# 2003 REU/PIA Projects

### What is The Large Magellanic Cloud?

The LMC is an irregular dwarf galaxy that is orbiting the Milky Way.  Unlike spiral and elliptical galaxies, irregular galaxies lack any appearance of organized structure. Like its neighboring Small Magellanic Cloud (SMC), the LMC appears as a huge and diffuse cloud in the southern nighttime sky.

### What is the goal?

We are investigating the presence of a possible warp in the Large Magellanic Cloud (LMC). We do this by producing color-magnitude diagrams from wide band photometry to identify red clump stars. The red clump stars are used as distance indicators, and therefore we are able to measure distances in various regions of the LMC.  The purpose of this is to understand the 3D geometry of the LMC's inner regions.

### Abstract

We attempt to build a more realistic model of the ringed bipolar planetary nebula, Mz 1, using a three-dimensional self-consistent photoionization code. The code divides the gaseous region of the nebula into numerous cubic cells. The code then calculates the physical conditions in each cell of the cube representing the nebula. From this we obtain electronic temperature and density, ionic fractional abundances, and emission-line luminosities. From observation taken at the Cerro Tololo Interamerican Observatory (CTIO) we create spectrophotometric line images and density maps and compare them with our model results. From this we obtain for the first time the luminosity and temperature of the ionizing source for Mz1. The results of this model will also help to get a broader understanding of the processes taking place in the shaping of planetary nebulae and their evolution.

### Introduction

For this project, our chief concern is how light of different frequencies is extinguished by dust and gas. This extinguishing effect is represented by the optical depth, $\tau$ and depends on, among other things, the frequency of the light. Things are said to be optically thick if they extinguish a lot of the light (large $\tau$) and optically thin if they have little extinguishing effect on the light (small $\tau$).

### Project Goals:

Our object is to examine images taken in B,V,R and I filters with Gemini's Acquisition Camera. Eventually, these will also be compared to J and K images that we took with the Blanco 4m telescope. We hope to reduce all of this data, and with it to determine the magnitude of CO Ori's secondary star and create color-color diagrams. This will enable us to determine its spectral type. It will be nice (but may not be possible given time constraints and issues with image saturation) to also pinpoint the magnitude and other characteristics of the primary star.

All of this information, gathered from photometric images, will then be compared with spectra of CO Ori gathered by Dr. Rodgers. These spectra are intruiging because emissions in them are slightly offset from the continuum. This could mean that contrary to expectaion, the secondary star is contributing significantly to the emission spectra.

Another eventual goal is to construct a spectral energy distribution (SED) for each star and to compare it to the combined SED for CO Ori. SED's in the infrared provide information about circumstellar material and its distribution and structure. Past investigations have shown that stars which are known binaries produce SED's not easily fit by stellar disk models (K. Malfait et al. 1997). If this is true of CO Ori, and if, as many suspect, more HAEBE stars are actually binary, then much of the work on interpretation of HAEBE SED's and disk modeling will need to be reexamined.

Ultimately, we would like to produce a paper to release the results.

### Abstract:

The detection and mapping of galaxy clusters is an important element of understanding the structure of the universe, its history and its future.  Presented here is a demonstration of a newer method of cluster detection, called the cluster red sequence method (CRS), which uses the observed red sequence of elliptical galaxies as a sign of a cluster.  The red sequence is an observed property of all rich clusters, which have cores composed of coeval elliptical galaxies.  At a particular redshift, the ellipticals that make up the sequence are redder than all normal galaxies at a lower redshift.  This fact allows us to eliminate contamination from foreground galaxies.  Other advantages are the relative ease of obtaining approximate redshifts and the need for images in only two common filters.  One limitation of the CRS method is that it assumes a particular definition of a cluster, i.e., a rich cluster with a core of ellipticals, and hence is may not be capable of finding younger clusters, groups, or other structures that do not fit this definition, such as dark clusters.

We analyze one subfield (F1p22) of the Deep Lens Survey (DLS) in order to test the usefulness and expediency of the red sequence method of cluster detection.  With limited results, we find that the method can be a sucessful and expedient way of detecting galaxy clusters.

### Abstract:

A characterization of the kinematics of the ansae in NGC 7009 was made using high dispersion echelle spectra and archive narrow band HST images for measuring radial velocities and proper motions, respectively. Assuming that the ansae are moving at equal and opposite velocity from the central star we obtain an average system radial velocity of -53 ± 2 km/s, the eastern ansa approaching and the western ansa receding at v_r= 6 ± 1 km/s respect to this value. The proper motion of the eastern ansa could be measured, leading to 3 ± 1.5 arcsec/century, or V = (130 ± 40) d km/s, where d is the distance to the nebula in kpc.  Additionally, the electron temperature and density for each ansa was measured using line intensity ratios. The results are T_e ~ 9000 K and n_e  ~ 2000 cm-3. We estimate the age of the ansae in ~ 900 yr and the proper motion of the central star in 1 mas/yr.