Confusion noise from Galactic binaries for Taiji

TL;DR

This paper models the confusion noise from galactic binaries for the Taiji space-based gravitational wave detector, estimating the number of resolvable sources and comparing sensitivity with LISA over various observation periods.

Contribution

It provides the first detailed simulation of galactic binary signals for Taiji, including source subtraction and noise estimation, highlighting its improved resolvability over LISA.

Findings

Taiji's sensitivity curve is slightly lower than LISA's at certain frequencies.

More than 29,000 sources are resolvable with Taiji after 4 years.

Taiji can subtract approximately 20% more sources than LISA.

Abstract

Gravitational waves (GWs) from tens of millions of compact binaries in our Milky Way enter the milli-Hertz band of space-based detection. The majority of them cannot be resolved individually, resulting in a foreground confusion noise for Laser Interferometer Space Antenna (LISA). The concept of Taiji mission is similar to LISA's with slightly better sensitivity, which means that the galactic GW signals will also affect the detection with Taiji. Here we generate the GW signals from 29.8 million galactic binaries for Taiji and subtract the `resolvable' sources. The confusion noise is estimated and fitted in an analytic form with 6-month, 1-year, 2-year and 4-year observation time. We find that the full sensitivity curve is slightly lower for Taiji than for LISA at frequencies of $\leq 0.8$ mHz and around 2~mHz. For a 4-year lifetime, more than 29 thousand sources are resolvable with Taiji. Compared to LISA, Taiji can subtract $\sim 20 \%$ more sources and the distribution of them in our Milky Way is consistent with that of the resolvable sources with LISA. At frequencies around 2~mHz or with the chirp masses ranging from $0.2 M_\odot$ to $0.4 M_\odot$, more sources become resolvable with Taiji.