The Gemini Observatory is an astronomical observatory consisting of two 8.1-metre (26.6 ft) telescopes, Gemini North and Gemini South, which are located at two separate sites in Hawaii and Chile, respectively. The twin Gemini telescopes provide almost complete coverage of both the northern and southern skies. They are currently among the largest and most advanced optical/infrared telescopes available to astronomers. (See List of largest optical reflecting telescopes).The National Science Foundation (NSF) of the United States, the National Research Council of Canada, CONICYT of Chile, MCTI of Brazil, and MCTIP of Argentina own and operate the Gemini Observatory. The NSF is currently (2017) the majority partner, contributing approximately 70% of the funding needed to operate and maintain both telescopes. The operations and maintenance of the observatory is managed by the Association of Universities for Research in Astronomy (AURA), through a cooperative agreement with NSF. NSF acts as the Executive Agency on behalf of the international partners.The Gemini telescopes house a suite of modern instruments, offer superb performance in the optical and near-infrared, and employ sophisticated adaptive optics technology to compensate for the blurring effects of the Earth's atmosphere. Gemini is a world-leader in wide-field adaptive optics assisted infrared imaging, and has recently commissioned the Gemini Planet Imager, an instrument that allows researchers to directly image and analyze exoplanets that are a millionth as bright as the host star around which they orbit. Gemini continues to support research in almost all areas of modern astronomy, including the Solar System, exoplanets, star formation and evolution, the structure and dynamics of galaxies, supermassive black holes, distant quasars, and the structure of the Universe on the largest scales.Past participants in the Gemini Observatory include Australia and the United Kingdom. The UK dropped out of the partnership at the end of 2012 and the Gemini Observatory has responded to the loss of funding by significantly reducing its operating costs, streamlining its operations, and implementing energy savings measures at each site. Both telescopes are also now operated remotely from Base Facility Operations centers in Hilo, Hawaii, and La Serena, Chile.
We present an extensive photometric and spectroscopic ultraviolet–optical–infrared campaign on the luminous fast blue optical transient (LFBOT) AT 2024wpp over the first ∼100 days. AT 2024wpp is the most luminous LFBOT discovered to date, with L _pk ≈ (2–4) × 10 ^45 erg s ^−1 (5–10 times that of the prototypical AT 2018cow). This extreme luminosity enabled the acquisition of the most detailed LFBOT UV light curve thus far. In the first ∼45 days, AT 2024wpp radiated >10 ^51 erg, surpassing AT 2018cow by an order of magnitude and requiring a power source beyond the radioactive ^56 Ni decay of traditional supernovae. Like AT 2018cow, the UV–optical spectrum of AT 2024wpp is dominated by a persistently blue thermal continuum throughout our monitoring, with blackbody parameters at a peak of T > 30,000 K and R _BB / t ≈ 0.2 c –0.3 c . We find evidence for cooling until ∼10 days; thereafter, T ≳ 20,000 K is maintained. We interpret the featureless spectra as a consequence of continuous energy injection from a central source of high-energy emission that maintains high ejecta ionization. After 35 days, faint (equivalent width (EW) ≲ 10 Å) H and He spectral features with kinematically separate velocity components centered at 0 and −6400 km s ^−1 emerge, implying spherical symmetry deviations. A near-infrared excess of emission above the optical blackbody emerges between 20 and 30 days, with a power-law spectrum F _ν _,NIR ∝ ν ^−0.3 at 30 days. We interpret this distinct emission component as either reprocessing of early UV emission in a dust echo or free–free emission in an extended medium above the optical photosphere. LFBOT asphericity and multiple outflow components (including mildly relativistic ejecta), together with the large radiated energy, are naturally realized by super-Eddington accretion disks around neutron stars or black holes and their outflows.
The spectra of exoplanet atmospheres are affected by aerosols (clouds and hazes) of uncertain origin. Proposed aerosol formation mechanisms include gas condensation or photochemical reactions. We measured the transmission spectrum of the tidally locked gas giant exoplanet WASP-94A b and identified asymmetry in its atmosphere. The morning limb is cooler and cloudy, whereas the evening limb is hotter and exhibits gaseous water absorption features. We interpret this difference as being due to the formation of cloud droplets near the morning limb, which evaporate during circulation to the evening limb. The dominant aerosols are clouds cycling between the day and night sides of the atmosphere, not photochemical hazes. The resulting asymmetry can severely bias chemical abundance measurements, unless limb-resolved spectroscopy is available.
Context. As galaxies evolve in dense cluster and protocluster environments, they interact and quench their star formation. This gradually transforms the dominant galaxy population from star-forming galaxies to quiescent red galaxies. This transformation is identifiable by observing the galaxy colors and can also be seen in the morphological transformation of late-type galaxies into early-type galaxies, which creates the morphology-density relation observed when populations in clusters are compared to field galaxies at a given epoch. However, high-z (z > 2) galaxy morphology studies are hindered by the high angular resolution necessary to characterize the morphology. Aims. We studied HST WFC3 F160W observations of protoclusters from the MAMMOTH survey (BOSS1244 and BOSS1542) at z ∼ 2.23 with populations of previously identified Hα emitters. Methods. By measuring the Sérsic index of 151 Hα emitters, we searched for the early morphological transformation of high-z star-forming galaxies in these well-studied large nonvirialized protoclusters, which we think are the precursors of present-day galaxy clusters. Results. The morphology of the populations of star-forming galaxies in protoclusters does not differ from that of their field counterparts. However, we also identified a population of clumpy potentially merging galaxies, which might increase the population of early-type galaxies within these structures. In BOSS1244, which has two previously identified massive quiescent galaxies including a brightest cluster galaxy (BCG), we additionally found an abundance of early-type galaxies near the BCG and two coeval high-z quasars. Conclusions. Although the morphology of field and protocluster galaxies are very similar, the population of early-type star-forming galaxies surrounding the spectroscopically confirmed quiescent BCG in BOSS1244, which is not observed in BOSS1542, might indicate differences in the evolutionary state of these two coeval protoclusters. It might be a sign of an early forming cluster core in BOSS1244.
We apply the angular two-point correlation function (TPCF) to the spatial distributions of young star clusters (YSCs) in four nearby star forming galaxies (NGC 628, NGC 4449, M51, and M83) in order to investigate their underlying hierarchical structuring. Using newly constructed catalogs of YSCs in the emerging phase (eYSCs), identified in the infrared with JWST, and optical YSCs detected in archival Hubble Space Telescope data, we compute the TPCFs for various cluster samples and age bins across the four galaxies, as part of the Feedback in Emerging extrAgalactic Star ClusTers (FEAST) program. We find clear evidence of hierarchical structuring, especially in eYSCs and YSCs with ages <10 Myr (referred to as oYSCs), which show similar TPCFs within each galaxy. NGC 628 exhibits a clear distinction between the TPCFs of eYSCs and oYSCs, implying a shorter randomization timescale. In contrast, clusters aged 10-300 Myr exhibit progressively more random spatial distributions, becoming effectively random after similar to 100 Myr, consistent with earlier studies. The two-dimensional fractal index D-2 values of the YSCs' underlying distributions are calculated from model fits to the TPCFs. Our values of D-2 derived from the youngest YSC populations align better with the expected value of D-2 similar to 1.3 for a universal star formation process compared to previous findings.
Supernova (SN) 2025coe at a distance of similar to 25 Mpc is the second-closest calcium-strong transient. It was discovered at a large projected offset of similar to 34 kpc from its potential host galaxy NGC 3277. Multiband photometry of SN 2025coe indicates the presence of two peaks at day similar to 2 and day similar to 11 after explosion. Modeling the bolometric light curve, we find that the first peak can be reproduced either by shock cooling of a compact envelope (Renv approximate to 6-40 R circle dot; Menv approximate to 0.1-0.2 M circle dot) or by interaction with close-in circumstellar material (CSM; RCSM less than or similar to 6 & times; 1014 cm), or a combination of both. The second peak is dominated by radioactive decay of 56Ni (Mej approximate to 0.4-0.5 M circle dot; M56Ni approximate to 1.4 & times;10-2 M circle dot). SN 2025coe rapidly evolves from the photospheric phase dominated by He I P Cygni profiles to nebular phase spectra dominated by strong [Ca ii] lambda lambda 7291, 7323 and weak [O i] lambda lambda 6300, 6364 emission lines. Simultaneous line profile modeling of [Ca ii] and [O i] at nebular phases shows that an asymmetric core-collapse explosion of a low-mass (less than or similar to 3.3 M circle dot) He-core progenitor can explain the observed line profiles. Alternatively, lack of local star formation at the site of the SN explosion combined with a low ejecta mass is also consistent with a thermonuclear explosion due to a low-mass hybrid He-C/O white dwarf +C/O white dwarf merger.
