Aggressive Victims, Passive Victims, and Bullies: Developmental Continuity or Developmental Change?

We evaluated the extent to which aggressive victims show unique developmental pathways that are different from those of passive victims, bullies, and uninvolved children. A total of 1,722 children were followed from 4th grade to 6th grade, and the prevalence and stability of each group were assessed. Aggressive victims became less prevalent and passive victims and bullies became more prevalent with age. Although it was common for aggressive victims and bullies to move from one group to the other across time, there was little overlap with the passive victim group. Stability estimates were higher for the bully and aggressive victim groups than for the passive victim group, and patterns of stability were influenced by peer rejection and exposure to violence

A Multiwavelength Study on the Fate of Ionizing Radiation in Local Starbursts

The fate of ionizing radiation is vital for understanding cosmic ionization, energy budgets in the interstellar and intergalactic medium, and star formation rate indicators. The low observed escape fractions of ionizing radiation have not been adequately explained, and there is evidence that some starbursts have high escape fractions. We examine the spectral energy distributions of a sample of local star-forming galaxies, containing thirteen local starburst galaxies and ten of their ordinary star-forming counterparts, to determine if there exist significant differences in the fate of ionizing radiation in these galaxies. We find that the galaxy-to-galaxy variations in the SEDs is much larger than any systematic differences between starbursts and non-starbursts. For example, we find no significant differences in the total absorption of ionizing radiation by dust, traced by the 24um, 70um, and 160um MIPS bands of the Spitzer Space Telescope, although the dust in starburst galaxies appears to be hotter than that of non-starburst galaxies. We also observe no excess ultraviolet flux in the GALEX bands that could indicate a high escape fraction of ionizing photons in starburst galaxies. The small H-alpha fractions of the diffuse, warm ionized medium in starburst galaxies are apparently due to temporarily boosted H-alpha luminosity within the star-forming regions themselves, with an independent, constant WIM luminosity. This independence of the WIM and starburst luminosities contrasts with WIM behavior in non-starburst galaxies and underscores our poor understanding of radiation transfer in both ordinary and starburst galaxies.Comment: 10 pages, 8 figures, accepted to ApJ 10/11/1

Cosmic clocks: A Tight Radius - Velocity Relationship for HI-Selected Galaxies

HI-Selected galaxies obey a linear relationship between their maximum detected radius Rmax and rotational velocity. This result covers measurements in the optical, ultraviolet, and HI emission in galaxies spanning a factor of 30 in size and velocity, from small dwarf irregulars to the largest spirals. Hence, galaxies behave as clocks, rotating once a Gyr at the very outskirts of their discs. Observations of a large optically-selected sample are consistent, implying this relationship is generic to disc galaxies in the low redshift Universe. A linear RV relationship is expected from simple models of galaxy formation and evolution. The total mass within Rmax has collapsed by a factor of 37 compared to the present mean density of the Universe. Adopting standard assumptions we find a mean halo spin parameter lambda in the range 0.020 to 0.035. The dispersion in lambda, 0.16 dex, is smaller than expected from simulations. This may be due to the biases in our selection of disc galaxies rather than all halos. The estimated mass densities of stars and atomic gas at Rmax are similar (~0.5 Msun/pc^2) indicating outer discs are highly evolved. The gas consumption and stellar population build time-scales are hundreds of Gyr, hence star formation is not driving the current evolution of outer discs. The estimated ratio between Rmax and disc scale length is consistent with long-standing predictions from monolithic collapse models. Hence, it remains unclear whether disc extent results from continual accretion, a rapid initial collapse, secular evolution or a combination thereof.Comment: 14 pages, 7 figures, 3 in colour. Published in MNRAS. This v2 corrects wrong journal in the references section (all instances of "Astrophysics and Space Sciences" should have been ApJ). The Posti+2017 has also been updated. An erratum has been submitted to MNRA

The Next 50 Years: Considering Gender as a Context for Understanding Young Children’s Peer Relationships

The study of children’s peer relationships has been well represented within the pages of Merrill-Palmer Quarterly. Particularly over the last decade, the pace of publishing studies on peer relationships has increased. Despite this upswing in interest in peer relationships, significant gaps remain. In this article, we focus on a particularly overlooked and significant area of peer relationships, namely, the role of sex-segregated peer interactions and how these relate to development in early childhood. We review why this topic is important for researchers to consider and highlight promising directions for research that we hope will appear in future volumes of Merrill-Palmer Quarterly

Order and disorder in the triangular-lattice t-J-V model at 2/3 electron density

Motivated by the recent discovery of superconductivity in Na$_x$CoO$_2\cdot y$H$_2$O, we use series expansion methods and cluster mean-field theory to study spontaneous charge order, Neel order, ferromagnetic order, dimer order and phase-separation in the triangular-lattice t-J-V model at 2/3 electron density. We find that for t<0, the charge ordered state, with electrons preferentially occupying a honeycomb lattice, is very robust. Quite surprisingly, hopping to the third sublattice can even enhance Neel order. At large negative t and small V, the Nagaoka ferromagnetic state is obtained. For large positive t, charge and Neel order vanish below a critical V, giving rise to an itinerant antiferromagnetically correlated state.Comment: 4 pages, 5 figure

GOODS-Herschel: the far-infrared view of star formation in active galactic nucleus host galaxies since z ≈ 3

We present a study of the infrared properties of X-ray selected, moderate-luminosity (i.e. L_X= 10^(42)–10^(44) erg s^(−1)) active galactic nuclei (AGNs) up to z ≈ 3, in order to explore the links between star formation in galaxies and accretion on to their central black holes. We use 100 and 160 μ m fluxes from GOODS-Herschel – the deepest survey yet undertaken by the Herschel telescope – and show that in the vast majority of cases (i.e. >94 per cent) these fluxes are dominated by emission from the host galaxy. As such, these far-infrared bands provide an uncontaminated view of star formation in the AGN host galaxies. We find no evidence of any correlation between the X-ray and infrared luminosities of moderate AGNs at any redshift, suggesting that global star formation is decoupled from nuclear (i.e. AGN) activity in these galaxies. On the other hand, we confirm that the star formation rates of AGN hosts increase strongly with redshift, by a factor of 43^(+27)_(−18) from z < 0.1 to z = 2–3 for AGNs with the same range of X-ray luminosities. This increase is entirely consistent with the factor of 25–50 increase in the specific star formation rates (SSFRs) of normal, star-forming (i.e. main-sequence) galaxies over the same redshift range. Indeed, the average SSFRs of AGN hosts are only marginally (i.e. ≈20 per cent) lower than those of main-sequence galaxies at all surveyed redshifts, with this small deficit being due to a fraction of AGNs residing in quiescent (i.e. low SSFR) galaxies. We estimate that 79 ± 10 per cent of moderate-luminosity AGNs are hosted in main-sequence galaxies, 15 ± 7 per cent in quiescent galaxies and <10 per cent in strongly starbursting galaxies. We derive the fractions of all main-sequence galaxies at z < 2 that are experiencing a period of moderate nuclear activity, noting that it is strongly dependent on galaxy stellar mass (M_(stars)), rising from just a few per cent at M_(stars) ∼ 10^(10) M_⊙ to ≳20 per cent at M_(stars)≥ 10^(11) M_⊙. Our results indicate that it is galaxy stellar mass that is most important in dictating whether a galaxy hosts a moderate-luminosity AGN. We argue that the majority of moderate nuclear activity is fuelled by internal mechanisms rather than violent mergers, which suggests that high-redshift disc instabilities could be an important AGN feeding mechanism

Science Validation of the Spitzer Source List

The Spitzer Science Center will produce a source list (SL) of photometry for a large subset of imaging data in the Spitzer Heritage Archive (SHA). The list will enable a large range of science projects. The primary requirement on the SL is very high reliability — with areal coverage, completeness and limiting depth being secondary considerations. The SHA at the NASA Infrared Science Archive (IRSA) will serve the SL as an enhanced data product. The SL will include data from the four channels of IRAC (3–8 microns) and the 24 micron channel of MIPS. The Source List will include image products (mosaics) and photometric data for Spitzer observations of about 1500 square degrees and include around 30 million sources. We describe ongoing science validation of the Spitzer Source List, and discuss the range of use cases which will be supported

The Spitzer Archival Far-InfraRed Extragalactic Survey

We present the Spitzer Archival Far-InfraRed Extragalactic Survey (SAFIRES). This program produces refined mosaics and source lists for all far-infrared extragalactic data taken during the more than six years of the cryogenic operation of the Spitzer Space Telescope. The SAFIRES products consist of far-infrared data in two wavelength bands (70 um and 160 um) across approximately 180 square degrees of sky, with source lists containing far-infrared fluxes for almost 40,000 extragalactic point sources. Thus, SAFIRES provides a large, robust archival far-infrared data set suitable for many scientific goals.Comment: 7 pages, 6 figures, published in ApJ

Dust Emission from Evolved and Unevolved HII Regions in the Large Magellanic Cloud

We present a study of the dust properties of 12 classical and superbubble HII regions in the Large Magellanic Cloud. We use infrared photometry from Spitzer (8, 24, 70, and 160 \mum bands), obtained as part of the Surveying the Agents of a Galaxy's Evolution (SAGE) program, along with archival spectroscopic classifications of the ionizing stars to examine the role of stellar sources on dust heating and processing. Our infrared observations show surprisingly little correlation between the emission properties of the dust and the effective temperatures or bolometric magnitudes of stars in the HII regions, suggesting that the HII region evolutionary timescale is not on the order of the dust processing timescale. We find that the infrared emission of superbubbles and classical HII regions shows little differentiation between the two classes, despite the significant differences in age and morphology. We do detect a correlation of the 24 \mum emission from hot dust with the ratio of 70 to 160 \mum flux. This correlation can be modeled as a trend in the temperature of a minority hot dust component, while a majority of the dust remains significantly cooler.Comment: 15 pages, 5 figures. Accepted to Ap

Cosmic Ray Electrons in Groups and Clusters of Galaxies: Primary and Secondary Populations from a Numerical Cosmological Simulation

We study the generation and distribution of high energy electrons in cosmic environment and their observational consequences by carrying out the first cosmological simulation that includes directly cosmic ray (CR) particles. Starting from cosmological initial conditions we follow the evolution of primary and secondary electrons (CRE), CR ions (CRI) and a passive magnetic field. CRIs and primary CREs are injected and accelerated at large scale structure shocks. Secondary CREs are continuously generated through inelastic p-p collisions. We include spatial transport, adiabatic expansion/compression, Coulomb collisions, bremsstrahlung, synchrotron (SE)and inverse Compton (IC) emission. We find that, from the perspective of cosmic shock energy and acceleration efficiency, the few detections of hard X-ray radiation excess could be explained in the framework of IC emission of primary CREs in clusters undergoing high accretion/merger phase. Instead, IC emission from both primary and secondary CREs accounts at most for a small fraction of the radiation excesses detected in the extreme-UV (except for the Coma cluster as reported by Bowyer et al.1999). Next, we calculate the SE after normalizing the magnetic field so that for a Coma-like cluster ^1/2~3 \muG. Our results indicate that the SE from secondary CREs reproduces several general properties of radio halos, including the recently found P_1.4GHz vs T relation, the morphology and polarization of the emitting region and, to some extent, the spectral index. Moreover, SE from primary CREs turns out sufficient to power extended regions resembling radio relics observed at the outskirts of clusters. Again we find striking resemblance between morphology, polarization and spectral index of our synthetic maps and those reported in the literature.Comment: emulateapj, 27 pages, 10 figures, 5 tables; ApJ in pres