scholarly journals HST Far–UV Imaging of M 31, M 32 and NGC 205

1995 ◽  
Vol 164 ◽  
pp. 444-444
Author(s):  
F. Bertola ◽  
C. Chiosi ◽  
A. Bressan ◽  
L.M. Buson ◽  
D. Burstein ◽  
...  
Keyword(s):  
Broad Band ◽  
Agb Stars ◽  
Population Synthesis ◽  
Stellar Content ◽  
Hot Stars ◽  
Uv Emission ◽  
Luminosity Functions ◽  
Scientific Goal ◽  
M 31 ◽  
Direct Measures

Direct measures of luminosity functions, UV fluxes and colors of the hot stars that produce the UV turn–up in the SED of ellipticals and spiral bulges is the scientific goal of the HST observations presented here (see Bertola et al. 1995 for details). We concentrated our analysis on the hot stellar content of the M31 bulge. HST/FOC f/48 images were analyzed as observed (before the repair mission) through the F150W broad-band UV filter. We find that both individual stars and unresolved objects contribute to about 50% of the UV (1200-2450 Å) flux. Making use of the isochrones calculated by Bertelli et al. (1994) and Chiosi et al. (1994) together with the models of population synthesis presented by Bressan et al. (1994), we constructed theoretical CMDs to be compared with the CMD obtained by combining our F150W observations with the F175W observations of King et al. (1992). We conclude that the stars we resolved in M31 are classical P-AGB stars belonging to an old standard metallicity population. However, the P-EAGB and AGB-manqué stages as well as H-HB stars could be the source of the diffuse UV emission.

Calibrating TP-AGB stellar models and chemical yields through resolved stellar populations in the Small Magellanic Cloud

2018 ◽  
Vol 14 (S343) ◽  
pp. 269-272
Author(s):  
Giada Pastorelli ◽  
Paola Marigo ◽  
Léo Girardi ◽  
Keyword(s):  
Mass Loss ◽  
Magellanic Cloud ◽  
Star Formation History ◽  
Agb Stars ◽  
Population Synthesis ◽  
Small Magellanic Cloud ◽  
Luminosity Functions ◽  
Formation History ◽  
Best Fitting ◽  
The Impact

AbstractMost of the physical processes driving the TP-AGB evolution are not yet fully understood and they need to be modelled with parameterised descriptions. We present the results of the on-going calibration of the TP-AGB phase based on a complete sample of AGB stars in the Small Magellanic Cloud (SAGE-SMC survey). We computed large grids of TP-AGB models with several combinations of third dredge-up and mass-loss prescriptions with the COLIBRI code. The SMC AGB population is modelled with the population synthesis code TRILEGAL according to the space-resolved star formation history derived with the deep photometry from the VISTA survey of the Magellanic Clouds. We put quantitative constraints on the efficiencies of the third dredge-up and mass loss by requiring the models to reproduce the star counts and the luminosity functions of the observed Oxygen-, Carbon-rich and extreme-AGB stars and we investigate the impact of the best-fitting prescriptions on the chemical yields.

scholarly journals The Ultraviolet Spectra of Old Stellar Populations

1996 ◽  
Vol 171 ◽  
pp. 367-367
Author(s):  
Ben Dorman ◽  
Robert W. O'Connell
Keyword(s):  
Main Sequence ◽  
Uv Light ◽  
Stellar Populations ◽  
Uv Spectra ◽  
Population Synthesis ◽  
Stellar Content ◽  
Hot Stars ◽  
Loss Mechanism ◽  
Optical Wavelengths ◽  
Uv Upturn

We investigate the utility of UV spectra of old stellar populations as diagnostics of galaxy properties. For λ < 3800 Å, the integrated light of old stellar populations is dominated by two components: the hot stars which give rise to the UV upturn phenomenon at far-UV wavelengths, and the stars (i.e. main sequence, and subgiants) that lie closest to the turnoff. The mid-UV radiation from the turnoff varies strongly with metallicity, and less so with age; mid-UV light must be correct for the effect of the independent far-UV upturn component, but this is straightforward. Population synthesis models that account for the flux from the UV upturn can therefore determine the characteristics of the underlying stellar content from the mid-UV spectral region. The age & metallicity dependence of the far-UV 1550 Å is not well understood (see Dorman, O'Connell & Rood 1995, ApJ 442,105) since the mass loss mechanism on the RGB that produces very blue HB stars has no physical model. In contrast mid-UV indicators derive from the turnoff population which best represents the quantities we wish to measure, and are in addition visible at favourable optical wavelengths for z ≲ 1.

scholarly journals From rest-frame luminosity functions to observer-frame colour distributions: tackling the next challenge in cosmological simulations

2020 ◽  
Vol 497 (3) ◽  
pp. 3026-3046 ◽  
Author(s):  
Matías Bravo ◽  
Claudia del P Lagos ◽  
Aaron S G Robotham ◽  
Sabine Bellstedt ◽  
Danail Obreschkow
Keyword(s):  
Survey Design ◽  
Target Selection ◽  
Broad Band ◽  
Complex Mixture ◽  
Far Infrared ◽  
Bimodal Distribution ◽  
Spectral Energy ◽  
Recent Success ◽  
Luminosity Functions ◽  
Radiation Output

ABSTRACT Galaxy spectral energy distributions (SEDs) remain among the most challenging yet informative quantities to reproduce in simulations due to the large and complex mixture of physical processes that shape the radiation output of a galaxy. With the increasing number of surveys utilizing broad-band colours as part of their target selection criteria, the production of realistic SEDs in simulations is necessary for assisting in survey design and interpretation of observations. The recent success in reproducing the observed luminosity functions (LFs) from far-ultraviolet (UV) to far-infrared (IR), using the state-of-the-art semi-analytic model shark and the SED generator ProSpect, represents a critical step towards better galaxy colour predictions. We show that with shark and ProSpect we can closely reproduce the optical colour distributions observed in the panchromatic Galaxy And Mass Assembly (GAMA) survey. The treatment of feedback, star formation, central–satellite interactions, and radiation reprocessing by dust are critical for this achievement. The first three processes create a bimodal distribution, while dust attenuation defines the location and shape of the blue and red populations. While a naive comparison between observation and simulations displays the known issue of overquenching of satellite galaxies, the introduction of empirically motivated observational errors and classification from the same group finder used in GAMA greatly reduces this tension. The introduction of random reassignment of ${\sim} 15{{\ \rm per\ cent}}$ of centrals/satellites as satellites/centrals on the simulation classification closely resembles the outcome of the group finder, providing a computationally less intensive method to compare simulations with observations.

scholarly journals Identifications of Faint IRAS Sources

1996 ◽  
Vol 171 ◽  
pp. 402-402
Author(s):  
M.W. Kümmel ◽  
S.J. Wagner
Keyword(s):  
Broad Band ◽  
Far Infrared ◽  
Power Laws ◽  
Point Sources ◽  
Spectral Energy ◽  
Energy Distributions ◽  
The North ◽  
Luminosity Functions ◽  
Error Circle ◽  
Radio Band

From overlapping scans in the IRAS all-sky survey and additional pointed observations the deepest far infrared survey before ISO exists in the region around the North Ecliptic Pole (NEP) (Hacking P. and Houck J.R., ApJS 63 p. 311). This survey contains detections up to 10 and fluxes up to 100 times fainter than the IRAS survey. In the central square degree around the NEP we combine the far IR-survey with deep radio data at 151 MHz and 1.5 GHz (Visser, A.E. et al., A&AS 110 p. 419, Kollgaard, R.I. et al., ApJS 93 p. 145) and own observation at 2.2μm (K′) and 435nm (B). The error circle around the IRAS source was chosen to include the true source with 85% probability (1.4 sigma). For 29 of the 32 IRAS sources we found at least one possible counterpart. Ten of the objects have multiple (up to four) counterparts in K′. Four of the IRAS sources have counterparts in the 1.5 GHz survey. The higher accuracy of the radio position (∼ 1″) allowed an unambiguous identification of the K′ counterpart. None of the IRAS sources could be found in the 151 MHz survey. The broad band spectra of the three galaxies with measured radio flux exhibit maximum emission between the radio band and 100μm which corresponds to emission by cool dust (< 50 K). Contrary to the infrared luminosity functions at 12μm and 60μm which show power laws, the K′ luminosity function is bimodal. The brightest K′ objects are all point sources. Due to the small number statistics the power law indices of the luminosity functions can not be distinguished. We find a linear relationship between the K′ flux and the flux at 60μm and 12μm over at least one decade. The large deviations by individual sources make an identification of the correct counterpart through this relation impossible. The spectral energy distributions of unambiguously identified sources span only one decade in energy (vSv), i.e. they have flat energy distributions. This suggests an identification of K′ objects with flat energy distribution in case of multiple counterparts.

scholarly journals Photometric Models for Globular Clusters from Population Synthesis

1988 ◽  
Vol 126 ◽  
pp. 559-560
Author(s):  
R. Capuzzo Dolcetta
Keyword(s):  
Structural Properties ◽  
Globular Clusters ◽  
Magellanic Cloud ◽  
Stellar Systems ◽  
Population Synthesis ◽  
Stellar Content ◽  
Cloud Clusters ◽  
Metal Abundance ◽  
Theoretical Frame

Integral fluxes (Bolometric and U, B, V) are computed in a completely theoretical frame in order to investigate the structural properties and stellar content of coeval stellar systems of various ages and metal abundance. Some results concerning the problem of the color gap in the distribution of the sample of Magellanic Cloud clusters are discussed.

HII regions and young star clusters in the Magellanic Clouds

1991 ◽  
Vol 148 ◽  
pp. 207-208
Author(s):  
Myung Gyoon Lee
Keyword(s):  
Main Sequence ◽  
Star Clusters ◽  
Hii Regions ◽  
Young Star ◽  
Magellanic Clouds ◽  
Stellar Content ◽  
Ccd Photometry ◽  
Luminosity Functions ◽  
Young Star Clusters ◽  
Mass Functions

Using U BV CCD photometry, the stellar content of HII regions and young star clusters in the Magellanic Clouds has been studied: (1) the reddenings have been determined, and ages of OB associations and young star clusters have been measured; (2) the stellar initial mass functions have been determined by using the main-sequence luminosity functions; and (3) U BV CCD surface photometry of nine young star clusters has been obtained and their structural properties investigated.

scholarly journals Globular clusters in the outer halo of M 31

2019 ◽  
Vol 623 ◽  
pp. A65 ◽  
Author(s):  
Song Wang ◽  
Jun Ma ◽  
Jifeng Liu
Keyword(s):  
Globular Clusters ◽  
Selection Effect ◽  
Population Synthesis ◽  
Clear Trend ◽  
Intermediate Band ◽  
Near Ultraviolet ◽  
Poor Group ◽  
History Of ◽  
M 31 ◽  
Far Ultraviolet

In this paper, we present photometry of 53 globular clusters (GCs) in the M 31 outer halo, including the GALEX far-ultraviolet (FUV) and near-ultraviolet (NUV), SDSS ugriz, 15 intermediate-band filters of BATC, and 2MASS JHKs bands. By comparing the multicolour photometry with stellar population synthesis models, we determine the metallicities, ages, and masses for these GCs, aiming to probe the merging/accretion history of M 31. We find no clear trend of metallicity and mass with the de-projected radius. The halo GCs younger than ∼8 Gyr are mostly located at the de-projected radii around 100 kpc, but this may be due to a selection effect. We also find that the halo GCs have consistent metallicities with their spatially associated substructures, which provides further evidence of the physical association between them. Both the disc and halo GCs in M 31 show a bimodal luminosity distribution. However, we should emphasise that there are more faint halo GCs which are not seen in the disc. The bimodal luminosity function of the halo GCs may reflect a different origin or evolution environment in their original hosts. The M 31 halo GCs include one intermediate metallicity group (−1.5 < [Fe/H] < −0.4) and one metal-poor group ([Fe/H] < −1.5), while the disc GCs have one metal-rich group more. There are considerable differences between the halo GCs in M 31 and the Milky Way (MW). The total number of GCs in M 31 is approximately three times greater than in the MW, however M 31 has about six times more halo GCs than the MW. Compared to the halo GCs of M 31, those of the MW are mostly metal-poor. Both the numerous halo GCs and the higher-metallicity component are suggestive of an active merger history of M 31.

scholarly journals Asymptotic Giant Branch Stars in the Magellanic Clouds

1991 ◽  
Vol 148 ◽  
pp. 363-364
Author(s):  
Neill Reid ◽  
J. R. Mould
Keyword(s):  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Magellanic Clouds ◽  
Asymptotic Giant Branch ◽  
Red Giants ◽  
Asymptotic Giant Branch Stars ◽  
Agb Stars ◽  
Satellite Systems ◽  
Luminosity Functions ◽  
Theoretical Predictions

Since the pioneering objective prism surveys by Westerlund (1960) and Blanco et al. (1980), the Magellanic Clouds have proved a fruitful site for exploring the evolution of AGB stars. We have used photometric techniques to extend the prism C-star surveys to M- and S-type AGB stars, constructing luminosity functions and obtaining spectra of individual stars for comparison with theoretical predictions. We have concentrated on the Large Magellanic Cloud (LMC), but we have recently obtained observations of luminous red giants in a region of the Small Magellanic Cloud (SMC). In this paper we compare the results from these studies of the two satellite systems.

Visual and Near-Infrared Photometry of Nearby Dwarf Spheroidals

1999 ◽  
Vol 192 ◽  
pp. 455-458 ◽  
Author(s):  
F. Kerschbaum ◽  
W. Nowotny ◽  
J. Hron ◽  
M. Schultheis
Keyword(s):  
Near Infrared ◽  
Broad Band ◽  
Feasibility Studies ◽  
Asymptotic Giant Branch ◽  
Agb Stars ◽  
Faint Object ◽  
Nearby Galaxies ◽  
Dwarf Spheroidals ◽  
Faint Object Spectrograph ◽  
Infrared Survey

This paper is based on photometry from two different observational approaches. Both are of an explorative character and act as feasibility studies. For the future we plan to use these methods to study Asymptotic Giant Branch (AGB) stars in nearby galaxies.First, we present results on broad-band photometry in Bessell V and I, as well as narrow-band measurements in the Wing 778 nm and 812 nm filters of a galactic globular cluster using the new Austrian Oe-FOSC (Oesterreich Faint Object Spectrograph and Camera), a copy of the ESO Instrument EFOSC mounted on our 1.5 m-telescope.The second part of the contribution deals with the possibilities of using Gunn I, J and KS measurements originating from the DENIS (DEep Near Infrared Survey of the Southern Sky) project on similar objects. A few southern dwarf spheroidals already observed within DENIS (covering now some 40% of the southern hemisphere) are selected.

scholarly journals New IR-Observations of Post AGB Stars and Proto-Planetary Nebulae

1989 ◽  
Vol 131 ◽  
pp. 445-445 ◽  
Author(s):  
W.E. van der Veen ◽  
H. J. Habing ◽  
T. R. Geballe
Keyword(s):  
Selection Criteria ◽  
Large Fraction ◽  
Broad Band ◽  
Planetary Nebulae ◽  
Asymptotic Giant Branch ◽  
Agb Stars ◽  
Be Stars ◽  
Ir Sources ◽  
Visual Magnitude ◽  
Small Band

A sample was selected from the IRAS Point Source Catalogue based on the following selection criteria: very red (“cold”) IRAS-colours: roughly F25/F12 > 2.5 and F60/F25 < 1.2; and low IR-variability: VAR < 30. These non-variable IR-sources may be stars that have evolved beyond the AGB (Asymptotic Giant Branch); a large fraction (40%) is associated with known planetary nebulae (Van der Veen and Habing, 1987, Astron. Astrophys., in press). To determine the nature of the other 60% additional observations were made mainly in the infrared: 1–13 μm, during 4 observing runs: ESO (La Silla, Chile) in July 1986 and June 1987; UKIRT (Hawaii) in August 1986 and June 1987. A total number of 58 sources was observed. A summary of the observations: -IR broad band photometry at 1.2, 1.6, 2.2, 3.8 and 4,6 μm for all 58 sources. -IR broad band photometry at 8.4, 9.7 and 12.8 μm for 19 sources. -IR small band photometry for 4 sources in the ranges 2–2.5 μm and 3–3.5 μm. -IR spectroscopy for 10 sources in the ranges 2–2.5 μm and 3–3.5 μm, -V, R, I observations (0.55, 0.7 and 0.9 μm) for 5 sources associated with a star of visual magnitude 8–9. These observations were carried out by D. de Winter (Amsterdam) with the 0.5-m ESO telescope at La Silla (Chile). -Walraven photometry (0.32, 0.36, 0.38, 0.43 and 0.54 μm) for 21 stars brighter than V = 15 and within 10“ from the IRAS position. These observations were carried out by M. van Haarlem (Leiden) with the 0.9-m Dutch telescope at La Silla (Chile).

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