7 research outputs found
Attenuation modified by DIG and dust as seen in M31
The spatial distribution of dust in galaxies affects the global attenuation,
and hence inferred properties, of galaxies. We trace the spatial distribution
of dust in five fields (at 0.6-0.9 kpc scale) of M31 by comparing optical
attenuation with the total dust mass distribution. We measure the attenuation
from the Balmer decrement using Integral Field Spectroscopy and the dust mass
from Herschel far-IR observations. Our results show that M31's dust attenuation
closely follows a foreground screen model, contrary to what was previously
found in other nearby galaxies. By smoothing the M31 data we find that spatial
resolution is not the cause for this difference. Based on the emission line
ratios and two simple models, we conclude that previous models of dust/gas
geometry need to include a weakly or non-attenuated diffuse ionized gas (DIG)
component. Due to the variation of dust and DIG scale heights with galactic
radius, we conclude that different locations in galaxies will have different
vertical distributions of gas and dust and therefore different measured
attenuation. The difference between our result in M31 with that found in other
nearby galaxies can be explained by our fields in M31 lying at larger galactic
radii than the previous studies that focused on the centres of galaxies.Comment: 20 pages, 13 figures, ApJ accepted and in pres
GASP and MaNGA Surveys Shed Light on the Enigma of the Gas Metallicity Gradients in Disk Galaxies
Making use of both MUSE observations of 85 galaxies from the survey GASP (GAs Stripping Phenomena in galaxies with MUSE) and a large sample from MaNGA (Mapping Nearby Galaxies at Apache Point Observatory survey), we investigate the distribution of gas metallicity gradients as a function of stellar mass for local cluster and field galaxies. Overall, metallicity profiles steepen with increasing stellar mass up to 1010.3 M o˙ and flatten out at higher masses. Combining the results from the metallicity profiles and the stellar mass surface density gradients, we propose that the observed steepening is a consequence of local metal enrichment due to in situ star formation during the inside-out formation of disk galaxies. The metallicity gradient-stellar mass relation is characterized by a rather large scatter, especially for 109.8 < M ∗/M o˙ < 1010.5, and we demonstrate that metallicity gradients anti-correlate with the galaxy gas fraction. Focusing on the galaxy environment, at any given stellar mass, cluster galaxies have systematically flatter metallicity profiles than their field counterparts. Many subpopulations coexist in clusters: galaxies with shallower metallicity profiles appear to have fallen into their present host halo sooner and have experienced the environmental effects for a longer time than cluster galaxies with steeper metallicity profiles. Recent galaxy infallers, like galaxies currently undergoing ram pressure stripping, show metallicity gradients more similar to those of field galaxies, suggesting they have not felt the effect of the cluster yet
GASP XXIII: A jellyfish galaxy as an astrophysical laboratory of the baryonic cycle
With MUSE, Chandra, VLA, ALMA and UVIT data from the GASP programme we study
the multiphase baryonic components in a jellyfish galaxy (JW100) with a stellar
mass 3.2 X 10^{11} M_sun hosting an AGN. We present its spectacular extraplanar
tails of ionized and molecular gas, UV stellar light, X-ray and radio continuum
emission. This galaxy represents an excellent laboratory to study the interplay
between different gas phases and star formation, and the influence of gas
stripping, gas heating, and AGN. We analyze the physical origin of the emission
at different wavelengths in the tail, in particular in-situ star formation
(related to Halpha, CO and UV emission), synchrotron emission from relativistic
electrons (producing the radio continuum) and heating of the stripped
interstellar medium (ISM) (responsible for the X-ray emission). We show the
similarities and differences of the spatial distributions of ionized gas,
molecular gas and UV light, and argue that the mismatch on small scales (1kpc)
is due to different stages of the star formation process. We present the
relation Halpha--X-ray surface brightness, which is steeper for star-forming
regions than for diffuse ionised gas regions with high [OI]/Halpha ratio. We
propose that ISM heating due to interaction with the intracluster medium
(either for mixing, thermal conduction or shocks) is responsible for the X-ray
tail, the observed [OI]-excess and the lack of star formation in the northern
part of the tail. We also report the tentative discovery in the tail of the
most distant (and among the brightest) currently known ULX, a point-like
ultraluminous X-ray source commonly originating in a binary stellar system
powered either by an intermediate-mass black hole or a magnetized neutron star.Comment: accepted for publication in Ap
13 CO/C 18 O Gradients across the Disks of Nearby Spiral Galaxies
International audienc
¹³CO/C¹⁸O Gradients across the Disks of Nearby Spiral Galaxies
We use the IRAM Large Program EMPIRE and new high-resolution ALMA data to measure 13CO(1-0)/C18O(1-0)
intensity ratios across nine nearby spiral galaxies. These isotopologues of 12CO are typically optically thin across
most of the area in galaxy disks, and this ratio allows us to gauge their relative abundance due to chemistry or
stellar nucleosynthesis effects. Resolved 13CO/C18O gradients across normal galaxies have been rare due to the
faintness of these lines. We find a mean 13CO/C18O ratio of 6.0 ± 0.9 for the central regions of our galaxies. This
agrees well with results in the Milky Way, but differs from results for starburst galaxies (3.4 ± 0.9) and
ultraluminous infrared galaxies (1.1 ± 0.4). In our sample, the 13CO/C18O ratio consistently increases with
increasing galactocentric radius and decreases with increasing star formation rate surface density. These trends
could be explained if the isotopic abundances are altered by fractionation; the sense of the trends also agrees with
those expected for carbon and oxygen isotopic abundance variations due to selective enrichment by massive stars.F.B., M.J., and D.C. acknowledge support from DFG grant
BI 1546/1-1. A.H. acknowledges support from the Centre
National d’Etudes Spatiales (CNES). A.U. acknowledges
support from Spanish MINECO grants FIS2012-32096 and
ESP2015-68964. The work of A.K.L. is partially supported by
the National Science Foundation under grants No. 1615105 and
1615109. M.R.K. acknowledges support from ARC
DP160100695. The National Radio Astronomy Observatory
is a facility of the National Science Foundation operated under
cooperative agreement by Associated Universities, Inc. This
paper makes use of the following ALMA data: ADS/JAO.
ALMA #2011.0.00004.SV. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS
(Japan), together with NRC (Canada), NSC and ASIAA
(Taiwan), and KASI (Republic of Korea), in cooperation with
the Republic of Chile. The Joint ALMA Observatory is
operated by ESO, AUI/NRAO and NAOJ
Post-starburst Galaxies in the Centers of Intermediate-redshift Clusters
International audienceWe present results from MUSE spatially resolved spectroscopy of 21 post-starburst galaxies in the centers of eight clusters from z ~ 0.3 to z ~ 0.4. We measure spatially resolved star formation histories (SFHs), the time since quenching (t Q ), and the fraction of stellar mass assembled in the past 1.5 Gyr (μ 1.5). The SFHs display a clear enhancement of star formation prior to quenching for 16 out of 21 objects, with at least 10% (and up to >50%) of the stellar mass being assembled in the past 1.5 Gyr and t Q ranging from less than 100 to ~800 Myr. By mapping t Q and μ 1.5, we analyze the quenching patterns of the galaxies. Most galaxies in our sample have quenched their star formation from the outside in or show a side-to-side/irregular pattern, both consistent with quenching by ram pressure stripping. Only three objects show an inside-out quenching pattern, all of which are at the high-mass end of our sample. At least two of them currently host an active galactic nucleus. In two post-starbursts, we identify tails of ionized gas indicating that these objects had their gas stripped by ram pressure very recently. Post-starburst features are also found in the stripped regions of galaxies undergoing ram pressure stripping in the same clusters, confirming the link between these classes of objects. Our results point to ram pressure stripping as the main driver of fast quenching in these environments, with active galactic nuclei playing a role at high stellar masses