Click on the name of the presenters to download a pdf file with the slides for each lecture.
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School dinner |
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The sessions devoted to students presentations will be of 1.5 hr duration, with 7 presentations in each session. Presentations are 10 minutes, plus 2-3 minutes for questions and discussion.
Students 1: Abedi, Blanco Cuaresma, de Bokx, Fabbian, Feuillet, Howes, Hunt
Students 2: Irrgang, Laevens, Martins, Murareva, Palaversa, Rybizki, Sampedro
Students 3: Sibbons, Silva, Thygesen, Vasquez, Wegg, Ziegerer, Balbinot
LECTURES PROGRAM
Stellar distribution models
-- Leo Girardi (Osservatorio Astronomico di Padova, INAF, Italy)
1- The basics
- overview of stellar evolution as a function of mass and metallicity
- from evolutionary tracks to isochrones
- quick overview of chemical changes at the stellar surface
2- More on isochrones
- bolometric corrections and Teff-color relations
- populating isochrones, and the IMF
- simulating star clusters
- simulating apparent and detached binaries
- simulating interacting binaries
3- From star clusters to external galaxies
- basic methods
- age and metallicity distribution functions for different stars,
including main sequence, red clump, RGB, AGB
4- From external galaxies to the Milky Way
- basic equation of stellar statistics, computational methods
- overview of available MW codes
- expected populations X photometric depth and galactic coordinates
5- Some current problems and opportunities
- simulating kinematics
- simulating variables
- simulating non-solar scaled populations
- simulating rare and extreme populations (e.g. X-ray sources, PNe,
hot-WDs, AGB-manque', C stars, IR-emission by mass-losing stars)
- opportunities opened by asteroseismology
Chemical Abundances
-- Francesca Primas (European Southern Observatory)
1- Basic principles of stellar nucleosynthesis
- main stellar nucleosynthetic processes, from the light/alpha and iron-peak elements to heavy elements
- main transitions of each element
2- Methods and available tools
- how stellar abundances can be derived, starting from basic input parameters (stellar parameters, lines identification, line lists) to the actual measurement of equivalent widths and computation synthetic spectra.
- examples of both methods applied to different spectra (in terms of quality and/or spectral region of interest)
3- Interpretation of the results
- interpretation of the derived abundance ratios
- comparison between the Milky Way and other galaxies
4- A specific application
- the "light elements", Li Be and B.
- big bang nucleosynthesis and 'mixing' in stars
Dynamics of the Milky Way
-- Ortwin Gerhard (Max-Planck-Institut fuer extraterrestrische Physik, Germany)
1- Fundamental stellar dynamics
- relaxation, collisionless dynamics
- distribution functions, Jeans eqs, etc.
2- Stellar orbits and dynamical models
- orbits in various potentials, Jeans Thm, DF models, Schwarzschild, M2M
3- Galactic disk dynamics
4- The Galactic bulge
- structure
- dynamics
- origin
5- The Galactic halo
- mass, extent, shape
- substructure, inner/outer halo
Galactic Surveys: astrometry, photometry and spectroscopy
-- Carlos Allende Prieto (Instituto de Astrofísica de Canarias, Spain)
1- Astrometry and photometry
- Hipparcos, Gaia, full-sky and large-area photometric surveys
- fitting models to data
- algorithms and tools
2- Spectra
- APOGEE, RAVE, SDSS/SEGUE/BOSS, Gaia-ESO
- Spectral classification
- radial velocities
- automated data analysis
3- Other spectroscopic surveys and analysis strategies
- eBOSS, BigBOSS, HETDEX, WEAVE, 4MOST
- data mashup: astrometry, photometry and spectroscopy together
- reconstructing the Galaxy
- 'observing' galaxy simulations
- discovery and follow-up of interesting/exotic targets: HVS, UMPS, CEMPS, RCrBs...
Simulations: N-body, etc.
-- Jerry Sellwood (Rutgers University, USA)
1- The use and abuse of N-body codes
- relaxation in spheres and disks, collective enhancement
- code structure, block time steps
2- Poisson solvers
- trees
- fixed and adaptive grids
- parallelization
3- Setting up equilibrium models
- choosing from a DF, Jeans equations and their limitations
- disk-bulge-halo models
4- Analysis "on the fly"
- code testing
- made-to-measure
5- SPH basics
- numerical viscosity
- Kelvin-Helmholtz instabilities
- other problems and their amelioration
Stellar Populations: chemical composition, kinematics, morphology
-- Ken Freeman (Australian National University, Australia)
1- Overview of the structure of our Galaxy in the context of other galaxies
- the basic components
- dark matter properties
- general ideas about galaxy assembly
2- The thin disk.
- observational issues with the star formation history and the dynamical evolution of the thin disk.
- continuing gas accretion
- theoretical ideas about the formation and evolution of the thin disk.
3- The thick disk in the context of other disk galaxies
- systematics of thick disks in other galaxies
- chemical, structural and dynamical properties of the Galactic thick disk
- ideas about how thick disks form
4- The stellar halo of the Galaxy
- more on dark matter in the Galaxy
- chemical tagging and reconstructing the star formation history of the Galactic disk.
5- The Galactic bulge
- observational status on bulge kinematics and chemical properties in the context of other bulges
- ideas about the formation of the bulge
ORAL CONTRIBUTIONS:
Hoda Abedi
Title: First steps towards a Galactic Warp dynamical model in the Gaia Era
Abstract: We have developed a simplified dynamical code that adiabatically imposes a warp in the Galactic disk potential. Its application to a set of simulated Red Clump stars allowed us to deeply analyze the expected kinematic signature of the warp in the observational space of Galactic proper motions. These kinematic trends is compared to the real signature obtained from the recently published UCAC4 catalog. Similar to what the Hipparcos young star population revealed a decade ago (Smart et al., 1999), the real Red Clump stars shows a trend that is completely opposite to what is expected from the model. Models including additional effects such as precession are being developed and tested. Furthermore, using Gaia observational constraints and astrometric error models we evaluate the Gaia capabilities to parameterize the Galactic warp.
Eduardo Balbinot
Title: Weighting the Milky Way using the tidal tails of Palomar 5
Abstract: Globular clusters slowly dissolve while orbiting the Milky Way (MW) forming a stream of stars. The curvature of these streams and observed velocities of stars within the streams can be used to measure the local gravitational acceleration, even in remote places of the Milky Way, which are inaccessible to other methods. This was a very degenerated problem which has proven to be a challenge to modern observations and models. Here we explore the existence of gaps and clumps in globular clusters tidal tails to break model degeneracies and boost the accuracy of the orbit determination. To show how its stream substructure can be understood and utilized, we present a model of the MW globular cluster Palomar 5 and its extended stellar stream. Using a careful analysis of the tails we derive the position and significance of the substructures and from a large set of models we find the one that reproduces the shape of the stream, the velocities of stars in the stream and the observed gaps and clumps exceptionally well.
Sergi Blanco Cuaresma
Title: Testing the chemical tagging with old Open Clusters
Short abstract: De Silva et al. 2007 demonstrated the chemical homogeneity of two open clusters and one moving group together with the uniqueness of their abundance patterns. These findings open the possibility of using the technique of chemical tagging to identify common formation sites in the disk as proposed by Freeman & Bland-Hawthorn 2002. In order to apply this technique to high resolution spectra we have developed our own spectral analysis code, which we have used for the analysis of old Open Clusters observed by NARVAL spectrograph (Bernard Lyot Telescope located at the Pic du Midi in the French Pyrenees). We present the astrophysical parameters (AP) and abundances determined for those clusters and we compare the performance.
Richelle de Bokx
Title: Star Cluster Simulations with Nbody6tt
Short abstract: Open star clusters are simulated inside a galaxy potential using nbody6tt, which is a direct n-body code including stellar and binary evolution and uses a 4th order Hermite integration scheme. There are very few star cluster simulations that concentrate purely on the dispersion of open clusters in a galactic tidal field. Most of the literature on this subject concentrates on the formation of star clusters or attempts to simulate observed phenomena that are the result of two-body interactions inside the cluster. Nbody6tt is a new version of nbody6, and it allows the user to specify any analytic galaxy potential in which to evolve the star cluster. The performance of nbody6tt is compared to that of nbody6 for a cluster in a point mass galaxy potential and one in a potential consisting of a disk and a halo. The dispersion of the star cluster in these potentials is followed by means of the mass loss and phase space evolution of its members.
Damian Fabbian
Title: 3D effects in Arcturus as a yardstick for the SDSS-III/APOGEE survey
Short abstract: We investigate the differential 3D-1D effects in Arcturus using theoretical model atmospheres, to assess the importance that departures from the approximations of homogeneity and plane-parallelism have in terms of the derivation of stellar parameters, and in particular its order-of-magnitude impact on chemical abundances for the ~10^5 red giant stars in the SDSS-III/APOGEE survey.
Diane Feuillet
Title: Using APOGEE at NMSU
Short abstract: SDSSIII's APOGEE is obtaining high resolution IR spectra of 100,000 Milky Way stars for the purpose of studying Galactic chemical evolution. There are several projects underway at NMSU involving the APOGEE survey and instrument. I will be discussing my part in some of these projects, including optical observations of APOGEE stars and observations of nearby stars with the APOGEE instrument.
Louise Howes
Title: Discovery of the oldest stars in the Galactic bulge.
Short Abstract: Despite frequent attempts over many years, the elusive first stars of the Universe have yet to be found. Searches for these "Population III" objects have targeted the old and metal-poor Galactic halo. However according to models of the formation of galaxies like the Milky Way, the oldest stars should lie in the centre of the Galaxy - in the bulge. Until now, problems with overcrowding and extinction have made searching the bulge an impossible task; the most metal-poor star previously known has [Fe/H]=-2.1. Our dedicated search, using SkyMapper photometry to pre-select low metallicity candidates, will discover >100 bulge stars with [Fe/H]<-3, all confirmed using AAOmega on the Anglo-Australian Telescope.
Here we present the first results of the ongoing survey: >2000 stars with [Fe/H]<-1, and from the pilot study, high-resolution spectroscopy of 14 stars (10 with MIKE on Magellan, and 4 as part of the Gaia-ESO survey using FLAMES UVES on the VLT). These high-resolution data have confirmed the discovery of the bulge's most metal-poor stars yet. They have allowed us to derive detailed chemical abundances of these stars, including alpha and s-process elements, which we have compared to the other components of the Galaxy.
Jason Hunt
Title: Particle-by-Particle M2M Algorithm: PRIMAL
Short abstract: We have developed our particle-by-particle adaptation of the made-to-measure (M2M) method, with the aim of modelling the Galactic disc from upcoming Galactic stellar survey data. In our new particle-by-particle M2M algorithm, PRIMAL, the observables of the target system are compared with those of the model galaxy at the position of the target stars. The mass of the model particles are changed to reproduce the observables of the target system, and the gravitational potential is automatically adjusted by the changing mass of the particles. We applied PRIMAL to mock barred disc galaxy data created by an N-body simulation in a known dark matter potential, with the expected Gaia errors in the observables, using bright stars as tracers. We show that PRIMAL can recover the structure and kinematics of the target discs, along with the apparent bar structure and pattern speed of the bar despite the error in the target data.
Andreas Irrgang
Title: Milky Way mass models for orbit calculations
Short abstract: Studying the trajectories of objects like stars, globular clusters, or satellite galaxies in the Milky Way allows the dark matter halo to be traced but requires reliable models of its gravitational potential. Realistic, yet simple and fully analytical, models have already been presented in the past. However, improved, as well as new, observational constraints have become available in the meantime, calling for a recalibration of the respective model parameters. We have revisited three widely used model potentials and thus derived an estimate for the mass of the dark matter halo.(See Irrgang et al. 2013, A&A, 549, A137 for details.)
B. Laevens
Title: Search for new Milky Way Dwarf Galaxies with Pan-STARRS 1 data
Short abstract: In recent years, the idea of dwarf galaxies being distributed in a plane around the Milky Way has increased in popularity. However, the dwarf galaxy searches based on the SDSS survey have mainly been limited to the northern Galactic cap, an area that coincides with the proposed plane of satellites around the Milky Way. On the other hand, the Pan-STARRS 1 survey, with its far larger spatial coverage, especially in the southern hemisphere, can help reinforce or contradict the anisotropy of Milky Way satellites. I will present the on-going search for dwarf galaxies in the current Pan-STARRS 1 3-pi-coverage, i.e. either discuss newly discovered faint dwarf galaxies or present the limits of the search and the significance of the absence of discoveries for the Milky Way satellite distribution.
Andre Martins
Title: Constraining Milky Way Formations and Evolution from the SEGUE Survey
Short abstract: We present a comparative study of stars taken from the low latitude plates of SDSS database with recent simulations from the Besancon galaxy model. For the comparison we use a photometric (dr9) sample and spectroscopic data (dr8). We compare simulations from the Besancon Galaxy model with photometric and spectroscopic data in order to constrain SFR history, age of the population, shape, IMF, chemical evolution. In special we are developing a MCMC code that will constrain the Warp and Flare parameters of the Milky Way.
Tatiana Muraveva
Title: "The structure of the Large Magellanic Cloud from Classical Cepheids, RR Lyrae stars and binaries"
Short abstract: By studying different distance indicators in the Large Magellanic Cloud (CCs, RR Lyrae stars and hot binaries) we probe the structure of this galaxy which is first step of the cosmic distance ladder.
Lovro Palaversa
Title: Exploring the Variable Sky with LINEAR
Short abstract: We describe the construction of a highly reliable sample of 7,000 optically faint periodic variable stars with light curves obtained by the asteroid survey LINEAR across 10,000 deg$^2$ of sky. The majority of these variables have not been catalogued yet. The sample flux limit is several magnitudes fainter than for most other wide-angle surveys. Light curves include on average 250 data points, collected over about a decade. Using SDSS-based photometric recalibration of the LINEAR data for about 25 million objects, we selected $\sim$200,000 most probable candidate variables with $r<17$ and visually confirmed and classified $\sim$7,000 periodic variables using phased light curves. The reliability and uniformity of visual classification across eight human classifiers was calibrated and tested using a catalogue of variable stars from the SDSS Stripe 82, and verified using unsupervised machine learning approach. The resulting sample of periodic LINEAR variables is dominated by 3,900 RR Lyrae stars and 2,700 eclipsing binary stars of all subtypes, and includes small fractions of relatively rare populations such as asymptotic giant branch stars and SX Phoenicis stars. We discuss the distribution of these mostly uncatalogued variables in various diagrams constructed with optical-to-infrared SDSS, 2MASS and WISE photometry, and with LINEAR light curve features. We find that combination of light curve features and colours enables classification schemes much more powerful than when colours or light curves are each used separately. An interesting side result is a robust and precise quantitative description of a strong correlation between the light-curve period and colour/spectral type for close and contact eclipsing binary stars ($\beta$ Lyrae and W UMa). These large samples of robustly classified variable stars will enable detailed statistical studies of Galactic structure and physics of binary and other stars, and we make them publicly available.
Jan Rybizki
Title: Chemical Evolution of the Milky Way - What does the local neighbourhood tell us?
Short abstract: Predictions from different analytical models are compared to abundance data of the solar neighbourhood.
Laura Maria Sampedro
Title: CHASING CLUSTER MEMBERS IN THE GES CATALOGS
Short abstract: We present the preliminary results obtained applying a new geometrical methodology (Sampedro et al. 2013, in prep.) to the GES catalogs, aiming at determining the potential members of a stellar cluster, in a N-dimension space. The N-variables have to satisfy the condition of being more densely distributed for the cluster members than for the field stars, as positions, proper motions, radial velocities, parallaxes, metallicities, abundances or combinations of thereof. As the number of input variables can be set, this geometric method makes the analysis more flexible, addressing the member identification problem from different perspectives. The first step of the method consists in the normalization of the variables where the outliers determination is a crucial step. Once the variables are normalized, a N-distance between every star and the cluster center is computed. By the application of a parametric method, where the distances are approximated as two gaussians functions, it turns out possible the determination of the gaussian parameter estimations along with the star classification at the same time. To check this methodology, 243 mock catalogs, made up of field stars and cluster members, were simulated. The results (Sampedro et al. 2013, in prep.) show that the methodology can, not only recover more than the 95%, of the simulated cluster members, but also the misclassificated stars are lower than the 8%, in most of the simulated configurations.
L. Sibbons
Title: The resolved stellar population in two Local Group Irregular dwarf galaxies
Short abstract: Dwarf galaxies offer us a unique opportunity to study resolved stellar populations in systems that are typically less evolved than the massive spiral galaxies of the Local Group like the Milky Way. The dynamics and stellar content of these systems provide us with a window on galactic evolution at an earlier time.
Two irregular dwarf galaxies, NGC 6822 and IC 1613, have been studied using near-infrared (NIR) photometry and optical spectroscopy in order to isolated and classify their intermediate-age (1-10 Gyr) asymptotic giant branch (AGB) population. Using the NIR photometry of NGC 6822 criteria for the selection of C- (carbon rich) and M-type (oxygen rich) AGB stars were derived. The accuracy of these initial classification criteria were then tested using spectroscopic data of selected stars in NGC 6822 in order to confirm their spectral class. Revised photometric criteria were then applied to the photometric data of IC 1613 for the selection of C- and M-type stars in IC 1613. The classifications of several hundred AGB stars in NGC 6822 photometric catalogue were also revised. By selecting C- and M-type stars in these two galaxies we have been able to derive their number ratio, the C/M ratio, and from there derive the a value for the global [Fe/H] abundance in each galaxy at the time these stars formed using the C/M vs. [Fe/H] relation. Using this technique we have derived a global metallicity of -1.29 ± 0.07 dex for NGC 6822 and -1.26 ± 0.07 dex for IC 1613.
Manuel Silva
Title: Runaway stars as tracers of the spiral arms
Short abstract: The spiral arms are readily visible in photographic images of face-on spiral galaxies. They are usually traced, in visible light, by young hot stars and respective ionised Hydrogen regions. They are the preferred sites of star formation. Our position within the Galactic disc is an obstacle to a direct observation of the spiral arms of the Milky Way, as they appear superimposed along our line of sight and are heavily obscured by dust. The obscuration is more severe in the direction of the Galactic centre, such that the region of the disc behind the centre is particularly poorly known. We propose a new method based on the analysis of the birthplaces of high Galactic latitude runaway stars to map the spiral arms and determine their dynamics. These stars provide the means to reach the poorly known regions of the disc, as they are less obscured by dust and thus visible at greater distances. We show how the method performs with data obtained by the Hipparcos satellite mission, and how data by the upcoming Gaia mission will improve upon it.
Anders Thygesen
Title: The isotopic mixture of Magnesium in 47 Tucanae
Short abstract: By now it is well-known that most (if not all) globular clusters harbour at least two generations of stars. This fact is observed in, for instance, anticorrelations of [Na/Fe]-[O/Fe] and [Mg/Fe]-[Al/Fe]. These correlations are believed to be caused by self-enrichment from an earlier generation of stars. However, the nature of these first-generation polluters is still a matter of debate, being AGB stars, Very Massive Fast Rotators or massive binaries. In cases where isotopic mixtures can be measured, additional constraints can be put on the first generation cluster stars and on the nucleosynthesis history of the cluster. Here we present results on Mg-isotopic ratios in giant stars in the metal-rich globular cluster 47 Tucanae. This is the most metal-rich cluster in which such an analysis has been performed to date and provides an important test of nucleosynthesis in a high-metallicity environment."
Sergio Vasquez
Title: The Galactic inner bulge spectroscopic survey, first results. (survey session)
Short abstract: In the last years the Galactic bulge has been proved more complex than it was expected. The access to kinematics and metallicities for extended regions in the bulge provide the key to understand it morphology, stellar distribution and formation. In this talk I want to present the first results from our spectroscopic survey in the inner bulge region.
Chris Wegg
Title: The 3d Density of the Galactic Bulge
Short abstract: Using red clump giants as a standard candle we have inferred the density in the inner Galactic bulge. I will present the method, and the key features of the resultant model.
Eva Ziegerer
Title: The nature and origin of Hypervelocity Stars
Short abstract: When Hypervelocity Stars (HVSs) were first discovered in 2005 dynamical ejection from a massive black hole in the Galactic Center (GC) was thought as their only origin because the stars move so fast that they are unbound to the Galaxy. This scenario was challenged for example by HVS 3 for which an origin in the LMC was suggested because of traveltime considerations (the traveltime from the GC exceeds its lifetime by a factor of 3) and its abundance pattern matches that of the LMC. Several other objects challenge the scenario. Radial velocity surveys have increased the number of HVSs to 22, but in most cases their space velocities are unknown due to the lack of precise proper motions for full 6D kinematic studies. The spatial and velocity distribution of HVSs provides significant constraints on the shape and density distribution of the Galactic dark matter halo.
POSTER CONTRIBUTIONS:
Dorothee Brauer
Title: Chemo-dynamical constraints in the Milky Way with RAVE and SEGUE.
Short abstract: We present first results from our chemo-dynamical study of a sample of local G-dwarfs selected from SEGUE. Using the fact that giant stars from RAVE and dwarf stars from SEGUE are covering a similar volume we directly compare our dataset to the sample of giants from Boeche et al. 2013 finding a good agreement between both surveys. In addition we compare our results with those from chemo-dynamical models (theory) and the predictions from TRILEGAL.
Sotirios Chatzopoulos
Title: Rotation and dynamics of the old nuclear cluster at the Galactic centre (GNC)
Short abstract: The main goal of this project is to put constraints on the mass, rotation, orbit structure and statistical parallax of the GNC. For this we combine star counts and kinematic data in various fields from Fritz et al. (2013), including 2500 radial velocities and 10000 proper motions obtained with VLT instruments, and 200 maser velocities. First we fit the surface density with a 2-component oblate-spheroidal model. Then we use the fitted density to calculate the 2-integral DF using the contour integral method of Hunter & Qian (1993). We add rotation self-consistently by adding an odd part in Lz to the initially even DF(E,Lz). The addition of sel-fconsistent rotation to the model does not affect the projected dispersions along the l & b directions. The difference between σl and σb can only be explained by assuming an axial ratio of 1/q = 1.4±0.1 for r<70''. The orbit structure of the 2-I DF is also able to predict the observed double peak in the velocity histogramms (VHs). This is independent of the net rotation, but depends of the flattening of the GNC.
Ricardo Dorta
Title: Red Supergiants as tracers of Perseus Arm structure.
Short abstract: We have performed a systematic search for red supergiants in the Perseus Arm (from l=95º up to l=150º). For this purpose we made a selection of candidates through photometric criteria, using data from UCAC, USNO and 2MASS catalogs. 747 stars were observed in the spectral region around infrared Ca triplet (8400 - 8900 Angstroms) at R~10000, using the Intermediate Dispersion Spectrograph (IDS) on the Isaac Newton Telescope (INT, Roque de los Muchachos Observatory). From these data we have obtained radial velocities, spectral type and luminosity class, finding 353 supergiants. Using them we have analysed the distribution in the radial velocity-galactic latitude diagram, tracing the young clusters and galactic structure in this region.
Xiaoting FU
Poster 1: Title: New PARSEC isochrones for metal poor stellar populations
Short abstract: We are computing new PARSEC stellar evolutionary tracks and isochrones for metal poor stellar populations. Taking as a reference for the solar abundances the recent compilation by Caffau et al. 2011, we are considering low metallicity elemental partitions with [alpha/Fe]=+0.2 and +0.4, which are suitable for the analysis of galactic Globular Clusters (GC) and the Halo Population. The comparison with colour-magnitude diagrams of selected GCs will provide useful constraints on the input physics adopted in the new models.
Poster 2: Title: Discovery of super-Li rich red giants in dwarf spheroidal galaxies
Short abstract: Stars destroy lithium (Li) in their normal evolution. The convective envelopes of evolved red giants reach temperatures of millions of K, hot enough for the 7Li(p,ɑ)4He reaction to burn Li efficiently. Nonetheless, Li-rich red giants do exist. We present 15 Li-rich red giants—14 of which are new discoveries—among a sample of 2054 red giants in Milky Way dwarf satellite galaxies. Our sample more than doubles the number of low-mass, metal-poor ([Fe/H]≤-0.7) Li-rich red giants, and it includes the most-metal-poor Li enhanced star known ([Fe/H]=-2.82, A(Li)NLTE = 3.15). Because most of the stars have Li abundances larger than the universe’s primordial value, the Li in these stars must have been created rather than saved from destruction. These Li-rich stars appear like other stars in the same galaxies in every measurable regard other than Li abundance. We consider the possibility that Li enrichment is a universal phase of evolution that affects all stars, and it seems rare only because it is brief.
Leonardos Gkouvelis
Title: Spectral classification and physical parameters of Be stars in the Perseus arm with the BCD system
Short abstract: IPHAS (the INT/WTC Photometric Ha Survey of the Northern Galactic Plane, www.iphas.org) is a survey carried out, in H-alpha, r and i filters, with the Wide Field Camera on the Isaac Newton Telescope in La Palma. Besides the photometric survey, the IPHAS collaboration is conducting follow up spectroscopic observations of selected emission line objects detected from the photometry. Most of the observed targets turned out to be classical Be stars. In this work we present the analysis of about 60 classical Be stars spectra, obtained with the INT and NOT telescopes in La Palma, by means of the BCD (Barbier-Chalonge-Divan) classification system. We have developed a semi-authomatic procedure, based on the BCD techniques, to obtain the physical parameters of classical Be stars, including effective temperature, luminosity class, interstellar reddening and absolute magnitude. We compare our results with those obtained for the same stellar sample with standard spectroscopic techniques by Raddi et al. (MNRAS, in press), in order to validate our procedure. Our final goal is to apply our technique to a much larger sample of Be star spectra through the northern galactic plane, in order to obtain their physical parameters and use them to trace the galactic structure.
Cheng Liu
Title: Finding the lost siblings of the Sun
Short abstract: We selected 57 solar sibling candidates from Hipparcos catalogue based on selection criteria in parallax and proper motion space and colour cut at (B–V) < 0.4. Currently, we did an accurately spectral analysis on 18 candidates which were observed with high resolution spectroscopies. Stellar parameters were first obtained by fitting the spectrum with synthetic spectra. We also obtained abundances of four αelements and one iron peak element. We found that only one potential candidate -HIP 40317- has solar metallicity and might have an age comparable to that of the Sun. The abundance of this star is very close to the Sun. However, when we taken into account systematic errors in stellar parameters, the large uncertainty to the age of the star does not permit us to be sure about it as a possible solar sibling.
Rafael Lopez Fernández
Title: SFH of galaxies using spectroscopy in the optical range of the CALIFA sample and ultraviolet photometry of the GALEX mission
Short abstract: Why study the stellar populations? Different evolutionary processes leave a different fossil record in the stellar population properties of galaxies. A very powerful method to study the formation and evolution of galaxies is to reconstruct the star formation history through the properties of stars that form them. Currently is used the evolutionary synthesis technique to infer the properties of the stellar population through the integrated light of all the stars, assuming an initial mass function (IMF) and a star formation rate. To analyze the data we use the code STARLIGHT.
The spectral range of the CALIFA sample is ideal for the study of stellar populations, as it contains the lines of the Balmer series and the Balmer jump. However, the method can present age-metallicity-extinction degenerations, producing uncertainties in determining the physical properties of the stellar population characteristics. So we combine CALIFA spectroscopic data with photometric data in the ultraviolet range obtained with the GALEX mission in order to break these degeneracies, including data that provide additional information about the young stellar populations, which contribute to a lesser extent in the optical range.
Clara Martínez
Title: Searching for chemical inhomogeneities in Open Clusters
Short abstract: The total mass of a cluster, being the main parameter determining its ability to host more than one stellar generation, may constitute a threshold below which the cluster is able to form only a single stellar population. Our goal is to investigate the existence of star-to-star variations of CN and CH band strengths, related to the N and C abundances, respectively, among the stars in five open cluster (NGC 2158, NGC 2420, NGC 2682, NGC 7789 and Berkeley 29) similar to those observed in globular clusters and linked with the existence of multiple populations therein. Since these systems are less massive than globulars, our results may allow us to constrain the lower mass necessary to form more than one stellar population. We measured the strength of the CN and CH bands, which correlate with the C and N abundances, using four molecular indices in low-resolution SDSS/SEGUE spectra. We found that for four of the open clusters (NGC 2158, NGC 2420, NGC 2682 and Berkeley 29) all the stars studied in each of them have similar CN and CH band strengths within the uncertainties since neither anomalous spreads nor bimodalities have been detected in their CN and CH distributions. In contrast, for NGC 7789 we found an anomalous spread in the strength of the CN molecular band at 3839 Å which is larger than the uncertainties. However, the small number of stars studied in this cluster implies that further analysis is needed to confirm the existence of chemical inhomogeneties in this cluster.
Berenice Pila Diez
Title: "Finding halo streams with a pencil-beam survey: the Sagittarius, the Orphan and the Palomar 5 streams"
Short abstract: In this work we make use of a deep photometric pencil-beam survey with the CFHT-MegaCam of only two colour-filters to detect and characterize stellar streams in the halo of the Milky Way. Due to the nature of our survey (pencil-beam, two bands), it is neither possible to enhance the CMDs (Colour Magnitude Diagrams) by substracting the foreground stars, nor possible to obtain clean selections of turnoff-point or red clump stars based on colour-colour criteria. Thus we present a cross-correlation method that allows us to override these problems and obtain photometric distances based on the main sequence turnoff point of the streams. We show our results and compare them to previous works from other groups for the Sagittarius stream (both the faint and the brigh branches), the Palomar5 stream and the Orphan stream.
Maider Sancho
Title: The Distribution of Metals in the Thick Disk
Short abstract: We present the radial metallicity gradient as a function of height above the galactic plane within a suite of chemo-dynamical simulations, realised as part of the MAking Galaxies In a Cosmological Context (MaGICC) project, spanning a range of masses, feedback prescriptions, and initial conditions/assembly history. Our preliminary work reveals the radial metallicity gradients of the kinematically-defined disk stars to be negative in the mid-plane of the simulated discs but when we reach ~1kpc above the plane the radial gradients become inverted (i.e. more metal-rich in the outskirts, relative to the inner parts of their respective discs). Such behaviour is consistent with that inferred from SEGUE data (e.g. Cheng et al 2012; Carrell et al 2012). The radial gradients as a function of scaleheight above the disc provide an insight into the formation and evolution of the Galaxy; the chemical properties of the discs, along with their stellar radial migration patterns, will be presented.