates can only be obtained through deep spectroscopy (e.g.…”