Confusion noise from Galactic binaries for Taiji
Chang Liu, Wen-Hong Ruan, Zong‐Kuan Guo
Abstract
Gravitational waves (GWs) from tens of millions of compact binaries in our Milky Way enter the millihertz band of space-based detection. The majority of them cannot be resolved individually, resulting in foreground confusion noise for the Laser Interferometer Space Antenna (LISA). The concept of the Taiji mission is similar to LISA's with slightly better sensitivity, which means that Galactic GW signals will also affect detection with Taiji. Here, we generate 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 times. We find that the full sensitivity curve is slightly lower for Taiji than for LISA at frequencies of $\ensuremath{\le}0.8\text{ }\text{ }\mathrm{mHz}$ and around 2 mHz. For a 4-year lifetime, more than 29 thousand sources are resolvable with Taiji. Compared to LISA, Taiji can subtract $\ensuremath{\sim}20%$ 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 to $0.4\text{ }\text{ }{M}_{\ensuremath{\bigodot}}$, more sources become resolvable with Taiji.