General
Galaxy formation and evolution is a fundamental Astrophysical problem. Its study requires “travelling back in time”, for which there are two complementary approaches. One is to analyse galaxy properties as a function of red-shift. Our team focuses on the other approach, called “Galactic Archaeology”. It is based on the determination of galaxy properties from the study of their resolved stars. Depending on their mass, stars can live as long as a Hubble time, thus allowing to study in exquisite detail how galaxies have evolved from the early Universe to the present time. This research is one of the main drivers of major international projects, both observational (such as the on-going Gaia mission and SDSS surveys, and the planned WHT/WEAVE, LSST, VISTA/4MOST, DESI, E-ELT/HARMONI, to name a few), and theoretical (such as Nihao, Magic and Auriga hydrodynamical cosmological simulations), in most of which members of our team are involved. This ensures that Galactic Archaelogy will be at the forefront of astronomical research for a long time.
The objective of this project is to understand the formation and evolution of galaxies of different morphological types, using the many local examples that can be resolved into individual stars, and which, therefore can be studied in a detail impossible elsewhere. In particular, the Local Group and its immediate surroundings contain about 80 galaxies of different morphological types. Among these, the largest are spiral galaxies (the Milky Way, M31 and M33), a dozen of them are (dwarf) irregulars and the rest are early-type systems. Thus, we can study galaxies of different morphological types, from the Milky Way down to the smallest galactic scales, which are those challenging our understanding of what a "galaxy" is.
We aim to derive their evolutionary history using a set of complementary techniques: I) using deep photometry reaching the old main sequence turn-offs, it is possible to derive the full star formation history over the entire galaxy's life; ii) spectroscopic studies of individual stars add direct information on the kinematics and chemical abundances of the different stellar populations; iii) for the most nearby systems, the inclusion of accurate astrometric measurements yields information on the distance (and thus absolute brightness), the orbital motion of the system and can even deliver the full 6D phase-space information of sub-samples of stars; iv) the study of variable stars such as Cepheids and RR Lyrae provide independent constraints on metallicities and ages of the populations they belong to. These observations offer invaluable, rich information, that can be interpreted using hydrodynamic cosmological simulations of galaxy formation that model a wide range of important physical processes.
Members
Results
Below a list of highlights from the group activities in 2020-2021. For a more general overview see publication list and this webpage.
1. Using HST data of the ultra-faint dwarf (UFD) Eridanus II, we determined (Gallart+2021) that its only star formatio event, occurred 13 Gyr ago, was very short (100-500Myr). The associated SNe energy could be enough to expel the remaining gas, casting doubts on the need to invoke cosmic reionization as the preferred explanation for the early quenching of UFD galaxies.
2. The various star formation episodes, extended to few hundred million years ago, which we have precisely dated in the dwarf spheroidal galaxies Fornax (Rusakov+2021) and Leo I (Ruiz-Lara+2021), have shed light on the effects of interactions and mergers in the star formation history of dwarf galaxies.
3. By performing for the first time a joint dynamical modeling of the internal stellar and HI gas kinematics of a Local Group dwarf galaxy, WLM, we were able to determine that its dark matter halo is likely both cored and has a prolate shape, where the co-existence of these features might pose a problem for self-interacting dark matter models (Leung+2021).
4. For the first time using cosmological simulations, we demonstrated that mergers are a viable explanation for the presence of prolate rotation in the stellar component of galaxies also on the scale of dwarf galaxies (Cardona-Barrero+2021)
5. Robert Grand ran the highest resolution MHD cosmological Milky Way simulation in the world (Grand+2021), run on MPCDF Raven large compute system for which the PI had rolling access as an MPA fellow.
Scientific activity
Related publications
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SMASH: Survey of the MAgellanic Stellar HistoryThe Large and Small Magellanic Clouds are unique local laboratories for studying the formation and evolution of small galaxies in exquisite detail. The Survey of the MAgellanic Stellar History (SMASH) is an NOAO community Dark Energy Camera (DECam) survey of the Clouds mapping 480 deg2 (distributed over ∼2400 square degrees at ∼20% filling factor)Nidever, D. L. et al.
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Arm and interarm abundance gradients in CALIFA spiral galaxiesSpiral arms are the most singular features in disc galaxies. These structures can exhibit different patterns, namely grand design and flocculent arms, with easily distinguishable characteristics. However, their origin and the mechanisms shaping them are unclear. The overall role of spirals in the chemical evolution of disc galaxies is anotherSánchez-Menguiano, L. et al.
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72017 -
Observational hints of radial migration in disc galaxies from CALIFAContext. According to numerical simulations, stars are not always kept at their birth galactocentric distances but they have a tendency to migrate. The importance of this radial migration in shaping galactic light distributions is still unclear. However, if radial migration is indeed important, galaxies with different surface brightness (SB)Ruiz-Lara, T. et al.
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72017 -
APOGEE Chemical Abundances of the Sagittarius Dwarf GalaxyThe Apache Point Observatory Galactic Evolution Experiment provides the opportunity of measuring elemental abundances for C, N, O, Na, Mg, Al, Si, P, K, Ca, V, Cr, Mn, Fe, Co, and Ni in vast numbers of stars. We analyze thechemical-abundance patterns of these elements for 158 red giant stars belonging to the Sagittarius dwarf galaxy (Sgr). This isHasselquist, S. et al.
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82017 -
The Apache Point Observatory Galactic Evolution Experiment (APOGEE)The Apache Point Observatory Galactic Evolution Experiment (APOGEE), one of the programs in the Sloan Digital Sky Survey III (SDSS-III), has now completed its systematic, homogeneous spectroscopic survey sampling all major populations of the Milky Way. After a three-year observing campaign on the Sloan 2.5 m Telescope, APOGEE has collected a halfMajewski, S. R. et al.
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92017 -
Atypical Mg-poor Milky Way Field Stars with Globular Cluster Second-generation-like Chemical PatternsWe report the peculiar chemical abundance patterns of 11 atypical Milky Way (MW) field red giant stars observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE). These atypical giants exhibit strong Al and N enhancements accompanied by C and Mg depletions, strikingly similar to those observed in the so-called second-generationFernández-Trincado, J. G. et al.
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92017 -
Observational constraints to boxy/peanut bulge formation timeBoxy/peanut bulges are considered to be part of the same stellar structure as bars and both could be linked through the buckling instability. The Milky Way is our closest example. The goal of this Letter is to determine if the mass assembly of the different components leaves an imprint in their stellar populations allowing the estimation the timePérez, I. et al.
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92017 -
The open cluster King 1 in the second quadrantWe analyse the poorly studied open cluster King 1 in the second Galactic quadrant. From wide-field photometry, we have studied the spatial distribution of this cluster. We determined that the centre of King 1 is located at α2000 = 00h22m and δ2000 = +64°23΄. By parameterizing the stellar density with a King profile, we have obtained a centralCarrera, R. et al.
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102017 -
OCCASO - II. Physical parameters and Fe abundances of red clump stars in 18 open clustersOpen clusters have long been used to study the chemodynamical evolution of the Galactic disc. This requires a homogeneously analysed sample covering a wide range of ages and distances. In this paper, we present the Open Clusters Chemical Abundances from Spanish Observatories (OCCASO) second data release. This comprises a sample of high-resolutionCasamiquela, L. et al.
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102017 -
Multiband study of RX J0838-2827 and XMM J083850.4-282759: a new asynchronous magnetic cataclysmic variable and a candidate transitional millisecond pulsarIn a search for the counterpart to the Fermi-LAT source 3FGL J0838.8-2829, we performed a multiwavelength campaign: in the X-ray band with Swift and XMM-Newton; in the infrared and optical with OAGH, ESO-NTT and IAC80; and in the radio with ATCA observations. We also used archival hard X-ray data obtained by INTEGRAL. We report on three X-rayCasares, J. et al.
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The Magellanic Inter-Cloud Project (MAGIC) III: first spectroscopic evidence of a dwarf stripping a dwarfThe Magellanic Bridge (MB) is a gaseous stream that links the Large (LMC) and Small (SMC) Magellanic Clouds. Current simulations suggest that the MB forms from a recent interaction between the Clouds. In this scenario, the MB should also have an associated stellar bridge formed by stars tidally stripped from the SMC by the LMC. There are severalLópez Sánchez, Ángel R. et al.
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A unified model for age-velocity dispersion relations in Local Group galaxies: disentangling ISM turbulence and latent dynamical heatingWe analyse age-velocity dispersion relations (AVRs) from kinematics of individual stars in eight Local Group galaxies ranging in mass from Carina (M* ˜ 106 M⊙) to M31 (M* ˜ 1011 M⊙). Observationally the σ versus stellar age trends can be interpreted as dynamical heating of the stars by giant molecular clouds, bars/spiral arms or merging subhaloesde Boer, T. J. L. et al.
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122017 -
Sloan Digital Sky Survey IV: Mapping the Milky Way, Nearby Galaxies, and the Distant UniverseWe describe the Sloan Digital Sky Survey IV (SDSS-IV), a project encompassing three major spectroscopic programs. The Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2) is observing hundreds of thousands of Milky Way stars at high resolution and high signal-to-noise ratios in the near-infrared. The Mapping Nearby Galaxies at ApacheMao, Shude et al.
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72017 -
Towards a new classification of galaxies: principal component analysis of CALIFA circular velocity curvesWe present a galaxy classification system for 238 (E1-Sdm) CALIFA (Calar Alto Legacy Integral Field Area) galaxies based on the shapes and amplitudes of their circular velocity curves (CVCs). We infer the CVCs from the de-projected surface brightness of the galaxies, after scaling by a constant mass-to-light ratio based on stellar dynamics -Kalinova, V. et al.
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82017 -
A Photometric Study of the Outer Halo Globular Cluster NGC 5824Multi-wavelength CCD photometry over 21 years has been used to produce deep color–magnitude diagrams (CMDs) together with light curves for the variables in the Galactic globular cluster NGC 5824. Twenty-one new cluster RR Lyrae stars are identified, bringing the total to 47, of which 42 have reliable periods determined for the first time. The CMDDall’Ora, M. et al.
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72017 -
LITTLE THINGS in 3D: robust determination of the circular velocity of dwarf irregular galaxiesDwarf irregular galaxies (dIrrs) are the smallest stellar systems with extended H i discs. The study of the kinematics of such discs is a powerful tool to estimate the total matter distribution at these very small scales. In this work, we study the H i kinematics of 17 galaxies extracted from the 'Local Irregulars That Trace Luminosity ExtremesNipoti, Carlo et al.
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42017 -
Timing the Evolution of the Galactic Disk with NGC 6791: An Open Cluster with Peculiar High-α Chemistry as Seen by APOGEEWe utilize elemental-abundance information for Galactic red giant stars in five open clusters (NGC 7789, NGC 6819, M67, NGC 188, and NGC 6791) from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) DR13 data set to age-date the chemical evolution of the high- and low-α element sequences of the Milky Way (MW). Key to this timeLinden, Sean T. et al.
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62017 -
Variable Stars in Local Group Galaxies. III. And VII, NGC 147, and NGC 185: Insight into the Building Blocks of the M31 HaloWe present the discovery of 1568 RR Lyrae stars in three of the most luminous M31 satellites: And VII (573), NGC 147 (177), and NGC 185 (818). We use their properties to study the formation history of Local Group spiral haloes, and in particular, to infer about the nature of their possible building blocks by comparison with available data for RRMonelli, M. et al.
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62017 -
A stellar overdensity associated with the Small Magellanic CloudWe report the discovery of a stellar overdensity 8° north of the centre of the Small Magellanic Cloud (SMC; Small Magellanic Cloud Northern Over-Density; SMCNOD), using data from the first 2 yr of the Dark Energy Survey (DES) and the first year of the MAGellanic SatelLITEs Survey (MagLiteS). The SMCNOD is indistinguishable in age, metallicity andPieres, A. et al.
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62017 -
Baade's window and APOGEE. Metallicities, ages, and chemical abundancesContext. Baade's window (BW) is one of the most observed Galactic bulge fields in terms of chemical abundances. Owing to its low and homogeneous interstellar absorption it is considered the perfect calibration field for Galactic bulge studies. Aims: In the era of large spectroscopic surveys, calibration fields such as BW are necessary for crossSchultheis, M. et al.
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