Automatic observation rendering (AMORE)

Ng, Y. K.; Brogt, Erik; Chiosi, C.; Bertelli, G.

doi:10.1051/0004-6361:20020760

Cited by 22 publications

(24 citation statements)

References 48 publications

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“…Additionally, for the stars between the limits and outside the orange regions, a 3σ clipping in color-at fixed magnitude-is used to exclude outliers. We use this new technique instead of the one described in the above work or CMD template fitting (see e.g., Harris & Zaritsky 2001;Dolphin 2002;Ng et al 2002;Vergely et al 2002;Cignoni et al 2006;Aparicio & Hidalgo 2009) because for our problem, repeatedly simulating individual CMDs is less computationally intensive than computing the tables of likelihood functions required for the Gennaro et al (2015) approach or the CMD templates required for the template fitting approach. The mechanics of the fitting procedure can be broken into two largely independent parts: a function for quantitatively comparing CMDs, and an algorithm for using that comparison to explore a probability distribution.…”

Section: Fitting Techniquementioning

confidence: 99%

Evidence of a Non-universal Stellar Initial Mass Function. Insights from HST Optical Imaging of Six Ultra-faint Dwarf Milky Way Satellites^∗

Gennaro

Tchernyshyov

Brown

et al. 2018

ApJ

103

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Using deep observations obtained with the Advanced Camera for Surveys (ACS) on board the Hubble Space Telescope (HST), we demonstrate that the sub-solar stellar initial mass function (IMF) of six ultra-faint dwarf Milky Way satellites (UFDs) is more bottom light than the IMF of the Milky Way disk. Our data have a lowermass limit of ∼0.45 M e , while the upper limit is ∼0.8 M e , set by the turnoff mass of these old, metal-poor systems. If formulated as a single power law, we obtain a shallower IMF slope than the Salpeter value of −2.3, ranging from −1.01 for Leo IV to −1.87 for BoötesI. The significance of these deviations depends on the galaxy and is typically 95% or more. When modeled as a log-normal, the IMF fit results in a higher peak mass than in the Milky Way disk, but a Milky Way disk value for the characteristic system mass (∼0.22 M e ) is excluded at only 68% significance, and only for some UFDs in the sample. We find that the IMF slope correlates well with the galaxy mean metallicity, and to a lesser degree, with the velocity dispersion and the total mass. The strength of the observed correlations is limited by shot noise in the number of observed stars, but future space-based missions like the James Webb Space Telescope (JWST) and the Wide-Field Infrared Survey Telescope (WFIRST) will enhance both the number of dwarf Milky Way satellites that can be studied in such detail and the observation depth for individual galaxies.

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Section: Fitting Techniquementioning

confidence: 99%

Evidence of a Non-universal Stellar Initial Mass Function. Insights from HST Optical Imaging of Six Ultra-faint Dwarf Milky Way Satellites^∗

Gennaro

Tchernyshyov

Brown

et al. 2018

ApJ

103

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“…The result of these assumptions was that the underlying density distributions within d ⌢ Ω were to a good approximation constant (if the survey was not too deep in magnitude and hence r hel not too deep). To solve the starcount equation under these approximations was a trivial exercise and in the past decades it has been indeed done by several works in this research area (e.g., Robin et al 2003;Méndez et al 2000;Vallenari et al 2006;Ng et al 2002;Girardi et al 2005, , and references therein). If the hypothesis of small d ⌢ Ω = dldb cos b is to be relaxed, the computing of this number has to be performed numerically as follows:…”

Section: Star-count Equation For Large Sky Coveragementioning

confidence: 99%

“…In the process of CMD fitting the genetic algorithm has a long history in the Padua group starting from the works of Ng et al (2002) and has been implemented in the kinematic fitting of observational data in Vallenari et al (2006). The algorithm has been run on true data to reproduce radial velocities (Gilmore, Wyse & Norris 2002), the GSC-II proper motion catalogue Vallenari et al (2006) and the RAVE dataset equipped with 2MASS proper motions in Pasetto et al (2012b), and Pasetto et al (2012c).…”

Section: Machine Learningmentioning

confidence: 99%

Spiral arm kinematics for Milky Way stellar populations

Pasetto

Natale

Kawata

et al. 2016

Mon. Not. R. Astron. Soc.

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We present a new theoretical population synthesis model (the Galaxy Model) to examine and deal with large amounts of data from surveys of the Milky Way and to decipher the present and past structure and history of our own Galaxy.We assume the Galaxy to consist of a superposition of many composite stellar populations belonging to the thin and thick disks, the stellar halo and the bulge, and to be surrounded by a single dark matter halo component. A global model for the Milky Way's gravitational potential is built up self-consistently with the density profiles from the Poisson equation. In turn, these density profiles are used to generate synthetic probability distribution functions (PDFs) for the distribution of stars in colour-magnitude diagrams (CMDs). Finally, the gravitational potential is used to constrain the stellar kinematics by means of the moment method on a (perturbed)-distribution function. Spiral arms perturb the axisymmetric disk distribution functions in the linear response framework of density-wave theory where we present an analytical formula of the so-called 'reduction factor' using Hypergeometric functions.Finally, we consider an analytical non-axisymmetric model of extinction and an algorithm based on the concept of probability distribution function to handle colour magnitude diagrams with a large number of stars. A genetic algorithm is presented to investigate both the photometric and kinematic parameter space.This galaxy model represents the natural framework to reconstruct the structure of the Milky Way from the heterogeneous data set of surveys such as Gaia-ESO, SEGUE, APOGEE2, RAVE and the Gaia mission.

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“…To explore this wide parameter space, we have combined a well-tested genetic algorithm (GA), Pikaia 18 , with a local search routine. As shown in various papers (see, e.g., Ng et al 2002;Aparicio & Hidalgo 2009;Small et al 2013), GAs allow us to find a global optimum more efficiently than a local search alone. In our approach, the synergy of the GA and a local search combines the advantages of both worlds.…”

Section: Stellar Massmentioning

confidence: 99%

Hubble Tarantula Treasury Project. Ii. The Star-Formation History of the Starburst Region NGC 2070 in 30 Doradus

Cignoni

Sabbi

Marel

et al. 2015

ApJ

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We present a study of the recent star formation (SF) of 30 Doradus in the Large Magellanic Cloud (LMC) using the panchromatic imaging survey Hubble Tarantula Treasury Project. In this paper we focus on the stars within 20 pc of the center of 30 Doradus, the starburst region NGC 2070. We recovered the SF history by comparing deep optical and near-infrared color-magnitude diagrams (CMDs) with state-of-the-art synthetic CMDs generated with the latest PAdova and TRieste Stellar Evolution Code (PARSEC) models, which include all stellar phases from pre-main-sequence to post-main-sequence. For the first time in this region we are able to measure the SF using intermediate-and low-mass stars simultaneously. Our results suggest that NGC 2070 experienced prolonged activity. In particular, we find that the SF in the region (1) exceeded the average LMC rate ≈ 20 Myr ago, (2) accelerated dramatically ≈ 7 Myr ago, and (3) reached a peak value 1-3 Myr ago. We did not find significant deviations from a Kroupa initial mass function down to M 0.5  . The average internal reddening E B V ( ) -is found to be between 0.3 and 0.4 mag.

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Automatic observation rendering (AMORE)

Cited by 22 publications

References 48 publications

Evidence of a Non-universal Stellar Initial Mass Function. Insights from HST Optical Imaging of Six Ultra-faint Dwarf Milky Way Satellites^∗

Evidence of a Non-universal Stellar Initial Mass Function. Insights from HST Optical Imaging of Six Ultra-faint Dwarf Milky Way Satellites^∗

Spiral arm kinematics for Milky Way stellar populations

Hubble Tarantula Treasury Project. Ii. The Star-Formation History of the Starburst Region NGC 2070 in 30 Doradus

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Automatic observation rendering (AMORE)

Cited by 22 publications

References 48 publications

Evidence of a Non-universal Stellar Initial Mass Function. Insights from HST Optical Imaging of Six Ultra-faint Dwarf Milky Way Satellites∗

Evidence of a Non-universal Stellar Initial Mass Function. Insights from HST Optical Imaging of Six Ultra-faint Dwarf Milky Way Satellites∗

Spiral arm kinematics for Milky Way stellar populations

Hubble Tarantula Treasury Project. Ii. The Star-Formation History of the Starburst Region NGC 2070 in 30 Doradus

Contact Info

Product

Resources

About

Evidence of a Non-universal Stellar Initial Mass Function. Insights from HST Optical Imaging of Six Ultra-faint Dwarf Milky Way Satellites^∗

Evidence of a Non-universal Stellar Initial Mass Function. Insights from HST Optical Imaging of Six Ultra-faint Dwarf Milky Way Satellites^∗