Supermassive Dark Star candidates seen by JWST? (2304.01173v2)

Abstract: The first generation of stars in the Universe is yet to be observed. There are two leading theories for those objects that mark the beginning of the cosmic dawn: hydrogen burning Population~III stars and Dark Stars, made of hydrogen and helium but powered by Dark Matter heating. The latter can grow to become supermassive ($M_\star\sim 10^6\Msun$) and extremely bright ($L\sim 10^9L_\odot$). We show that each of the following three objects: JADES-GS-z13-0, JADES-GS-z12-0, and JADES-GS-z11-0 (at redshifts $z\in[11,14]$) are consistent with a Supermassive Dark Star interpretation, thus identifying, for the first time, Dark Star candidates.

• The paper proposes that three high-redshift JWST objects match supermassive dark star models with 95% confidence.
• The methodology involves fitting dark star spectral models to photometry and isolating key features like the He II λ1640 absorption line.
• The findings imply that dark matter-powered stars might seed early supermassive black holes, offering an alternative to Population III star formation.

Analysis of "Supermassive Dark Star Candidates Seen by JWST?"

The paper "Supermassive Dark Star Candidates Seen by JWST?" introduces the concept of Dark Stars (DSs) as a plausible interpretation for unidentified high-redshift astronomical objects observed by the James Webb Space Telescope (JWST). The authors propose that some of these objects, namely JADES-GS-z13-0, JADES-GS-z12-0, and JADES-GS-z11-0, could potentially be supermassive Dark Stars rather than conventional galaxy formations, like those consisting of Population III stars.

In the canonical cosmological framework, the earliest stellar bodies were expected to be hydrogen-burning Population III stars, forming within 100 to 400 million years post-Big Bang. These stars are anticipated to be within minihalos formed by the gravitational collapse of molecular hydrogen clouds. The Dark Star hypothesis diverges by suggesting that some early stars were powered instead by dark matter heating through annihilation processes, allowing them to maintain low surface temperatures and avoid early onset of fusion.

Key Findings

The authors identified three JWST high-redshift objects as consistent with the characteristics of Supermassive Dark Stars (SMDSs). They argue that these objects demonstrate the spectral energy distributions (SEDs) anticipated for DS models, which are puffy and cool, with low ionization. Among the four spectroscopically-confirmed high-redshift objects identified by JWST's JADES (James Webb Space Telescope Advanced Deep Extragalactic Survey), three were matched with DS model predictions at a 95% confidence level. The methodology used involved fitting DS spectra to JWST photometry and evaluating gravitational lensing effects, with implications for both the magnification parameter and stellar mass considered in the analyses.

The paper identifies the He II $\lambda1640$ absorption line as a crucial spectral signature for DSs, contrasting it with expected emission lines for conventional early galaxies populated by Population III stars. The DS candidates' spectra should show a Balmer break plus additional absorption features if they are genuine DSs rather than galaxy clusters.

Implications

The identification of DSs, if confirmed by subsequent high-resolution spectroscopy, could have substantial implications for both cosmology and astrophysics. Dark Stars, which collapse into black holes upon exhausting their dark matter, could serve as seeds for the supermassive black holes detected in the early Universe. This formation pathway offers an alternative explanation for the presence and rapid growth of massive black holes at high redshifts, challenging current models reliant on stellar accretion processes or direct collapse scenarios.

The analysis also underscores the importance of JWST's capabilities in revealing early cosmic phenomena. By potentially validating DS candidates, JWST data could push theoretical models to account for dark matter's influence on stellar evolution. The paper emphasizes the need for improved spectroscopic data and complementary analysis to discriminate between DSs and conventional high-redshift galaxies, potentially ushering in a new phase in observational cosmology.

Future Outlook

Future research should focus on refining the modeling of DSs, including the effects of surrounding nebulae on spectral outputs, as the authors acknowledge the need for applying codes such as CLOUDY to simulate these environments accurately. Improved JWST observations or other instruments capable of differentiating spectroscopic features will be critical for conclusively verifying the DS hypothesis.

Overall, this proposition introduces an intriguing aspect of early Universe cosmology: the DS hypothesis enriches our understanding of stellar genesis and lays the groundwork for exploring interactions between baryonic physics and dark matter in stellar contexts. Moreover, the implication that dark matter dynamics could directly fuel early star formation offers expansive research reflections within particle physics and cosmology.