Numerical methods of star formation history measurement and applications to seven dwarf spheroidals

By A. Dolphin. 2001

487 citations recorded by the source corpus.

A comprehensive study of the measurement of star formation histories from colour-magnitude diagrams (CMDs) is presented, with an emphasis on a variety of subtle issues involved in the generation of model CMDs and maximum likelihood solution. Among these are the need for a complete sampling of the synthetic CMD, the use of proper statistics for dealing with Poisson-distributed data (and a demonstration of why Χ 2 must not be used), measuring full uncertainties in all reported parameters, quantifying the goodness-of-fit, and questions of binning the CMD and incorporating outside information. Several example star formation history measurements are given. Two examples involve synthetic data, in which the input and recovered parameters can be compared to locate possible flaws in the methodology (none were apparent) and measure the accuracy with which ages, metallicities and star formation rates can be recovered. Solutions of the histories of seven Galactic dwarf spheroidal companions (Carina, Draco, Leo I, Leo II, Sagittarius, Sculptor and Ursa Minor) illustrate the ability to measure star formation histories given a variety of conditions -numbers of stars, complexity of star formation history and amount of foreground contamination. Significant measurements of ancient >8 Gyr star formation are made in all seven galaxies. Sculptor, Draco and Ursa Minor appear entirely ancient, while the other systems show varying amounts of younger stars.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/105fdf239bced60760bbab78283ee2a283a26751

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Citations in the corpus

Stellar Chemical Signatures and Hierarchical Galaxy Formation (2004, background): “On the other hand, the stars in Draco, also in Figure 7 (right), show uniformly low [ /Fe] values at all metallicities, even though Draco is thought to have had a very similar SFH to Sculptor (mostly old stars, Dolphin 2002).”
CONVERTING FROM 3.6 AND 4.5 μm FLUXES TO STELLAR MASS (2012, background): “The uncertainties in the recovered star formation rates from CMD synthesis are difficult to ascertain (Harris & Zaritsky 2001; Dolphin 2002; Weisz et al. 2011).”
“Sculptor-ing” the Galaxy? The Chemical Compositions of Red Giants in the Sculptor Dwarf Spheroidal Galaxy (2004, methodology): “This compares very well with the mean of 1:5 0:3 found by Tolstoy et al. (2001) and the mean of 1.5 found by Dolphin (2002).”
The Detailed Star Formation History in the Spheroid, Outer Disk, and Tidal Stream of the Andromeda Galaxy (2006, methodology): “This method is similar to most of the star formation history methods used in the literature (e.g., Dolphin 2002; Skillman et al. 2003).”
THE ACS NEARBY GALAXY SURVEY TREASURY. VIII. THE GLOBAL STAR FORMATION HISTORIES OF 60 DWARF GALAXIES IN THE LOCAL VOLUME (2011, methodology): “Here, we briefly summarize the technique of measuring a SFH based on the full methodology described in Dolphin (2002).”
THE STAR FORMATION HISTORIES OF LOCAL GROUP DWARF GALAXIES. I. HUBBLE SPACE TELESCOPE/WIDE FIELD PLANETARY CAMERA 2 OBSERVATIONS (2014, methodology): “…al. (2000) Fornax Hunter (2001) IC 10 Miller et al. (2001) LGS 3 Wyder (2001) NGC 6822 Carrera et al. (2002) Ursa Minor Dohm-Palmer et al. (2002) Sex A Dolphin (2002) Carina, Draco, Leo I, Leo II, Sagittarius, Sculptor, Ursa Minor Sarajedini et al. (2002) Cetus Schulte-Ladbeck et al. (2002) Leo A…”
MESA ISOCHRONES AND STELLAR TRACKS (MIST). I. SOLAR-SCALED MODELS (2016, methodology): “We plan to perform more robust CMD fitting with MATCH (Dolphin 2002) in future work.”
THE NATURE OF STARBURSTS. I. THE STAR FORMATION HISTORIES OF EIGHTEEN NEARBY STARBURST DWARF GALAXIES (2010, methodology): “To match these features, MATCH fits a distance modulus and total extinction value (i.e., foreground plus internal extinction) to each galaxy.”
Constraining the thermally pulsing asymptotic giant branch phase with resolved stellar populations in the Large Magellanic Cloud (2019, methodology): “It is computed following the χ2-like statistics defined by Dolphin (2002), i.e. assuming that the stars are distributed into Hess diagram cells following a Poisson statistics: χ2LF = 1 N N∑ i=1 2 [ mi − ni + ni ln ( ni mi )] , (1) where n and m are the number of simulated and observed stars,…”
The star formation and chemical evolution history of the Fornax dwarf spheroidal galaxy (2012, methodology): “The difference between model and observed CMD and MDF is minimized according to a Poisson equivalent of χ2 (Dolphin 2002).”
The search for failed supernovae with the Large Binocular Telescope: first candidates (2014, methodology): “Using the DOLPHOT software package (Dolphin 2002) to perform photometry and convert to Vega magnitudes and correcting for Galactic extinction, we find Candidate 1 magnitudes of 22.15 ± 0.01 in the V band and 20.28 ± 0.01 mag in the I band.”
Cusp-core transformations in dwarf galaxies: observational predictions (2012, background): “We should also emphasize that the core forms after only 0.5 Gyr in our reference feedback run, when only 10 per cent of the stars have formed.”
Riding the Spiral Waves: Implications of Stellar Migration for the Properties of Galactic Disks (2008, methodology): “…properties of stars in a given region of a disk are used to construct a color-magnitude diagram, which in turn is used to constrain stellar population synthesis models to yield a best-fit star formation history and therefore provide information about the formation of the disk (Dolphin 2002).”
A REVISED PARALLEL-SEQUENCE MORPHOLOGICAL CLASSIFICATION OF GALAXIES: STRUCTURE AND FORMATION OF S0 AND SPHEROIDAL GALAXIES (2011, methodology): “Hernandez et al. (2000) used an HST color-magnitude diagram to get qualitatively similar results: bursts happened ∼ 8, 5, and 3 Gyr ago with some star formation extending to 1 Gyr ago (see also Dolphin 2002).”
THE ACS NEARBY GALAXY SURVEY TREASURY (2007, background): “In addition to the wide fields, deep fields with high completeness in the red clump were planned for the 12 galaxies that dominate the K-band luminosity of the ANGST volume; this depth provides strong constraints on the the ancient star formation history (e.g., Dolphin 2002).”
THE STELLAR INITIAL MASS FUNCTION OF ULTRA-FAINT DWARF GALAXIES: EVIDENCE FOR IMF VARIATIONS WITH GALACTIC ENVIRONMENT (2013, methodology): “The model and observed Hess diagrams are then compared using the Maximum Likelihood statistic of Dolphin (2002), using the stars defined as members of each galaxy (Figure 1).”
Dark matter heats up in dwarf galaxies (2018, background): “From each photometric catalogue we initially select point-like sources6 within circular apertures of sufficient angular radius (1.5◦ for each of Draco, Fornax, Sculptor, Sextans, and Ursa Minor; 1◦ for Leo I and Leo II and 0.9◦ for Carina) to enclose all plausibly bound member stars.”