Forecasting Supernova Observations with the CSST: I. Photometric Samples

TL;DR

The paper simulates the CSST's ability to detect and classify millions of supernovae over a decade, highlighting its potential for advancing transient astronomy despite not being dedicated to time-domain studies.

Contribution

It provides the first detailed simulation of supernova detection and classification capabilities of the CSST, including early alerts and shock-cooling event detection.

Findings

Approximately 5 million SNe expected over 10 years.

About 7,400 SNe Ia, 2,200 SNe Ibc, 6,500 SNe II with high classification accuracy.

Early detection of SNe candidates at least two days before maximum light.

Abstract

The China Space Station Telescope (CSST, also known as Xuntian) is a serviceable two-meter-aperture wide-field telescope operating in the same orbit as the China Space Station. The CSST plans to survey a sky area of 17,500 deg$^2$ of the medium-to-high Galactic latitude to a depth of 25-26 AB mag in at least 6 photometric bands over 255-1000 nm. Within such a large sky area, slitless spectra will also be taken over the same wavelength range as the imaging survey. Even though the CSST survey is not dedicated to time-domain studies, it would still detect a large number of transients, such as supernovae (SNe). In this paper, we simulate photometric SN observations based on a strawman survey plan using the Sncosmo package. During its 10-year survey, the CSST is expected to observe about 5 million SNe of various types. With quality cuts, we obtain a "gold" sample that comprises roughly 7,400 SNe Ia, 2,200 SNe Ibc, and 6,500 SNe II candidates with correctly classified percentages reaching 91%, 63%, and 93% (formally defined as classification precision), respectively. The same survey can also trigger alerts for the detection of about 15,500 SNe Ia (precision 61%) and 2,100 SNe II (precision 49%) candidates at least two days before the light maxima. Moreover, the near-ultraviolet observations of the CSST will be able to catch hundreds of shock-cooling events serendipitously every year. These results demonstrate that the CSST can make a potentially significant contribution to SN studies.