scholarly journals The Evolution of Field Galaxies

1996 ◽  
Vol 171 ◽  
pp. 209-216 ◽  
Author(s):  
S.J. Lilly ◽  
O. Le Fevre ◽  
F. Hammer ◽  
D. Crampton ◽  
D.J. Schade ◽  
...  
Keyword(s):  
Luminosity Function ◽  
Statistical Weight ◽  
List Type ◽  
Type Number ◽  
Local Populations ◽  
Redshift Surveys ◽  
Different Types ◽  
The Galaxy ◽  
Galaxy Population ◽  
Number Counts

During the late 1980's, successively deeper redshift surveys carried out with multi-object spectrographs on 4-m class telescopes produced growing evidence for evolution in the galaxy population. While some evolution had been expected from analysis of the galaxy number counts, the surprising indication from the first deep redshift surveys was that this appeared to involve moderate luminosity galaxies lying at moderate redshifts (Broadhurst et al. 1988, Colless et al. 1990, Cowie et al. 1991). However, while the results were suggestive, these early surveys suffered a number of significant problems that hampered their interpretation: (a)the samples were small, especially at the faintest levels, so the statistical weight was limited and analysis was based on crude parameterizations of the data such as the median redshift of samples;(b)the typical redshifts were small (z << 0.5), so that evolutionary effects could only be seen against “local” populations whose selection was often quite different - indeed the local luminosity function of galaxies is still poorly defined (Loveday et al. 1992, Marzke et al. 1994);(c)the samples were selected in the observed B-band, so that comparison with local samples was based on the poorly constrained ultraviolet properties and relative numbers of galaxies of different types.

The K-Band Luminosity Function of Galaxies

1998 ◽  
Vol 179 ◽  
pp. 278-280
Author(s):  
J. P. Gardner ◽  
R. M. Sharples ◽  
C. S. Frenk ◽  
B. E. Carrasco
Keyword(s):  
Luminosity Function ◽  
Near Infrared ◽  
Mass Function ◽  
Solar Mass ◽  
The Galaxy ◽  
Statistical Studies ◽  
The Absolute ◽  
Number Counts ◽  
Luminosity Evolution ◽  
K Band

The luminosity function of galaxies is central to many problems in cosmology, including the interpretation of faint number counts. The near-infrared provides several advantages over the optical for statistical studies of galaxies, including smooth and well-understood K-corrections and expected luminosity evolution. The K–band is dominated by near-solar mass stars which make up the bulk of the galaxy. The absolute K magnitude is a measure of the visible mass in a galaxy, and thus the K–band luminosity function is an observational counterpart of the mass function of galaxies.

scholarly journals The WIRCam Ultra Deep Survey (WUDS)

2018 ◽  
Vol 620 ◽  
pp. A51 ◽  
Author(s):  
R. Pelló ◽  
P. Hudelot ◽  
N. Laporte ◽  
Y. Mellier ◽  
H. J. McCracken ◽  
...  
Keyword(s):  
Luminosity Function ◽  
Formation Rate ◽  
Forthcoming Paper ◽  
Spectroscopic Studies ◽  
Photometric Redshifts ◽  
Near Ir ◽  
Luminosity Functions ◽  
The Galaxy ◽  
Deep Survey ◽  
Galaxy Population

The aim of this paper is to introduce the WIRCam Ultra Deep Survey (WUDS), a near-IR photometric survey carried out at the CFH Telescope in the field of the CFHTLS-D3 field (Groth Strip). WUDS includes four near-IR bands (Y, J, H and Ks) over a field of view of ∼400 arcmin2. The typical depth of WUDS data reaches between ∼26.8 in Y and J, and ∼26 in H and Ks (AB, 3σ in 1.3″ aperture), whereas the corresponding depth of the CFHTLS-D3 images in this region ranges between 28.6 and 29 in ugr, 28.2 in i and 27.1 in z (same S/N and aperture). The area and depth of this survey were specifically tailored to set strong constraints on the cosmic star formation rate and the luminosity function brighter or around L⋆ in the z ∼ 6 − 10 redshift domain, although these data are also useful for a variety of extragalactic projects. This first paper is intended to present the properties of the public WUDS survey in details: catalog building, completeness and depth, number counts, photometric redshifts, and global properties of the galaxy population. We have also concentrated on the selection and characterization of galaxy samples at z ∼ [4.5 − 7] in this field. For these purposes, we include an adjacent shallower area of ∼1260 arcmin2 in this region, extracted from the WIRCam Deep Survey (WIRDS), and observed in J, H and Ks bands. UV luminosity functions were derived at z ∼ 5 and z ∼ 6 taking advantage from the fact that WUDS covers a particularly interesting regime at intermediate luminosities, which allows a combined determination of M⋆ and Φ⋆ with increased accuracy. Our results on the luminosity function are consistent with a small evolution of both M⋆ and Φ⋆ between z = 5 and z = 6, irrespective of the method used to derive them, either photometric redshifts applied to blindly-selected dropout samples or the classical Lyman Break Galaxy color-preselected samples. Our results lend support to higher Φ⋆ determinations at z = 6 than usually reported. The selection and combined analysis of different galaxy samples at z ≥ 7 will be presented in a forthcoming paper, as well as the evolution of the UV luminosity function between z ∼ 4.5 and 9. WUDS is intended to provide a robust database in the near-IR for the selection of targets for detailed spectroscopic studies, in particular for the EMIR/GTC GOYA Survey.

Bilingualism and cognition: A focus on mechanisms

2014 ◽  
Vol 18 (1) ◽  
pp. 47-50 ◽  
Author(s):  
VIRGINIA VALIAN
Keyword(s):  
Young Adults ◽  
Executive Function ◽  
Executive Functions ◽  
List Type ◽  
Type Number ◽  
Old People ◽  
Daily Lives ◽  
Different Types ◽  
Children And Young Adults ◽  
Underlying Mechanisms

The goal of my keynote article, “Bilingualism and Cognition” (Valian, 2014), was to resolve the inconsistencies in effects of bilingualism on executive functions, whether the individuals were children, young adults, or old people. To summarize (and sharpen) my argument: 1.Especially in children and young adults, benefits of bilingualism for executive functions are not reliable. In old people, there are benefits for executive functions but contradictory results on delay of cognitive impairment, depending on whether studies are retrospective or prospective.2.All experiences that have benefits for executive functions and aging – and there are many – yield inconsistent effects. Bilingualism is not alone.3.Three reasons for inconsistencies in bilingualism and other experiences are: a.Executive function and cognitive reserve are broad cover terms for a variety of mechanisms, most of which are ill-understood. Because we mean different things by ‘executive function’ from one experiment to the next, we can both think we don't have an effect when we do and think we have an effect when we don’t.b.Tasks are impure: apparently similar tasks measure different aspects of executive function and measure other aspects of cognition as well. Because we lack a good analysis of tasks, we too often do not know what we are measuring. I encourage readers to examine the demos in the supplementary materials of the keynote article to see for themselves what the tasks are like.c.Individuals engage in many different activities that may be on a par with bilingualism in their benefits.4.Different types of bilingual experience are unlikely to explain the variability of findings, given the inconsistencies in extant data on varieties of bilingualism.5.There is a benefit of bilingualism, but bilingualism competes with other sources of benefits. Especially for children and young adults, whose daily lives are full of cognitively enriching and challenging experiences, we should expect variability in effects of being bilingual.6.The way forward is to focus on underlying mechanisms.

scholarly journals Beyond the Galaxy Luminosity Function

2004 ◽  
Vol 21 (4) ◽  
pp. 344-351 ◽  
Author(s):  
Simon Driver
Keyword(s):  
Surface Brightness ◽  
Luminosity Function ◽  
Large Scale ◽  
Evolutionary Processes ◽  
Multivariate Distributions ◽  
Independent Investigation ◽  
Current State ◽  
The Galaxy ◽  
Galaxy Population ◽  
Galaxy Luminosity Function

AbstractWith the advent of large-scale surveys (i.e. Legacy Surveys) it is now possible to start looking beyond the galaxy luminosity function (LF) to more detailed statistical representations of the galaxy population, i.e multivariate distributions. In this review I first summarise the current state-of-play of the B-band global and cluster LFs and then briefly present two promising bivariate distributions: the luminosity–surface brightness plane (LSP) and the colour–luminosity plane (CLP). In both planes galaxy bulges and galaxy disks form marginally overlapping but distinct distributions, indicating two key formation/evolutionary processes (presumably merger and accretion). Forward progress in this subject now requires the routine application of reliable bulge–disk decomposition codes to allow independent investigation of these two key components.

scholarly journals The Galaxy UV Luminosity Function Before the Epoch of Reionization

2015 ◽  
Vol 11 (S319) ◽  
pp. 33-33 ◽  
Author(s):  
Charlotte A. Mason ◽  
Michele Trenti ◽  
Tommaso Treu
Keyword(s):  
Dark Matter ◽  
Star Formation ◽  
Degrees Of Freedom ◽  
Luminosity Function ◽  
High Redshift ◽  
Dark Matter Halos ◽  
Redshift Surveys ◽  
The Galaxy ◽  
Mass Dependent

AbstractWe present a model for the evolution of the galaxy ultraviolet (UV) luminosity function (LF) where star formation is linked to the assembly of dark matter halos under the assumption of a mass dependent, but redshift independent, efficiency. With a calibration at a single redshift, and no further degrees of freedom, our model captures the evolution of the UV LF over all available observations (0≲ z ≲ 10). We make predictions for reionization and future high-redshift surveys with JWST and WFIRST.

scholarly journals Summary of a contribution on “the Magellanic Clouds”

1959 ◽  
Vol 10 ◽  
pp. 51-51
Author(s):  
M. W. Feast ◽  
A. D. Thackeray ◽  
A. J. Wesselink
Keyword(s):  
Magellanic Clouds ◽  
List Type ◽  
Type Number ◽  
The Galaxy

Combined spectroscopic and photo-electric observations of bright stars in the two Magellanic Clouds show that: 1)There is no marked difference between the stars observed in the two Clouds when compared with each other or with normal galactic supergiants, as judged by: (a)direct spectroscopic comparison,(b)Hertzsprung-Russell diagram,(c)U, B, V plot.2)Stars observed in both Clouds suffer a small amount of absorption, the precise amount depending on the intrinsic colours adopted. How much of the absorption takes place within the Clouds remains to be determined.3)A reddening path has been determined by comparison of Cloud stars (little reddened) and galactic supergiants (heavily reddened). The observations are consistent with a single reddening path and have not yet suggested any difference in the absorbing properties of dust in the Clouds and in the Galaxy. A conclusion on this latter point must await observations of heavily reddened stars in the Clouds.

scholarly journals C. Proper Motions and Radial Velocities

1955 ◽  
Vol 1 ◽  
pp. 33-42
Keyword(s):  
Stellar System ◽  
Radial Velocities ◽  
Detailed Account ◽  
List Type ◽  
Type Number ◽  
Proper Motions ◽  
Extensive Data ◽  
System A ◽  
The Galaxy

One of the most important fields for co-ordination in galactic research is the organization of programmes for proper motions and radial velocities. The need for accurate and more extensive data on stellar motions is strongly felt in connexion with the studies of the structure of the Galaxy and of the relation between the physical and the kinematical characteristics of the stars. Not long ago it seemed that meridian astronomy and photographic astrometry were rather remote from the main problems in astrophysics. It is realized now, that the study of stellar motions gives highly important information on the evolution of the stars and of the stellar system. A detailed account of the needs in this field, as discussed at the conference, follows: (1)propermotions: photographicastrometryoffaintstars

scholarly journals The Older Clusters in the Magellanic Clouds

1980 ◽  
Vol 85 ◽  
pp. 305-315 ◽  
Author(s):  
S.C.B. Gascoigne
Keyword(s):  
Globular Clusters ◽  
Magellanic Clouds ◽  
Parameter Family ◽  
List Type ◽  
Type Number ◽  
Cloud Clusters ◽  
The Galaxy ◽  
Long Time ◽  
The Subject ◽  
Two Parameter

We begin with Fig. 1, which somewhat aged though it may be still illustrates important aspects of the subject (Gascoigne 1971) (i)There is a clear division of cloud clusters into a blue and red group. The division corresponds to the mass around 2.51M⊙, at which core degeneracy first develops in stars approaching the giant branch. Such stars spend about three times as long on the giant branch and travel higher up it than the slightly heavier non-degenerate stars, and so dominate the colours of the clusters in which they occur.(ii)The red clusters are somewhat less luminous than the globular clusters in the galaxy. Freeman and Chun (1972) have shown from dynamic arguments that the cloud clusters are also less massive, by enough to keep the M/L ratios roughly the same as those in the galaxy.(iii)For a long time it has been taken that the blue clusters are young and the red clusters old. Thus the clouds present us with a truly two-parameter family of globular-like clusters, the parameters being of course age and abundance.

scholarly journals The faint-end of galaxy luminosity functions at the Epoch of Reionization

2017 ◽  
Vol 12 (S333) ◽  
pp. 52-55
Author(s):  
B. Yue ◽  
M. Castellano ◽  
A. Ferrara ◽  
A. Fontana ◽  
E. Merlin ◽  
...  
Keyword(s):  
Star Formation ◽  
Formation Process ◽  
Luminosity Function ◽  
Feedback Effects ◽  
Circular Velocity ◽  
Luminosity Functions ◽  
The Galaxy ◽  
Turn Over ◽  
Number Counts ◽  
Galaxy Luminosity Function

AbstractDuring the Epoch of Reionization (EoR), feedback effects reduce the efficiency of star formation process in small halos or even fully quench it. The galaxy luminosity function (LF) may then turn over at the faint-end. We analyze the number counts of z > 5 galaxies observed in the fields of four Frontier Fields (FFs) clusters and obtain constraints on the LF faint-end: for the turn-over magnitude at z ∼ 6, MUVT ≳-13.3; for the circular velocity threshold of quenching star formation process, vc* ≲ 47 km s−1. We have not yet found significant evidence of the presence of feedback effects suppressing the star formation in small galaxies.

scholarly journals Dynamical interpretations of the galactic center region

1979 ◽  
Vol 84 ◽  
pp. 383-392 ◽  
Author(s):  
Robert H. Sanders
Keyword(s):  
Mass Distribution ◽  
Central Region ◽  
Galactic Center ◽  
List Type ◽  
Type Number ◽  
Center Region ◽  
The Galaxy

I will define the central region of the Galaxy as being the inner four kiloparsecs. The distinguishing characteristics of this region are: 1)The dominance of a central spheroidal component in the mass distribution – a bulge.2)An apparent deficiency of gas, at least between radii of 500 pc and 4000 pc.3)High non-circular gas velocities. Now let us consider these characteristics in some detail.

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