Reddening law and interstellar dust properties along Magellanic sight-lines

This study establishes that SMC, LMC and Milky Way extinction curves obey the same extinction law which depends on the 2200A bump size and one parameter, and generalizes the Cardelli, Clayton and Mathis (1989) relationship. This suggests that extinction in all three galaxies is of the same nature. The role of linear reddening laws over all the visible/UV wavelength range, particularly important in the SMC but also present in the LMC and in the Milky Way, is also highlighted and discussed.Comment: accepted for publication in Astrophysics and Space Science. 16 pages, 12 figures. Some figures are colour plot

On the accretion disc properties in eclipsing dwarf nova EM Cyg

In this paper we analyzed the behavior of the unusual dwarf nova EM Cyg using the data obtained in April-October, 2007 in Vyhorlat observatory (Slovak Republic) and in September, 2006 in Crimean Astrophysical Observatory (Ukraine). During our observations EM Cyg has shown outbursts in every 15-40 days. Because on the light curves of EM Cyg the partial eclipse of an accretion disc is observed we applied the eclipse mapping technique to reconstruct the temperature distribution in eclipsed parts of the disc. Calculations of the accretion rate in the system were made for the quiescent and the outburst states of activity for different distances.Comment: 6 pages, 3 figures, accepted in Astrophysics and Space Scienc

Fitting the integrated Spectral Energy Distributions of Galaxies

Fitting the spectral energy distributions (SEDs) of galaxies is an almost universally used technique that has matured significantly in the last decade. Model predictions and fitting procedures have improved significantly over this time, attempting to keep up with the vastly increased volume and quality of available data. We review here the field of SED fitting, describing the modelling of ultraviolet to infrared galaxy SEDs, the creation of multiwavelength data sets, and the methods used to fit model SEDs to observed galaxy data sets. We touch upon the achievements and challenges in the major ingredients of SED fitting, with a special emphasis on describing the interplay between the quality of the available data, the quality of the available models, and the best fitting technique to use in order to obtain a realistic measurement as well as realistic uncertainties. We conclude that SED fitting can be used effectively to derive a range of physical properties of galaxies, such as redshift, stellar masses, star formation rates, dust masses, and metallicities, with care taken not to over-interpret the available data. Yet there still exist many issues such as estimating the age of the oldest stars in a galaxy, finer details ofdust properties and dust-star geometry, and the influences of poorly understood, luminous stellar types and phases. The challenge for the coming years will be to improve both the models and the observational data sets to resolve these uncertainties. The present review will be made available on an interactive, moderated web page (sedfitting.org), where the community can access and change the text. The intention is to expand the text and keep it up to date over the coming years.Comment: 54 pages, 26 figures, Accepted for publication in Astrophysics & Space Scienc

DirtyGrid II: An Analysis of the Dust and Stellar Properties in Nearby Star-forming Galaxies

We study the dust and stellar properties of the Spitzer Infrared Nearby Galaxies Survey galaxies by fitting the ultraviolet (UV) to far-infrared (FIR) spectral energy distributions using the DirtyGrid stellar and dust radiative transfer models. We find a minimum of two components of different stellar ages are needed, representing a young and an old stellar population, in order to obtain good fits for most of the galaxies. Our total dust masses agree with literature dust masses to within a factor of 2, and the residuals correlate most strongly with the stellar mass surface density of the old component. The LMC-2 dust grain model best describes the dust found in these normal star-forming galaxies. The derived attenuation curves are steeper than those found previously for starburst galaxies, and possess a weak 2175 Å feature. The relative contribution of the young and old stellar components as a function of wavelength reveals that the young component dominates the far-UV and MIPS24 bands, the old component dominates the optical/near-IR bands, and both components are important for the FIR bands. The DirtyGrid star formation rates (SFRs) are consistent with a number of literature SFR indicators within a factor of 2. The differences we find are primarily due to the influence of the old stellar population that are accounted for by the DirtyGrid SFRs fitting on a galaxy-by-galaxy basis using the information present in the full UV-FIR spectral energy distribution. © 2021. The American Astronomical Society. All rights reserved..Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Milky Way Mid-Infrared Spitzer Spectroscopic Extinction Curves: Continuum and Silicate Features

We measured the mid-infrared (MIR) extinction using Spitzer photometry and spectroscopy (3.6-37 μm) for a sample of Milky Way sight lines (mostly) having measured ultraviolet extinction curves. We used the pair method to determine the MIR extinction that we then fit with a power law for the continuum and modified Drude profiles for the silicate features. We derived 16 extinction curves having a range of A(V) (1.8-5.5) and R(V) values (2.4-4.3). Our sample includes two dense sight lines that have 3 μm ice feature detections and weak 2175 Å bumps. The average A(λ)/A(V) diffuse sight-line extinction curve we calculate is lower than most previous literature measurements. This agrees better with literature diffuse dust grain models, though it is somewhat higher. The 10 μm silicate feature does not correlate with the 2175 Å bump, for the first time providing direct observational confirmation that these two features arise from different grain populations. The strength of the 10 μm silicate feature varies by ∼2.5 and is not correlated with A(V) or R(V). It is well fit by a modified Drude profile with strong correlations seen between the central wavelength, width, and asymmetry. We do not detect other features with limits in A(λ)/A(V) units of 0.0026 (5-10 μm), 0.004 (10-20 μm), and 0.008 (20-40 μm). We find that the standard prescription of estimating R(V) from C E(K s - V)/E(B - V) has C = -1.14 and a scatter of ∼7%. Using the IRAC 5.6 μm band instead of K s gives C = -1.03 and the least scatter of ∼3%. © 2021. The American Astronomical Society. All rights reserved..Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Spitzer observations of the SCUBA/VLA sources in the Lockman Hole: Star formation history of infrared-luminous galaxies

We present Spitzer Space Telescope imaging observations at 3.6, 4.5, 5.8, 8.0, and 24 mum of the SCUBA submillimeter sources and muJy VLA radio sources in a 5' x 5' area in the Lockman Hole East region. Out of the similar to 40 SCUBA/VLA sources in the field, Spitzer counterparts were detected for nearly all except for the few low-weight SCUBA detections. We show that the majority (80% - 90%) of the detected sources are cold (i.e., starburst-like) infrared-luminous galaxies (L-IR > 10(11) L-.) at redshift 0.5 < z < 3.5, whose star-formation rate density (SFRD) is comparable to that of the optically selected star-forming galaxies

Submillimeter detections of Spitzer Space Telescope galaxy populations

We present submillimeter statistical detections of galaxies discovered in the 5' x 5' Spitzer Early Release Observations (to similar to4 - 15 muJy 5 sigma at 3.6 - 8 mum, 170 muJy at 24 mum) through a stacking analysis of our reanalyzed SCUBA 8 mJy survey maps and a Spitzer identification of a new submillimeter point source in the 8 mJy survey region. For sources detected at 5.8 or 8 mum ( 154 and 111 sources, respectively), we detect positive skews in the submillimeter flux distributions at 99.2% - 99.8% confidence using Kolmogorov-Smirnov tests, at both 850 and 450 mum. We also marginally detect the Spitzer 24 mum galaxies at 850 mum at 97% confidence and place limits on the mean submillimeter fluxes of the 3.6 and 4.5 mum sources. Integrating the submillimeter fluxes of the Spitzer populations, we find the 5.8 mum galaxies contribute 0.12 +/- 0.05 nW m(-2) sr(-1) to the 850 mum background and 2.4 +/- 0.7 nWm(-2) sr(-1) to the 450 mum background; similar contributions are made by the 8 mum-selected sample. We infer that the populations dominating the 5.8 and 8 mum extragalactic background light also contribute around a quarter of the 850 mum background and the majority of the 450 mum background

Spitzer Observations of MAMBO Galaxies: Weeding Out Active Nuclei in Starbursting Protoellipticals

We present 3.6 - 24 mum Spitzer observations of an unbiased sample of nine luminous, dusty galaxies selected at 1200 mum by MAMBO on the IRAM 30 m telescope, a population akin to the well-known submillimeter or SCUBA galaxies ( hereafter SMGs). Owing to the coarse resolution of submillimeter/millimeter cameras, SMGs have traditionally been difficult to identify at other wavelengths. We compare our multiwavelength catalogs to show that the overlap between 24 and 1200 mum must be close to complete at these flux levels. We find that all (4/4) of the most secure greater than or equal to4 sigma SMGs have greater than or equal to 4 sigma counterparts at 1.4 GHz, while the fraction drops to 7/9 using all greater than or equal to 3 sigma SMGs. We show that combining mid-infrared (MIR) and marginal ( greater than or equal to 3 sigma) radio detections provides plausible identifications in the remaining cases, enabling us to identify the complete sample. Accretion onto an obscured central engine is betrayed by the shape of the MIR continuum emission for several sources, confirming Spitzer's potential to weed out active galaxies. We demonstrate the power of an S-24 mum/S-8 mum versus S-8 mum/S-4.5 mum color-color plot as a diagnostic for this purpose. However, we conclude that the majority ( similar to 75%) of SMGs have rest-frame mid/far-IR spectral energy distributions commensurate with obscured starbursts. Sensitive 24 mum observations are clearly a useful route to identify and characterize reliable counterparts to high-redshift far-IR-bright galaxies, complementing what is possible via deep radio imaging

The Complex Interplay of Dust and Star Light in Spiral Galaxy Discs

Interstellar dust grains efficiently absorb and scatter UV and optical radiation in galaxies, and therefore can significantly affect the apparent structure of spiral galaxies. We discuss the effect of dust attenuation on the observed structural properties of bulges and discs. We also present some first results on modelling the dust content of edge-on spiral galaxies using both optical and Herschel far-infrared data. Both of these results demonstrate the complex interplay of dust and star light in spiral galaxies.Comment: 6 pages, 2 figures, to appear in "Galaxies and their Masks", eds. D. L. Block, K. C. Freeman & I. Puerari, Springer (New York