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CURRICULUM VITÆ of ROSARIA TANTALO
Address
Department of Astronomy - Vicolo Osservatorio 3 -
University of Padova -35122 Padova - Italy
Phon: +39-049-8278253 (office)
Fax: +39-049-8278212
E-mail: rosaria.tantalo@unipd.it
Personal Data
Born in Matera, Italy, July 10, 1966
Married with Francesco Macino on June 22, 1996.
EDUCATION
July 1984: Diploma di maturità: “Tecnico di Laboratorio Chimico e Biologico”
July 25, 1994: Laurea in Astronomy, at the University of Padova (Italy)
Thesis title: ``Spectro-Photomery of Elliptical Galaxies: Models with Infall``.
Supervisors Prof. Cesare Chiosi, Prof. Alessandro Bressan, and Dr. Franco Fagotto)
May 13, 1998: Dottorato di Ricerca in Astronomy at the University of Padova (Italy)
Thesis title: ``GALAXY FORMATION AND EVOLUTION: Spectro- photometric Models of
Elliptical Galaxies``.
Supervisor Prof. Cesare Chiosi
Fellowships
1. Post-Doc fellowship of 2 years at the Padova University from March the 1 st 1999 to March the 1 st , 2001;
2. Assegno di Ricerca for the research project: Age of Elliptical Galaxies at the University of Padova from 1 st of
April 2002 to March 31, 2004;
3. Assegno di Ricerca for the research project: Stars with low metallicity in Early-Type Galaxies at the
University of Padova from 1 st of April, 2004 to December 31, 2004;
Research Experience
Evolution of stellar population, chemical evolution and photometry of galaxies.
Theaching Activities
• April 2004: “Theory of the Mixing Length” (6 hours) during the course of “Astrofisica II” c/o the department
of Astronomy of the Padova University (Prof. Cesare Chiosi)
• May 2005: “Theory of the Mixing Length” (5 hours) during the course of “Astrofisica II” c/o the department
of Astronomy of the Padova University (Prof. Cesare Chiosi)
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STAGES BY FOREIGN INSTITUTES
1. From January 12 to February 8, 1997 c/o MSSSO in Camberra, Australia, to work with Dr. Brad Gibson.
During this period I have given a seminar on: Is the stronger Mg2 index an indicator of [Mg/Fe]
enhancement?
2. From May 24 to June 12, 2004 c/o I.A.C. (Istituto de Astrofisica de Canarias) in Tenerife (Spain), to work
with Dr. Alexandre Vazdekis. During this period I have given a seminar on: Absorption-line indices from
high-resolution spectra
Languages
(1) English: good (reading, writing, speaking)
(2) Spanish: good (reading, writing, speaking)
Informatics
LANGUAGES AND INFORMATICS KNOWLEDGES
(1) FORTRAN (very good)
(2) Operation Systems: UNIX, WINDOWS, LinuX (good)
(3) Object Languages: JAVA (medium)
ACTUAL POSITION
Technical-scientific position for outreach activity and data elaboration at the University of Padova, in the field of
the Educational Project “Il Cielo come Laboratorio” which include some lessons for high schools students.
NATIONAL AND INTERNATIONAL SCHOOL
1. Student of European Astrophysics Doctoral Network Predoctoral School VIII: Structure of the Universe.
Leiden, Netherland, July 13-22, 1995
2. National School of Astrophysics, I cycle (1995-1996), III course: AGN-Ogetti Collassati-Evoluzione Stellare.
Giulianova Lido, Italy, May 5-11, 1996
3. VIII Canary Islands Winter School: Stellar Astrophysics for the Local Group: A first step to the Universe.
Tenerife, Canary Islands (Spain), December 2-13, 1996
4. National School of Astrophysics, II cycle (1996-1997), I course: Galassie - Fisica Solare e Stellare. Acireale,
Italy, May 25-30, 1997
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5. XI Canary Islands Winter School: Galaxies at High Redshift. Santa Cruz de Tenerife, Tenerife, Canary Islands
(Spain), November 15-26, 1999
6. National School of Astrophysics, V cycle (1999-2000), IV course: Galaxies Formation - Active Galactic
Nuclei. Asiago, Italy, September 10-16, 2000
7. National School of Astrophysics, VI cycle (2000-2001), II course: Chemical Evolution of Galaxies - High
Resolution Spectroscopy. Trieste, Italy, October 15-19, 2001
8. XIII Canary Islands Winter School: COSMOCHEMISTRY. The Melting Pot of elements. Puerto de la Cruz,
Tenerife, Canary Islands (Spain), November 19-30, 2001
MEETINGS AND CONFERENCES
1. PASP Conference: From Stars to Galaxies: The impact of Stellar Physics on Galaxy Evolution. Crete, Greece,
October 9-13, 1995
2. The IAU Symposium 189: Fundamental Stellar Properties: The Interaction between Observation and Theory.
Sydney, Australia, January 12-17, 1997
3. TMR Workshop: Semi-analytical models of Galaxy Formation. MPA in Munich, Germany, March 21-22,
1997
4. 1997 TMR Annual Meeting: Galaxy Formation and Evolution. Ringberg, Germany, May 19-24, 1997
5. 38 th Herstmonceux Conference: The Stellar Initial Mass Function. Cambridge, UK, July 14-18, 1997
6. DM-ITALIA-97, Dark-matter: Prospettive e Progetti. Trieste, Italy, December 9-11, 1997.
7. Evolving Evolution: Evoluzione stellare in Italia, lo stato dell'Arte. CarloForte, Isola di San Pietro, Italy, June
8-11, 1998.
8. Euroconference on The Evolution of Galaxies on Cosmological Timescales. Puerto de la Cruz, Tenerife, Spain,
November 30 – December 5, 1998.
9. 1 st Workshop del Network Italiano on Formazione ed Evoluzione delle Galassie. Padova, Italy, May 18-19,
1999
10. Guillermo Haro Workshop 99: Large Scale Structure & Clusters of Galaxies. Tonantzintla, Puebla, Mexico,
From June 14 to July 30, 1999
11. 2 nd Mini-Workshop on Sintesi di popolazione (Italian Network on: Formazione ed Evoluzione delle Galassie)
Padova, Italy, December 3, 1999
12. International Workshop on: Tracing Cosmic Evolution with Galaxy Clusters. Sesto Pusteria, Bolzano, Italy,
July 3-6, 2001
13. GAIA Workshop: Radial Velocity Spectrometer Workshop n.2. Asiago, Vicenza, Italy, February 7-9, 2002
14. XLVI Congresso Nazionale della SAIt. Padova, Italy, April 10-12, 2002
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15. International Conference on: New Horizons in Globular Cluster Astronomy. Padova, Italy, June 24-28, 2002
16. Ringberg Workshop on: The Chemical Evolution of Dwarf Galaxies - Present Status and Perspectives.
Ringberg Castle, Bavaria, Germany, July 29 – August 2, 2002
17. Monte Rosa International Conference: GAIA Spectroscopy, Science and Technology. Gressoney St. Jean
(Aosta), Italy, September 9-12, 2002
18. GAIA Workshop: Radial Velocity Spectrometer Workshop IV. Gressoney St. Jean (Aosta), Italy, September
13, 2002
19. Cosmo 2002: VII Congresso Nazionale di Cosmologia. Monte Porzio Catone (Roma), Italy, November 5-8,
2002
20. Stars in Galaxies: IV Workshop Nazionale su Stellar Astrophysics. Santa Cruz de La Palma, Spain, March 7-
11, 2003
21. International Conference: Stellar Populations 2003. Garching, Germany, October 6-10, 2003
22. International Conference: IMF@50: The inital mass function 50 years later. Abbazia di Spineto, Siena, Italy,
May 16-20, 2004
23. International Workshop: The Spectral Energy Distribution of Gas Rich Galaxies: Confronting Models with
Data. Heidelberg, Germany, October 4-8, 2004
24. International Workshop: Stellar Pulsation and Evolution. Monte Porzio Catone, Roma, Italy, June 19-24,
2005
25. EARA Workshop 2006: Galactic Bulges. Padova, Italy, January 25-26, 2006
26. International Conference: From Stars to Galaxies: building the piece sto build up the Universe. Venice, Italy,
October 16-20, 2006
27. The IAU Symposium 241: Stellar Population as building blocks of Galaxies. St. Cruz de La Palma, Canary
Islands, Spain, December 10-16, 2006
Journals with Referee
PUBLICATION LIST
1. Spectro-photometric Evolution of Elliptical Galaxies. II. Models with Infall. R. Tantalo, A. Bressan, C. Chiosi,
F. Fagotto, 1996. A&A, 311, 361.
2. Probing the Age of Elliptical Galaxies. A. Bressan, C. Chiosi, R. Tantalo, 1996. A&A, 311, 425. (astroph9602032)
3. Ages and Metallicities in Elliptical Galaxies from the Hβ, 〈Fe〉, and Mg2 Diagnostics. R. Tantalo, C. Chiosi, A.
Bressan, 1998b. A&A, 333, 419.
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4. Spectro-photometric Evolution of Elliptical Galaxies. III. Infall models with gradients in mass density and star
formation. R. Tantalo, C. Chiosi, A. Bressan, L. Portinari, P. Marigo, 1998a. A&A, 335, 823. (astroph/9710079)
5. A new scenario of galaxy evolution under a universal Initial Mass Function. C. Chiosi, A. Bressan, L.
Portinari, R. Tantalo 1998. A&A, 339, 335.
6. Enhancement of a-elements in Dinamical Models of Elliptical Galaxies. R. Tantalo, C. Chiosi, 2002. A&A,
388, 396.
7. Shells of dust around AGB stars: effects on the integrated spectrum of single stellar populations. L. Piovan, R.
Tantalo, C. Chiosi, 2003. A&A, 408, 559.
8. On the Mass-to-Light ratio and the Initial Mass Function in galactic discs. L. Portinari, J. Sommer-Larsen, R.
Tantalo, 2004. MNRAS, 347, 691.
9. Star Formation History of Early Type Galaxies. I. The line absorption Indices diagnostics. R. Tantalo, C.
Chiosi, 2004. MNRAS, 353, 405.
10. Measuring age, metallicity and abundance ratios from absorption line indices. R. Tantalo, C. Chiosi, 2004.
MNRAS, 353, 917.
11. Modelling galaxy spectra in presence of interstellar dust. I. The model of ISM and the library of dusty SSPs.
L. Piovan, R. Tantalo, C. Chiosi, 2006, MNRAS, 366, 923.
12. Modelling galaxy spectra in presence of interstellar dust. II. From the UV to the far infrared. L. Piovan, R.
Tantalo, C. Chiosi, 2006, MNRAS, 370, 1454.
13. New response functions for absorption-line indices from high-resolution spectra. R. Tantalo, C. Chiosi, L.
Piovan, 2007, A&A, 462, 481.
14. The Galaxy Evolution Explorer UV emission in shell galaxies: tracing galaxy `rejuvenation' episode. R.
Rampazzo, A. Marino, R. Tantalo, D. Bettoni, L.M. Buson, C. Chiosi, G. Galletta,, R. Grützbauch, R.M. Rich,
2007, MNRAS, 381, 245
15. XMM-Newton X-ray and Optical Monitor far UV observations of NGC 7070A and ESO 2400100 shell
galaxies. G. Trinchieri, R. Rampazzo, C. Chiosi, R. Grützbauch, A. Marino, R. Tantalo, 2008, in press
Conference Proceedings
1. Integrated Infrared Colors of Star Cluster in the Galaxy and M 31. A. Vallenari, C. Chiosi, R. Tantalo, 1996.
ESO Astrophysics Symposia 1996, p.113. D. Minniti (eds.)
2. Spectro-photometric Models of Elliptical Galaxies with Infall. R. Tantalo, C. Chiosi, A. Bressan, F. Fagotto,
1996. ASP Conference Series, Vol. 98, p.42. C. Leitherer, U.-Fritze Von Alvensleben and J. Huchra (eds.)
3. Elliptical Galaxies: The Age Metallicity Dilemma. A. Bressan, C. Chiosi, R. Tantalo, 1996. ASP Conference
Series, Vol. 98, p.49. C.Leitherer, U.-Fritze Von Alvensleben and J. Huchra (eds.)
4. A DATA BASE FOR GALAXY EVOLUTION MODELLING. C. Leitherer et al. 1996. PASP, Vol. 108, p.996.
5. Models of Elliptical Galaxies: the Gradients. R. Tantalo, C. Chiosi, A. Bressan, 1997. ESO Workshop held
November 1996, p.396. L.N. da Costa and A. Renzini (eds.)
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6. Is the stronger Mg2 index an indicator of [Mg/Fe] enhancement? R. Tantalo 1998. IAU Symposium 189,
p.104. T.R. Bedding, A.J. Booth and J. Davis (eds.)
7. The Problem of α-elements Enhancement in Elliptical Galaxies. R. Tantalo, 1999. Proceedings of the 1 st
Workshop of the Italian Network on: “Formation and Evolution of Galaxies”, p.141. C. Chiosi, L. Portinari
and R. Tantalo (eds.)
8. Properties of Elliptical Galaxies from Spectral Indices. R. Tantalo, 1999. Proceedings of the 2 nd Workshop of
the Italian Network on: “Formation and Evolution of Galaxies - Stellar Population Synthesis”, p.1. B.M.
Poggianti (eds.)
9. Ages, Metallicities and Abundances in Elliptical Galaxies. R. Tantalo, 2001. Ap&SS, Vol. 276, p.1189, J.
Dyson and S.A. Lamb (eds.)
10. Indices for SSPs with enhanced mix of α-elements. R. Tantalo, 2002. PASP Conference Series, Vol. 268,
p.445. S. Borgani, M. Mezzetti and R. Valdarnini (eds.)
11. Line indices as age, metallicity and abundance ratio indicators. R. Tantalo, C. Chiosi, 2003. Mem. SAIt.,
Vol. 74, p.518
12. Line indices as age, metallicity and abundance ratio indicators. R. Tantalo, C. Chiosi, 2003. APS Conference
Series, Vol. 298, p.477, U. Munari (eds.)
13. The Mass to Light ratio and the Initial Mass Function in galactic discs. L. Portinari, J. Sommer-Larsen, R.
Tantalo, 2003. Ap&SS, Vol. 284, p.723. G. Hensler et al. (eds.)
14. Measuring age, metallicity and abundance ratios from absorption line indices. R. Tantalo, 2004. Mem. SAIt.,
Vol. 75, p.202
15. Mass to Light ratio,Initial Mass Function and chemical evolution in disc galaxies. L. Portinari, J. Sommer-
Larsen, R. Tantalo, 2004. PASA, Vol. 21, p.144. B.K. Gibson and D. Kawata (eds.)
16. The stellar Mass-to-Light ratio in disc galaxies. L. Portinari, J. Sommer-Larsen, R. Tantalo, 2004. IAU
Symposium 220, p.309
17. New database of SSPs with different IMFs. R. Tantalo, 2005. ASSL (Astrophysics and Space Science
Library), Vol. 327, p.235, E. Cobelli, F. Palla and H. Zinnecher (eds.)
18. Synthetic Galactic Spectra in presence of dust: from the UV to the far-IR. L. Piovan, R. Tantalo, C. Chiosi,
2005. AIP Conference Series, Vol. 716, p.91, C.C. Popescu and R.J. Tuff (eds.)
19. Spectral energy distribution in presence of shells of dust around AGB stars. L. Piovan, R. Tantalo, C. Chiosi,
2006. Mem. SAIt. Vol. 77, p.873
20. Insight about induced SFR in the shell system of early-type galaxies from UV observations. L. Buson, D.
Bettoni, R. Rampazzo, A. Marino, G. Galletta, C. Chiosi, R. Tantalo, R.M. Rich, 2007. IAU Symposium,
Vol.235, p.305. F. Combes and J. Palous (eds.)
21. New response functions for absorption-line indices from high-resolution spectra. R. Tantalo, C. Chiosi, L.
Piovan, 2007, IAU Symposium 241, p.143. A. Vazdekis and R.F. Peletier (eds.)
22. Effects of Dust on Galactic Spectral Energy Distributions. L. Piovan, R. Tantalo, C. Chiosi, 2007, ASP
Conference Series, Vol.374, p.355. A. Vallenari, R. Tantalo, L. Portinari and A. Moretti (eds.)
23. New Response Functions for Absorption-Line Indices from High-Resolution Spectra. R. Tantalo, C. Chiosi, L.
Piovan, 2007, ASP Conference Series, Vol.374, p.373. A. Vallenari, R. Tantalo, L. Portinari and A. Moretti
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(eds.)
24. Photometric Properties of Early-Type Galaxies from Simulations. S. Chinellato, R. Tantalo, C. Chiosi, 2007,
ASP Conference Series, Vol.374, p.493. A. Vallenari, R. Tantalo, L. Portinari and A. Moretti (eds.)
25. Tracing Galaxy Evolution in the Field: the UV Emission in shell galaxies mapped by GALEX. D. Bettoni, A.
Marino, L. Buson, C. Chiosi, G. Galletta, R. Ramazzo, R. Tantalo, M. Rich, 2008, Mapping the Galaxy and
Nearby Galaxies, p.311, K. Wada and F. Combes (eds.)
26. The GALEX UV emission in shell galaxies. A. Marino, R. Rampazzo, R. Tantalo, D. Bettoni, L.M. Buson, C.
Chiosi, G. Galletta, 2008, ASP Conference Series, in press
Accepted paper not published
1. To what extent are Mg2 and 〈Fe〉 indicators of Mg and Fe abundances? . R. Tantalo, A. Bressan, C. Chiosi,
1997. Submitted to A&A and accepted (astro-ph/9710101)
2. Diagnostic of chemical abundances and ages from the line strength indices Hβ, 〈Fe〉 and Mg2: what do they
really imply? R. Tantalo, A. Bressan, C. Chiosi, 1997. Submitted to A&A (astro-ph/9705060)
CURRENT RESEARCH INTERESTS
1. Scientific rationale and summary of my past and present research interests
The main issue with elliptical galaxies (EGs) concerns their formation and evolution. Are the EGs formed via
mergers of sub-structures composed by gas and stars? Is every event followed by stellar activity? Or, otherwise,
are the EGs formed in early epochs from a initial mass of gas transformed in stars without subsequent star
formation (SF)? Related to this general topic, there are several problems which I have been working on during
the past few years. They are shortly presented. In the section below I will describe in some detail my own
contribution to each of them.
(1) Colour-Magnitude Relation (CMR)
Brighter EGs seem to be also redder. The CMR for EGs in galaxy clusters is tight and this means that these
objects are old (say 12--13 Gyr) and coeval (Bower et al. 1992). The CMR for the field and group galaxies is
more disperse and seems to suggest prolonged history of star formation (Schweitzer & Seitzer 1992).
(2) The SGWM
Along the CMR for EGs the metallicity increases with their luminosity (mass). Larson (1974) has suggested
the Supernovae Galactic Wind Model (SGWM) to explain the higher metallicity associated to brighter
galaxies (longer SF).
(3) α−Elements
The gradients of Mg2, 〈Fe〉 and other indices seems to reflect gradients in the chemical abundance ratios
[α/Fe] (Matteucci 1997). The ratio tends to increase with the galactic luminosity suggesting that the duration
of the SF activity decreases at increasing mass: ΔtSF ∝ MG −1 , the opposite of what is required by the SGWM.
(4) UV-Excess
Another important property of the EGs is the so-called ultraviolet-excess (UV-excess). Observations in the
UV band have shown that these, apparently old, objects emit a significant fraction of their luminosity in the
far-UV (spectral region shortward of 2,000 Å). While the UV-flux seems to change among EGs, the infrared
flux is nearly the same for all of them. This behaviour suggests the presence of a hot stellar component in the
stellar of EGs. The UV-excess is currently measured by the (1550−V) colour. It is correlated with the
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luminosity, velocity dispersion σ (mass in turn) and Mg2. As Mg2 is considered a metallicity indicator,
Burstein et al. (1988) argued that the UV-excess increases with the galaxy metallicity.
(5) Age and metallicity
The simultaneously analysis of some indices (such Hβ, Mg2, [MgFe], 〈Fe〉, etc.), the colour (1550-V), and the
velocity dispersion σ, have shown that:
a. Most of EGs cover the range of metallicity Z < Z < 3Z (Bressan, Chiosi, Tantalo 1996, Greggio 1996);
b. Contrary to the straight conclusions that the scatter in Hβ implies a large age dispersion (Gonzàlez 1993,
Worthey et al. 1994, Trager et al. 2000), it seems that all ellipticals are old but characterised by different
SF histories.
Indeed, for some of them the SF is short and occurs at the beginning of their evolution, whereas for others it
can be longer. It has been shown that the duration of the SF activity see to decrease with velocity dispersion σ,
i.e. the galaxy mass (Bressan, Chiosi, Tantalo 1996; Tantalo et al. 1998a).
(6) Isolated and interacting EGs
In the Hβ versus [MgFe] plane, pair- and shell-galaxies (interacting galaxies) and normal- and isolated
galaxies shown the same distribution (Longhetti et al. 1999, 2000). Does the secondary episode of SF not
depend from interaction?
(7) Galaxies captures
An episode of SF in an EG involving only 5-10% of the total mass and occurred 5-6 Gyr ago implies bluer
(B−V) colour with a spread of approximately 0.95 ± 0.05 (Chiosi 2000). This means that mergers followed by
SF activity are unlikely unless the SF has been very low. If the hierarchical scenario is at work for the
formation of massive galaxies, then mergers must be occurred very early on (approximately half of the Hubble
time).
(8) Initial mass function (IMF)
One of the fundamental parameters driving the chemical evolution of the galaxies is the IMF. Given the mass
distribution of stars in a single stellar population, the ratio of low- to high mass stars affects the chemical
enrichment of the population. Over the years, different studies on the IMF have shown that the number of lowmass
stars is lower predicted by the Salpeter power-law. Padoan et al. (1997, 2000), Chiosi et al. (1998),
Larson (1998) and Chabrier (2003), have proposed lognormal IMF, whose shape a peak mass changes with on
the physical conditions at which stars are formed. Systematic changes with the galaxy type and redshift of
galaxy formation are also expected.
(9) The effects of dust on integrated spectra of galaxies
The advent of modern infrared astronomy has brought into evidence the role played by the
interstellar dust in the subject of galaxy formation and evolution. Among other effects, dust absorbs
the UV-optical light emitted by stars and return it into the far-infrared (far-IR). Therefore, to fully
exploit modern data, models of galactic population synthesis must include this important component.
Owing to the presence of interstellar dust, precious information on the star formation history (SFH)
of galaxies, that in principle is derived from the UV/optical region of the spectrum are in reality
hidden IR spectral region so that new tools suited to this kind of analysis have to be found.
(10) High-resolution spectra
Recently, high-resolution spectra for large samples of stars and galaxies have become available. To analyse
these new data it is necessary to improve the population synthesis models including new spectral libraries
(theoretical and/or empirical) calculated with high-resolution. This would give us models of stellar
populations and/or galaxies that can be directly compared with the new generation of data. In addition to this,
in order to fully explore the data, we have to generate libraries of stellar populations in which the effects of
enhancement in α-elements are taken into account.
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2. Results obtained in the above items
Chemical and photometric evolution of model galaxies
The main tool I have adopted and partly developed during the past years is the chemical and spectrophotometric
evolutionary model for elliptical galaxies (Bressan et al. 1994, Tantalo 1996, Tantalo et al. 1998).
Applying this models, I have investigated a number of properties of EGs such as the CMR, the UV-excess, the
broad-band colours etc. Key parameters of the model are the SFR, the accretion rate (infall), the IMF, the stellar
nucleosynthesis yields (taken from Portinari et al. 1998 and Marigo 2002), the energy input from supernova
explosion and stellar winds, the efficiency of galactic wind, the potential well of dark matter. The model predicts
different degree of chemical enrichment passing from massive to dwarf EGs. In this context I have examined in
great detail the supernova driven galactic wind model by Larson (1974), the analogue of the G-Dwarf problems,
the effects of infall on chemical enrichment, and the nature of the UV-excess (Tantalo 1994,1996 and Tantalo et
al. 1996,1998). In addition to this, I have combined the SFH resulting from the dynamical models of Chiosi &
Carraro (2002) with a detailed chemical description in order estimate and test of the corresponding chemical
enrichment history (Tantalo & Chiosi 2002).The result obtained for a dwarf and a normal EG have shown that
massive galaxies have higher degree of enhancement which is explained by their short duration of star formation,
whereas dwarf galaxies, with their prolonged stellar activity in the burst mode have a lower degree of
enhancement (Tantalo & Chiosi 2002). Furthermore I have suggested that the observed dispersion in the Mg2-σ
plane is essentially due to the metallicity-σ-mass relation rather than dispersion in age and/or enhancement in αelements
(Tantalo & Chiosi 2002).
The UV-excess
Several different hypotheses have been proposed to interpret this emission. The first one suggested by Lee
(1994) and Lee & Park (1997) assumes as candidates for the UV-excess the old and metal-poor stars; the second
one proposed by different groups (Bressan et al. 1994, Dorman et al. 1995, Yi et al. 1998) suggests as candidates
the old, metal-rich stars. The two scenarios predict different ages for the onset of the UV flux in nearby galaxies:
in the first case, EGs should be 3 Gyr older than typical globular clusters, whereas with the second scenario age is
normal (say 12-13 Gyr) but another mechanism is at work. Greggio & Renzini (1990) examined all plausible
candidates for the UV-excess. In particular they suggest that it can be due to the combination of four kind of
objects: (i) Post-AGB stars (stars that leave the AGB phase after the thermal pulsing phase, the so-called
Planetary Nebulae) that are considered as the “classical” sources; (ii) very hot horizontal branch (VH-HB) stars;
(iii) hot-horizontal branch (H-HB) stars; and last (iv) the AGB-manquè stars, old star with high metallicity that
“fails” the AGB phase because either they lose the envelope either during the red-giant branch (RGB) phase due
to stellar wind or the burn it from inside by nuclear burning in the H-shell or both.
Tantalo et al. (1996,1998a) incorporated these ideas in galaxy models showing that the best candidates for the
UV-excess are high metallicity AGB-manquè stars of high Teff. For two times solar metallicity the classical AGB
phase is turned into the AGB- manquè. For even higher metallicity (three times solar) the HB evolution occurs at
high Teff and the AGB phase is eventually suppressed. The models show that a small fraction of the stellar
content of a galaxy at high metallicity is sufficient to power the UV-flux. The colour-magnitude diagrams (CMD)
in the V and I passbands for clusters in the galactic bulge show objects that for their magnitude and colour could
perhaps be associated to H-HB and AGB-manquè stars (Bertelli et al. 1996). UV surveys of these clusters could
confirm this result. The dependence on the metallicity is particularly interesting because the same parameter can
explain the CMR and the UV-excess.
Furthermore, as the temporal evolution of the theoretical spectra of EGs in the optical and IR regions does not
show features that can be adopted to estimate the age of these objects (the SED of old objects are almost age
independent), whereas the spectral region from 1,000 to 3,000 Å, dominated by the emission of Post-AGB, VH-
HB, H-HB e AGB-manquè stars turns out to be sensitive to the age, the interesting possibility of dating galaxies
by their UV-excess arises. As the UV radiation is emitted at different ages at changing the dominant mechanism,
one can define suitable ultraviolet colours displaying a significant variation at a certain age or redshift. Using the
theoretical models by Tantalo et al. (1996,1998a) we can estimate the redshift at which the “up-turn” occurs.
More precisely, the (1550−V) starts blue due to young Post-AGB stars and then as the galaxy evolves gets
redder down to a certain value, after which it becomes blue again when the galaxy is old enough to develop the
first hot horizontal branch (H-HB) and/or AGB-manquè stars. As more fuel is burned, these evolutionary phases
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last longer than the “classical” Post-AGB phase. Form the cosmological point of view, the age at which the
ultraviolet “up-turn” occurs can be associated to a certain redshift (from z=0.15 to z=0.5, depending on the
cosmological parameters). Modern instrumentation can easily reach this redshift interval.
To this aim systematic searches in nearby galaxy clusters (i.e. Coma which contains objects with muv

correlated with age (i.e. Hβ, Hγ, Hδ) or with metallicity and/or enhancement (indices like Mg2 and 〈Fe〉).
In Tantalo et al. (1998b), see also Bressan, Chiosi, Tantalo (1996), a new method has been proposed (the socalled
Δ–method) based on theoretical indices for single stellar populations (SSPs) that are calculated with the
fitting functions (FFs) of Worthey et al. (1992) and Worthey & Ottaviani (1997) and the calibration of Borges et
al. (1995). Suitable relationships expressing the indices (Mg2, 〈Fe〉 and Hβ) as a function of age, metallicity and
abundance of α-elements are then derived. Analysing the sample of Gonzàlez (1993) we concluded that for the
bulk of galaxies the nucleus are younger, more metal rich with and more α-enhanced than the external regions.
Looking at a small group of EGs that seem to define an upper limit to the galaxy ages (see the relation Δlog(t)-
MV in Tantalo et al. 1998b), we suggested that the duration of the star formation activity was shorter in the
massive galaxies and longer in the low-mass ones.
Owing to the complexity of this subject and the far reaching implications of determining ages, metallicities
and degree of α-enhancement in EGs we have undertaken a systematic analysis of the problem (Tantalo & Chiosi
2004a). The aim was to understand how different stellar models, different chemical compositions, different
pattern of α−enhanced elements at fixed total metallicity and degree of α-enhancement, different sources of
fitting functions, and different algorithms to pass from solar-scaled to α-enhanced indices, the so-called response
functions (RFs) of Tripicco & Bell (1995) in particular, would reflect onto ages, metallicities and α-
enhancement assigned to EGs. The dispersion of the observed data in the two-index diagrams (e.g. Hβ versus
[MgFe]) is customarily interpreted as an age spread. In contrast, we have suggested that part of the scatter among
old objects can be due to a dispersion in the degree of α-enhancement. The spread could be the signature of
different star formation histories and chemical enrichment from galaxy to galaxy.
Along with this subject, the two-indices (ex. Hβ versus [MgFe]) diagrams have been analysed in great detail,
considering both the probable spread in the chemical composition and possible later burst of stellar activity
(Tantalo & Chiosi 2004b). The bottom line of the study tried to answer the question: do interacting galaxies have
a different behaviour in this kind of diagnostic planes? Using the results Longhetti et al. (2000) for interacting
galaxies, and assuming very simple models to simulate bursts of SF, the behaviour of the indices in these kind of
diagrams has been studied. Once again, most of the spread observed in this diagrams is explained by a different
chemical composition. However for a small number of objects, with very high values of Hβ a burst of SF has to
be invoked. Whether this is due to interactions or internal causes cannot be said. In any case, the burst of stellar
activity ought to involve a small per cent of the total galaxy mass. It was shown that, after a burst of SF, the
broad-band colours and indices go back to their original values on a certain period of time (recovering time),
which does not depend on the galaxy age or the epoch of the burst, but only on the burst intensity (engaged
mass). It was shown that if real galaxies have undergone periods of strong stellar activity (due to merges and/or
interaction and/or accretion), either these had to occur in early epochs or if they occurred later they had to involve
only small fractions of the galaxy mass.
The IMF
One of the most important “parameter” driving the evolution of a stellar population is the initial mass function
(IMF). In current chemical evolutionary models for EGs the standard Salpeter (1954) law is assumed. However,
during the past few years many efforts have devoted to check whether this is a good assumptions or other IMFs
ought to be adopted. It was argued in particular whether the IMF could vary with the physical conditions of the
medium in which stars are formed. Along this line of thought is the “variable-IMF” proposed by Padoan et al.
(1997), which is expected to change as a function of the gas temperature, density and velocity dispersion. The
Padoan et al. (1997) IMF has been included in the evolutionary population synthesis by Chiosi et al. (1998). For
the conditions typical of the solar-neighbourhood, the Padoan IMF recovers the Salpeter law. In Chiosi et al.
(1998) has been shown that this new IMF can solve the contradiction between the requirement set by the αenhancement
problem (short duration of SF in massive EGs) and the interpretation of the CMR with the Larson
(1974) SDGW model (long duration of SF in massive EGs in order to get high metallicities).
Other IMFs can be found in literature, e.g. the combination of power law and exponential (Larson 1998); the
lognormal by Chabrier (2003), which predict a peak mass toward the low mass end (bottom-light IMF), both
secure few low-mass stars in favour of the massive ones (more progenitors of the SNeII able to produce αelements);
the power-law or multi-power IMF proposed by Kennicutt (1993) and Kroupa (1998,2001,2003).
These last show a plateau towards the low-mass end and follow the Salpeter law at for high masses. In order to
explore and predict the effect of different on the chemical properties of galaxies and the spectro-photometric ones
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of SSPs, I have calculated large grids of SSPs with different IMF, ages and metallicity. The results are all
available also on the website http://dipastro.pd.astro.it/galadriel/SSPs.htm.
These results have also been used to study the mass-luminosity ratios (M/L) of disk galaxies (Portinari,
Sommer-Larsen, Tantalo 2004) and to reproduce the values suggested by comparing the observed Tully-Fisher
relation with cosmological simulations of disk galaxy formation. The conclusions is that the bottom-light IMFs
better reproduce the observed M/L of the disc galaxies.
Finally, a new IMF has been proposed by Weidner & Kroupa (2004) for which the upper mass and slope are
functions of the maximum cluster mass or in other words functions of the galaxy SF. The new IMF has been
implemented in our galaxy models and the analysis is currently underway (Portinari, Tantalo, Widener, Chiosi
2005, in preparation).
High-resolution spectral libraries
In recent years many high resolution spectral libraries for stars and galaxies have become available. Thanks to
this, data of unprecedented accuracy and richness are to our disposal. In order to keep the same pace and to fully
exploit the new data, the theoretical spectral energy distributions (SEDs) must be derived from theoretical and/or
empirical spectral libraries at high-resolution. The Asiago group (Munari et al. 2004) has recently provided a new
library of stellar spectra with a resolution R=20,000. The library covers all the atmospheric parameters
(metallicity, temperature and gravity) in the HR-diagram (HR-D). Almost 200,000 spectra have been calculated
both for solar-scaled and α-enhanced pattern of abundances ([α/Fe]=+0.4).
Tantalo et al. (2004), using a partial release of this library, have calculated extended grids of spectral energy
distributions and companion absorption line indices for SSPs. In particular, the present the modern version of the
RFs long ago introduced by Tripicco & Bell (1995). The database of the new response RFs is available on the
website http://dipastro.pd.astro.it/galadriel/New_RF.htm.
In addition to this Tantalo et al. (2004) have suggested a new self-consistency method to correct the solarscaled
for enhancement the indices of the Lick system. The new method has been compared with the old one
proposed by Trager et al. (2000) and adopted by Tantalo & Chiosi (2004a). The most important results (which are
also in agreement with Tantalo & Chiosi 2004a,b) are (i) the dependence of indices like Hβ on the degree of
enhancement is confirmed (this has long been a vividly debated and controversial issue); (ii) part of the
dispersion in the two-index diagram (e.g. Hβ versus [MgFe]) can be explained assuming a spread in the initial
chemical composition of the data.
Synthetic spectra in presence of the interstellar medium: the role of dust
The advent of modern infrared (IR) instrumentation (e.g. IRAS, ISO, CIRB and COBE) has revealed the
existence of thousands of galaxies emitting most of their light in the IR and of a bright isotropic background in
the far IR/sub-mm regions whose origin is currently attributed to the emission by dust in primeval galaxies
absorbing and scattering the stellar light and returning it at long wavelengths. It become soon clear that precious
information on the star formation history (SFH) of galaxies and the universe as a whole was hidden in the UVoptical
and IR ranges of the spectral energy distribution (SED).
Dust can be either associated to stars and/or dispersed in the interstellar medium (ISM). Very young stars are
for a certain fraction of their lifetime embedded in the parental molecular clouds. The duration of this obscured
period is short, however the effect of it on the light emitted by these stars cannot be neglected as a significant
fraction of the light (initially almost all) is shifted to the IR. In addition, stars undergoing the so-called asymptotic
giant branch (AGB) phase, due to the combined effect of the He-burning shell thermal instability, deep mixing
and mass-loss, may form an outer dust-rich shell of material obscuring and reprocessing the radiation emitted by
the star underneath. Finally, thanks to the continuous emission of metal-rich material by stellar wind, the ISM
acquires over the years a dust-rich component. The UV-optical radiation emitted by stars passing through the
dust-rich intergalactic gas is first absorbed and then re-emitted in the far-IR (Piovan, Tantalo, Chiosi 2003).
Classical population synthesis models, in which the spectra are obtained folding the spectra on many SSPs, of
different ages composition, with the past SFH, do not take into account the dust effects. In models such as those
by Bressan et al. (1994) and Tantalo et al. (1996,1998a) the effect of the ISM is limited to applying a mean
extinction to dim the total stellar flux. This approximation is acceptable in the case of early-type galaxies (almost
transparent to the radiation emitted by stars), but fails in gas- and dust-rich spirals and irregulars overestimating
the UV flux and underestimating the IR flux.
To properly account for the presence of the ISM increases the complexity of the problem. Indeed it is strictly
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necessary to consider the distribution of energy sources (stars) inside the ISM. This means that the geometry and
morphology of a galaxy become very important ingredients of the model. The same considerations hold for
transport of radiation across the galaxy medium.
Starting from the pioneer study by Silva (1999) and Takagi et al. (2003) we have developed new galaxy
models that presented in the series of papers by Piovan, Tantalo, Chiosi (2004a,b,c). In brief, the gas of a galaxy
is divided in two phases: the star forming molecular clouds and the diffuse medium. Both young stars enshrouded
in their parental molecular clouds and AGB stars surrounded by shells of dust are included. The SED of both
types of star is derived from the radiative transport theory. The model for the ISM takes into account effects of
very small grains and polycyclic aromatic hydrocarbons (PAHs). Finally, both stars and ISM are framed in a
suitable geometrical distribution. The first paper deals with the extinction and emission properties of the ISM.
The second paper analyses the effects of dust on the radiation by young stars and AGB and presents complete
libraries of SEDs for SSPs. Finally, the third paper contains detailed chemo-spectro-photometric models for
early- and late-type galaxies in presence of ISM.
3. Future projects
New synthetic indices from high-resolution libraries
Adopting the new generation of spectral libraries with high-resolution, I plan to develop modern models of
galaxies and SSPs. For these latter in particular I plan to calculate large grids of synthetic-spectra, indices and/or
colours. As far as indices are concerned they now can be derived without passing through the theoretical FFs.
This means that, in addition to the Lick indices, other new indices (e.g. CaT, D4000 or others in the mid-UV) can
be obtained directly from the integrated spectra and compared with the observational data. In addition new
spectral features can be analysed to look for and to obtain “indices” that are better related to age, metallicity
chemical abundances and degree of enhancement. A point to remark is that thanks to the large grids of αenhanced
stellar spectra with high-resolution to our disposal, indices can be calculated without assuming
correcting methods or passing through response functions.
The first generation of this type of models has been presented by Bruzual & Charlot (2003) who adopt an
empirical library of stellar spectra. On my side, I plan to calculate indices from purely theoretical spectra using
the Asiago library. The project is currently underway.
Chemo-spectro-photometric evolutionary models of galaxies
In this area I would like to pursue three lines of work:
a. Develop a modern version of the Padova chemical evolution code, and explore the space of parameters so that
all possible cases are considered.
b. Explore the effects of different IMF. As already said the IMF bears very much on the chemical history of a
galaxy. The aim would be to pin down which IMF yield models simultaneously reproducing all the
observational properties. Convolving the resulting enrichment law and SFH with the new spectral libraries one
can obtain integrated SEDs at high-resolution and from which broad-band colours and line strength indices
can be derived and compared with the new generation of high-resolution data. In additions to this, adopting a
cosmological model of the Universe, one could follow the spectral evolution of a galaxy as a function of
redshift and predict the variation with it of important scaling relations such as the fundamental plane.
c. Finally, I would like to couple the results from the new generation of dynamical Tree-SPH models calculated
by Chiosi & Carraro (2002) and Merlin & Chiosi (2004 in preparation) with my spectro-photometric tool to
predict realistic simulations of the SED of galaxies.
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