The Effect of Method of Constructing the Mass Distribution on Single Stellar Populations

We use two methods of constructing the initial mass distribution, the traditional way and Monte Carlo simulation, to obtain integrated U - B, B - V, V-R and V-I colours and absorption-line indices denned by the Lick Observatory image dissector scanner (referred to as Lick/IDS), for instantaneous burst solarmetallicity single stellar populations with ages in the range 1-15 Gyr. We find that the evolutionary curves of all colours obtained by the traditional method are smoother than those by Monte Carlo simulation, that the U - B and B - V colours obtained by the two methods agree with one another, while the V - R and V - I colours by the traditional method are bluer than those by Monte Carlo simulation. A comparison of the Lick/IDS absorption-line indices shows that the variations in all the indices by the traditional method are smoother than that for the Monte Carlo simulation, and that all the indices except for TiO1 and TiO2 are consistent with those for the Monte Carlo simulation.     

The next generation stellar population synthesis library

Most of the analysis of absorption lines in galaxies is done in the Lick system, defined in the 1970's and 1980's by Faber, Burstein and collaborators. Working in this system is difficult, since it is based on low resolution spectra taken with a non-linear detector without flux-calibration. Due to intrinsic errors in the published indices the Lick system limits the accuracy with which one can analyse galaxy spectra. In the last 2 years we have observed a new stellar library to replace the Lick system. It consists of 1100 stars, covering a wide range in metallicity, abundance ratio, temperature and gravity, observed at a resolution of 2.0Å (9 for Lick) from 3500–7500Å, and calibrated in flux. With this library galaxy spectra can be analysed much more accurately than before, and in much more detail. Most important, the library now makes it possible to study absorption lines of galaxies at intermediate and high redshift, something which was impossible with the Lick system. With this library it will be possible for the first time to synthesise full Spectral energy distributions of galaxies in the optical based fully on observational spectra.     

Observations of Lick standard stars with the SCORPIO multislit unit at the SAO 6-m telescope

We present Lick line-index measurements for standard stars from Worthey’s list. The spectra were taken with the multislit unit of the SCORPIO spectrograph at the 6-m Special Astrophysical observatory telescope. We describe in detail our method of analysis and explain the importance of using the Lick index system for studying extragalactic globular clusters. Our results show that the calibration of our instrumental system to the standard Lick system can be performed with high confidence. The article was translated by the authors in English. Published in Russian in Pis’ma v Astronomicheskiĭ Zhurnal, 2006, Vol. 32, No. 3, pp. 209–216.     

Bimodality in low-luminosity E and S0 galaxies

Stellar population characteristics are presented for a sample of low-luminosity early-type galaxies (LLEs) in order to compare them with their more luminous counterparts. Long-slit spectra of a sample of 10 LLEs were taken with the ESO New Technology Telescope, selected for their low luminosities. Line strengths were measured on the Lick standard system. Lick indices for these LLEs were correlated with velocity dispersion (σ), alongside published data for a variety of Hubble types. The LLEs were found to fall below an extrapolation of the correlation for luminous ellipticals and were consistent with the locations of spiral bulges in plots of line strengths versus σ. Luminosity weighted average ages, metallicities and abundance ratios were estimated from  χ²  fitting of 19 Lick indices to predictions from simple stellar population models. The LLEs appear younger than luminous ellipticals and of comparable ages to spiral bulges. These LLEs show a bimodal metallicity distribution, consisting of a low-metallicity group (possibly misclassified dwarf spheroidal galaxies) and a high-metallicity group (similar to spiral bulges). Finally, they have low α-element to iron peak abundance ratios indicative of slow, extended star formation.     

Fitting formulae for the effects of binary interactions on lick indices and colors of stellar populations

More than about 50% of stars are in binaries, but most stellar population studies take single star stellar population (ssSSP) models, which do not take binary interactions into account. In fact, the integrated peculiarities of ssSSPs are different from those of stellar populations with binary interactions (bsSSPs). Therefore, it is necessary to investigate the effects of binary interactions on the Lick indices and colors of populations in detail.We show some formulae for calculating the difference between the Lick indices and colors of bsSSPs, and those of ssSSPs. Twenty-five Lick indices and 12 colors are studied in this work. The results can be conveniently used for calculating the effects of binary interactions on stellar population studies and for adding the effects of binary interactions into present ssSSP models. The electronic data and fortran procedures in the paper can be obtained on request from the authors.     

Inclusion of binaries in evolutionary population synthesis

Using evolutionary population synthesis we present integrated colours, integrated spectral energy distributions and absorption-line indices defined by the Lick Observatory image dissector scanner (referred to as the Lick/IDS) system, for an extensive set of instantaneous-burst binary stellar populations with and without binary interactions. The ages of the populations are in the range 1–15 Gyr and the metallicities are in the range 0.0001–0.03. By comparing the results for populations with and without binary interactions we show that the inclusion of binary interactions makes the integrated U – B , B – V , V – R and R – I colours and all Lick/IDS spectral absorption indices (except for H_β) substantially smaller. In other words, binary evolution makes a population appear bluer. This effect raises the derived age and metallicity of the population.
We calculate several sets of additional solar-metallicity binary stellar populations to explore the influence of the binary evolution algorithm input parameters (the common-envelope ejection efficiency and the stellar wind mass-loss rate) on the resulting integrated colours. We also look at the dependence on the choice of distribution functions used to generate the initial binary population. The results show that variations in the choice of input model parameters and distributions can significantly affect the results. However, comparing the discrepancies that exist between the colours of various models, we find that the differences are less than those produced between the models with and those without binary interactions. Therefore it is very necessary to consider binary interactions in order to draw accurate conclusions from evolutionary population synthesis work.     

An optimized Hβ index for disentangling stellar population ages

We have defined a new Hβ absorption index definition,  Hβ_o  , which has been optimized as an age indicator for old and intermediate age stellar populations. Rather than using stellar spectra, we employed for this purpose a library of stellar population spectral energy distributions of different ages and metallicities at moderately high resolution.  Hβ_o  provides us with improved abilities for lifting the age–metallicity degeneracy affecting the standard Hβ Lick index definition. The new index, which has also been optimized against photon noise and velocity dispersion, is fully characterized with wavelength shift, spectrum shape, dust extinction and [α/Fe] abundance ratio effects.  Hβ_o  requires spectra of similar qualities as those commonly used for measuring the standard Hβ Lick index definition. Aiming at illustrating the use and capabilities of  Hβ_o  as an age indicator we apply it to Milky Way globular clusters and to a well selected sample of early-type galaxies covering a wide range in mass. The results shown here are particularly useful for applying this index and understand the involved uncertainties.     

Spectroscopic binaries near the north galactic pole

Photoelectric radial-velocity measurements confirm and refine the preliminary orbit derived for HR 4668 by Christie on the basis of eight Lick spectrograms taken more than 50 years ago.     

IMF and Velocity-Dispersion Effects on Optical Spectroscopic Absorption Features

We explore the behaviour of the most popular spectroscopic absorption features in the optical region as a function of the initial mass function (IMF), while taking into account the spectral resolution and galaxy velocity dispersion. We conclude that the IMF produces a negligible effect on the Lick indices contained in the wavelength interval λ 3800–5500 Å, except the Mg₁ index, for which the IMF could be as important as the metallicity. We also show that the IMF is irrelevant for most of the Rose (1994) indicators, except for various indices that show a non-negligible sensitivity. In contrast to the Lick indices, some of the Rose indicators vary their age–metallicity–IMF trends as a function of the spectral resolution.     

The spectrum of the manganese star ι Coronae Borealis

Iota Coronae Borealis is a manganese mercury star with a rich spectrum of sharp lines. We tabulate equivalent widths element by element from data obtained at Lick 120-inch telescope.     

On the relativistic ejection of a particle by radiation pressure

The Poynting-Robertson formulae are used to evaluate the motion and terminal velocity of a particle ejected from rest in a powerful radiation field due to a point source, generalizing the results of Chandrasekhar (1934) to the relativistic case.Contributions from the Lick Obsrvatory, No. 335.     

南天自行计划的进展和精度

ＴｈｅＹａｌｅ／ＳａｎＪｕａｎ南天自行计划简ＳＰＭ。ＳＰＭ是美国里克天文台北天自行计划在南天的延伸。根据ＳＰＭ计划，最终在南天相对的星系测定出大约一百万颗天体的绝对自行、位置、星等和颜色。ＳＰＭ最初目的是研究角河系结构。     

Additional evidence for the accuracy of galactic reddenings from ScI galaxies and quasars

The relevance of the galactic reddeningsE(B-V) derived by Teerikorpi (1978, 1981) from ScI galaxies and quasars, is further confirmed by considerations of close pairs in the sky, the Lick counts, and the counts/NHi ratio. The compact dust clouds suggested by Teerikorpi (1981) could not be detected directly by the counts. However, the counts/NHi ratio showed a behaviour expected if the reddenings really describe the division of the dust in the Local Spiral into compact clouds and a more diffuse medium, in the way suggested in the previous study.     

宇宙大尺度分形结构的上限

本文给出了用几种达到不同极限星等的星系表确定宇宙分形结构上限截止尺度的公式.利用Zwicky星系表、Shane-Wirtanen星系表和Jagellonian天区的星系表的数据,可以估计这一截止尺度R_c至少为60—70Mpc,且R_c随着自相似分布所占比例f的减小而增大,或可大到约270Mpc的尺度.     

Stochastic simulation of fields of galaxies,III

Stochastic simulations of galaxy fields, using the cluster multiplicity function obtained for the Lick galaxy counts, reproduces satisfactorily the observed distribution of galaxies from COSMOS measures on a deep UKST and AAT plate limited atB22.0 andB23.2, respectively. The results imply that no strong evolutionary effect is present in the clustering of galaxies, at least out to redshiftsz ^*0.65.     

Triaxial ellipsoid dimensions and rotational poles of seven asteroids from Lick Observatory adaptive optics images, and of Ceres

Seven main belt asteroids, 2 Pallas, 3 Juno, 4 Vesta, 16 Psyche, 87 Sylvia, 324 Bamberga, and 707 Interamnia, were imaged with the adaptive optics system on the 3 m Shane telescope at Lick Observatory in the near infrared, and their triaxial ellipsoid dimensions and rotational poles have been determined with parametric blind deconvolution. In addition, the dimensions and pole for 1 Ceres are derived from resolved images at multiple epochs, even though it is an oblate spheroid.     

Spectroscopic study of globular clusters in the halo of M31 with the Xinglong 2.16 m telescope

We present spectroscopic observations for 11 confirmed globular clusters(GCs) of M31 with the OMR spectrograph on the 2.16 m telescope at the Xinglong site of National Astronomical Observatories,Chinese Academy of Sciences.Nine of our sample clusters are located in the halo of M31 and the most remote one is out to a projected radius of 78.75 kpc from the galactic center.For all our sample clusters,we measured the Lick absorption-line indices and radial velocities.It is noted that most GCs in our sample are ...     

Modelling the April 15 spectrum of Supernova 1993 J

We present the modeling of the ultraviolet and optical spectra obtained simultaneously on 1993 April 15 with the HST and at Lick Observatory. A Monte Carlo code is employed in the modeling and a comparison is made between models reported by different groups. With an atmosphere similar to the Sun in chemical composition, the observed spectral lines are well reproduced by a power law density structure of index around 20 except the strong H and HeI λ5876 lines which have peculiar absorption profiles. The photospheric velocity is found to be 9500 km/s and the blackbody temperature of the spectrum is 7990 K. For H and HeI λ5876, we suggest a two-component density structure which has a smoother layer located immediately outside the steeply decreasing inner envelope. The power law indices are most probably 20 and 3, respectively, with the transition point at about 13 000 km/s. In addition, this outer smooth layer serves to flatten the far UV spectrum as observed.     

New data on the variability of the spectrum of Kaz 163

The results of new spectral observations of the Seyfert component of the close binary galaxy with UV excess Kaz 163 are presented. Two new spectra have been obtained: with the 3-m telescope of Lick Observatory in 1986 and with the 1.8-m telescope of Asiago Observatory in 1993. It is shown that there was no short-term (about one month) variability in the spectrum. The emission lines Hell 4686 and Hel 5876 strengthen significantly between 1984 and 1986.Translated fromAstrofizika, Vol. 37, No. 1, pp. 5–12, January–March, 1994.     

Charge conservation and CCD aperture photometry

The Lick Observatory's CCD controller is a new type controller. It has the ability to exchange MPP (Multi-pinned phase) mode and normal operation within one CCD system. There are at least 4 CCD cameras using this type of controller in China since 2002. The weakness of this controller is that blooming occurs before nonlinearity and long before saturation. However, although it is no good for observation of bright extended sources and for constructing the point spread function from observing bright stars, aperture photometry of bright point sources (stars) is still feasible due to the principle of charge conservation. This point is confirmed in this paper.