SPISEA: A Python-based Simple Stellar Population Synthesis Code for Star Clusters

Abstract

We present Stellar Population Interface for Stellar Evolution and Atmospheres (SPISEA), an open-source Python package that simulates simple stellar populations. The strength of SPISEA is its modular interface which offers the user control of 13 input properties including (but not limited to) the initial mass function, stellar multiplicity, extinction law, and the metallicity-dependent stellar evolution and atmosphere model grids used. The user also has control over the initial–final mass relation in order to produce compact stellar remnants (black holes, neutron stars, and white dwarfs). We demonstrate several outputs produced by the code, including color–magnitude diagrams, HR-diagrams, luminosity functions, and mass functions. SPISEA is object-oriented and extensible, and we welcome contributions from the community. The code and documentation are available on GitHub (https://github.com/astropy/SPISEA) and ReadtheDocs (https://spisea.readthedocs.io/en/latest/), respectively.

An isolated mass gap black hole or neutron star detected with astrometric microlensing

“…Software: Galaxia (Sharma et al 2011), astropy (Astropy Collaboration et al 2013, Matplotlib (Hunter 2007), NumPy (van der Walt et al 2011), SciPy (Virtanen et al 2019), SPISEA (Hosek et al 2020), PopSyCLE (Lam et al 2020), dynesty (Speagle 2020), PyMultiNest (Buchner et al 2014;Feroz et al 2009), dustmaps (Green 2018) , hst1pass (Anderson & King 2006) APPENDIX A. RESCALING OF UNCERTAINTIES For each epoch, hst1pass returns the standard deviation of positions and magnitudes over multiple frames σ x , σ y and σ m , respectively. For our uncertainties, we use the error on the mean σ/ √ N , where N is the number of frames the star is detected in.…”

“…To calculate 2), we use the simple stellar population synthesis code SPISEA (Hosek et al 2020) to generate a suite of star clusters to simulate the possible lens population. We use the MISTv1.2 solar metallicity isochrones (Choi et al 2016), get merged atmosphere atmosphere model 22 , Damineli et al (2016) reddening law, and Kroupa (2001) initial mass function (IMF) over the mass range 0.1M < M < 120M .…”

“…22 This is a combination of the ATLAS9 (Castelli & Kurucz 2004), PHOENIX v16 (Husser et al 2013), BTSettl (Baraffe et al 2015), abd Koester10 (Koester 2010) models. For further details see Appendix B of (Hosek et al 2020).…”

Measuring the alpha-abundance of subsolar-metallicity stars in the Milky Way's central half-parsec: testing globular cluster and dwarf galaxy infall scenarios

“…We fit the K-band spectra of these stars using the methodology outlined above. For this fit, we use a prior on value of log g from Ks photometry from Schödel et al (2010) and the SPISEA isochrone fitting package (Hosek et al 2020) with MIST isochrones (Choi et al 2016). We infer that log g = 0.6 for NE1-1-003 and log g = 0.9 for N2-1-002 (Appendix 8.3).…”

“…The surface gravity values for the Galactic center stars were determined using stellar evolutionary models for stars with similar ages and metallicities as the Galactic center. MIST evolutionary models (Choi et al 2016) with merged atmosphere models (more details on merged atmosphere models in Hosek et al 2020) for [M/H]=0.5 and [M/H]=-1.0, at ages of 10 Gyr and 5 Gyr suggested log g=0.6 for NE1-1-003 and log g=0.9 for N2-1-002 would be appropriate for both the subsolar and supersolar metallicity populations at the two stars' respective magnitudes. A sample isochrone used is shown in Figure 12.…”