Browsing by Author "Hunt, L. K."

Now showing 1 - 6 of 6
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    Comprehensive comparison of models for spectral energy distributions from 0.1 μm to 1mm of nearby star-forming galaxies
    (2019) Hunt, L. K.; De Looze, I; Boquien, M.; Nikutta, R.; Rossi, A.; Bianchil, S.; Dale, D. A.; Granato, G. L.; Kennicutt, R. C.; Silva, L.; Ciesla, L.; Relano, M.; Viaene, S.; Brandl, B.; Calzetti, D.; Croxall, K., V; Draine, B. T.; Galametz, M.; Gordon, K. D.; Groves, B. A.; Helou, G.; Herrera-Camus, R.; Hinz, J. L.; Koda, J.; Salim, S.; Sandstrom, K. M.; Smith, J. D.; Wilson, C. D.; Zibetti, S.
    We have fit the far-ultraviolet (FUV) to sub-millimeter (850 mu m) spectral energy distributions (SEDs) of the 61 galaxies from the Key Insights on Nearby Galaxies: A Far-Infrared Survey with Herschel (KINGFISH). The fitting has been performed using three models: the Code for Investigating GALaxy Evolution (CIGALE), the GRAphite-SILicate approach (GRASIL), and the Multiwavelength Analysis of Galaxy PHYSical properties (MAGPHYS). We have analyzed the results of the three codes in terms of the SED shapes, and by comparing the derived quantities with simple "recipes" for stellar mass (M-star), star-formation rate (SFR), dust mass (M-dust), and monochromatic luminosities. Although the algorithms rely on different assumptions for star-formation history, dust attenuation and dust reprocessing, they all well approximate the observed SEDs and are in generally good agreement for the associated quantities. However, the three codes show very different behavior in the mid-infrared regime: in the 5-10 mu m region dominated by PAH emission, and also between 25 and 70 mu m where there are no observational constraints for the KINGFISH sample. We find that different algorithms give discordant SFR estimates for galaxies with low specific SFR, and that the standard recipes for calculating FUV absorption overestimate the extinction compared to the SED-fitting results. Results also suggest that assuming a "standard" constant stellar mass-to-light ratio overestimates Mstar relative to the SED fitting, and we provide new SED-based formulations for estimating Mstar from WISE W1 (3.4 mu m) luminosities and colors. From a principal component analysis of M-star, SFR, M-dust, and O/H, we reproduce previous scaling relations among Mstar, SFR, and O/H, and find that Mdust can be predicted to within similar to 0.3 dex using only M-star and SFR.
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    Gas, dust, and the CO-to-molecular gas conversion factor in low-metallicity starbursts⋆
    (2023) Hunt, L. K.; Belfiore, F.; Lelli, F.; Draine, B. T.; Marasco, A.; Garcia-Burillo, S.; Venturi, G.; Combes, F.; Weiss, A.; Henkel, C.; Menten, K. M.; Annibali, F.; Casasola, V.; Cignoni, M.; McLeod, A.; Tosi, M.; Beltran, M.; Concas, A.; Cresci, G.; Ginolfi, M.; Kumari, N.; Mannucci, F.
    The factor relating CO emission to molecular hydrogen column density, X-CO, is still subject to uncertainty, in particular at low metallicity. In this paper, to quantify X-CO at two different spatial resolutions, we exploited a dust-based method together with ALMA 12-m and ACA data and H I maps of three nearby metal-poor starbursts, NGC 625, NGC 1705, and NGC 5253. Dust opacity at 250 pc resolution was derived based on dust temperatures estimated by fitting two-temperature modified blackbodies to Herschel PACS data. By using the HI maps, we were then able to estimate dust-to-gas ratios in the regions dominated by atomic gas, and, throughout the galaxy, to infer total gas column densities and H-2 column densities as the difference with HI. Finally, from the ACA CO(1-0) maps, we derived X-CO. We used a similar technique with 40 pc ALMA 12-m data for the three galaxies, but instead derived dust attenuation at 40 pc resolution from reddening maps based on VLT/MUSE data. At 250 pc resolution, we find X-CO  & SIM; 10(22) - 10(23) cm(-2)/K km s(-1), 5-1000 times the Milky Way value, with much larger values than would be expected from a simple metallicity dependence. Instead, at 40 pc resolution, X-CO again shows large variation, but is roughly consistent with a power-law metallicity dependence, given the Z  & SIM; 1/3 Z(& ODOT;) metal abundances of our targets. The large scatter in both estimations could imply additional parameter dependence, which we have investigated by comparing X-CO with the observed velocity-integrated brightness temperatures, I-CO, as predicted by recent simulations. Indeed, larger X-CO is significantly correlated with smaller I-CO, but with slightly different slopes and normalizations than predicted by theory. Such behavior can be attributed to the increasing fraction of CO-faint (or dark) H-2 gas with lower spatial resolution (larger beams). This confirms the idea the X-CO is multivariate, depending not only on metallicity but also on the CO brightness temperature and beam size. Future work is needed to consolidate these empirical results by sampling galaxies with different metal abundances observed at varying spatial resolutions.
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    Identifying the host galaxy of the short GRB 100628A
    (EDP SCIENCES S A, 2015) Guelbenzu, A. Nicuesa; Klose, S.; Palazzi, E.; Greiner, J.; Michalowski, M. J.; Kann, D. A.; Hunt, L. K.; Malesani, D.; Rossi, A.; Savaglio, S.; Schulze, S.; Xu, D.; Afonso, P. M. J.; Elliott, J.; Ferrero, P.; Filgas, R.; Hartmann, D. H.; Kruehler, T.; Knust, F.; Masetti, N.; Olivares E, F.; Rau, A.; Schady, P.; Schmidl, S.; Tanga, M.; Updike, A. C.; Varela, K.
    We report on the results of a comprehensive observing campaign to reveal the host galaxy of the short GRB 100628A. This burst was followed by a faint X-ray afterglow but no optical counterpart was discovered. However, inside the X-ray error circle a potential host galaxy at a redshift of z = 0.102 was soon reported in the literature. If this system is the host, then GRB 100628A was the cosmologically most nearby unambiguous short burst with a measured redshift so far. We used the multi-colour imager GROND at the ESO/La Silla MPG 2.2 in telescope. ESO/VLT spectroscopy, and deep Australia Telescope Compact Array (ATCA) radio-continuum observations together with publicly available Gemini imaging data to study the putative host and the galaxies in the field of GRB 100628A. We confirm that inside the X-ray error circle the most probable host-galaxy candidate is the morphologically disturbed, interacting galaxy system at z = 0.102. The interacting galaxies are connected by a several kpc long tidal stream, which our VLT/FORS2 spectroscopy reveals strong emission lines of [O II] [O III], H alpha and H beta, characteristic for the class of extreme emission-line galaxies and indicative of ongoing star formation. The latter leaves open the possibility that the ORB progenitor was a member of a young stellar population. However, we indentify a second host-galaxy candidate slightly outside the X-ray error circle. It is a radio-bright, luminous elliptical galaxy at a redshift z = 0.311. With a K-band luminosity of 2 x 10(11) L-circle dot this galaxy resembles the probable giant elliptical host of the first well-localized short burst. GRB 050509B. If this is the host, then the progenitor of GRB 100628A was a member of an old stellar population.
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    INSPIRE: INvestigating Stellar Population In RElics III. Second data release (DR2): testing the systematics on the stellar velocity dispersion
    (2023) D'Ago, G.; Spiniello, C.; Coccato, L.; Tortora, C.; La Barbera, F.; Arnaboldi, M.; Bevacqua, D.; Ferre-Mateu, A.; Gallazzi, A.; Hartke, J.; Hunt, L. K.; Martin-Navarro, I.; Napolitano, N. R.; Pulsoni, C.; Radovich, M.; Saracco, P.; Scognamiglio, D.; Zibetti, S.
    Context. The project called INvestigating Stellar Population In RElics (INSPIRE) is based on VLT/X-shooter data from the homonymous on-going ESO Large Program. It targets 52 ultra-compact massive galaxies at 0.1 < z < 0.5 with the goal of constraining their kinematics and stellar population properties in great detail and of analysing their relic nature.
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    Shaken, but not expelled: Gentle baryonic feedback from nearby starburst dwarf galaxies
    (2023) Marasco, A.; Belfiore, F.; Cresci, G.; Lelli, F.; Venturi, G.; Hunt, L. K.; Concas, A.; Marconi, A.; Mannucci, F.; Mingozzi, M.; McLeod, A. F.; Kumari, N.; Carniani, S.; Vanzi, L.; Ginolfi, M.
    Baryonic feedback is expected to play a key role in regulating the star formation of low-mass galaxies by producing galaxy-scale winds associated with mass-loading factors of beta similar to 1-50. We test this prediction using a sample of 19 nearby systems with stellar masses of 10(7) M-star/M-circle dot < 10(10), mostly lying above the main sequence of star-forming galaxies. We used MUSE at VLT optical integral field spectroscopy to study the warm ionised gas kinematics of these galaxies via a detailed modelling of their H alpha emission line. The ionised gas is characterised by irregular velocity fields, indicating the presence of non-circular motions of a few tens of km s(-1) within galaxy discs, but with intrinsic velocity dispersion of 40-60 km s(-1) that are only marginally larger than those measured in main-sequence galaxies. Galactic winds, defined as gas at velocities larger than the galaxy escape speed, encompass only a few percent of the observed fluxes. Mass outflow rates and loading factors are strongly dependent on M-star, the star formation rate (SFR), SFR surface density, and specific SFR (sSFR). For M-star of 10(8) M-circle dot we find beta similar or equal to 0.02, which is more than two orders of magnitude smaller than the values predicted by theoretical models of galaxy evolution. In our galaxy sample, baryonic feedback stimulates a gentle gas cycle rather than causing a large-scale blow-out.
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    The interstellar medium of dwarf galaxies : new insights from Machine Learning analysis of emission-line spectra
    (2019) Ucci, G.; Ferrara, A.; Gallerani, S.; Pallottini, A.; Cresci, G.; Kehrig, C.; Hunt, L. K.; Vilchez, J. M.; Vanzi, Leonardo