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 J-PLUS: Two-dimensional analysis of the stellar population in NGC 5473 and NGC 5485

2019 ◽  
Vol 622 ◽  
pp. A181 ◽  
Author(s):  
I. San Roman ◽  
P. Sánchez-Blázquez ◽  
A. J. Cenarro ◽  
L. A. Díaz-García ◽  
C. López-Sanjuan ◽  
...  
Keyword(s):  
Stellar Population ◽  
Low Cost ◽  
Stellar Populations ◽  
Star Formation History ◽  
Early Type ◽  
Intermediate Band ◽  
Spatially Resolved ◽  
Radial Profiles ◽  
Field Unit ◽  
The Impact

Context. The spatial variations of stellar population properties within a galaxy are intimately related to their formation process. Therefore, spatially resolved studies of galaxies are essential to uncover their formation and assembly. Although the arrival of integral field unit (IFU) surveys has brought a significant breakthrough in the field, recent techniques that combine photometric multifilter surveys with spectral fitting diagnostics have opened a new, relatively low-cost way to disentangle the stellar population of spatially resolved galaxies compared to IFU surveys. Aims. The Javalambre Photometric Local Universe Survey (J-PLUS) is a dedicated multifilter designed to observed ∼8500 deg2 of the northern sky using 12 narrowband, intermediate-band, and broadband filters in the optical range. In this study, we test the potential of the multifilter observation carried out with J-PLUS to investigate the properties of spatially resolved nearby galaxies. Methods. We present detailed 2D maps of stellar population properties, i.e., age, metallicity, extinction, and stellar mass surface density, for two early-type galaxies observed in the J-PLUS and CALIFA surveys. These galaxies are NGC 5473 and NGC 5485. Radial structures are also compared and luminosity- and mass-weighted profiles are derived. We use MUFFIT to process the J-PLUS photometric multifilter observations, and STARLIGHT and STECKMAP to analyze IFU CALIFA data. Results. We demonstrate the scientific potential of J-PLUS/MUFFIT to explore the spatially resolved stellar populations of local galaxies. We find significant discrepancies between the results from the various analysis methods. While radial stellar population gradients obtained with J-PLUS/MUFFIT and the IFU technique CALIFA/STECKMAP are more in agreement, radial stellar population gradients largely differ when CALIFA/STARLIGHT methodology is used. A comparison of the absolute values reveals the existence of intrinsic systematic differences. Age and metallicity radial profiles derived from J-PLUS/MUFFIT are very similar when luminosity- or mass-weighted properties are used, suggesting that the contribution of a younger component is small and the star formation history of these early-type galaxies are well represented by mainly an old single stellar population component. Conclusions. We present the potential of J-PLUS to explore the unresolved stellar populations of spatially extended local galaxies. A comparison between the three methodologies reveals some discrepancies suggesting that the specific characteristics of each method causes important differences. We conclude that the ages, metallicities, and extinction derived for individual galaxies not only depend on the chosen models but also depend on the method used. Future work is required to evaluate in detail the origin of these differences and to quantify the impact that different fitting routines have on the derived stellar population properties.

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.

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 stellar populations of massive galaxies in the local Universe

2012 ◽  
Vol 8 (S295) ◽  
pp. 290-299
Author(s):  
Richard M. McDermid
Keyword(s):  
Star Formation ◽  
Galaxy Formation ◽  
Stellar Population ◽  
Stellar Populations ◽  
Early Type ◽  
Massive Galaxies ◽  
Spatially Resolved ◽  
Low Mass ◽  
Galaxy Environment ◽  
Star Formation Histories

AbstractI present a brief review of the stellar population properties of massive galaxies, focusing on early-type galaxies in particular, with emphasis on recent results from the ATLAS3D Survey. I discuss the occurence of young stellar ages, cold gas, and ongoing star formation in early-type galaxies, the presence of which gives important clues to the evolutionary path of these galaxies. Consideration of empirical star formation histories gives a meaningful picture of galaxy stellar population properties, and allows accurate comparison of mass estimates from populations and dynamics. This has recently provided strong evidence of a non-universal IMF, as supported by other recent evidences. Spatially-resolved studies of stellar populations are also crucial to connect distinct components within galaxies to spatial structures seen in other wavelengths or parameters. Stellar populations in the faint outer envelopes of early-type galaxies are a formidable frontier for observers, but promise to put constraints on the ratio of accreted stellar mass versus that formed ‘in situ’ - a key feature of recent galaxy formation models. Galaxy environment appears to play a key role in controlling the stellar population properties of low mass galaxies. Simulations remind us, however, that current day galaxies are the product of a complex assembly and environment history, which gives rise to the trends we see. This has strong implications for our interpretation of environmental trends.

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.

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