scholarly journals High-resolution, 3D radiative transfer modelling

2020 ◽  
Vol 643 ◽  
pp. A90
Author(s):  
Angelos Nersesian ◽  
Sébastien Viaene ◽  
Ilse De Looze ◽  
Maarten Baes ◽  
Emmanuel M. Xilouris ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Radiative Transfer ◽  
Radiation Field ◽  
Stellar Population ◽  
Spectral Energy Distribution ◽  
Stellar Populations ◽  
Infrared Emission ◽  
Spectral Energy ◽  
Combined System ◽  
Energy Fraction

Context. Investigating the dust heating mechanisms in galaxies provides a deeper understanding of how the internal energy balance drives their evolution. Over the last decade radiative transfer simulations based on the Monte Carlo method have emphasised the role of the various stellar populations heating the diffuse dust. Beyond the expected heating through ongoing star formation, older stellar populations (≥8 Gyr) and even active galactic nuclei can both contribute energy to the infrared emission of diffuse dust. Aims. In this particular study we examine how the radiation of an external heating source, such as the less massive galaxy NGC 5195 in the M 51 interacting system, could affect the heating of the diffuse dust of its parent galaxy NGC 5194, and vice versa. Our goal is to quantify the exchange of energy between the two galaxies by mapping the 3D distribution of their radiation field. Methods. We used SKIRT, a state-of-the-art 3D Monte Carlo radiative transfer code, to construct the 3D model of the radiation field of M 51, following the methodology defined in the DustPedia framework. In the interest of modelling, the assumed centre-to-centre distance separation between the two galaxies is ∼10 kpc. Results. Our model is able to reproduce the global spectral energy distribution of the system, and it matches the resolved optical and infrared images fairly well. In total, 40.7% of the intrinsic stellar radiation of the combined system is absorbed by dust. Furthermore, we quantify the contribution of the various dust heating sources in the system, and find that the young stellar population of NGC 5194 is the predominant dust-heating agent, with a global heating fraction of 71.2%. Another 23% is provided by the older stellar population of the same galaxy, while the remaining 5.8% has its origin in NGC 5195. Locally, we find that the regions of NGC 5194 closer to NGC 5195 are significantly affected by the radiation field of the latter, with the absorbed energy fraction rising up to 38%. The contribution of NGC 5195 remains under the percentage level in the outskirts of the disc of NGC 5194. This is the first time that the heating of the diffuse dust by a companion galaxy is quantified in a nearby interacting system.

Stellar Population Models of Distant Radio Galaxies

1996 ◽  
Vol 175 ◽  
pp. 588-590
Author(s):  
D. Villani ◽  
S. Di Serego Alighieri
Keyword(s):  
Energy Distribution ◽  
Galaxy Formation ◽  
Stellar Population ◽  
Spectral Energy Distribution ◽  
Formation Rate ◽  
Stellar Populations ◽  
Radio Galaxies ◽  
Initial Mass Function ◽  
Spectral Energy ◽  
The Galaxy

Stellar populations of high redshift radio galaxies (HzRG) (z up to 4.2) are the oldest stellar systems known, that is the ones formed at the earliest cosmological epochs. Therefore they are the best objects for providing us with information about the epoch of galaxy formation. The information on the stellar populations in HzRG are obtained from the study of their Integrated Spectral Energy Distribution (ISED) which are gathered both from spectra and integrated magnitudes. The most common approach for the interpretation of colors and spectral features of the energy distribution of galaxies is the Evolutionary Population Synthesis (EPS), which has been introduced for the first time by Tinsley in 1972. EPS models have often been used in the past to interpret the ISED of HzRG (Chambers & Charlot 1990; Lilly & Longair 1984; di Serego Alighieri et al. 1994) in order to draw conclusions on the age of the stellar populations and therefore on the epoch of galaxy formation. The results are sometimes conflicting and a number of very recent EPS models have become available (Bressan et al. 1995; Bruzual & Charlot 1993; Buzzoni 1989; Guiderdoni & Rocca-Volmerange 1987): we are therefore analysing the differences between the various EPS models with the aim of assessing their suitability to study the stellar population at early epochs. The EPS models assume for stars a given Initial Mass Function(IMF) as well as a Star Formation Rate (SFR). Then one can compute the number of stars with given mass present in the galaxy as a function of time. The position of each star in the HR diagram is determined by means of the isochrones, which are calculated from stellar evolutionary models. The ISED of a galaxy is obtained from the superposition of the spectra of single stars obtained from a stellar spectral library. Thus these models describe the galaxy ISED as a function of the time, giving a complete evolutionary picture.

scholarly journals UV upturn versus UV weak galaxies: differences and similarities of their stellar populations unveiled by a de-biased sample

2020 ◽  
Vol 500 (2) ◽  
pp. 1870-1883
Author(s):  
M L L Dantas ◽  
P R T Coelho ◽  
P Sánchez-Blázquez
Keyword(s):  
Star Formation ◽  
Stellar Population ◽  
Spectral Energy Distribution ◽  
Formation Rate ◽  
Principal Component ◽  
Stellar Populations ◽  
Spectral Energy ◽  
Two Samples ◽  
Star Formation Histories ◽  
Uv Upturn

ABSTRACT The ultraviolet (UV) upturn is characterized by an unexpected up-rise of the UV flux in quiescent galaxies between the Lyman limit and 2500 Å. By making use of colour–colour diagrams, one can subdivide UV bright red-sequence galaxies in two groups: UV weak and upturn. With these two groups, we propose a comparison between their stellar population properties with the goal of establishing differences and similarities between them. We make use of propensity score matching to mitigate potential biases between the two samples, by selecting similar objects in terms of redshift and stellar mass. Also, we take advantage of spectral energy distribution (SED) fitting results from magphys made available by the GAMA collaboration. The analyses are made by comparing the distributions from the SED fitting directly, as well as investigating the differences in correlations between their parameters, and finally by using principal component analysis. We explore important differences and similarities between UV weak and upturn galaxies in terms of several parameters, such as: metallicity, age, specific star formation rate, time of last burst of star-formation, to mention a few. Notable differences are those concerning (g − r) colour, metallicity, and time since last burst of star-formation: UV upturn are redder in the optical, more metallic, and their last burst of star-formation happened earlier in time. These differences suggest that UV upturn systems have shorter star-formation histories (i.e. have been evolving more passively) when compared to UV weak galaxies. Consequently, these last seem to have a higher diversity of stellar populations.

scholarly journals The ALHAMBRA survey: 2D analysis of the stellar populations in massive early-type galaxies at z < 0.3

2017 ◽  
Vol 609 ◽  
pp. A20 ◽  
Author(s):  
I. San Roman ◽  
A. J. Cenarro ◽  
L. A. Díaz-García ◽  
C. López-Sanjuan ◽  
J. Varela ◽  
...  
Keyword(s):  
Stellar Population ◽  
Low Cost ◽  
Voronoi Tessellation ◽  
Spectral Energy Distribution ◽  
Stellar Populations ◽  
Spectral Energy ◽  
Early Type ◽  
Distribution Fitting ◽  
Spatially Resolved ◽  
Field Unit

We present a technique that permits the analysis of stellar population gradients in a relatively low-cost way compared to integral field unit (IFU) surveys. We developed a technique to analyze unresolved stellar populations of spatially resolved galaxies based on photometric multi-filter surveys. This technique allows the analysis of vastly larger samples and out to larger galactic radii. We derived spatially resolved stellar population properties and radial gradients by applying a centroidal Voronoi tessellation and performing a multicolor photometry spectral energy distribution fitting. This technique has been successfully applied to a sample of 29 massive (M⋆ > 1010.5M⊙) early-type galaxies at z < 0.3 from the ALHAMBRA survey. We produced detailed 2D maps of stellar population properties (age, metallicity, and extinction), which allow us to identify galactic features. Radial structures were studied, and luminosity-weighted and mass-weighted gradients were derived out to 2–3.5 Reff. We find that the spatially resolved stellar population mass, age, and metallicity are well represented by their integrated values. We find the gradients of early-type galaxies to be on average flat in age (∇log AgeL = 0.02 ± 0.06 dex/Reff) and negative in metallicity (∇[Fe/H]L = −0.09 ± 0.06 dex/Reff). Overall,the extinction gradients are flat (∇Av = −0.03 ± 0.09 mag/Reff ) with a wide spread. These results are in agreement with previous studies that used standard long-slit spectroscopy, and with the most recent IFU studies. According to recent simulations, these results are consistent with a scenario where early-type galaxies were formed through major mergers and where their final gradients are driven by the older ages and higher metallicity of the accreted systems. We demonstrate the scientific potential of multi-filter photometry to explore the spatially resolved stellar populations of local galaxies and confirm previous spectroscopic trends from a complementary technique.

scholarly journals The MOSDEF survey: an improved Voronoi binning technique on spatially resolved stellar populations at z ∼ 2

2020 ◽  
Vol 498 (4) ◽  
pp. 5009-5029
Author(s):  
Tara Fetherolf ◽  
Naveen A Reddy ◽  
Alice E Shapley ◽  
Mariska Kriek ◽  
Brian Siana ◽  
...  
Keyword(s):  
Stellar Population ◽  
Field Survey ◽  
Spectral Energy Distribution ◽  
Stellar Populations ◽  
Spectral Energy ◽  
Star Forming ◽  
N Distribution ◽  
Spatially Resolved ◽  
Best Fitting ◽  
Stellar Masses

ABSTRACT We use a sample of 350 star-forming galaxies at 1.25 &lt; z &lt; 2.66 from the Multi-Object Spectrograph For Infra-Red Exploration (MOSFIRE) Deep Evolution Field survey to demonstrate an improved Voronoi binning technique that we use to study the properties of resolved stellar populations in z ∼ 2 galaxies. Stellar population and dust maps are constructed from the high-resolution CANDELS/3D-HST multiband imaging. Rather than constructing the layout of resolved elements (i.e. Voronoi bins) from the signal-to-noise (S/N) distribution of the H160-band alone, we introduce a modified Voronoi binning method that additionally incorporates the S/N distribution of several resolved filters. The spectral energy distribution (SED)-derived resolved E(B − V)stars, stellar population ages, star-formation rates (SFRs), and stellar masses that are inferred from the Voronoi bins constructed from multiple filters are generally consistent with the properties inferred from the integrated photometry within the uncertainties, with the exception of the inferred E(B − V)stars from our z ∼ 1.5 sample due to their UV slopes being unconstrained by the resolved photometry. The results from our multifilter Voronoi binning technique are compared to those derived from a ‘traditional’ single-filter Voronoi binning approach. We find that single-filter binning produces inferred E(B − V)stars that are systematically redder by 0.02 mag, on average, but could differ by up to 0.20 mag and could be attributed to poorly constrained resolved photometry covering the UV slope. Overall, we advocate that our methodology produces more reliable SED-derived parameters due to the best-fitting resolved SEDs being better constrained at all resolved wavelengths – particularly those covering the UV slope.

scholarly journals Dust attenuation and Hα emission in a sample of galaxies observed with Herschel at 0.6 < z < 1.6

2018 ◽  
Vol 619 ◽  
pp. A135 ◽  
Author(s):  
V. Buat ◽  
M. Boquien ◽  
K. Małek ◽  
D. Corre ◽  
H. Salas ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Stellar Population ◽  
Spectral Energy Distribution ◽  
Line Emission ◽  
Young Stars ◽  
Spectral Energy ◽  
Attenuation Curve ◽  
Radiative Transfer Models ◽  
Dust Attenuation ◽  
Transfer Models

Context. Dust attenuation shapes the spectral energy distribution of galaxies. It is particularly true for dusty galaxies in which stars experience a heavy attenuation. The combination of UV to IR photometry with the spectroscopic measurement of the Hα recombination line helps to quantify dust attenuation of the whole stellar population and its wavelength dependence. Aims. We want to derive the shape of the global attenuation curve and the amount of obscuration affecting young stars or nebular emission and the bulk of the stellar emission in a representative sample of galaxies selected in IR. We will compare our results to the commonly used recipes of Calzetti et al. and Charlot and Fall, and to predictions of radiative transfer models. Methods. We selected an IR complete sample of galaxies in the COSMOS 3D-HST CANDELS field detected with the Herschel satellite with a signal to noise ratio larger than five. Optical to NIR photometry is available as well as NIR spectroscopy for each source. We reduced the sample to the redshift range 0.6 < z < 1.6 to include the Hα line in the G141 grism spectra. We have used a new version of the CIGALE code to fit simultaneously the continuum and Hα line emission of the 34 selected galaxies. Results. Using flexible attenuation laws with free parameters, we are able to measure the shape of the attenuation curve for each galaxy as well as the amount of attenuation of each stellar population, the former being in general steeper than the starburst law in the UV-optical with a large variation of the slope among galaxies. The attenuation of young stars or nebular continuum is found on average about twice the attenuation affecting older stars, again with a large variation. Our model with power-laws, based on a modification of the Charlot and Fall recipe, gives results in better agreement with the radiative transfer models than the global modification of the slope of the Calzetti law.

scholarly journals The Stellar Mass of M31 as inferred by the Andromeda Optical & Infrared Disk Survey

2014 ◽  
Vol 10 (S311) ◽  
pp. 82-85 ◽  
Author(s):  
Jonathan Sick ◽  
Stephane Courteau ◽  
Jean-Charles Cuillandre ◽  
Julianne Dalcanton ◽  
Roelof de Jong ◽  
...  
Keyword(s):  
Stellar Population ◽  
Spectral Energy Distribution ◽  
Major Axis ◽  
Stellar Mass ◽  
Spectral Energy ◽  
Population Synthesis ◽  
Disk Formation ◽  
Infrared Spectral ◽  
Inside Out ◽  
Additional Constraints

AbstractOur proximity and external vantage point make M31 an ideal testbed for understanding the structure of spiral galaxies. The Andromeda Optical and Infrared Disk Survey (ANDROIDS) has mapped M31's bulge and disk out to R=40 kpc in ugriJKs bands with CFHT using a careful sky calibration. We use Bayesian modelling of the optical-infrared spectral energy distribution (SED) to estimate profiles of M31's stellar populations and mass along the major axis. This analysis provides evidence for inside-out disk formation and a declining metallicity gradient. M31's i-band mass-to-light ratio (M/Li*) decreases from 0.5 dex in the bulge to ~ 0.2 dex at 40 kpc. The best-constrained stellar population models use the full ugriJKs SED but are also consistent with optical-only fits. Therefore, while NIR data can be successfully modelled with modern stellar population synthesis, NIR data do not provide additional constraints in this application. Fits to the gi-SED alone yield M/Li* that are systematically lower than the full SED fit by 0.1 dex. This is still smaller than the 0.3 dex scatter amongst different relations for M/Li via g – i colour found in the literature. We advocate a stellar mass of M*(30 kpc) = 10.3+2.3-1.7 × 1010 M⊙ for the M31 bulge and disk.

scholarly journals Stellar Population Models

2012 ◽  
Vol 8 (S295) ◽  
pp. 272-281 ◽  
Author(s):  
Claudia Maraston
Keyword(s):  
Galaxy Formation ◽  
Stellar Population ◽  
High Redshift ◽  
Spectral Energy Distribution ◽  
Cosmic Time ◽  
Mass Function ◽  
Initial Mass Function ◽  
Asymptotic Giant Branch ◽  
Spectral Energy ◽  
Massive Galaxies

AbstractModelling stellar populations in galaxies is a key approach to gain knowledge on the still elusive process of galaxy formation as a function of cosmic time. In this review, after a summary of the state-of-art, I discuss three aspects of the modelling, that are particularly relevant to massive galaxies, the focus of this symposium, at low and high-redshift. These are the treatment of the Thermally-Pulsating Asymptotic Giant Branch phase, evidences of an unusual Initial Mass Function, and the effect of modern stellar libraries on the model spectral energy distribution.

scholarly journals Multiwavelength radio observations of a brightest cluster galaxy at z = 1.71: detection of a modest active galactic nucleus and evidence for extended star formation

2019 ◽  
Vol 487 (1) ◽  
pp. 1210-1217 ◽  
Author(s):  
Ariane Trudeau ◽  
Tracy Webb ◽  
Julie Hlavacek-Larrondo ◽  
Allison Noble ◽  
Marie-Lou Gendron-Marsolais ◽  
...  
Keyword(s):  
Star Formation ◽  
Active Galactic Nucleus ◽  
Spectral Energy Distribution ◽  
Galaxy Cluster ◽  
Far Infrared ◽  
Infrared Emission ◽  
Spectral Energy ◽  
Radio Observations ◽  
Cluster Galaxy ◽  
Star Forming

ABSTRACT We present deep, multiwavelength radio observations of SpARCS104922.6 + 564032.5, a z = 1.71 galaxy cluster with a starbursting core. Observations were made with the Karl G. Jansky Very Large Array (JVLA) in three bands: 1–2 GHz, 4–8 GHz, and 8–12 GHz. We detect a radio source coincident with the brightest cluster galaxy (BCG) that has a spectral index of α = 0.44 ± 0.29 and is indicative of emission from an active galactic nucleus. The radio luminosity is consistent with the average luminosity of the lower redshift BCG sample, but the flux densities are 6σ below the predicted values of the star-forming spectral energy distribution based on far infrared data. Our new fit fails to simultaneously describe the far infrared and radio fluxes. This, coupled with the fact that no other bright source is detected in the vicinity of the BCG implies that the star formation region, traced by the infrared emission, is extended or clumpy and not located directly within the BCG. Thus, we suggest that the star-forming core might not be driven by a single major wet merger, but rather by several smaller galaxies stripped of their gas or by a displaced cooling flow, although more data are needed to confirm any of those scenarios.

scholarly journals A radiative transfer model for the spiral galaxy M33★

2020 ◽  
Vol 495 (1) ◽  
pp. 835-863 ◽  
Author(s):  
Jordan J Thirlwall ◽  
Cristina C Popescu ◽  
Richard J Tuffs ◽  
Giovanni Natale ◽  
Mark Norris ◽  
...  
Keyword(s):  
Star Formation ◽  
Radiative Transfer ◽  
Energy Distribution ◽  
Surface Density ◽  
Main Sequence ◽  
Spectral Energy Distribution ◽  
Radiative Transfer Model ◽  
Spectral Energy ◽  
Geometrical Parameters ◽  
Transfer Model

ABSTRACT We present the first radiative transfer (RT) model of a non-edge-on disc galaxy in which the large-scale geometry of stars and dust is self-consistently derived through the fitting of multiwavelength imaging observations from the ultraviolet to the submm. To this end, we used the axisymmetric RT model of Popescu et al. and a new methodology for deriving geometrical parameters, and applied this to decode the spectral energy distribution (SED) of M33. We successfully account for both the spatial and spectral energy distribution, with residuals typically within $7{{\ \rm per\ cent}}$ in the profiles of surface brightness and within $8{{\ \rm per\ cent}}$ in the spatially integrated SED. We predict well the energy balance between absorption and re-emission by dust, with no need to invoke modified grain properties, and we find no submm emission that is in excess of our model predictions. We calculate that $80\pm 8{{\ \rm per\ cent}}$ of the dust heating is powered by the young stellar populations. We identify several morphological components in M33, a nuclear, an inner, a main and an outer disc, showing a monotonic trend in decreasing star formation surface density (ΣSFR) from the nuclear to the outer disc. In relation to surface density of stellar mass, the ΣSFR of these components defines a steeper relation than the ‘main sequence’ of star-forming galaxies, which we call a ‘structurally resolved main sequence’. Either environmental or stellar feedback mechanisms could explain the slope of the newly defined sequence. We find the star formation rate to be ${\rm SFR}=0.28^{+0.02}_{-0.01}{\rm M}_{\odot }{\rm yr}^{-1}$.

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