The local space density of dwarf galaxies

We estimate the luminosity function of field galaxies over a range of ten magnitudes (-22 < M_{B_J} < -12 for H_0 = 100 km/s/Mpc) by counting the number of faint APM galaxies around Stromlo-APM redshift survey galaxies at known distance. The faint end of the luminosity function rises steeply at M_{B_J} \approx -15, implying that the space density of dwarf galaxies is at least two times larger than predicted by a Schechter function with flat faint-end slope. Such a high abundance of dwarf galaxies at low redshift can help explain the observed number counts and redshift distributions of faint galaxies without invoking exotic models for galaxy evolution.Comment: 20 pages, 5 included postscript figures, uses AAS LaTex macros. Accepted for publication in the Astrophysical Journal. Two figures and associated discussion added; results and conclusions unchange

Two-Dimensional Topology of the 2dF Galaxy Redshift Survey

We study the topology of the publicly available data released by the 2dFGRS. The 2dFGRS data contains over 100,000 galaxy redshifts with a magnitude limit of b_J=19.45 and is the largest such survey to date. The data lie over a wide range of right ascension (75 degree strips) but only within a narrow range of declination (10 degree and 15 degree strips). This allows measurements of the two-dimensional genus to be made. The NGP displays a slight meatball shift topology, whereas the SGP displays a bubble like topology. The current SGP data also have a slightly higher genus amplitude. In both cases, a slight excess of overdense regions are found over underdense regions. We assess the significance of these features using mock catalogs drawn from the Virgo Consortium's Hubble Volume LCDM z=0 simulation. We find that differences between the NGP and SGP genus curves are only significant at the 1 sigma level. The average genus curve of the 2dFGRS agrees well with that extracted from the LCDM mock catalogs. We compare the amplitude of the 2dFGRS genus curve to the amplitude of a Gaussian random field with the same power spectrum as the 2dFGRS and find, contradictory to results for the 3D genus of other samples, that the amplitude of the GRF genus curve is slightly lower than that of the 2dFGRS. This could be due to a a feature in the current data set or the 2D genus may not be as sensitive as the 3D genus to non-linear clustering due to the averaging over the thickness of the slice in 2D. (Abridged)Comment: Submitted to ApJ A version with Figure 1 in higher resolution can be obtained from http://www.physics.drexel.edu/~hoyle

Introduction

Introduction to issu

Black gold, the scenic rim and the theory of the firm: implications of the exploration for coal and coal seam gas in the scenic rim of south east Queensland for the evolving theory of the firm

The implicit social contract between Australian society, government and business does not provide an environment in which communities within the Scenic Rim of South East Queensland believe that their values and development desires are adequately protected. Consequently, the communities are insisting that their local values, particularly regarding the environment, good quality agricultural land and water, be recognised and respected by both governments and mining companies. This changing social contract has significant implications for: (i) the nature of the engagement between communities and mining companies that might result in a more equitable distribution of both the benefits and disadvantages of mining; and; (ii) the evolving theory of the firm. This change applies particularly to those theories that focus on the reasons for existence of corporations, their relationship with external stakeholders and the values placed on corporate resources. The thesis is based on qualitative research into the values and development desires of communities and companies active within the Scenic Rim of South East Queensland and draws heavily on archival material available from both Australian and Queensland government sources. A model for evaluating the utility of theories of the firm is developed and twelve existing groups of theory are analysed. Few of the theories meet many of the criteria proposed in the model (particularly regarding tests of their validity and reliability) and characteristics of an enhanced theory of the firm applicable to all companies are identified

TASS Mark IV Photometric Survey of the Northern Sky

The Amateur Sky Survey (TASS) is a loose confederation of amateur and professional astronomers. We describe the design and construction of our Mark IV systems, a set of wide-field telescopes with CCD cameras which take simultaneous images in the $V$ and $I_C$ passbands. We explain our observational procedures and the pipeline which processes and reduces the images into lists of stellar positions and magnitudes. We have compiled a large database of measurements for stars in the northern celestial hemisphere with $V$-band magnitudes in the range 7 < V < 13. This paper describes data taken over the four-year period starting November, 2001. One of our results is a catalog of repeated measurements on the Johnson-Cousins system for over 4.3 million stars.Comment: Accepted for publication in December, 2006, issue of PASP. 44 pages including 20 figures. Patches catalog available at http://spiff.rit.edu/tass/patches

Testing the Hubble Law with the IRAS 1.2 Jy Redshift Survey

We test and reject the claim of Segal et al. (1993) that the correlation of redshifts and flux densities in a complete sample of IRAS galaxies favors a quadratic redshift-distance relation over the linear Hubble law. This is done, in effect, by treating the entire galaxy luminosity function as derived from the 60 micron 1.2 Jy IRAS redshift survey of Fisher et al. (1995) as a distance indicator; equivalently, we compare the flux density distribution of galaxies as a function of redshift with predictions under different redshift-distance cosmologies, under the assumption of a universal luminosity function. This method does not assume a uniform distribution of galaxies in space. We find that this test has rather weak discriminatory power, as argued by Petrosian (1993), and the differences between models are not as stark as one might expect a priori. Even so, we find that the Hubble law is indeed more strongly supported by the analysis than is the quadratic redshift-distance relation. We identify a bias in the the Segal et al. determination of the luminosity function, which could lead one to mistakenly favor the quadratic redshift-distance law. We also present several complementary analyses of the density field of the sample; the galaxy density field is found to be close to homogeneous on large scales if the Hubble law is assumed, while this is not the case with the quadratic redshift-distance relation.Comment: 27 pages Latex (w/figures), ApJ, in press. Uses AAS macros, postscript also available at http://www.astro.princeton.edu/~library/preprints/pop682.ps.g

Mg II Absorber Number Density at z~0.05: Implications for Omega_DLA Evolution

An unbiased sample of 147 quasar/AGN spectra, obtained with the FOS/HST, has been searched for intervening MgII absorbers over the redshift range 0<z<0.15. The total redshift path searched is 18.8, with the survey being 80% complete to a 5-sigma rest-frame equivalent width, W_r(2796), of 0.6 Ang. Main results of this work are: [1] Four systems were found, with a mean redshift of =0.06, yielding a redshift number density dN/dz=0.22(+0.12)(-0.09) for absorbers with W_r(2796)>0.6 Ang. This is consistent with the value expected if these systems do not evolve from higher redshifts (z=2.2). [2] No systems with W_r(2796)<0.6 Ang were found. It is a 2-sigma result to have a null detection of smaller W_r(2796) systems. If this implies a turnover in the low W_r(2796) region of the equivalent width distribution at z~0, then there is at least a 25% reduction in the average galaxy gas cross section from z<0.2 galaxies. [3] These systems have strong FeII absorption and are good candidates for damped Ly-alpha absorbers DLAs (see Rao & Turnshek 2000, ApJS, 130, 1). This translates to a redshift number density of dN/dz=0.08(+0.09)(-0.05) for DLAs at z~0. In tandem with the data analyzed by Rao & Turnshek, these results indicate that the redshift number density of DLAs does not evolve from z~4 to z~0. If the HI mass function does not evolve from z~0.5 to z~0, then the cosmological HI mass density is also deduced to not evolve from z~4 to z~0. These z~0 results for MgII absorption-selected DLAs are at odds with those based upon 21-cm emission from HI galaxies by a factor of five to six.Comment: 23 pages, 7 Figures, accepted to ApJ. Replaced version includes additional figures and tables and substantial modifications to the tex

Occurrence statistics of cold, streaming ions in the near‐Earth magnetotail: Survey of Polar‐TIDE observations

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95347/1/jgra17705.pd

Evidence for the Evolution of Young Early-Type Galaxies in the GOODS/CDF-S Field

We have developed an efficient photometric technique for identifying young early-type galaxy candidates using a combination of photometric redshifts, spectral-type classification, and optical/near-infrared colors. Applying our technique to the GOODS HST/ACS and VLT/ISAAC data we have selected a complete and homogeneous sample of young elliptical candidates among early-type field galaxies. The distribution of structural parameters for these candidates shows that their selection, which is based on early spectral types, is fully consistent with early morphological types. We investigate the evolution of their luminosities and colors as a function of redshift and galaxy mass and find evidence for an increasing starburst mass fraction in these young early-type galaxy candidates at higher redshifts, which we interpret in terms of massive field galaxies experiencing more massive/intense starbursts at higher redshifts. Moreover, we find indications for a systematically larger young elliptical fraction among sub-L*/2 early-type galaxies compared to their brighter counterparts. The total fraction among the field early-type galaxies increases with redshift, irrespective of galaxy luminosity. Our results are most consistent with galaxy formation scenarios in which stars in massive early-type field galaxies are assembled earlier than in their low-mass counterparts.Comment: 11 pages, 10 figures, accepted for publication in A