A review of elliptical and disc galaxy structure, and modern scaling laws

A century ago, in 1911 and 1913, Plummer and then Reynolds introduced their models to describe the radial distribution of stars in `nebulae'. This article reviews the progress since then, providing both an historical perspective and a contemporary review of the stellar structure of bulges, discs and elliptical galaxies. The quantification of galaxy nuclei, such as central mass deficits and excess nuclear light, plus the structure of dark matter halos and cD galaxy envelopes, are discussed. Issues pertaining to spiral galaxies including dust, bulge-to-disc ratios, bulgeless galaxies, bars and the identification of pseudobulges are also reviewed. An array of modern scaling relations involving sizes, luminosities, surface brightnesses and stellar concentrations are presented, many of which are shown to be curved. These 'redshift zero' relations not only quantify the behavior and nature of galaxies in the Universe today, but are the modern benchmark for evolutionary studies of galaxies, whether based on observations, N-body-simulations or semi-analytical modelling. For example, it is shown that some of the recently discovered compact elliptical galaxies at 1.5 < z < 2.5 may be the bulges of modern disc galaxies.Comment: Condensed version (due to Contract) of an invited review article to appear in "Planets, Stars and Stellar Systems"(www.springer.com/astronomy/book/978-90-481-8818-5). 500+ references incl. many somewhat forgotten, pioneer papers. Original submission to Springer: 07-June-201

Deciphering the stem cell machinery as a basis for understanding the molecular mechanism underlying reprogramming

Stem cells provide fascinating prospects for biomedical applications by combining the ability to renew themselves and to differentiate into specialized cell types. Since the first isolation of embryonic stem (ES) cells about 30 years ago, there has been a series of groundbreaking discoveries that have the potential to revolutionize modern life science. For a long time, embryos or germ cell-derived cells were thought to be the only source of pluripotency—a dogma that has been challenged during the last decade. Several findings revealed that cell differentiation from (stem) cells to mature cells is not in fact an irreversible process. The molecular mechanism underlying cellular reprogramming is poorly understood thus far. Identifying how pluripotency maintenance takes place in ES cells can help us to understand how pluripotency induction is regulated. Here, we review recent advances in the field of stem cell regulation focusing on key transcription factors and their functional interplay with non-coding RNAs

Structure of bright 2MASS galaxies: 2D fits to the K-S-band surface brightness profiles

The unprecedented sky coverage and photometric uniformity of the Two Micron All Sky Survey (2MASS) provides a rich resource for obtaining a detailed understanding of the galaxies populating our local (z\u3c0.1) Universe. A full characterization of the physical structure of nearby galaxies is essential for theoretical and observational studies of galaxy evolution and structure formation. We have begun a quantified description of the internal structure and morphology of 10,000 bright (10\u3c11) 2MASS galaxies through multi-component model fits to the 2D surface brightness profiles using GIM2D. From our initial Monte Carlo tests on 77 galaxies drawn at random from the RC3, we find that the model derived structural parameter errors due to sky uncertainies are typically less than 10%

Large scale structure in the two micron all sky survey

The unprecedented sky coverage and photometric uniformity of the Two Micron All Sky Survey (2MASS) [1] provides a rich resource for obtaining an understanding of the galaxies populating the local Universe. Characterizing the large-scale clustering distribution is important for theoretical studies of structure formation. 2MASS offers an all-sky view at two microns, unbiased by young stellar light and minimally affected by dust. We use 2MASS to measure the clustering dipole in the Ks band and compare this to the velocity of the Local Group as measured by the CMB dipole [2]. We also measure the angular correlation function and from this infer the K-band three dimensional power spectrum [3]

Large scale structure in the two micron all sky survey

The unprecedented sky coverage and photometric uniformity of the Two Micron All Sky Survey (2MASS) [1] provides a rich resource for obtaining an understanding of the galaxies populating the local Universe. Characterizing the large-scale clustering distribution is important for theoretical studies of structure formation. 2MASS offers an all-sky view at two microns, unbiased by young stellar light and minimally affected by dust. We use 2MASS to measure the clustering dipole in the Ks band and compare this to the velocity of the Local Group as measured by the CMB dipole [2]. We also measure the angular correlation function and from this infer the K-band three dimensional power spectrum [3]

The clustering dipole of the local universe from the Two Micron All Sky Survey

The unprecedented sky coverage and photometric uniformity of the Two Micron All Sky Survey (2MASS) provides a rich resource for investigating the galaxies populating the local universe. A full characterization of the large-scale clustering distribution is important for theoretical studies of structure formation. 2MASS offers an all-sky view of the local galaxy population at 2.15 μm, unbiased by young stellar light and minimally affected by dust. We use 2MASS to map the local distribution of galaxies, identifying the largest structures in the nearby universe. The inhomogeneity of these structures causes an acceleration on the Local Group of galaxies, which can be seen in the dipole of the cosmic microwave background (CMB). We find that the direction of the 2MASS clustering dipole is 16° from the CMB dipole, confirming that the local galaxy distribution accelerates the Local Group. From the magnitude of the dipole, we find a value of the linear bias parameter b = 1.06 ± 0.17 in the Ks band. Thus, the linear bias parameter of Ks-selected galaxies is similar to the bias parameter found in other wave bands

Structure of bright 2MASS galaxies: 2D fits to the K-S-band surface brightness profiles

The unprecedented sky coverage and photometric uniformity of the Two Micron All Sky Survey (2MASS) provides a rich resource for obtaining a detailed understanding of the galaxies populating our local (z\u3c0.1) Universe. A full characterization of the physical structure of nearby galaxies is essential for theoretical and observational studies of galaxy evolution and structure formation. We have begun a quantified description of the internal structure and morphology of 10,000 bright (10\u3c11) 2MASS galaxies through multi-component model fits to the 2D surface brightness profiles using GIM2D. From our initial Monte Carlo tests on 77 galaxies drawn at random from the RC3, we find that the model derived structural parameter errors due to sky uncertainies are typically less than 10%

The galaxy angular correlation functions and power spectrum from the Two Micron All Sky Survey

We calculate the angular correlation function of galaxies in the Two Micron All Sky Survey. We minimize the possible contamination by stars, dust, seeing, and sky brightness by studying their cross correlation with galaxy density and limiting the galaxy sample accordingly. We measure the correlation function at scales between 1\u27 \u3c θ \u3c 18° using a half-million galaxies. We find that a best-fit power law to the correlation function has a slope of -0.79 ± 0.02 and an amplitude at 1° of 0.10 ± 0.01 in the range 1\u27-2fdg5. However, there are statistically significant oscillations around this power law. The largest oscillation occurs at about 0fdg8, corresponding to 700 h-1 kpc at the median redshift of our survey, as expected in halo occupation distribution descriptions of galaxy clustering. In addition, there is a break in the power-law shape of the correlation function at θ \u3e 2fdg5. Our results are in good agreement with other measurements of the angular correlation function. We invert the angular correlation function using singular value decomposition to measure the three-dimensional power spectrum and find that it too is in good agreement with previous measurements. A dip seen in the power spectrum at small wavenumber k is statistically consistent with cold dark matter (CDM) type power spectra. A fit of CDM-type power spectra in the linear regime (k \u3c 0.15 h Mpc-1) gives constraints of Ωmh = 0.13 ± 0.07 and σ8 = 1.0 ± 0.09 for a spectral index of 1.0. This suggests a Ks-band linear bias of 1.1 ± 0.2. These measurements are in good agreement with other measurements of the power spectrum on linear scales. On small scales the power-law shape of our power spectrum is shallower than that derived for the Sloan Digital Sky Survey. This may imply a biasing for these different galaxies that could be either waveband- or luminosity-dependent. The power spectrum derived here in combination with the results from other surveys can be used to constrain models of galaxy formation