18 research outputs found
The Formation and Evolution of the First Massive Black Holes
The first massive astrophysical black holes likely formed at high redshifts
(z>10) at the centers of low mass (~10^6 Msun) dark matter concentrations.
These black holes grow by mergers and gas accretion, evolve into the population
of bright quasars observed at lower redshifts, and eventually leave the
supermassive black hole remnants that are ubiquitous at the centers of galaxies
in the nearby universe. The astrophysical processes responsible for the
formation of the earliest seed black holes are poorly understood. The purpose
of this review is threefold: (1) to describe theoretical expectations for the
formation and growth of the earliest black holes within the general paradigm of
hierarchical cold dark matter cosmologies, (2) to summarize several relevant
recent observations that have implications for the formation of the earliest
black holes, and (3) to look into the future and assess the power of
forthcoming observations to probe the physics of the first active galactic
nuclei.Comment: 39 pages, review for "Supermassive Black Holes in the Distant
Universe", Ed. A. J. Barger, Kluwer Academic Publisher
Galaxy And Mass Assembly (GAMA): end of survey report and data release 2
The Galaxy And Mass Assembly (GAMA) survey is one of the largest contemporary spectroscopic surveys of low-redshift galaxies. Covering an area of ~286 deg^2 (split among five survey regions) down to a limiting magnitude of r < 19.8 mag, we have collected spectra and reliable redshifts for 238,000 objects using the AAOmega spectrograph on the Anglo-Australian Telescope. In addition, we have assembled imaging data from a number of independent surveys in order to generate photometry spanning the wavelength range 1 nm - 1 m. Here we report on the recently completed spectroscopic survey and present a series of diagnostics to assess its final state and the quality of the redshift data. We also describe a number of survey aspects and procedures, or updates thereof, including changes to the input catalogue, redshifting and re-redshifting, and the derivation of ultraviolet, optical and near-infrared photometry. Finally, we present the second public release of GAMA data. In this release we provide input catalogue and targeting information, spectra, redshifts, ultraviolet, optical and near-infrared photometry, single-component S\'ersic fits, stellar masses, H-derived star formation rates, environment information, and group properties for all galaxies with r < 19.0 mag in two of our survey regions, and for all galaxies with r < 19.4 mag in a third region (72,225 objects in total). The database serving these data is available at http://www.gama-survey.org/
Evolution of active galactic nuclei
[Abriged] Supermassive black holes (SMBH) lurk in the nuclei of most massive
galaxies, perhaps in all of them. The tight observed scaling relations between
SMBH masses and structural properties of their host spheroids likely indicate
that the processes fostering the growth of both components are physically
linked, despite the many orders of magnitude difference in their physical size.
This chapter discusses how we constrain the evolution of SMBH, probed by their
actively growing phases, when they shine as active galactic nuclei (AGN) with
luminosities often in excess of that of the entire stellar population of their
host galaxies. Following loosely the chronological developments of the field,
we begin by discussing early evolutionary studies, when AGN represented beacons
of light probing the most distant reaches of the universe and were used as
tracers of the large scale structure. This early study turned into AGN
"Demography", once it was realized that the strong evolution (in luminosity,
number density) of the AGN population hindered any attempt to derive
cosmological parameters from AGN observations directly. Following a discussion
of the state of the art in the study of AGN luminosity functions, we move on to
discuss the "modern" view of AGN evolution, one in which a bigger emphasis is
given to the physical relationships between the population of growing black
holes and their environment. This includes observational and theoretical
efforts aimed at constraining and understanding the evolution of scaling
relations, as well as the resulting limits on the evolution of the SMBH mass
function. Physical models of AGN feedback and the ongoing efforts to isolate
them observationally are discussed next. Finally, we touch upon the problem of
when and how the first black holes formed and the role of black holes in the
high-redshift universe.Comment: 75 pages, 35 figures. Modified version of the chapter accepted to
appear in "Planets, Stars and Stellar Systems", vol 6, ed W. Keel
(www.springer.com/astronomy/book/978-90-481-8818-5). The number of references
is limited upon request of the editors. Original submission to Springer: June
201
Music as a Manifestation of Life: Exploring Enactivism and the ‘Eastern Perspective’ for Music Education
The enactive approach to cognition is developed in the context of music and music education. I discuss how this embodied point of view affords a relational and bio-cultural perspective on music that decentres the Western focus on language, symbol and representation as the fundamental arbiters of meaning. I then explore how this ‘life-based’ approach to cognition and meaning-making offers a welcome alternative to standard Western academic approaches to music education. More specifically, I consider how the enactive perspective may aid in developing deeper ecological understandings of the transformative, extended and interpenetrative nature of the embodied musical mind; and thus help (re)connect students and teachers to the lived experience of their own learning and teaching. Following this, I examine related concepts associated with Buddhist psychology in order to develop possibilities for a contemplative music pedagogy. To conclude, I consider how an enactive-contemplative perspective may help students and teachers awaken to the possibilities of music education as ‘ontological education.’ That is, through a deeper understanding of ‘music as a manifestation of life’ rediscover their primordial nature as autopoietic and world-making creatures and thus engage more deeply with musicality as a means of forming richer and more compassionate relationships with their peers, their communities and the ‘natural’ and cultural worlds they inhabit
Galaxy And Mass Assembly (GAMA): Data Release 4 and the z < 0.1 total and z < 0.08 morphological galaxy stellar mass functions
In Galaxy And Mass Assembly Data Release 4 (GAMA DR4), we make available our full spectroscopic redshift sample. This includes 248 682 galaxy spectra, and, in combination with earlier surveys, results in 330 542 redshifts across five sky regions covering similar to 250 deg(2). The redshift density, is the highest available over such a sustained area, has exceptionally high completeness (95 per cent to r(KiDS) = 19.65 mag), and is well-suited for the study of galaxy mergers, galaxy groups, and the low redshift (z < 0.25) galaxy population. DR4 includes 32 value-added tables or Data Management Units (DMUs) that provide a number of measured and derived data products including GALEX, ESO KiDS, ESO VIKING, WISE, and HerschelSpace Observatory imaging. Within this release, we provide visual morphologies for 15 330 galaxies to z < 0.08, photometric redshift estimates for all 18 million objects to r(KiDS) similar to 25 mag, and stellar velocity dispersions for 111 830 galaxies. We conclude by deriving the total galaxy stellar mass function (GSMF) and its sub-division by morphological class (elliptical, compact-bulge and disc, diffuse-bulge and disc, and disc only). This extends our previous measurement of the total GSMF down to 10(6.75) M-circle dot h(70)(-2) and we find a total stellar mass density of rho(*) = (2.97 +/- 0.04) x 10(8) M-circle dot h(70) Mpc(-3) or Omega(*)=(2.17 +/- 0.03) x 10(-3) h(70)(-1). We conclude that at z < 0.1, the Universe has converted 4.9 +/- 0.1 per cent of the baryonic mass implied by big bang Nucleosynthesis into stars that are gravitationally bound within the galaxy population
Galaxy And Mass Assembly (GAMA): Data Release 4 and the z < 0.1 total and z < 0.08 morphological galaxy stellar mass functions
In Galaxy And Mass Assembly Data Release 4 (GAMA DR4), we make available our full spectroscopic redshift sample. This includes 248 682 galaxy spectra, and, in combination with earlier surveys, results in 330 542 redshifts across five sky regions covering ∼250 deg2. The redshift density, is the highest available over such a sustained area, has exceptionally high completeness (95 per cent to rKiDS = 19.65 mag), and is well-suited for the study of galaxy mergers, galaxy groups, and the low redshift (z < 0.25) galaxy population. DR4 includes 32 value-added tables or Data Management Units (DMUs) that provide a number of measured and derived data products including GALEX, ESO KiDS, ESO VIKING, WISE, and HerschelSpace Observatory imaging. Within this release, we provide visual morphologies for 15 330 galaxies to z < 0.08, photometric redshift estimates for all 18 million objects to rKiDS ∼ 25 mag, and stellar velocity dispersions for 111 830 galaxies. We conclude by deriving the total galaxy stellar mass function (GSMF) and its sub-division by morphological class (elliptical, compact-bulge and disc, diffuse-bulge and disc, and disc only). This extends our previous measurement of the total GSMF down to 106.75 M⊙h−270 and we find a total stellar mass density of ρ* = (2.97 ± 0.04) × 108 M⊙h70 Mpc−3 or Ω∗=(2.17±0.03)×10−3h−170. We conclude that at z < 0.1, the Universe has converted 4.9 ± 0.1 per cent of the baryonic mass implied by big bang Nucleosynthesis into stars that are gravitationally bound within the galaxy population
Does corporate reputation matter? Role of social media in consumer intention to purchase innovative food product
The exponential growth of the corporate reputation in food industry has resulted in innovations in every link of its supply chain. There have been studies that have characterized innovation in various industries from the perspective of technology, but far fewer in the area of corporate reputation, consumer perception, and intention towards innovations in food products. This research analyses the innovations in the food industry from the perspective of the consumer and provides a conceptual framework of food innovation stages. The study also investigates the relationship between corporate reputation and intention towards food innovation along with the other components of TPB model with an extension of social media engagement. The results from India and US samples confirm that social media engagement have a significant role to play in creating intention to purchase innovative food products. The study compares the US and Indian samples and identifies differences in subjective norms and perceived behavioural control