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"McCabe, Tyler"
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Investigating Faint Light and Diffuse Gas Around Galaxies in Group Environments
One of the fundamental questions in extragalactic astronomy is understanding how galaxies grow and evolve. The answer to this question is rooted in a galaxy’s ability to accrete fresh gas to sustain star formation as well as the environment in which a galaxy is located. In this dissertation, diffuse light in the outskirts of galaxies is investigated using ~28 hours of r-band imaging with the Large Binocular Telescope (LBT) of the GOODS-N field. Optimal resolution and optimal depth mosaics were created to investigate the ability for the same dataset to enhance galaxy substructure as well as faint light and tidal tails and interactions. This technique was applied to ~35 hours of U-band LBT imaging of the COSMOS field where an optimal depth mosaic was created and combined with a catalog of galaxy groups to search for intragroup light (IGrL). By using two methods to stack groups and search for IGrL, robust upper limits were derived and compared with other studies providing insight for the origins and buildup of IGrL. Lastly, the intragroup medium (IGrM) was directly traced with the Hubble Space Telescope (HST) using quasar absorption spectroscopy. For a sample of 18 galaxy groups, a patchy, multiphase IGrM was observed with cool and hot ionization states aligned with minimal velocity offsets. While no volume filling component of the IGrM was detected, the impact of the IGrM on group evolution is discussed as well as future ways to study the IGrM.
Dissertation
Deep Large Binocular Camera r-band Observations of the GOODS-N Field
We obtained 838 Sloan r-band images (∼28 hr) of the GOODS-North field with the Large Binocular Camera (LBC) on the Large Binocular Telescope in order to study the presence of extended, low surface brightness features in galaxies and investigate the trade-off between image depth and resolution. The individual images were sorted by effective seeing, which allowed for optimal resolution and optimal depth mosaics to be created with all images with seeing FWHM < 0”.9 and FWHM < 2”.0, respectively. Examining bright galaxies and their substructure as well as accurately deblending overlapping objects requires the optimal resolution mosaic, while detecting the faintest objects possible (to a limiting magnitude of m
AB ∼ 29.2 mag) requires the optimal depth mosaic. The better surface brightness sensitivity resulting from the larger LBC pixels, compared to those of extant WFC3/UVIS and ACS/WFC cameras aboard the Hubble Space Telescope allows for unambiguous detection of both diffuse flux and very faint tidal tails. Azimuthally-averaged radial surface brightness profiles were created for the 360 brightest galaxies in each of the two mosaics. On average, these profiles showed minimal difference between the optimal resolution and optimal depth surface brightness profiles. However, ≲15% of the profiles show excess flux in the galaxy outskirts down to surface brightness levels of
μ
r
AB
≃
31
mag arcsec−2. This is relevant to Extragalactic Background Light (EBL) studies as diffuse light in the outer regions of galaxies are thought to be a major contribution to the EBL. While some additional diffuse light exists in the optimal depth profiles compared to the shallower, optimal resolution profiles, we find that diffuse light in galaxy outskirts is a minor contribution to the EBL overall in the r-band.
Journal Article
Deep Large Binocular Camera r-band Observations of the GOODS-N Field
We obtained 838 Sloan r -band images (∼28 hr) of the GOODS-North field with the Large Binocular Camera (LBC) on the Large Binocular Telescope in order to study the presence of extended, low surface brightness features in galaxies and investigate the trade-off between image depth and resolution. The individual images were sorted by effective seeing, which allowed for optimal resolution and optimal depth mosaics to be created with all images with seeing FWHM < 0.″9 and FWHM < 2.″0, respectively. Examining bright galaxies and their substructure as well as accurately deblending overlapping objects requires the optimal resolution mosaic, while detecting the faintest objects possible (to a limiting magnitude of m AB ∼ 29.2 mag) requires the optimal depth mosaic. The better surface brightness sensitivity resulting from the larger LBC pixels, compared to those of extant WFC3/UVIS and ACS/WFC cameras aboard the Hubble Space Telescope allows for unambiguous detection of both diffuse flux and very faint tidal tails. Azimuthally-averaged radial surface brightness profiles were created for the 360 brightest galaxies in each of the two mosaics. On average, these profiles showed minimal difference between the optimal resolution and optimal depth surface brightness profiles. However, ≲15% of the profiles show excess flux in the galaxy outskirts down to surface brightness levels of μ r AB ≃ 31 mag arcsec −2 . This is relevant to Extragalactic Background Light (EBL) studies as diffuse light in the outer regions of galaxies are thought to be a major contribution to the EBL. While some additional diffuse light exists in the optimal depth profiles compared to the shallower, optimal resolution profiles, we find that diffuse light in galaxy outskirts is a minor contribution to the EBL overall in the r -band.
Journal Article
Detection of a Multiphase Intragroup Medium: Results from the COS-IGrM Survey
We present the results of the COS Intragroup Medium (COS-IGrM) Survey that used the Cosmic Origins Spectrograph on the Hubble Space Telescope to observe a sample of 18 UV bright quasars, each probing the intragroup medium (IGrM) of a galaxy group. We detect Ly\\(\\alpha\\), C II, N V, Si II, Si III, and O VI in multiple sightlines. The highest ionization species detected in our data is O VI, which was detected in 8 out of 18 quasar sightlines. The wide range of ionization states observed provide evidence that the IGrM is patchy and multiphase. We find that the O VI detections generally align with radiatively cooling gas between \\(10^{5.8}\\) and \\(10^6\\) K. The lack of O VI detections in 10 of the 18 groups illustrates that O VI may not be the ideal tracer of the volume filling component of the IGrM. Instead, it either exists at trace levels in a hot IGrM or is generated in the boundary between the hotter IGrM and cooler gas.
Paper
DIISC -- VI (COS-DIISC): UV Metal Absorption Relative to the H I disk of Galaxies
As part of the Deciphering the Interplay between the Interstellar medium, Stars, and the Circumgalactic medium (DIISC) survey, we present the UV metal absorption features in the Circumgalactic Medium (CGM) near the H I gas disk (\\(<\\)4.5\\(R_\\mathrm{HI}\\)) of 31 nearby galaxies through quasar absorption line spectroscopy. Of the ions under study, Si III \\(\\lambda1206\\) was most frequently detected (18 of 31 sight lines), while C II \\(\\lambda1334\\) and Si II \\(\\lambda1260\\) were detected in 17 and 15 of 31 sight lines, respectively. Many components were consistent with photoionization equilibrium models, most of the cold and cool gas phase clouds were found to have lengths smaller than 2 kpc. Sight lines with smaller impact parameters (\\(\\rho\\)) normalized by the galaxy's virial radius (\\(R_\\mathrm{vir}\\)) and H I radius (\\(R_\\mathrm{HI}\\)) tend to have more components and larger rest-frame equivalent widths (\\(W_r\\)) than those that probe the CGM at larger radii. In particular, we find that the location of metals are better traced by \\(\\rho\\) / \\(R_\\mathrm{HI}\\) rather than the traditional \\(\\rho\\) / \\(R_\\mathrm{vir}\\). Larger covering fractions are found closer to galaxies, with a radial decline that depends on the \\(W_r\\) limit used. Our results provide new insights into the spatial distribution of metals around the H I disks of low-redshift galaxies.
Paper
Searching for Intragroup Light in Deep U-band Imaging of the COSMOS Field
We present the results of deep, ground based U-band imaging with the Large Binocular Telescope of the Cosmic Evolution Survey (COSMOS) field as part of the near-UV imaging program, UVCANDELS. We utilize a seeing sorted stacking method along with night-to-night relative transparency corrections to create optimal depth and optimal resolution mosaics in the U-band, which are capable of reaching point source magnitudes of AB 26.5 mag at 3 sigma. These ground based mosaics bridge the wavelength gap between the HST WFC3 F27W and ACS F435W images and are necessary to understand galaxy assembly in the last 9-10 Gyr. We use the depth of these mosaics to search for the presence of U-band intragroup light (IGrL) beyond the local Universe. Regardless of how groups are scaled and stacked, we do not detect any U-band IGrL to unprecedented U-band depths of 29.1-29.6 mag/arcsec2, which corresponds to an IGrL fraction of less than 1% of the total group light. This stringent upper limit suggests that IGrL does not contribute significantly to the Extragalactic Background Light at short wavelengths. Furthermore, the lack of UV IGrL observed in these stacks suggests that the atomic gas observed in the intragroup medium (IGrM) is likely not dense enough to trigger star formation on large scales. Future studies may detect IGrL by creating similar stacks at longer wavelengths or by pre-selecting groups which are older and/or more dynamically evolved similar to past IGrL observations of compact groups and loose groups with signs of gravitational interactions.
Paper
PEARLS: Discovery of Point-Source Features Within Galaxies in the North Ecliptic Pole Time Domain Field
The first public 0.9-4.4{\\mu}m NIRCam images of the North Ecliptic Pole (NEP) Time Domain Field (TDF) uncovered galaxies displaying point-source features in their cores as seen in the longer wavelength filters. We visually identified a sample of 66 galaxies (~1 galaxy per arcmin2) with point-like cores and have modeled their two-dimensional light profiles with GalFit, identifying 16 galactic nuclei with measurable point-source components. GalFit suggests the visual sample is a mix of both compact stellar bulge and point-source galaxy cores. This core classification is complemented by spectral energy distribution (SED) modeling to infer the sample's active galactic nucleus (AGN) and host-galaxy parameters. For galaxies with measurable point-source components, the median fractional AGN contribution to their 0.1-30.0{\\mu}m flux is 0.44, and 14/16 are color-classified AGN. We conclude that near-infrared point-source galaxy cores are signatures of AGN. In addition, we define an automated sample-selection criterion to identify these point-source features. These criteria can be used in other extant and future NIRCam images to streamline the search for galaxies with unresolved IR-luminous AGN. The James Webb Space Telescope's superb angular resolution and sensitivity at infrared wavelengths is resurrecting the morphological identification of AGN.
Paper
The UV luminosity function at 0.6 < z < 1 from UVCANDELS
UVCANDELS is a HST Cycle-26 Treasury Program awarded 164 orbits of primary ultraviolet (UV) F275W imaging and coordinated parallel optical F435W imaging in four CANDELS fields: GOODS-N, GOODS-S, EGS, and COSMOS, covering a total area of \\(\\sim426\\) arcmin\\(^2\\). This is \\(\\sim2.7\\) times larger than the area covered by previous deep-field space UV data combined, reaching a depth of about 27 and 28 ABmag (\\(5\\sigma\\) in \\(0.2\"\\) apertures) for F275W and F435W, respectively. Along with the new photometric catalogs, we present an analysis of the rest-frame UV luminosity function (LF), relying on our UV-optimized aperture photometry method yielding a factor of \\(1.5\\times\\) increase than the H-isophot aperture photometry in the signal-to-noise ratios of galaxies in our F275W imaging. Using well tested photometric redshift measurements we identify 5810 galaxies at redshifts \\(0.6
Paper
Deep Large Binocular Camera r-band Observations of the GOODS-N Field
We obtained 838 Sloan r-band images (~28 hrs) of the GOODS-North field with the Large Binocular Camera (LBC) on the Large Binocular Telescope in order to study the presence of extended, low surface brightness features in galaxies and investigate the trade-off between image depth and resolution. The individual images were sorted by effective seeing, which allowed for optimal resolution and optimal depth mosaics to be created with all images with seeing FWHM < 0.9\" and FWHM < 2.0\", respectively. Examining bright galaxies and their substructure as well as accurately deblending overlapping objects requires the optimal resolution mosaic, while detecting the faintest objects possible (to a limiting magnitude of \\(m_{AB}\\) ~ 29.2 mag) requires the optimal depth mosaic. The better surface brightness sensitivity resulting from the larger LBC pixels, compared to those of extant WFC3/UVIS and ACS/WFC cameras aboard the Hubble Space Telescope (HST) allows for unambiguous detection of both diffuse flux and very faint tidal tails. We created azimuthally-averaged radial surface brightness profiles for the 360 brightest galaxies in the mosaics. We find little difference in the majority of the light profiles from the optimal resolution and optimal depth mosaics. However, \\(\\lesssim\\) 15% of the profiles show excess flux in the galaxy outskirts down to surface brightness levels of \\(\\mu^{AB}_{r} \\) \\(\\simeq\\) 31 mag arcsec \\(^{-2}\\). This is relevant to Extragalactic Background Light (EBL) studies as diffuse light in the outer regions of galaxies are thought to be a major contribution to the EBL. While some additional diffuse light exists in the optimal depth profiles compared to the shallower, optimal resolution profiles, we find that diffuse light in galaxy outskirts is a minor contribution to the EBL overall in the r-band.
Paper