We have measured the emission line profiles in Hα from populations of HII regions in nearby spiral galaxies, and extracted their non-thermal line widths. These are supersonic for the more luminous ...regions. We infer from plots of line width, σ, against Hα luminosity, a set of regions in virial equilibrium, and derive their masses summing all known components. The virial masses are considerably larger. If this discrepancy, and the supersonic line widths, are due to the presence of magnetic fields, we can estimate their strengths at a few microgauss. Observational confirmation is clearly required.
We present high-resolution Hα velocity fields and rotation curves of the circum nuclear star-forming regions of five barred galaxies. Two of the five objects show substantially smaller initial rises ...than the three others; these two objects also have spiral structure inside the circum nuclear star-forming ring.PUBLICATION ABSTRACT
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.
We present new JWST observations of the nearby, prototypical edge-on, spiral galaxy NGC 891. The northern half of the disk was observed with NIRCam in its F150W and F277W filters. Absorption is ...clearly visible in the mid-plane of the F150W image, along with vertical dusty plumes that closely resemble the ones seen in the optical. A $ kpc ^2$ area of the lower circumgalactic medium (CGM) was mapped with MIRI F770W at 12 pc scales. Thanks to the sensitivity and resolution of JWST, we detect dust emission out to $ 4$ kpc from the disk, in the form of filaments, arcs, and super-bubbles. Some of these filaments can be traced back to regions with recent star formation activity, suggesting that feedback-driven galactic winds play an important role in regulating baryonic cycling. The presence of dust at these altitudes raises questions about the transport mechanisms at play and suggests that small dust grains are able to survive for several tens of million years after having been ejected by galactic winds in the disk-halo interface. We lay out several scenarios that could explain this emission: dust grains may be shielded in the outer layers of cool dense clouds expelled from the galaxy disk, and/or the emission comes from the mixing layers around these cool clumps where material from the hot gas is able to cool down and mix with these cool cloudlets. This first set of data and upcoming spectroscopy will be very helpful to understand the survival of dust grains in energetic environments, and their contribution to recycling baryonic material in the mid-plane of galaxies.
We aim to provide observational signatures of the dust size evolution in the ISM. In particular, we explore indicators of the polycyclic aromatic hydrocarbon (PAH) mass fraction (\(q_{PAH}\)), ...defined as the mass fraction of PAHs relative to total dust grains. In addition, we validate our dust evolution model by comparing the observational signatures from our simulations to observations. We used the hydrodynamic simulation code, GADGET4-OSAKA to model the dust properties of Milky Way-like and NGC 628-like galaxies representing star-forming galaxies. This code incorporates the evolution of grain size distributions driven by dust production and interstellar processing. Furthermore, we performed post-processing dust radiative transfer with SKIRT based on the simulations to predict the observational properties. We find that the intensity ratio between 8 um and 24 um is correlated with \(q_{PAH}\) and can be used as an indicator of PAH mass fraction. However, this ratio is influenced by the radiation field. We suggest the 8 um-to-total infrared intensity ratio (\(\nu I_\nu(8 \mu m)/I\)(TIR)) as another indicator, since it is tightly correlated with \(q_{PAH}\). Furthermore, we explored the spatially resolved \(q_{PAH}\) in the simulated Milky Way-like galaxy using \(\nu I_\nu(8 \mu m)/I\)(TIR). We find that the spatially resolved \(q_{PAH}\) increases with metallicity at metallicity at Z<0.2 Zsun due to the interplay between accretion and shattering while it decreases at Z>0.2 Zsun because of coagulation. Finally, we compared the above indicators in the NGC 628-like simulation with those observed in NGC 628 by recent observations. Consequently, we find that our simulation underestimates the PAH mass fraction throughout the entire galaxy by a factor of \(\sim 8\) on average. This could be due to the efficient loss of PAHs by coagulation in our model.
We describe a set of Ha emission line profiles from populations of H II regions in nearby spiral galaxies. These are characterized by a strong Gaussian central peak, and lower intensity higher ...velocity wing features. From the peak we extract a non-thermal velocity component, due to the internal turbulence of the region. The plot of the widths of these non-thermal components against Ha luminosity shows a lower envelope in line width, which we assign to regions in, or close to virial equilibrium, although the region mass derived on this assumption is higher than the mass obtained by summing all known mass components. We speculate that this discrepancy, as well as the supersonicity of the line widths, can be explained by the presence of turbulent magnetic fields within the H II regions, and make a very rough estimate of the fields implied, of order a few tens of microgauss.
We present a multiwavelength (ultraviolet, infrared, optical, and CO) study of a set of luminous H II regions in M33: NGC 604, NGC 595, NGC 592, NGC 588, and IC131. We study the emission distribution ...in the interiors of the H II regions to investigate the relation between the dust emission at 8 {mu}m and 24 {mu}m and the location of the massive stars and gas. We find that the 24 {mu}m emission is closely related to the location of the ionized gas, while the 8 {mu}m emission is more related to the boundaries of the molecular clouds consistently with its expected association with photodissociation regions. Ultraviolet emission is generally surrounded by the H{alpha} emission. For NGC 604 and NGC 595, where CO data are available, we see a radial gradient of the emission distribution at the wavelengths studied here: from the center to the boundary of the H II regions we observe ultraviolet, H{alpha}, 24 {mu}m, 8 {mu}m, and CO emission distributions. We quantify the star formation for our H II regions using the integrated fluxes at the set of available wavelengths, assuming an instantaneous burst of star formation. We show that a linear combination of 24 {mu}m and H{alpha} emission better describes the star formation for these objects than the dust luminosities by themselves. For NGC 604, we obtain and compare extinction maps derived from the Balmer decrement and from the 24 {mu}m and H{alpha} emission line ratio. Although the maps show locally different values in extinction, we find similar integrated extinctions derived from the two methods. We also investigate here the possible existence of embedded star formation within NGC 604.
ALMA observations revealed the presence of significant amounts of dust in the first Gyr of Cosmic time. However, the metal and dust buildup picture remains very uncertain due to the lack of ...constraints on metallicity. JWST has started to reveal the metal content of high-redshift targets, which may lead to firmer constraints on high-redshift dusty galaxies evolution. In this work, we use detailed chemical and dust evolution models to explore the evolution of galaxies within the ALMA REBELS survey, testing different metallicity scenarios that could be inferred from JWST observations. In the models, we track the buildup of stellar mass by using non-parametric SFHs for REBELS galaxies. Different scenarios for metal and dust evolution are simulated by allowing different prescriptions for gas flows and dust processes. The model outputs are compared with measured dust scaling relations, by employing metallicity-dependent calibrations for the gas mass based on the CII158micron line. Independently of the galaxies metal content, we found no need for extreme dust prescriptions to explain the dust masses revealed by ALMA. However, different levels of metal enrichment will lead to different dominant dust production mechanisms, with stardust production dominant over other ISM dust processes only in the metal-poor case. This points out how metallicity measurements from JWST will significantly improve our understanding of the dust buildup in high-redshift galaxies. We also show that models struggle to reproduce observables such as dust-to-gas and dust-to-stellar ratios simultaneously, possibly indicating an overestimation of the gas mass through current calibrations, especially at high metallicities.
Supernova remnants (SNRs) are well-recognised 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 polarised dust emission in the Crab pulsar wind nebula, the second SNR with confirmed polarised dust emission after Cassiopeia A. We constrain the bulk composition of the dust with new SOFIA/HAWC+ polarimetric data in band C 89 um and band D 154 um. After correcting for synchrotron polarisation, we report dust polarisation 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 um, respectively. The detected polarised signal suggests the presence of large (> 0.05-0.1 um) grains in the Crab Nebula. With the observed polarisation, and polarised 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 40 K to 70 K and from 30 K to 50 K for carbonaceous and silicate grains, respectively. Dust masses range from 10^{-4} Msol to 10^{-2} Msol for carbonaceous grains and to 10^{-1} Msol for silicate grains, in three individual regions.
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