The Panchromatic Starburst Intensity Limit At Low And High Redshift

The integrated bolometric effective surface brightness S_e distributions of starbursts are investigated for samples observed in 1. the rest frame ultraviolet (UV), 2. the far-infrared and H-alpha, and 3. 21cm radio continuum emission. For the UV sample we exploit a tight empirical relationship between UV reddening and extinction to recover the bolometric flux. Parameterizing the S_e upper limit by the 90th percentile of the distribution, we find a mean S_{e,90} = 2.0e11 L_{sun}/kpc^2 for the three samples, with a factor of three difference between the samples. This is consistent with what is expected from the calibration uncertainties alone. We find little variation in S_{e,90} with effective radii for R_e ~ 0.1 - 10 kpc, and little evolution out to redshifts z ~ 3. The lack of a strong dependence of S_{e,90} on wavelength, and its consistency with the pressure measured in strong galactic winds, argue that it corresponds to a global star formation intensity limit (\dot\Sigma_{e,90} ~ 45 M_{sun}/kpc^2/yr) rather than being an opacity effect. There are several important implications of these results: 1. There is a robust physical mechanism limiting starburst intensity. We note that starbursts have S_e consistent with the expectations of gravitational instability models applied to the solid body rotation portion of galaxies. 2. Elliptical galaxies and spiral bulges can plausibly be built with maximum intensity bursts, while normal spiral disks can not. 3. The UV extinction of high-z galaxies is significant, implying that star formation in the early universe is moderately obscured. After correcting for extinction, the observed metal production rate at z ~ 3 agrees well with independent estimates made for the epoch of elliptical galaxy formation.Comment: 31 pages Latex (aas2pp4.sty,psfig.sty), 9 figures, accepted for publication in the Astronomical Journa

The Panchromatic Starburst Intensity Limit at Low and High Redshift

The integrated bolometric effective surface brightness S distributions of starbursts are investigated for samples observed in (1) the rest frame ultraviolet (UV), (2) the far-infrared and Hα, and (3) 21 cm radio continuum emission. For the UV sample we exploit a tight empirical relationship between UV reddening and extinction to recover the bolometric flux. Parameterizing the S upper limit by the 90th percentile of the distribution, we find a mean S = 2.0×10 L⊙kpc for the three samples, with a factor of 3 difference between the samples. This is consistent with what is expected from the calibration uncertainties alone. We find little variation in S with effective radii for R ∼0.1-10 kpc, and little evolution out to redshifts z≈3. The lack of a strong dependence of S on wavelength, and its consistency with the pressure measured in strong galactic winds, argue that it corresponds to a global star formation intensity limit (Σ ∼45. sript M sign⊙ kpc yr ) rather than being an opacity effect. There are several important implications of these results: (1) There is a robust physical mechanism limiting starburst intensity. We note that starbursts have S consistent with the expectations of gravitational instability models applied to the solid body rotation portion of galaxies. (2) Elliptical galaxies and spiral bulges can plausibly be built with maximum intensity bursts, while normal spiral disks cannot. (3) The UV extinction of high-z galaxies is significant, implying that star formation in the early universe is moderately obscured. After correcting for extinction, the observed metal production rate at z∼3 agrees well with independent estimates made for the epoch of elliptical galaxy formation. © 1997 American Astronomical Society. e e e,90 e,90 e e,90 e,90 e 11 -2 -2 -

Optical Morphologies of Millijansky Radio Galaxies Observed by HST and in the VLA FIRST Survey

We report on a statistical study of the 51 radio galaxies at the millijansky flux level from the Faint Images of the Radio Sky at Twenty centimeters, including their optical morphologies and structure obtained with the Hubble Space Telescope. Our optical imaging is significantly deeper (~2 mag) than previous studies with the superior angular resolution of space-based imaging. We that find 8/51 (16%) of the radio sources have no optically identifiable counterpart to AB~24 mag. For the remaining 43 sources, only 25 are sufficiently resolved in the HST images to reliably assign a visual classification: 15 (60%) are elliptical galaxies, 2 (8%) are late-type spiral galaxies, 1 (4%) is an S0, 3 (12%) are point-like objects (quasars), and 4 (16%) are merger systems. We find a similar distribution of optical types with measurements of the Sersic index. The optical magnitude distribution of these galaxies peaks at I~20.7+-0.5 AB mag, which is ~3 mag brighter than the depth of our typical HST field and is thus not due to the WFPC2 detection limit. This supports the luminosity-dependent density evolutionary model, where the majority of faint radio galaxies typically have L*-optical luminosities and a median redshift of z~0.8 with a relatively abrupt redshift cut-off at z>~2. We discuss our results in the context of the evolution of elliptical galaxies and active galactic nuclei.Comment: 20 pages, 8 figures, 51 galaxy images, and 5 tables. Uses emulateapj.cls and natbib.sty. Accepted to ApJS. High resolution images are available upon reques

The evolution of Radio Loud Quasar host galaxies: AO observations at z = 3

We report on ESO--VLT adaptive optics imaging of one radio-loud quasar at z $\sim$ 3. In spite of the large distance of the object we are able to detect its surrounding extended nebulosity the properties of which are consistent with an underlying massive galaxy of M$_K$ $\sim$ --27 and effective radius R$_e$ = 7 kpc. As far as we know this is the clearest detection of a radio loud quasar host at high redshift. The host luminosity is indicative of the existence of massive spheroids even at this early cosmic epoch. The host luminosity is about 1 magnitude fainter than the expected value based on the average trend of the host galaxies of RLQ at lower redshift. The result, which however is based on a single object, suggests that at z $\sim$ 3 there is a deviation from a luminosity--redshift dependence regulated only by passive evolution.Comment: 6 pages, 3 figures, TeX uses elsart.cls, from workshop "QSO Host Galaxies: Evolution and Environment" (Univ. Leiden, Aug. 22-26, 2005

The living and the dead; an investigation into the status of erasure within the floor of Bath Abbey

The floor of Bath Abbey offers a singular test of authenticity. Nineteenth century repairs and additions caused horizontal grave markers, which comprise the majority of the Abbey’s floor, to become separated from the burial sites they were intended to memorialize. A century and a half of further occupation has had the effect of removing many inscriptions as surfaces are worn smooth. The result is a patchwork of unintended edits and accidental poetry. This paper explores the notions of authenticity, essence, memorial and erasure as they pertain to the Abbey floor, in particular with regard to the role the body plays in inhabiting/eroding the floor—from both above and below. The author argues that the stones which are most out of place or worn to a state of erasure are no less authentic than their intact equivalents, but that they can be considered to have moved to another state of authenticity rich in resonance and meaning. This paper, in short, is a defense of erasure and that erosion through occupation may be considered a form of social memory; indeed, the marks of walking become the inscription. In other words, the undesigned (erasure, the cutting and repositioning of ledger stones, the missing inscriptions) becomes considered not as a form of dirt but as the positive traces of on-going and meaningful occupation

Marketing, the past and corporate heritage

Argues for a more expansive conceptualisation of the past’s relevance in, and for, marketing. Such a differentiated approach to the past is pregnant with possibilities in terms of advancing scholarship apropos temporal agency in marketing along with consumption practices. Symptomatic of this perspective is the increased mindfulness of the rich palate of past-related concepts. Significantly, the corporate heritage notion - because of its omni-temporal nature - represents a distinct and meaningful vector on the past by coalescing the past, present and future into a new type of temporality. As such, the authors reason this expansive conceptualisation of ‘the past-in-marketing’ is both timely and efficacious. Whilst sensitive of the importance of the historical method in marketing and the history of marketing scholarship and practice per se. This broader marketing approach to and of the past highlights the ideational and material manifestations of the past-in-the-present and an envisaged past-in-the future

A companion to a quasar at redshift 4.7

There is a growing consensus that the emergence of quasars at high redshifts is related to the onset of galaxy formation, suggesting that the detection of concentrations of gas accompanying such quasars should provide clues about the early history of galaxies. Quasar companions have been recently identified at redshifts up to $z \approx 3$. Here we report observations of Lyman-$\alpha$ emission (a tracer of ionised hydrogen) from the companion to a quasar at $z$=4.702, corresponding to a time when the Universe was less than ten per cent of its present age. We argue that most of the emission arises in a gaseous nebula that has been photoionised by the quasar, but an additional component of continuum light -perhaps quasar light scattered from dust in the companion body, or emission from young stars within the nebula- appears necessary to explain the observations. These observations may be indicative of the first stages in the assembly of galaxy-sized structures.Comment: 8 pages, 4 figures, plain LaTeX. Accepted for publication in Natur

The Nature of Compact Galaxies in the Hubble Deep Field (II): Spectroscopic Properties and Implications for the Evolution of the Star Formation Rate Density of the Universe

We present a spectroscopic study of 51 compact field galaxies with redshifts z < 1.4 and apparent magnitudes I < 23.74 in the flanking fields of the Hubble Deep Field. These galaxies are compact in the sense that they have small apparent half-light radii (r_e < 0.5 arcsec) and high surface brightnesses (SB_e < 22.2 mag arcsec^-2). The spectra, taken at the Keck telescope, show emission lines in 88% of our sample, and only absorption lines in the remaining 12%. Emission-line profiles are roughly Gaussian with velocity widths that range from the measurement limit of sigma = 35 km s^-1 to 150 km s^-1. Rest-frame [OII]3727 equivalent widths range from 5A to 94A , yielding star formation rates (SFR) of 0.1 to 14 M yr^-1. The analysis of various line diagnostic diagrams reveals that 60% of compact emission-line galaxies have velocity widths, excitations, Hbeta luminosities, SFRs, and mass-to-light ratios characteristic of young star-forming HII galaxies. The remaining 40% form a more heterogeneous class of evolved starbursts, similar to local starburst disk galaxies. We find that, although the compact galaxies at z>0.7 have similar SFRs per unit mass to those at z<0.7, they are on average 10 times more massive. Our sample implies a lower limit for the global comoving SFR density of 0.004 M yr^-1 Mpc^-3 at z = 0.55, and 0.008 M yr^-1 Mpc^-3 at z = 0.85 (assuming Salpeter IMF, Ho = 50 km s^-1 Mpc^-1, and qo = 0.5). These values, when compared to estimates for a sample of local compact galaxies selected in a similar fashion, support a history of the universe in which the SFR density declines by a factor 10 from z = 1 to today.Comment: LaTeX, 38 pages, 2 tables, 10 postscript figures. Accepted for publication in the Astrophysical Journa

Deep 1.1 mm-wavelength imaging of the GOODS-South field by AzTEC/ASTE -- II. Redshift distribution and nature of the submillimetre galaxy population

We report the results of the counterpart identification and a detailed analysis of the physical properties of the 48 sources discovered in our deep 1.1mm wavelength imaging survey of the GOODS-South field using the AzTEC instrument on the Atacama Submillimeter Telescope Experiment (ASTE). One or more robust or tentative counterpart candidate is found for 27 and 14 AzTEC sources, respectively, by employing deep radio continuum, Spitzer MIPS & IRAC, and LABOCA 870 micron data. Five of the sources (10%) have two robust counterparts each, supporting the idea that these galaxies are strongly clustered and/or heavily confused. Photometric redshifts and star formation rates (SFRs) are derived by analyzing UV-to-optical and IR-to-radio SEDs. The median redshift of z~2.6 is similar to other earlier estimates, but we show that 80% of the AzTEC-GOODS sources are at z>2, with a significant high redshift tail (20% at z>3.3). Rest-frame UV and optical properties of AzTEC sources are extremely diverse, spanning 10 magnitude in the i- and K-band photometry with median values of i=25.3 and K=22.6 and a broad range of red colour (i-K=0-6). These AzTEC sources are some of the most luminous galaxies in the rest-frame optical bands at z>2, with inferred stellar masses of (1-30) x 10^{10} solar masses and UV-derived star formation rates of SFR(UV) > 10-1000 solar masses per year. The IR-derived SFR, 200-2000 solar masses per year, is independent of redshift or stellar mass. The resulting specific star formation rates, SSFR = 1-100 per Gyr, are 10-100 times higher than similar mass galaxies at z=0, and they extend the previously observed rapid rise in the SSFR with redshift to z=2-5. These galaxies have a SFR high enough to have built up their entire stellar mass within their Hubble time. We find only marginal evidence for an AGN contribution to the near-IR and mid-IR SEDs. (abridged)Comment: 31 pages including 14 figures, accepted for publication in the MNRAS. A higher quality Figure 1 is also included as Figure1.jp