Observing Dark Stars with JWST

Abstract: We study the capability of the James Webb Space Telescope (JWST) to detect Supermassive Dark Stars (SMDS). If the first stars are powered by dark matter heating in triaxial dark matter haloes, they may grow to be very large and very bright, visible in deep imaging with JWST and even Hubble Space Telescope (HST). We use HST surveys to place bounds on the numbers of SMDSs that may be detected in future JWST imaging surveys. We showed that SMDS in the mass range $10^6-10^7 M_\odot$ are bright enough to be detected in all the wavelength bands of the NIRCam on JWST . If SMDSs exist at z ~10, 12, and 14, they will be detectable as J-band, H-band, or K-band dropouts, respectively. With a total survey area of 150 arcmin^2 (assuming a multi-year deep parallel survey with JWST), we find that typically the number of $10^6 M_\odot$ SMDSs found as H or K-band dropouts is ~10^5\fsmds, where the fraction of early DM haloes hosting DS is likely to be small, \fsmds<<1. If the SDMS survive down to z=10 where HST bounds apply, then the observable number of SMDSs as H or K-band dropouts with JWST is ~1-30. While individual SMDS are bright enough to be detected by JWST, standard PopIII stars are not, and would only be detected in first galaxies with total stellar masses of ~$10^6-10^8 M_\odot$. Differentiating first galaxies at z>10 from SMDSs would be possible with spectroscopy: the SMDS (which are too cool produce significant nebular emission) will have only absorption lines while the galaxies are likely to produce emission lines as well. Of particular interest would be the 1640 HeII emission line as well as H{\alpha} lines which would be signatures of early galaxies rather than SMDSs. The detection of SMDSs would not only provide alternative evidence for WIMPs but would also provide possible seeds for the formation of supermassive black holes that power QSOs at z~6.

• The paper investigates the potential of the James Webb Space Telescope to detect Supermassive Dark Stars powered by dark matter annihilation.
• Using simulations, the authors model SMDS observability with JWST, predicting detectability for $10^6-10^7 M_\odot$ objects based on theoretical abundance assumptions.
• SMDS detection with JWST could provide key insights into dark matter, seed black hole formation, and help distinguish them from early Pop III galaxies.

Observing Dark Stars with JWST: An Examination of Detection Capabilities and Cosmological Implications

The paper "Observing Dark Stars with JWST" by Ilie et al. presents a detailed investigation into the potential of the James Webb Space Telescope (JWST) to detect Supermassive Dark Stars (SMDS). The authors explore the hypothesis that some of the first stars in the Universe, known as dark stars, were powered by dark matter (DM) annihilation rather than nuclear fusion. These stars could theoretically grow to become supermassive with more than $10^6 M_\odot$ and immensely luminous, exceeding $10^9 L_\odot$. The implications of detecting such objects are profound, offering insights into dark matter properties and the origins of supermassive black holes.

Dark Stars and Their Theoretical Grounds

In standard cosmology, the formation of the first stars marks the end of the Universe's dark ages. Typically, these Pop III stars form from gas collapsing in dark matter mini-halos. However, if DM heating is significant, dark stars could form. These objects are primarily composed of hydrogen and helium, and they use energy from DM annihilation rather than fusion—despite their "dark" nomenclature, they shine due to this unique heat source.

The mechanism relies on Weakly Interacting Massive Particles (WIMPs) and their self-annihilation, which provides a continuous energy supply in high-density regions like proto-stellar clouds. This process can sustain a dark star long enough to allow accretion of surrounding baryonic matter, enabling it to grow to supermassive sizes.

Detection with JWST

This paper focuses on modeling and predicting the observability of SMDS with JWST, which is well-equipped to observe such objects due to its sensitivity in infrared wavelengths. The authors employ spectra generated with the TLUSTY stellar atmospheres code for zero-metallicity atmospheres to simulate the observational signatures of SMDS at high redshifts.

Two mechanisms for DM fuel that enable sustained growth of SMDS are considered: extended adiabatic contraction and WIMP capture. Both aim to provide the necessary conditions for the formation and evolution of these supermassive objects. The paper examines different scenarios, including SMDS formation at various epochs (z~10, 12, 15), impacting detectability due to different levels of observational window availability.

Numerical Results and JWST Prospects

Using simulations to determine the numbers of DM halos that could host SMDSs, the authors conclude that JWST can detect these objects, potentially confirming the existence of dark stars and offering indirect evidence for WIMPs. Various models show that $10^6-10^7 M_\odot$ SMDS could be visible as J, H, or K-band dropouts. However, detection limits depend heavily on assumptions about the fraction of early halos hosting such stars and their survival to the present epoch.

The practical outcome of this study indicates that, while specific bounds from HST have constrained our current understanding, JWST has a significant advantage in investigating uncharted high-redshift territories. The paper concludes that JWST could detect a few or up to thousands of these objects, contingent on the validity of theoretical assumptions and observational strategies of future deep-field surveys.

Challenges in Distinguishing SMDS from Pop III Galaxies

Perhaps the most intriguing challenge posed by the potential discovery of SMDS is distinguishing them from other high-redshift objects, notably galaxies composed of Pop III stars. Using synthetic models, the authors determine that JWST may tease apart these populations through dropout techniques and detailed spectral analysis.

Future Implications

Detecting SMDS could reshape our understanding of particle physics and the early universe. If JWST identifies SMDS, this would not only validate the existence of DM annihilation effects at cosmic dawn but also imply a mechanism for the formation of seed black holes, ultimately giving rise to the supermassive black holes powering quasars observed at z~6. Moreover, this would offer an unparalleled probe into the properties of DM, providing critical data complementary to terrestrial searches and collider experiments.

In summary, the paper provides an exhaustive technical framework for exploring one of cosmology's most tantalizing possibilities: that our Universe's first stellar objects were profoundly influenced by dark matter. The forthcoming data from JWST stand to either substantiate or challenge this conception, which bears significant consequences for astrophysics and beyond.