ELT Contributions to The First Explosions
J. Craig Wheeler, József Vinkó, Rafaella Margutti, Dan Milisavljevic, Maryam Modjaz, Sung-Chul Yoon
EELT Contributions to The First Explosions A Whitepaper Submitted to the Astro 2020 Decadal Survey Committee
J. Craig Wheeler (The University of Texas at Austin) József Vinkó (
Konkoly Observatory ) Rafaella Margutti (Northwestern University) Dan Milisavljevic (Purdue University) Maryam Modjaz (New York University) Sung-Chul Yoon (Seoul National University)
Contact information for Primary Author: J. Craig Wheeler Department of Astronomy, The University of Texas at Austin 2515 Speedway, C1400 Austin, TX 78712-1205 512-471-6407 [email protected] Adapted from a chapter in the 2018 edition of the Science Book of the Giant Magellan Telescope Project. he large aperture and sensitive optical and near infrared imager spectrographs will enable an ELT system to observe some supernovae at large distances, deep into cosmological history when supernovae first began to occur.
After the Big Bang, the Universe became dark. The cosmic dark ages ended with the formation of the first stars at z ~20, only ~200 Myr after the Big Bang. These stars started cosmic reionization, created the first heavy elements, and illuminated the first galaxies. Some of these early stars may have created the first black holes. No foreseeable facility will be able to directly detect those first stars, but some of them will explode to produce bright, detectable sources that will yield insight into the rate of production and nature of those first stars. The first explosions will also point the way to deep studies of the host environment. As we discuss below, a wide range of different kinds of supernovae may be visible in the first generations of stars. It has long been recognized that long, soft gamma-ray bursts should be detectable at very high redshifts. Because their continua rise to the blue, redshifting brings more flux into the observer frame and compensates for the increased distance. If the first stars produced GRBs, then their study can provide information on the nature of the explosion to complement the burgeoning body of evidence from relatively nearby events at redshifts less than 6 to 8. GRBs could be seen in principle at redshifts of 30 or more and track the literal onset of the end of the dark ages. The line-of-sight spectra of these events will probe the intergalactic media through which their flux propagates. Another potentially critical probe of the first stars are superluminous supernovae (SLSN). Hydrogen-deficient SLSN I, in particular, are commonly observed in low-metallicity, star-forming galaxies. This makes them especially promising events to track the rate of star formation at high redshift and to seek any evolution of the intrinsic properties of the explosion at the earliest era. SLSN I are especially bright in the UV, a property that will aide their detectability at high redshift. Their observed rate per unit volume increases at least to z ~ 4, beyond the peak in the star formation rate at z ~ 2 to 3 (Cooke et al. 2012). The large UV luminosity can last for months in the rest frame and correspondingly longer by 1 + z at higher redshift. LSST will have detection limits fainter than m AB ~ 24 mag; in principle LSST can see SLSN up to z ~ 3 (Figure 1). The redshift evolution of SLSN can provide evidence for the physical origin of SLSN and for how the stellar initial mass function changes with redshift. As an example of the power of an ELT system, we illustrate the potential of the proposed
GMACS low-dispersion spectrograph on the
Giant Magellan Telescope . Analogous arguments could be made for instruments on the
Thirty Meter Telescope . The
GMT could produce a 5 σ seeing-limited spectrum in an hour at 0.5 µ m at m AB = 25. ( GMACS will achieve a S/N ratio of about 10 in an hour-long exposure at a resolution of R = 2000 down to about 24 th magnitude. The performance of NIRMOS is expected to be comparable). For an SLSN I with M ~ -22 this corresponds to z ~ 3 (within the detection limits of the