Measuring stellar populations,dust attenuation and ionized gas at kpc scales in 10010 nearby galaxies using the integral field spectroscopy from MaNGA

As one of the three major experiments of the fourth-generation Sloan Digital Sky Survey(SDSS-IV),the Mapping Nearby Galaxies at Apatch Point Observatory(MaNGA)survey has obtained high-quality integral field spectroscopy(IFS)with a resolution of 1–2 kpc for104galaxies in the local universe during its six-year operation from July 2014 through August 2020.It is crucial to reliably measure the physical properties of the different components in each spectrum before one can use the data for any scientific study.In the past years we have made lots of efforts to develop a novel technique of full spectral fitting,which estimates a model-independent dust attenuation curve from each spectrum,thus allowing us to break the degeneracy between dust attenuation and stellar population properties when fitting the spectrum with stellar population synthesis models.We have applied our technique to the final data release of Ma NGA,and obtained measurements of stellar population properties and emission line parameters,as well as the kinematics and dust attenuation of both stellar and ionized gas components.In this paper we describe our technique and the content and format of our data products.The whole dataset is publicly available in Science Data Bank with the link https://doi.org/10.57760/sciencedb.j00113.00088.

The Blue Stragglers and the Integrated Spectral Energy Distribution of Single Stellar Populations

Blue stragglers are a common observational fact for the Galactic clusters. Single Stellar Populations (SSPs) are basic to the studies of galaxy structre and evolution. SSPs are mainly based either on the observation of the integrated properties of star clusters, or on the theoretical understandings of single star evolution. Both of the two ways of making SSPs suffer from either observational uncertainties concerning field contaminations or lack of good models for close binary systems. Based on the photometry of the classical open cluster M67 and the thorough membership survey, we made a color-magnitude diagram (CMD) of high membership stars for the cluster. We will show that by including the contributions of the bright blue stragglers that is common to open clusters, the integrated properties of the clusters are quite different from tranditional SSP models. We further conclude that these blue light contributors are very important to SSP models, and may cast new lights on its applications in the studies of galaxies.

Classification of stellar populations in globular clusters

Possessing multiple stellar populations has been accepted as a common feature of globular clusters（GCs）. Different stellar populations manifest themselves with different chemical features,e.g. the well-known O-Na anti-correlation. Generally, the first（primordial） population has O and Na abundances consistent with those of field stars with similar metallicity; while the second（polluted） population is identified by their Na overabundance and O deficiency. The fraction of the populations is an important constraint on the GC formation scenario. Several methods have been proposed for the classification of GC populations. Here we examine a criterion derived based on the distribution of Galactic field stars, which relies on Na abundance as a function of [Fe/H], to distinguish first and second stellar populations in GCs. By comparing the first population fractions of 17 GCs estimated by the field star criterion with those in the literature derived by methods related to individual GCs, we find that the field star criterion tends to overestimate the first population fractions. The population separation methods,which are related to an individual GC sample, are recommended because the diversity of GCs can be taken into consideration. Currently, more caution should be exercised if one wants to regard field stars as a reference for the identification of a GC population. However, further study on the connection between field stars and GCs populations is still needed.

Toward a stellar population catalog in the Kilo Degree Survey:The impact of stellar recipes on stellar masses and star formation rates

The Kilo Degree Survey(Ki DS)is currently the only sky survey providing optical(ugri)plus near-infrared(NIR,ZY H JKS)seeing matched photometry over an area larger than 1000 deg2.This is obtained by incorporating the NIR data from the VISTA Kilo Degree Infrared Galaxy(VIKING)survey,covering the same Ki DS footprint.As such,the Ki DS multi-wavelength photometry represents a unique dataset to test the ability of stellar population models to return robust photometric stellar mass(M_(*))and star-formation rate(SFR)estimates.Here we use a spectroscopic sample of galaxies for which we possess ugri ZY JHK_(s)“gaussianized”magnitudes from Ki DS data release 4.We fit the spectral energy distribution from the 9-band photometry using:(1)three different popular libraries of stellar population templates,(2)single burst,simple and delayed exponential star-formation history models,and(3)a wide range of priors on age and metallicity.As template fitting codes we use two popular softwares:Le Phare and CIGALE.We investigate the variance of the stellar masses and the star-formation rates from the different combinations of templates,star formation recipes and codes to assess the stability of these estimates and define some“robust”median quantities to be included in the upcoming Ki DS data releases.As a science validation test,we derive the mass function,the star formation rate function,and the SFR-M_(*)relation for a low-redshift(z<0.5)sample of galaxies,that result in excellent agreement with previous literature data.The final catalog,containing~290000 galaxies with redshift 0.01<z<0.9,is made publicly available.

The first comprehensive Milky Way stellar mock catalogue for the Chinese Space Station Telescope Survey Camera

The Chinese Space Station Telescope(CSST)is a cutting-edge two-meter astronomical space telescope currently under construction.Its primary Survey Camera(SC)is designed to conduct large-area imaging sky surveys using a sophisticated seven-band photometric system.The resulting data will provide unprecedented data for studying the structure and stellar populations of the Milky Way.To support the CSST development and scientific projects related to its survey data,we generate the first comprehensive Milky Way stellar mock catalogue for the CSST SC photometric system using the TRILEGAL stellar population synthesis tool.The catalogue includes approximately 12.6 billion stars,covering a wide range of stellar parameters,photometry,astrometry,and kinematics,with magnitude reaching down to g=27.5 mag in the AB magnitude system.The catalogue represents our benchmark understanding of the stellar populations in the Milky Way,enabling a direct comparison with the future CSST survey data.Particularly,it sheds light on faint stars hidden from current sky surveys.Our crowding limit analysis based on this catalogue provides compelling evidence for the extension of the CSST Optical Survey(OS)to cover low Galactic latitude regions.The strategic extension of the CSST-OS coverage,combined with this comprehensive mock catalogue,will enable transformative science with the CSST.