The Violent Youth of Bright and Massive Cluster Galaxies and their Maturation over 7 Billion Years

In this study we investigate the formation and evolution mechanisms of the brightest cluster galaxies (BCGs) over cosmic time. At high redshift ($z\sim0.9$), we selected BCGs and most massive cluster galaxies (MMCGs) from the Cl1604 supercluster and compared them to low-redshift ($z\sim0.1$) counterparts drawn from the MCXC meta-catalog, supplemented by SDSS imaging and spectroscopy. We observed striking differences in the morphological, color, spectral, and stellar mass properties of the BCGs/MMCGs in the two samples. High-redshift BCGs/MMCGs were, in many cases, star-forming, late-type galaxies, with blue broadband colors, properties largely absent amongst the low-redshift BCGs/MMCGs. The stellar mass of BCGs was found to increase by an average factor of $2.51\pm0.71$ from $z\sim0.9$ to $z\sim0.1$. Through this and other comparisons we conclude that a combination of major merging (mainly wet or mixed) and \emph{in situ} star formation are the main mechanisms which build stellar mass in BCGs/MMCGs. The stellar mass growth of the BCGs/MMCGs also appears to grow in lockstep with both the stellar baryonic and total mass of the cluster. Additionally, BCGs/MMCGs were found to grow in size, on average, a factor of $\sim3$, while their average S\'ersic index increased by $\sim$0.45 from $z\sim0.9$ to $z\sim0.1$, also supporting a scenario involving major merging, though some adiabatic expansion is required. These observational results are compared to both models and simulations to further explore the implications on processes which shape and evolve BCGs/MMCGs over the past $\sim$7 Gyr.Comment: Accepted for publication in MNRA

Emotional engagements predict and enhance social cognition in young chimpanzees

Social cognition in infancy is evident in coordinated triadic engagements, that is, infants attending jointly with social partners and objects. Current evolutionary theories of primate social cognition tend to highlight species differences in cognition based on human-unique cooperative motives. We consider a developmental model in which engagement experiences produce differential outcomes. We conducted a 10-year-long study in which two groups of laboratory-raised chimpanzee infants were given quantifiably different engagement experiences. Joint attention, cooperativeness, affect, and different levels of cognition were measured in 5- to 12-month-old chimpanzees, and compared to outcomes derived from a normative human database. We found that joint attention skills significantly improved across development for all infants, but by 12 months, the humans significantly surpassed the chimpanzees. We found that cooperativeness was stable in the humans, but by 12 months, the chimpanzee group given enriched engagement experiences significantly surpassed the humans. Past engagement experiences and concurrent affect were significant unique predictors of both joint attention and cooperativeness in 5- to 12-month-old chimpanzees. When engagement experiences and concurrent affect were statistically controlled, joint attention and cooperation were not associated. We explain differential social cognition outcomes in terms of the significant influences of previous engagement experiences and affect, in addition to cognition. Our study highlights developmental processes that underpin the emergence of social cognition in support of evolutionary continuity

The Properties of Radio Galaxies and the Effect of Environment in Large Scale Structures at z∼1z\sim1

In this study we investigate 89 radio galaxies that are spectroscopically-confirmed to be members of five large scale structures in the redshift range of $0.65 \le z \le 0.96$. Based on a two-stage classification scheme, the radio galaxies are classified into three sub-classes: active galactic nucleus (AGN), hybrid, and star-forming galaxy (SFG). We study the properties of the three radio sub-classes and their global and local environmental preferences. We find AGN hosts are the most massive population and exhibit quiescence in their star-formation activity. The SFG population has a comparable stellar mass to those hosting a radio AGN but are unequivocally powered by star formation. Hybrids, though selected as an intermediate population in our classification scheme, were found in almost all analyses to be a unique type of radio galaxies rather than a mixture of AGN and SFGs. They are dominated by a high-excitation radio galaxy (HERG) population. We discuss environmental effects and scenarios for each sub-class. AGN tend to be preferentially located in locally dense environments and in the cores of clusters/groups, with these preferences persisting when comparing to galaxies of similar colour and stellar mass, suggesting that their activity may be ignited in the cluster/group virialized core regions. Conversely, SFGs exhibit a strong preference for intermediate-density global environments, suggesting that dusty starbursting activity in LSSs is largely driven by galaxy-galaxy interactions and merging.Comment: 28 pages, 10 figures, accepted to MNRA

Designing a videoconference system for active networks

Active networks are receiving increasing attention due to their promises of great flexibility in tailoring services to applications. This capability stems from the exploitation of network devices whose behavior can be changed dynamically by applications, possibly using technologies and architectures originally conceived for mobile code systems. Notwithstanding the promises of active networks, real-world applications that clearly benefit by them are still missing. In this work we describe the design of a videoconference system conceived expressly for operation over active networks. The goal of this activity is to pinpoint the benefits that mobile code and active networks bring in this application domain and to provide insights for the exploitation of these concepts in other application domain

The plight of the sense-making ape

This is a selective review of the published literature on object-choice tasks, where participants use directional cues to find hidden objects. This literature comprises the efforts of researchers to make sense of the sense-making capacities of our nearest living relatives. This chapter is written to highlight some nonsensical conclusions that frequently emerge from this research. The data suggest that when apes are given approximately the same sense-making opportunities as we provide our children, then they will easily make sense of our social signals. The ubiquity of nonsensical contemporary scientific claims to the effect that humans are essentially--or inherently--more capable than other great apes in the understanding of simple directional cues is, itself, a testament to the power of preconceived ideas on human perception

N. E. Hansen\u27s Contributions to Alfalfa Breeding in North America

This bulletin provides biographical information about N.E. Hanson and his contributions to alfalfa breeding

Chronos and KAIROS: MOSFIRE observations of post-starburst galaxies in z ∼ 1 clusters and groups

We present an exploration of ∼500 spectroscopically confirmed galaxies in and around two large-scale structures (LSSs) at z ∼ 1 drawn from the Observations of Redshift Evolution in Large Scale Environments survey, an ongoing, wide-field photometric and spectroscopic campaign targeting a large ensemble of LSSs at 0.6 < z < 1.3. A sub-sample of these galaxies (∼150) was targeted for the initial phase of a near-infrared MOSFIRE spectroscopic campaign investigating the differences in selections of galaxies that had recently ended a burst of star formation and/or had rapidly quenched (i.e. post-starburst/K+A galaxies). Selection with MOSFIRE utilizing the H α and [N II] emission features resulted in a post-starburst sample more than double that selected by traditional z ∼ 1 (observed-frame optical) methods even after the removal of the relatively large fraction of dusty starburst galaxies selected through traditional methods. While the traditional post-starburst fraction increased with increasing global density, the MOSFIRE-selected post-starburst fraction was found to be constant across field, group, and cluster environments. However, this fraction computed relative to the number of star-forming galaxies was observed to elevate in the cluster environment. Post-starbursts selected with MOSFIRE exhibited moderately strong [O II] emission originating from activity other than star formation. Such galaxies, termed K+A with ImposteR [O II]-derived Star formation (KAIROS) galaxies, were found to be younger than and likely undergoing feedback absent or diminished in their optically selected counterparts. A comparison between the environments of the two types of post-starbursts suggested a picture in which the evolution of a post-starburst galaxy is considerably different in cluster environments than in the more rarefied environments of a group or the field

X-ray-emitting active galactic nuclei from z = 0.6 to 1.3 in the intermediate- and high-density environments of the ORELSE survey

We studied active galactic nucleus (AGN) activity in 12 large-scale structures (LSSs) in the Observations of Redshift Evolution in Large-Scale Environments (ORELSE) survey, at 0.65 < z < 1.28, using a combination of Chandra observations, optical and NIR imaging and spectroscopy. We located a total of 61 AGNs that were successfully matched to optical counterparts in the LSSs. We found that AGN populations across our sample had more recently had starburst events compared to the overall galaxy populations. We find no relation between AGN activity and location within the LSSs, suggesting triggering mechanisms that depend on global environment are at most sub-dominant. To focus on differences between our AGNs, we grouped them into four sub-samples based on the spectral properties of their parents LSSs. We found one of the sub-samples, SG0023 & SC1604, stood out from the others. AGNs in this sample were disproportionately luminous. These AGNs had the most recent starburst events, in contrast to their parent populations. Additionally, both the AGNs and the overall galaxy population in SG0023 & SC1604 had the largest fraction of close kinematic pairs, which indicates a higher rate of galaxy mergers and interactions. These results suggest that major mergers are driving AGN activity in SG0023 & SC1604, while other processes are likely triggering less luminous AGNs in the rest of our sample. Additionally, minor mergers are unlikely to play a significant role, since the same conditions that lead to more major mergers should also lead to more minor mergers, which is not observed in SG0023 & SC1604

Are chimpanzees really so poor at understanding imperative pointing? Some new data and an alternative view of canine and ape social cognition

There is considerable interest in comparative research on different species’ abilities to respond to human communicative cues such as gaze and pointing. It has been reported that some canines perform significantly better than monkeys and apes on tasks requiring the comprehension of either declarative or imperative pointing and these differences have been attributed to domestication in dogs. Here we tested a sample of chimpanzees on a task requiring comprehension of an imperative request and show that, though there are considerable individual differences, the performance by the apes rival those reported in pet dogs. We suggest that small differences in methodology can have a pronounced influence on performance on these types of tasks. We further suggest that basic differences in subject sampling, subject recruitment and rearing experiences have resulted in a skewed representation of canine abilities compared to those of monkeys and apes