Neutron stars (NS) are the most compact objects that can be directly observed. They can be used to study properties of matter at supranuclear densities. This in turn gives us information to separate between numerous theoretical equations of states of dense matter. Thermonuclear (type-I) X-ray bursts from low mass X-ray binaries can be used to address this issue. Some of these bursts can be so energetic that they cause the whole photosphere of the NS to expand. The cooling of these photospheric radius expansion bursts can be compared to theoretical atmosphere models to obtain the mass and radius measurements of the NS. These measurements can then be used to differentiate between the different equations of state. We present a set of differential equations needed to compute these atmospheric models. We introduce an exact treatment of Compton scattering via the relativistic integral equation and an angle-dependent redistribution function. Using these equations, we can construct a set of atmosphere models in plane-parallel approximation in a local thermodynamical equilibrium for hot NSs. The emergent spectra is then fitted by a diluted blackbody to obtain the dilution factor w and the colour-correction factor f_c. On the other hand, the observed spectra from X-ray bursting neutron stars are close to thermal and can be fitted with a blackbody with two free parameters: the observed blackbody temperature T_bb and the normalization K. By equating the dilution factor w and the normalization K, we obtain a relation between the theoretical atmosphere models and the observations. This connection is the main idea of the so called cooling tail method. We then introduce a small correction to this method and discuss the consequences. A common problem encountered using this method is that different bursts from a given system can yield completely different mass and radius measurements. This fact casts a doubt on the robustness of the entire method. We study the burst emission from 4U 1608--52 at various persistent fluxes. We find a strong dependence of the burst properties on the flux before the burst. Bursts that ignite during the hard state at a low accretion rate show strong evolution of the apparent blackbody radius which is consistent with the model predictions of the neutron star atmosphere models. On the other hand, bursts occurring during the soft state at a higher accretion rate show constant apparent radius, which is inconsistent with the models. We then use the hard state bursts only to constrain the neutron star mass and radius from our set of sources. By taking only the physically relevant results into account, we also get information of the chemical composition of the atmosphere. This then gives us a way to conclude if the atmosphere is hydrogen- or helium-rich. After we know the chemical composition, we constrain the NS radius to be between 12 and 16 km. This implies a stiff equation of state of neutron star matter.

In this thesis, the goal is to disentangle the real morphological evolution of galaxies from the observational effects, caused by redshift. This was done by taking a sample of ~1300 high-redshift (0.1 ≤ z ≤ 1.3) galaxies, observed with HST (Hubble Space telescope), from the GOODS-south field and then dividing them into six redshift bins of ∆z ≈ 0.2 and further into absolute magnitude bins of ∆M = 0.5. The sample was then matched to low-redshift (z ≤ 0.025) galaxies from the SDSS with the same comoving number density per ∆M-bin to create a sample of galaxies of the possible descendants of the high-redshift galaxies. Spectroscopic redshifts of the high-redshift sample were fetched from data provided by the 3DHST project. The low-redshift sample was then spatially scaled, dimmed and k-corrected to simulate redshift effects caused by the accelerating expansion of space. To appear as observed with the HST, the images were convolved with a new point-spread function (PSF), created by deconvolving the HST PSF with the SDSS PSF. This results in a change of the PSF 2D-distribution and a resolution change from 0.396”/pix (SDSS) to 0.03”/pix (HST). To achieve this the FERENGI and the KCORRECT codes were used. All three (low-redshift, high-redshift, redshifted) samples were then classified both visually and with CAS (concentration, asymmetry, smoothness) parameters. The results were compared between these samples. The redshifting process did not produce clumpy structures in the low-redshift galaxies as seen in real high-redshift galaxies. Visual classification becomes increasingly difficult for z ≥ 0.55. The concentration index hardly changes with redshift. The asymmetry of the high-redshift galaxies seem to be genuinely higher than that of the low-redshift galaxies. The smoothness parameter values increase with redshift, implying an increasing clumpiness, but some of the change could be due to the redshift effects. For the high-redshift sample, all the CAS parameters between redshift bins show very little evolution for a given morphological type and could be used to differentiate between them. We also note that we found a significant amount of “clumpy” galaxy types, already in the nearest redshift bin of 0.1 ≤ z ≤ 0.3, as opposed to previous studies.

<p> This thesis investigates connections between low albedo asteroids and carbonaceous chondrite meteorites using spectroscopy. Meteorites and asteroids preserve information about the early solar system including accretion processes and parent body processes active on asteroids at these early times. One process of interest is aqueous alteration. This is the chemical reaction between coaccreted water and silicates producing hydrated minerals. Some carbonaceous chondrites have experienced extensive interactions with water through this process. Since these meteorites and their parent bodies formed close to the beginning of the Solar System, these asteroids and meteorites may provide clues to the distribution, abundance and timing of water in the Solar nebula at these times. Chapter 2 of this thesis investigates the relationships between extensively aqueously altered meteorites and their visible, near and mid-infrared spectral features in a coordinated spectral-mineralogical study. Aqueous alteration is a parent body process where initially accreted anhydrous minerals are converted into hydrated minerals in the presence of coaccreted water. Using samples of meteorites with known bulk properties, it is possible to directly connect changes in mineralogy caused by aqueous alteration with spectral features. Spectral features in the mid-infrared are found to change continuously with increasing amount of hydrated minerals or degree of alteration. Building on this result, the degrees of alteration of asteroids are estimated in a survey of new asteroid data obtained from SOFIA and IRTF as well as archived the Spitzer Space Telescope data. 75 observations of 73 asteroids are analyzed and presented in Chapter 4. Asteroids with hydrated minerals are found throughout the main belt indicating that significant ice must have been present in the disk at the time of carbonaceous asteroid accretion. Finally, some carbonaceous chondrite meteorites preserve amorphous iron-bearing materials that formed through disequilibrium condensation in the disk. These materials are readily destroyed in parent body processes so their presence indicates the meteorite/asteroid has undergone minimal parent body processes since the time of accretion. Presented in Chapter 3 is the spectral signature of meteorites that preserve significant amorphous iron-bearing materials and the identification of an asteroid, (93) Minerva, that also appears to preserve these materials.</p><p>

<p>This thesis explores the ways in which observations of the low surface brightness universe can inform our views of galaxy evolution and, specifically, the extent to which galaxies assemble stellar mass through mergers and accretion events. I first present a study of the variation in the stellar halos of galaxies, using data from the Dragonfly Nearby Galaxies Survey (DNGS). The survey consists of wide field, deep (&mu;<i>g</i> > 31 mag aresec^-2) optical imaging of nearby galaxies using the Dragonfly Telephoto Array. The sample in question includes eight spiral galaxies with stellar masses similar to that of the Milky Way, inclinations of 16 &ndash; 90 degrees and distances between 7&ndash;18 Mpc. I construct stellar mass surface density profiles from the observed <i>g</i>-band surface brightness in combination with the <i>g</i> &ndash; <i>r</i> color as a function of radius, and compute the halo fractions from the excess stellar mass (relative to a disk+bulge fit) beyond 5 half-mass radii. I find a mean halo fraction of 0.009 &plusmn; 0.005 and a large RMS scatter of 1.01[special characters omitted] dex. The peak-to-peak scatter of the halo fraction is a factor of > 100 &ndash; while some galaxies feature strongly structured halos resembling that of M31, three of the eight have halos that are completely undetected in our data. I conclude from this sample that spiral galaxies as a class exhibit a rich variety in stellar halo properties, implying that their assembly histories have been highly non-uniform. I find no convincing evidence for an environmental or stellar mass dependence of the halo fraction in the sample.</p><p> In addition to being the future building blocks of the stellar halos of galaxies, dwarf satellite galaxies are a key probe of dark matter and of galaxy formation on small scales and of the dark matter halo masses of their central galaxies. They have very low surface brightness, however, which makes it difficult to identify and study them outside of the Local Group. I used the Dragonfly Telephoto Array to search for dwarf galaxies in the field of the massive spiral galaxy M101, and identified seven large, low surface brightness objects in this field, with effective radii of 10-30 arcseconds and central surface brightnesses of &mu;<i>g</i>,0 ~ 25.5 &ndash; 27.5 mag aresec^-2. Given their large apparent sizes and low surface brightnesses, these objects would likely be missed by standard galaxy searches in deep fields. Their radial surface brightness profiles are well fit by Sersic profiles with a very low Sersic index (<i>n</i> ~ 0.3 &ndash; 0.7). The properties of the sample are similar to those of well-studied dwarf galaxies in the Local Group, such as Sextans I and Phoenix.</p><p> Finally, follow-up observations of these low surface brightness objects with the Hubble Space Telescope subsequently revealed that three of the seven objects were bonafide satellite galaxies of the M101 group. I show that, unexpectedly, the other four galaxies are ultra-diffuse galaxies in a group environment. The galaxies have effective radii of 10 &ndash; 38 and central surface brightnesses of 25.6 &ndash; 27.7 mag aresec^-2 in the <i>g</i>-band. They remain persistently unresolved even with the spatial resolution of HST/ACS, which implies distances of <i>D</i> > 17.5 Mpc. I show that the galaxies are most likely associated with a background group at ~ 27 Mpc containing the massive ellipticaLs NGC 5485 and NGC 5473. At this distance, the galaxies have sizes of 2.6-4.9 kpc, and are classified as UDGs. They are similar to the populations that have been revealed in clusters such as Coma, Virgo, and Fornax, yet have on average even lower surface brightness. The discovery of four UDGs in a galaxy group demonstrates that the UDG phenomenon is not exclusive to cluster environments. Furthermore, their morphologies seem less regular than those of the cluster populations, which may suggest a different formation mechanism or be indicative of a threshold in surface density below which UDGs are unable to maintain stability.</p><p>

<p> Near-Earth Objects (NEOs) are generally small, dark, and fast-moving. Multiple observations over time are necessary to constrain NEO orbits. Orbits based on observational data are inherently uncertain. Here we describe code written in Python and Fortran used to generate synthetic asteroids and compare calculated orbital fit based on noisy ephemeris using the a distance criteria, D-value. Observational sessions separated by more than one month produce very good orbital fits (low D-values) even at the highest noise level. Daily observational sessions show the highest D-values, as expected, since observed points on the orbital ellipse are not well separated. D-value is closely correlated to differences in the eccentricity and inclination of compared orbits.</p><p>

One of the primary drivers in the development of large format millimeter detector arrays is the study of sub-millimeter galaxies (SMGs) - a population of very luminous high-redshift dust-obscured starbursts that are widely believed to be the dominant contributor to the Far-Infrared Background (FIB). The characterization of such a population requires the ability to map large patches of the (sub-)millimeter sky to high sensitivity within a feasible amount of time. I present this dissertation on the design, integration, and characterization of the 144-pixel AzTEC millimeter-wave camera and its application to the study of the sub-millimeter galaxy population. In particular, I present an unprecedented characterization of the “blank-field” (fields with no known mass bias) SMG number counts by mapping over 0.5 deg 2 to 1.1mm depths of ∼1mJy - a previously unattained depth on these scales. This survey provides the tightest SMG number counts available, particularly for the brightest and rarest SMGs that require large survey areas for a significant number of detections. These counts are compared to the predictions of various models of the evolving mm/sub-mm source population, providing important constraints for the ongoing refinement of semi-analytic and hydrodynamical models of galaxy formation. I also present the results of an AzTEC 0.15 deg 2 survey of the COSMOS field, which uncovers a significant over-density of bright SMGs that are spatially correlated to foreground mass structures, presumably as a result of gravitational lensing. Finally, I compare the results of the available SMG surveys completed to date and explore the effects of cosmic variance on the interpretation of individual surveys.

Bolometers are the most sensitive detectors for measuring millimeter and submillimeter wavelength astrophysical signals. Cameras comprised of arrays of bolometers have already made significant contributions to the field of astronomy. A challenge for bolometer cameras is obtaining observations at multiple wavelengths. Traditionally, observing in multiple bands requires a partial disassembly of the instrument to replace bandpass filters, a task which prevents immediate spectral interrogation of a source. More complex cameras have been constructed to observe in several bands using beam splitters and dichroic filters, but the added complexity leads to physically larger instruments with reduced efficiencies. The SPEctral Energy Distribution camera (SPEED) is a new type of bolometer camera designed to efficiently observe in multiple wavebands without the need for excess bandpass filters and beam splitters. SPEED is a ground-based millimeter-wave bolometer camera designed to observe at 2.1, 1.3, 1.1, and 0.85 mm simultaneously. SPEED makes use of a new type of bolometer, the frequency selective bolometer (FSB), to observe all of the wavebands within each of the camera’s four pixels. FSBs incorporate frequency selective dipole surfaces as absorbing elements allowing each detector to absorb a single, narrow band of radiation and pass all other radiation with low loss. Each FSB also contains a superconducting transition-edge sensor (TES) that acts as a sensitive thermistor for measuring the temperature of the FSB. This thesis describes the development of the SPEED camera and FSB detectors. The design of the detectors used in the instrument is described as well as the the general optical performance of frequency selective dipole surfaces. Laboratory results of both the optical and thermal properties of millimeter-wave FSBs are also presented. The SPEED instrument and its components are highlighted and the optical design of the optics which couple SPEED to the Heinrich Hertz Telescope is given. This thesis concludes with an introduction to the jiggle mapping data analysis of bolometer instruments like SPEED.

Galaxies detected by their thermal dust emission at submillimeter (submm) and millimeter (mm) wavelengths comprise a population of massive, intensely star-forming systems in the early Universe. These "submm/mm-galaxies", or SMGs, likely represent an important phase in the assembly and/or evolution of massive galaxies and are thought to be the progenitors of massive elliptical galaxies. While their projected number density as a function of source brightness provides key constraints on models of galaxy evolution, SMG surveys carried out over the past twelve years with the first generation of submm/mm-wavelength cameras have not imaged a large enough area to sufficient depths to provide the statistical power needed to discriminate between competing galaxy evolution scenarios. In this dissertation, we present the results from SMG surveys carried out over the past four years using the new sensitive mm-wavelength camera AzTEC. With the improved mapping speed of the AzTEC camera combined with dedicated telescope time devoted to deep, large-area extragalactic surveys, we have tripled both the area surveyed towards blank-fields (that is, regions with no known galaxy over-densities) at submm/mm wavelengths and the total number of detected SMGs. Here, we describe the properties and performance of the AzTEC instrument while operating on the James Clerk Maxwell Telescope (JCMT) and the Atacama Submillimeter Telescope Experiment (ASTE). We then present the results from two of the blank-field regions imaged with AzTEC: the JCMT/COSMOS field, which we discovered is over-dense in the number of very bright SMGs, and the ASTE survey of the Great Observatories Origins Deep-South field, which represents one of the deepest surveys ever carried out at submm/mm wavelengths. Finally, we combine the results from all of the blank-fields imaged with AzTEC while operating on the JCMT and the ASTE to calculate the most accurate measurements to date of the SMG number counts.

The physical and morphological properties of the atomic and molecular gas in early stage interacting systems are investigated in detail using two complementary approaches; (1) by studying the response of gas particles and its observational consequences using the results from a numerical simulation of an equal mass disk-disk collision, and (2) by mapping the distribution and kinematics of atomic (H I) and molecular (CO (1-0)) gas in 10 systems that show clear optical evidence of recent interaction. Stars in the simulation respond to the tidal interaction by forming both transient arms and long lived m = 2 bars, but the gas responds differently and flows directly toward the central regions within 108 years after the initial collision, where it forms a dense gas concentration that resembles a nuclear ring. It is further demonstrated that non-circular gas kinematics can produce distinct emission features in the “forbidden velocity quadrants” of the position-velocity diagram (PVD). These theoretical predictions are tested on an observational sample of 10 comparable-mass early stage interacting systems traced in H I and CO (1-0) emission. The H I and H2 masses range from (1.0–34.0) × 109[special characters omitted] and (0.7–44.7) × 109[special characters omitted] in H I and H2 (from CO (1-0)) respectively. The position velocity diagrams (PVDs) and the rotation curves are presented, some of which show observational signature of inflow and/or anomalous kinematical structure possibly related to a nuclear ring. It is found that the average molecular fraction is higher in interacting systems, and that the average Compactness (K) is much smaller, implying an extended and abundant nature of molecular gas in the perturbed disks. New high resolution CO (3-2) interferometric map of the IR-bright interacting galaxy system VV 114 observed with the Submillimeter Array (SMA) reveal a substantial amount (4 × 109[special characters omitted]) of warm and dense gas in the IR-bright but optically obscured galaxy, VV 114E, and the overlap region connecting the two nuclei. Extensive CO (2-1) emission is also detected, revealing detailed distribution and kinematics that are consistent with the earlier CO (1-0) results.

In this thesis I develop Bayesian approach to model galaxy surface brightness and apply it to a bulge-disc decomposition analysis of galaxies in near-infrared band, from Two Micron All Sky Survey (2MASS). The thesis has three main parts. First part is a technical development of Bayesian galaxy image decomposition package GALPHAT based on Markov chain Monte Carlo algorithm. I implement a fast and accurate galaxy model image generation algorithm to reduce computation time and make Bayesian approach feasible for real science analysis using large ensemble of galaxies. I perform a benchmark test of G ALPHAT and demonstrate significant improvement in parameter estimation with a correct statistical confidence. Second part is a performance test for full Bayesian application to galaxy bulge-disc decomposition analysis including not only the parameter estimation but also the model comparison to classify different galaxy population. The test demonstrates that GALPHAT has enough statistical power to make a reliable model inference using galaxy photometric survey data. Bayesian prior update is also tested for parameter estimation and Bayes factor model comparison and it shows that informative prior significantly improves the model inference in every aspects. Last part is a Bayesian bulge-disc decomposition analysis using 2MASS Ks-band selected samples. I characterise the luminosity distributions in spheroids, bulges and discs separately in the local Universe and study the galaxy morphology correlation, by full utilizing the ensemble parameter posterior of the entire galaxy samples. It shows that to avoid a biased inference, the parameter covariance and model degeneracy has to be carefully characterized by the full probability distribution.