A massive proto-cluster of galaxies at a redshift of z {\approx} 5.3

Massive clusters of galaxies have been found as early as 3.9 Billion years (z=1.62) after the Big Bang containing stars that formed at even earlier epochs. Cosmological simulations using the current cold dark matter paradigm predict these systems should descend from "proto-clusters" - early over-densities of massive galaxies that merge hierarchically to form a cluster. These proto-cluster regions themselves are built-up hierarchically and so are expected to contain extremely massive galaxies which can be observed as luminous quasars and starbursts. However, observational evidence for this scenario is sparse due to the fact that high-redshift proto-clusters are rare and difficult to observe. Here we report a proto-cluster region 1 billion years (z=5.3) after the Big Bang. This cluster of massive galaxies extends over >13 Mega-parsecs, contains a luminous quasar as well as a system rich in molecular gas. These massive galaxies place a lower limit of >4x10^11 solar masses of dark and luminous matter in this region consistent with that expected from cosmological simulations for the earliest galaxy clusters.Comment: Accepted to Nature, 16 Pages, 6 figure

X-shooter survey of young intermediate-mass stars – I. Stellar characterization and disc evolution

Intermediate-mass stars (IMSs) represent the link between low-mass and high-mass stars, and cover a key mass range for giant planet formation. In this paper, we present a spectroscopic survey of 241 young IMS candidates with IR-excess, the most complete unbiased sample to date within 300 pc. We combined VLT/X-Shooter spectra with BVR photometric observations and Gaia DR3 distances to estimate fundamental stellar parameters such as Teff, mass, radius, age, and luminosity. We further selected those stars within the intermediate-mass range 1.5 ≤ M⋆/M⊙ ≤ 3.5, and discarded old contaminants. We used 2MASS and WISE photometry to study the IR-excesses of the sample, finding 92 previously unidentified stars with IR-excess. We classified this sample into ‘protoplanetary’, ‘hybrid candidates’, and ‘debris’ discs based on their observed fractional excess at 12 μm, finding a new population of 17 hybrid disc candidates. We studied inner disc dispersal time-scales for λ<10μm and found very different trends for IMSs and low-mass stars (LMSs). IMSs show excesses dropping fast during the first 6 Myr independently of the wavelength, while LMSs show consistently lower fractions of excess at the shortest wavelengths, and increasingly higher fractions for longer wavelengths with slower dispersal rates. In conclusion, this study demonstrates empirically that IMSs dissipate their inner discs very differently than LMSs, providing a possible explanation for the lack of short period planets around IMSs

Can Gratitude and Kindness Interventions Enhance Well-Being in a Clinical Sample?

Grounded in Fredrickson's (Rev Gen Psychol 2(3):300-319, 1998) broaden and build model of positive emotions, the current study examines the efficacy of 2-week self-administered gratitude and kindness interventions within a clinical sample on a waiting-list for outpatient psychological treatment. Results demonstrate that we can reliably cultivate the emotional experiences of gratitude but not kindness in this brief period. Further, both the gratitude and kindness interventions built a sense of connectedness, enhanced satisfaction with daily life, optimism, and reduced anxiety compared to a placebo condition. These brief interventions did not impact on more overarching constructs, including general psychological functioning and meaning in life. These findings demonstrate that gratitude and kindness have a place in clinical practice; not just as end states, but as emotional experiences that can stimulate constructive change. Further, these strategies can serve as useful pre-treatment interventions that may reduce the negative impact of long waiting times before psychological treatment.Griffith Health, School of Applied PsychologyNo Full Tex