GENERATING ON-THE-FLY LARGE SAMPLES OF THEORETICAL SPECTRA THROUGH AN<i>N</i>-DIMENSIONAL GRID

Yip, Ching-Wa

doi:10.1088/0004-6256/139/2/342

Cited by 2 publications

(2 citation statements)

References 41 publications

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“…This work provides a factor of ≈ 100 reduction over the original data. Such a data compression will be crucial if we want to estimate simultaneously a large number (> 10) of galaxy parameters (Yip & Wyse 2007;Yip 2010) in the future, such as stellar age and metallicity, dust extinction, and high temporal resolution star formation history.…”

Section: Discussionmentioning

confidence: 99%

Objective Identification of Informative Wavelength Regions in Galaxy Spectra

Yip¹,

Mahoney²,

Szalay³

et al. 2014

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Understanding the diversity in spectra is the key to determining the physical parameters of galaxies. The optical spectra of galaxies are highly convoluted with continuum and lines which are potentially sensitive to different physical parameters. Defining the wavelength regions of interest is therefore an important question. In this work, we identify informative wavelength regions in a single-burst stellar populations model by using the CUR Matrix Decomposition. Simulating the Lick/IDS spectrograph configuration, we recover the widely used D n (4000), Hβ and Hδ A to be most informative. Simulating the SDSS spectrograph configuration with a wavelength range 3450-8350Å and a model-limited spectral resolution of 3Å, the most informative regions are: first region-the 4000Å break and the Hδ line; second region-the Fe-like indices; third region-the Hβ line; fourth region-the G band and the Hγ line. A Principal Component Analysis on the first region shows that the first eigenspectrum tells primarily the stellar age, the second eigenspectrum is related to the age-metallicity degeneracy, and the third eigenspectrum shows an anti-correlation between the strengths of the Balmer and the Ca K & H absorptions. The regions can be used to determine the stellar age and metallicity in early-type galaxies which have solar abundance ratios, no dust, and a single-burst star formation history. The region identification method can be applied to any set of spectra of the user's interest, so that we eliminate the need for a common, fixed-resolution index system. We discuss future directions in extending the current analysis to late-type galaxies.

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Section: Discussionmentioning

confidence: 99%

Objective Identification of Informative Wavelength Regions in Galaxy Spectra

Yip¹,

Mahoney²,

Szalay³

et al. 2014

Self Cite

View full text Add to dashboard Cite

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“…Note that the redshift z g is not required to be at one of the discrete simulation time steps, since we can integrate the star formation rate from the previous time step to the actual time t g . (The need of similar interpolation schemes has also been noticed by Yip 2010). In our reference model, we adopt the Chabrier initial mass function, with a fixed solar metallicity (Z = 0.02) and the standard dust model from Charlot & Fall (2000) (τ ν = 1 and µ = 0.3).…”

Section: Illuminating Galaxies In Dark Matter Halosmentioning

confidence: 99%

Simulating Deep Hubble Images With Semi-Empirical Models of Galaxy Formation

Taghizadeh-Popp

Fall

White

et al. 2015

ApJ

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We simulate deep images from the Hubble Space Telescope (HST ) using semi-empirical models of galaxy formation with only a few basic assumptions and parameters. We project our simulations all the way to the observational domain, adding cosmological and instrumental effects to the images, and analyze them in the same way as real HST images ("forward modeling"). This is a powerful tool for testing and comparing galaxy evolution models, since it allows us to make unbiased comparisons between the predicted and observed distributions of galaxy properties, while automatically taking into account all relevant selection effects.Our semi-empirical models populate each dark matter halo with a galaxy of determined stellar mass and scale radius. We compute the luminosity and spectrum of each simulated galaxy from its evolving stellar mass using stellar population synthesis models. We calculate the intrinsic scatter in the stellar mass-halo mass relation that naturally results from enforcing a monotonically increasing stellar mass along the merger history of each halo. The simulated galaxy images are drawn from cutouts of real galaxies from the Sloan Digital Sky Survey, with sizes and fluxes rescaled to match those of the model galaxies.The distributions of galaxy luminosities, sizes, and surface brightnesses depend on the adjustable parameters in the models, and they agree well with observations for reasonable values of those parameters. Measured galaxy magnitudes and sizes have significant magnitude-dependent biases, with both being underestimated near the magnitude detection limit. The fraction of galaxies detected and fraction of light detected also depend sensitively on the details of the model. 1 We use "halo" and "sub-halo" interchangeably, following Guo et al. (2010).

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GENERATING ON-THE-FLY LARGE SAMPLES OF THEORETICAL SPECTRA THROUGH ANN-DIMENSIONAL GRID

Cited by 2 publications

References 41 publications

Objective Identification of Informative Wavelength Regions in Galaxy Spectra

Objective Identification of Informative Wavelength Regions in Galaxy Spectra

Simulating Deep Hubble Images With Semi-Empirical Models of Galaxy Formation

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