SOFIA/HAWC + observations of the Crab Nebula: dust properties from polarized emission

Supernova remnants (SNRs) are well-recognized dust producers, but their net dust production rate remains elusive due to uncertainties in grain properties that propagate into observed dust mass uncertainties, and determine how efficiently these grains are processed by reverse shocks. In this paper, we present a detection of polarized dust emission in the Crab pulsar wind nebula, the second SNR with confirmed polarized dust emission after Cassiopeia A. We constrain the bulk composition of the dust with new SOFIA/HAWC+ polarimetric data in band C 89 mu m and band D 154 mu m. After correcting for synchrotron polarization, we report dust polarization fractions ranging between 3.7-9.6 per cent and 2.7-7.6 per cent in three individual dusty filaments at 89 and 154 mu m, respectively. The detected polarized signal suggests the presence of large (greater than or similar to 0.05-0.1 mu m) grains in the Crab Nebula. With the observed polarization, and polarized and total fluxes, we constrain the temperatures and masses of carbonaceous and silicate grains. We find that the carbon-rich grain mass fraction varies between 12 and 70 per cent, demonstrating that carbonaceous and silicate grains co-exist in this SNR. Temperatures range from similar to 40 to similar to 70 K and from similar to 30 to similar to 50 K for carbonaceous and silicate grains, respectively. Dust masses range from similar to 10(-4) to similar to 10(-2) M-circle dot for carbonaceous grains and to similar to 10(-1) M-circle dot for silicate grains, in three individual regions.European Research Council (ERC) European Commission 851622MCIN/AEI PID2020114414GB-100National Aeronautics & Space Administration (NASA) NNA17BF53CDeutsches SOFIA Institut (DSI) under DLR 50 OK 0901 URF\R1\21132

Dust grain size evolution in local galaxies: a comparison between observations and simulations

The evolution of the dust grain size distribution has been studied in recent years with great detail in cosmological hydrodynamical simulations taking into account all the channels under which dust evolves in the interstellar medium. We present a systematic analysis of the observed spectral energy distribution of a large sample of galaxies in the local Universe in order to derive not only the total dust masses but also the relative mass fraction between small and large dust grains ( D S / D L ). Simulations reproduce fairly well the observations except for the high-stellar mass regime where dust masses tend to be o v erestimated. We find that ∼45 per cent of galaxies exhibit D S / D L consistent with the expectations of simulations, while there is a subsample of massive galaxies presenting high D S / D L (log ( D S / D L ) ∼−0.5), and deviating from the prediction in simulations. For these galaxies which also have high-molecular gas mass fractions and metallicities, coagulation is not an important mechanism affecting the dust e volution. Including dif fusion, transporting large grains from dense regions to a more diffuse medium where they can be easily shattered, would explain the observed high D S / D L values in these galaxies. With this study, we reinforce the use of the small-to-large grain mass ratio to study the relative importance of the different mechanisms in the dust life cycle. Multiphase hydrodynamical simulations with detailed feedback prescriptions and more realistic subgrid models for the dense phase could help to reproduce the evolution of the dust grain size distribution traced by observations.MCIN/AEI PID2020-114414GB-100 Spanish Government AYA2017-84897-PJunta de Andalucia P2000334 A-FQM-510-UGR20FEDER/Junta de Andalucia-Consejeria de Transformacion Economica, Industria, Conocimiento y Universidades European Research Council (ERC) European Commission 851622HPCI System Research Project hp200041 hp210090Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT)Japan Society for the Promotion of ScienceGrants-in-Aid for Scientific Research (KAKENHI) JP17H01111 19H05810 20H00180Ministry of Science and Technology, China MOST 107-2923-M-001-003-MY3 MOST 108-2112-M-001-007-MY3Academia Sinica - Taiwan AS-IA-109-M02National Basic Research Program of China 2017YFA0402704Comunidad de Madrid 2018-T1/TIC-1103

Modeling Dust and Starlight in Galaxies Observed by Spitzer and Herschel: The KINGFISH Sample

Interstellar dust and starlight are modeled for the galaxies of the project “Key Insights on Nearby Galaxies: A FarInfrared Survey with Herschel.” The galaxies were observed by the Infrared Array Camera and the Multiband Imaging Photometer for Spitzer on Spitzer Space Telescope, and the Photodetector Array Camera and Spectrometer and the Spectral and Photometric Imaging Receiver on Herschel Space Observatory. With data from 3.6 to 500 μm, dust models are strongly constrained. Using a physical dust model, for each pixel in each galaxy we estimate (1) dust surface density, (2) dust mass fraction in polycyclic aromatic hydrocarbons (PAHs), (3) distribution of starlight intensities heating the dust, (4) total infrared (IR) luminosity emitted by the dust, and (5) IR luminosity originating in subregions with high starlight intensity. The dust models successfully reproduce the observed global and resolved spectral energy distributions. With the angular resolution of Herschel, we obtain well-resolved maps (available online) for the dust properties. As in previous studies, we find the PAH fraction qPAH to be an increasing function of metallicity, with a threshold oxygen abundance Z/Ze ≈ 0.1, but we find the data to be fitted best with qPAH increasing linearly with log O H ( ) above a threshold value of 0.15(O/H)e. We obtain total dust masses for each galaxy by summing the dust mass over the individual map pixels; these “resolved” dust masses are consistent with the masses inferred from a model fit to the global photometry. The global dust-to-gas ratios obtained from this study are found to correlate with galaxy metallicities. Systems with Z/Ze 0.5 have most of their refractory elements locked up in dust, whereas in systems with Z/Ze 0.3 most of these elements tend to remain in the gas phase. Within galaxies, we find that qPAH is suppressed in regions with unusually warm dust with nL L n ( ) 70 m 0.4 m dust. With knowledge of one long-wavelength flux density ratio (e.g., f160/f500), the minimum starlight intensity heating the dust (Umin) can be estimated to within ∼50%, despite a variation in Umin of more than two orders of magnitude. For the adopted dust model, dust masses can be estimated to within ∼0.2 dex accuracy using the f160/f500 flux ratio and the integrated dust luminosity, and to ∼0.07 dex accuracy using the 500 μm luminosity nLn ( ) 500 mm alone. There are additional systematic errors arising from the choice of dust model, but these are hard to estimate. These calibrated prescriptions for estimating starlight heating intensity and dust mass may be useful for studies of high-redshift galaxies

A 2D multiwavelength study of the ionized gas and stellar population in the Giant HII Region NGC 588

We present an analysis of NGC588 based on IFS data with PMAS, together with Spitzer images at 8 mi and 24 mi. The extinction distribution in the optical shows complex structure, with maxima correlating in position with those of the emission at 24 mi and 8 mi. The Ha luminosity absorbed by the dust within the GHIIR reproduces the structure observed in the 24 mi image, supporting the use of this band as a tracer of recent star formation. A velocity difference of ~50 km/s was measured between the areas of high and low surface brightness, which would be expected if NGC588 were an evolved GHIIR. Line ratios used in the BPT diagnostic diagrams show a larger range of variation in the low surface brightness areas. The ranges are ~0.5 to 1.2 dex for [NII]/Ha, 0.7 to 1.7 dex for [SII]/Ha, and 0.3 to 0.5 dex for [OIII]/Hb. Ratios corresponding to large ionization parameter (U) are found between the peak of the emission in Hb and the main ionizing source decreasing radially outwards within the region. Differences between the integrated and local values of the U tracers can be as high as ~0.8 dex. [OII]/Hb and [OIII]/[OII] yield similar local values for U and consistent with those expected from the integrated spectrum of an HII region ionized by a single star. The ratio [SII]/Ha departs significantly from the range predicted by this scenario, indicating the complex ionization structure in GHIIRs. There is a significant scatter in derivations of Z using strong line tracers as a function of position, caused by variations in the degree of ionization. The scatter is smaller for N2O3 which points to this tracer as a better Z tracer than N2. The comparison between integrated and local line ratio values indicates that measurements of the line ratios of GHIIR in galaxies at distances >~25 Mpc may be dominated by the ionization conditions in their low surface brightness areas.AM-I, EP-M and JMV acknowledge partial funding through research projects AYA2007-67965-C03-02 from the Spanish PNAYA and CSD2006-00070 1st Science with GTC of the MICINN. MR is supported by a Marie Curie Intra European Fellowship within the 7th European Community Framework Programme. CK, as a Humboldt Fellow, acknowledges support from the Alexander von Humboldt Foundation, Germany

Modeling the dust Spectral Energy Distribution of NGC 4214

To appear in 'The Spectral Energy Distribution of Galaxies' Proceedings IAU Symposium No 284, 2011.We have carried out a detailed modeling of the dust Spectral Energy Distribution (SED) of the nearby, starbursting dwarf galaxy NGC 4214. A key point of our modeling is that we distinguish the emission from (i) HII regions and their associated photodissociation regions (PDRs) and (ii) diffuse dust. For both components we apply templates from the literature calculated with a realistic geometry and including radiation transfer. The large amount of existing data from the ultraviolet (UV) to the radio allows the direct measurement of most of the input parameters of the models. We achieve a good fit for the total dust SED of NGC 4214. In the present contribution we describe the available data, the data reduction and the determination of the model parameters, whereas a description of the general outline of our work is presented in the contribution of Lisenfeld et al. in this volume