in extremely crowded fields Veronica Dike, UCLA Michael Rich - - PowerPoint PPT Presentation

Comparing the LSST standard

pipeline and psf-fitting photometry in extremely crowded fields

Veronica Dike, UCLA Michael Rich (UCLA), Christian Johnson (CfA), Željko Ivezić (UW), Colin Slater (UW), Chris Suberlak (UW)

Blanco DECam Bulge Survey (BDBS)

Credit: W. Clarkson PI: R. Michael Rich (UCLA), Co-PI Christian Johnson (CfA), NSF AST-1413755

Blanco DECam Bulge Survey (BDBS)

• Total field ~200

deg2 using Blanco 4m at CTIO

• ugrizY photometry
• ~8000 exposures
• f 62-CCD Dark

Energy Camera

BDBS Project Goals

• Map structure of bulge as a function of age &

metallicity using ugrizY photometric metallicity

• Look for spatial substructure of certain star

populations within the bulge, e.g. blue horizontal- branch stars, metal poor stars

• Match stars to Gaia

archive for kinematics

• Study boxy X-shaped

structure

• LSST-like dataset is useful

for pipeline comparison in crowded fields

BDBS Data Reduction

• Dataset greater than 50 TB
• Reduction uses psf-fitting

pipeline written by Christian Johnson

• Based on paralellized

version of DAOPHOT

• Input: NOAO calibrated fits

file for a single CCD

• Many CCDs can be run in

parallel

• Output: log file, psf

photometry file, aperture corrections

BDBS Data Reduction

• Images calibrated

using DAOGROW (Stetson 1990) on calibration fields for aperture correction and zeropoint

Calibrated color-magnitude diagram in Baade’s Window (l,b)=0.9,-4

Red clump Foreground disk blue HB MS TO

Potential LSST science includes mapping transients across the CMD; structure, ages, metallicities of populations; connection to the disk and halo

Pipeline Comparison

Single BDBS test CCD run through both the BDBS pipeline and LSST stack

Pipeline Comparison

• 0.3” matching radius
• Photometry residuals

show comparable matching

• More uncertainty in

matching shown at fainter end as photometry errors increase

Pipeline Comparison

• BDBS pipeline detects

8589 sources in this CCD exposure

• LSST stack detects

4406

• BDBS pipeline counts

more faint stars; why?

Future work

• Need to analyze more CCDs for a more complete picture
• Photemetric error of each pipeline needs to be compared
• LSST stack fails for the most crowded fields: approx.

500,000 sources/deg2 – as tested in Suberlak et al. LSST DTMN 077

• Incorporate some of the features of the BDBS pipeline

into the LSST stack?

Summary

• BDBS is a survey of the

Galactic bulge with the LSST-like Blanco DECam

• The BDBS pipeline can

be directly compared to the LSST stack

• There is work to be done

to make the LSST stack work well in crowded fields to allow for Galactic LSST science

Credit: CfA