1,107 research outputs found
Taxation and Corporate Financial Policy
A model of corporate financial policy (debt-equity ratios and dividend payout rates) is included in the Harberger general equilibrium model of incidence of the corporate income tax. Illustrative calculations of the distortions of financial policy and increases in risk premiums induced by the corporate tax are provided. Because risk premiums on corporate securities would be reduced, eliminating the corporate tax or integrating it into the personal tax would increase the income of non-corporate investors relatively more than that of investors in corporate securities, and is therefore less regressive than is commonly thought.
Unveiling the nature of bright z ~ 7 galaxies with the Hubble Space Telescope
We present new Hubble Space Telescope/Wide Field Camera 3 imaging of 25
extremely luminous (-23.2 < M_ UV < -21.2) Lyman-break galaxies (LBGs) at z ~
7. The sample was initially selected from 1.65 deg^2 of ground-based imaging in
the UltraVISTA/COSMOS and UDS/SXDS fields, and includes the extreme Lyman-alpha
emitters, `Himiko' and `CR7'. A deconfusion analysis of the deep Spitzer
photometry available suggests that these galaxies exhibit strong rest-frame
optical nebular emission lines (EW_0(H_beta + [OIII]) > 600A). We find that
irregular, multiple-component morphologies suggestive of clumpy or merging
systems are common (f_multi > 0.4) in bright z ~ 7 galaxies, and ubiquitous at
the very bright end (M_UV < -22.5). The galaxies have half-light radii in the
range r_1/2 ~ 0.5-3 kpc. The size measurements provide the first determination
of the size-luminosity relation at z ~ 7 that extends to M_UV ~ -23. We find
the relation to be steep with r_1/2 ~ L^1/2. Excluding clumpy, multi-component
galaxies however, we find a shallower relation that implies an increased
star-formation rate surface density in bright LBGs. Using the new, independent,
HST/WFC3 data we confirm that the rest-frame UV luminosity function at z ~ 7
favours a power-law decline at the bright-end, compared to an exponential
Schechter function drop-off. Finally, these results have important implications
for the Euclid mission, which we predict will detect > 1000 similarly bright
galaxies at z ~ 7. Our new HST imaging suggests that the vast majority of these
galaxies will be spatially resolved by Euclid, mitigating concerns over dwarf
star contamination.Comment: 26 pages, 11 figures and 5 tables. Updated to match MNRAS accepted
versio
Morphology and Redshifts of Extremely Red Galaxies in the GOODS/CDFS deep ISAAC field
We present the photometric redshift distribution of a sample of 198 Extremely
Red Galaxies (ERGs) with Ks3.92 (Vega), selected by Roche et al.
in 50.4 sq. arcmin of the Chandra Deep Field South (CDFS). The sample has been
obtained using ISAAC-VLT and ACS-HST GOODS public data. We also show the
results of a morphological study of the 72 brightest ERGs in the z band (z<25,
AB).Comment: 2 pages, 2 figures. To appear in the proceedings of the ESO/USM/MPE
Workshop "Multiwavelength Mapping of Galaxy Formation and Evolution", Venice,
October 13-16, 200
The Evolution of 3CR Radio Galaxies from z=1
We present the results of a comprehensive re-analysis of the images of a
virtually complete sample of 28 powerful 3CR radio galaxies with redshifts
0.6<z<1.8 from the HST archive. Using a two-dimensional modelling technique we
have derived scalelengths and absolute magnitudes for a total of 16 3CR
galaxies with a median redshift of z=0.8. Our results confirm the basic
conclusions of Best, Longair & R\"{o}ttgering (1997, 1998) in that we also find
z=1 3CR galaxies to be massive, well-evolved ellipticals, whose infrared
emission is dominated by starlight. However, we in fact find that the
scalelength distribution of 3CR galaxies at z \simeq 1 is completely
indistinguishable from that derived for their low-redshift counterparts from
our own recently-completed HST study of AGN hosts at z \simeq 0.2. There is
thus no evidence that 3CR radio galaxies at z \simeq 1 are dynamically
different from 3CR galaxies at low redshift. Moreover, for a 10-object
sub-sample we have determined the galaxy parameters with sufficient accuracy to
demonstrate, for the first time, that the z \simeq 1 3CR galaxies follow a
Kormendy relation which is indistinguishable from that displayed by
low-redshift ellipticals if one allows for purely passive evolution. The
implied rather modest level of passive evolution since z \simeq 1 is consistent
with that predicted from spectrophotometric models provided one assumes a high
formation redshift (z \ge 4) within a low-density Universe. We conclude that
there is no convincing evidence for significant dynamical evolution among 3CR
galaxies in the redshift interval 0<z<1, and that simple passive evolution
remains an acceptable interpretation of the K-z relation for powerful radio
galaxies.Comment: 10 pages, 5 figures, minor changes, accepted for publication in MNRA
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