• The Bulletin of The Korean Astronomical Society
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• v.38 no.1
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• pp.38.1-38.1
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• 2013

We present observational estimation of the infrared (IR) luminosity function (LF) of local (z < 0.3) star-forming (SF) galaxies derived from the AKARI NEP-Wide samples. We made an analysis of the NEP-Wide data with optical spectroscopic information allowing an accurate determination of luminosity function. Spectroscopic redshifts for about 1650 objects were obtained with MMT/Hectospec and WIYN/Hydra, and the median redshifts is about 0.22. To measure the contribution of SF galaxies to the luminosity function, we excluded AGN sample by comparing their SEDs with various model template. Spectroscopic redshifts and the AKARI's continuous filter coverage in the mid-IR (MIR) wavelength (2 ~ 25 micron) enable us to avoid large uncertainties from the mid-IR SED of galaxies and corresponding k-corrections. The 8-micron luminosity function shows a good agreement with the previous works in the bright-end, whereas it seems not easy to constrain the faint-end slope. The comparison with the results of the NEP-Deep data (Goto et al. 2010) suggests the luminosity evolution to the higher redshifts, which is consistent with the down-sizing evolutionary pattern of galaxies.

• Journal of The Korean Astronomical Society
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• v.21 no.1
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• pp.37-55
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• 1988

Combining the luminosity functions of main sequence stars in 3 associations and 22 open clusters, the initial luminosity function and mass function for these clusters are derived. For stars of m > $0.6m_{\odot}$, they are well consistent with those for the field stars.

• Journal of The Korean Astronomical Society
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• v.24 no.2
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• pp.161-171
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• 1991

We have derived the luminosity function for subdwarfs on the basis of the proper motion data in LHS Catalogue, utilizing the reduced proper motion diagram for the selection of sub dwarfs and the hybrid method combining the mean absolute magnitude method and V/$V_m$ method to estimate the distance and density of subdwarfs. The luminosity function found here is almost flat, showing a very slow increase up to $M_V\;=\;9$ or $M_B\;=\;10$, and the overall halo density is larger than those derived by Schmidt (1975), Chiu (1980), Reid (1984), Lee (1985), and Dawson (1986), but smaller than that by Eggen (1983). Comparison with 1/100 of disk stellar luminosity function implies that no conclusive dip in the halo luminosity function is found.

• Journal of The Korean Astronomical Society
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• v.28 no.1
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• pp.45-59
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• 1995

In the best observed Pleiades cluster, the luminosity function(LF) and mass function(MF) for main sequence(MS) stars extended to $Mv{\approx}15.5(V{\approx}21)$ are very similar to the initial luminosity function(ILF) and initial mass function(IMF) for field stars in the solar neighborhood showing a bump at log $m{\simeq}-0.05$ and a dip at log $m{\simeq}-0.12$. This dip is equivalent to the Wielen dip appearing in the LF for the field stars. The occurence of these bump and dip is independent of adopted mass-luminosity relation(MLR) . and their characteristics could be explained by a time-dependent bimodal IMF. The model with this IMF gives a total cluster mass of $\~700M_\bigodot,\;\~25$ brown dwarfs and $\~3$ white dwarfs if the upper mass limit of progenitor of white dwarf is greater than $4.5M_\bigodot$. The cluster age on the basis of LF for brightest stars is given by $\~8\times10^7yr$ and all stars in the cluster lie along the single age sequence in the C-M diagram without showing a large dispersion from the sequence.

• Journal of The Korean Astronomical Society
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• v.28 no.2
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• pp.139-146
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• 1995

The bright part of the halo luminosity function is derived from a sample of the 233 NLTT propermotion stars, which are selected by the 220 km/ see of cutoff velocity in transverse to rid the contamination by the disk stars and corrected for the stars omitted in the sample by the selection criterion. It is limited to the absolute magnitude range of $M_v=4-8$, but is based on the largest sample of halo stars up to now. This luminosity function provides a number density of $2.3{\cdot}10^{-5}pc^{-3}$ and a mass density of $2.3{\cdot}10^{-5}M_{o}pc^{-3}$ for 4 < $M_v$ < 8 in the solar neighborhood. These are not sufficient for disk stability. The kinematics of the sample stars are < U > = - 7 km/sec, < V > = - 228 km/sec, and < W > = -8 km/sec with (${\sigma_u},{\sigma_v},{\sigma_w}$) = (192, 84, 94) km/sec. The average metallicity of them is [Fe/H] = $- 1.7{\pm}0.8$. These are typical values for halo stars which are selected by the high cutoff velocity. We reanalyze the luminosity function for a sample of 57 LHS proper-motion stars. The newly derived luminosity function is consistent with the one derived from the NLTT halo stars, but gives a somewhat smaller number density for the absolute magnitude range covered by the LF from NLTT stars. The luminosity function based on the LHS stars seems to have a dip in the magnitude range corresponding to the Wielen Dip, but it also seems to have some fluctuations due to a small number of sample stars.

• Journal of The Korean Astronomical Society
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• v.35 no.2
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• pp.87-95
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• 2002

We have conducted VI CCD photometry of the open cluster NGC 6819 in order to understand the effects of dynamical evolution in old open clusters. Our photometry covers 18' $\times$ 18' on the sky, centered on the cluster, which seems to cover the whole cluster field. Our photometry reaches down to V $\approx$ 20.5, which allows us to analyze the luminosity function and spatial distribution of stars brighter than Mv $\approx$ 8.5. There is a clear evidence for mass segregation in NGC 6819, i.e., the giants and upper main-sequence stars are concentrated in the inner regions, whereas the lower main-sequence stars distribute almost uniformly throughout the cluster. The luminosity function of the main-sequence stars of NGC 6819 is almost flat. The flat luminosity function indicates that a large number of low mass stars has escaped from the cluster unless its initial mass function is much different from the Salpeter type (${\phi}(m){\propto} m^{-(1+x)},x = 1.35$).

• Publications of The Korean Astronomical Society
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• v.32 no.1
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• pp.263-265
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• 2017

We present the mid-infrared (MIR) luminosity function (LF) of local (z < 0.3) star-forming (SF) galaxies in the North Ecliptic Pole (NEP) field. This work is based on the NEP-Wide point source catalogue and the spectroscopic redshift (z) data for ~ 1700 galaxies obtained by the optical follow-up survey with MMT/Hectospec and WIYN/Hydra. The AKARI's continuous $2-24{\mu}m$ coverage and the spectroscopic redshifts enable us to determine the spectral energy distribution (SED) in the mid-infrared and derive the luminosity functions of galaxies. Our $8{\mu}m$ LF finds good agreements with the results from SWIRE field over the wide luminosity range, while showing significant difference from the NOAO deep data in the faint end. The comparison with higher-z sample shows significant luminosity evolution from z > 0.3 to local universe. $12{\mu}m$ LF also shows a clear indication of luminosity evolution.

• Journal of The Korean Astronomical Society
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• v.26 no.2
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• pp.141-152
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• 1993

The sample of sub dwarfs are selected from LHS catalogue on the bases of the reduced proper motion diagram utilizing Chui criteria, and confirmed with the available photometric and/or kinematic data. Among them, 20 sub dwarfs have trigonometric parallaxes with accuracy better than $20\%$. The color­absolute magnitude relation is derived with them. By adopting this color-magnitude relation and $V/V_m$ method, we have derived the sub dwarf luminosity function over the absolute magnitude range of $M_v$= 4.5 and 9.5. This halo luminosity function is consistent with that of Eggen(1987). By adopting the available mass-luminosity relations for halo stars, we have found that the halo IMF is steeper than disk IMFs of Scalo(1986) and Salpter(1955) in this small mass region.

• Journal of The Korean Astronomical Society
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• v.24 no.2
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• pp.173-190
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• 1991

Disk stellar luminosity function has been derived with stars in the Lowell Proper Motion Survey which contains about 9000 stars with ${\mu}\;{\geq}\;0".27$ of arc/yr, $8\;<\;m_{pg}\;<\;17$ and with bright stars in the Smithsonian Astrophysical Observatory (SAO) Star Catalogue, Luminosity function has been obtained with stars within 20 pc by Luyten's mean absolute magnitudes method using Reduced Proper Motion Diagram to select disk stars. Magnitudes and colors, in the SAO Star Catalogue as well as in the Lowell Proper Motion Survey have been transformed to the UBV system from the published UBV data. It has been found that stars which have higher proper motion than the original limit of the proper motion survey are missed, when the relation between the absolute magnitude and reduced proper motion is applied to sample stars without considering the dispersion in magnitude. Correction factors for missing stars have been estimated according to their limits of proper motion which are dependent on the absolute magnitude. Resulting luminosity function shows Wielen's dip at $M_B{\sim}10$, and systematic enhancement of stars on the average of about ${\Delta}\log\;{\Phi}\;(M_B){\sim}0.2$ compared with Luyten's luminosity function.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.461-462
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• 2015

Quasars are among the farthest and brightest objects known in the universe. Because quasars are mostly observed in the redshift range between 1 and 3, they can be used to study large scale structure in the universe, and its evolution over the past billion years. An important issue is the evolution of the quasar luminosity function, which has been investigated for relative small samples of the 2QZ catalog. Here we extend the study to 3 quasar samples, the most recent data of the Milliquas, Master and 2QZ quasar catalogs to determine the luminosity function of quasars and its evolution, using the Standard cosmological ${\Lambda}CDM$ model with ${\Omega}_{\Lambda}=0.73$, ${\Omega}_M=0.27$, and $H_0=70kms^{-1}Mpc^{-1}$. For the purpose of this analysis we initially used 0.25-mag bins and approximately 0.180-redshift bins, then calculated the comoving distance and comoving volume for each bin of redshift and calculated the number of objects in each bin per unit volume, in order to find the number density per absolute magnitude bin. Our analysis on the basis of these new and much more complete datasets is largely in agreement with earlier studies of the luminosity evolution of quasars.