Constraining the stochastic gravitational wave background with photometric surveys

Abstract

The detection of the Stochastic Gravitational Wave Background (SGWB) is essential for understanding black hole populations, especially for supermassive black hole binaries. The recent promising results from various Pulsar Timing Array (PTA) collaborations allude to an imminent detection. In this paper, we investigate the relative astrometric gravitational wave detection method, which can contribute to SGWB studies in the microhertz range. We consider the Roman Space Telescope and Gaia as candidates and quantitatively discuss the survey sensitivity in both the frequency and spatial domains. We emphasize the importance of survey specific constraints on performance estimates by considering mean field of view (FoV) signal subtraction and angular power spectrum binning. We conclude that if the SGWB is at a similar level as in PTA estimates, both Roman and Gaia have the potential to detect this frequency-domain power excess. However, both Roman and Gaia are subject to FoV limitations, and are unlikely to be sensitive to the spatial pattern of the SGWB.

Dissecting the stochastic gravitational wave background with astrometry

“…An alternative representation of SGWB signals in PTAs and astrometric observation is achieved through the use of spherical harmonic space, as demonstrated in prior works such as refs. [21,28,[38][39][40]. The key advantage of this representation lies in its ability to diagonalize both the signals and the SGWB-induced variances, simplifying the definition of estimators.…”

“…Gaia [31] and upcoming missions such as Roman [28,[33][34][35] and Theia [75,76] play pivotal roles in astrometric observations. The Gaia mission, having measured the proper motion of over ∼ 10 9 stars and ∼ 10 6 quasi-stellar objects (QSOs) for more than 10 years, has provided a rich dataset.…”

“…This opens a new window for GWs, exploring uncharted frequency ranges lying between PTAs and the Laser Interferometer Space Antenna (LISA) band [32]. For instance, the Nancy Grace Roman Space Telescope (Roman), with its significantly higher observing cadence, can indeed extend the frequency range to above 10 −4 Hz [28,[33][34][35]. Moreover, the presence of parity-odd correlations among astrometric observables or PTA-astrometry cross-correlations can reveal the existence of a chiral component of SGWB [21,30,36].…”

“…This phenomenon serves as the basis for astrometric detection of GWs, which relies on measuring correlated wobbling movements of stars on the sky [12][13][14][15][16]. Astrometry represents another promising avenue for the detection and characterization of gravitational waves, providing a complementary perspective to the PTA approach [17][18][19][20][21][22][23][24][25][26][27][28][29][30]. While astrometry currently has less constraining power than PTAs [23,27,29], complete JCAP05(2024)030 datasets from space-borne astrometry missions like Gaia [31], including full time series, have the potential to provide sensitivity comparable to PTAs.…”

Gravitational wave measurement in the mid-band with atom interferometers

“…In the next decades, various collaborations aim to extend the frequency coverage of GW detectors from nHz to kHz and above, with the greatest sensitivity possible, similarly to what has been achieved in the electromagnetic spectrum, where observatories operate from the 10 MHz range up to gamma-ray detectors that have observed PeV photons. Achieving a broad GW frequency coverage will require a variety of different detector techniques: proposals include astrometry [14][15][16][17][18][19][20][21][22], ranging between asteroids [23], studying orbital perturbations of astrophysical binaries [24,25], future atomic [26][27][28][29][30][31][32][33][34] or laser [35][36][37][38][39][40][41][42][43] interferometers on Earth or in space, atomic clocks in space [44,45], lunar GW detectors [46][47][48][49][50][51], and various types of terrestrial detectors with coverage at higher (MHz-GHz) frequencies; see, e.g., ref. [52] for a recent review.…”