Using SAOImage DS9 & Hubble Space Telescope Data to Identify Globular Clusters in IC 219

Globular clusters are tightly bound spherical clusters of stars located within the halo of elliptical and spiral galaxies. They are among the oldest stars found in a galaxy, and their presence and abundance in a galaxy’s halo offer insight on the age, composition, and formation of the galaxy.1 I used a Hubble Space Telescope (HST) image and SAOImage DS9, a powerful imaging tool used to analyze astronomical data, to identify the size and locate the position of globular cluster (GC) candidates in IC 219

The occulting galaxy pair UGC 3995 : dust properties from HST and CALIFA data.

UGC 3995 is an interacting and occulting galaxy pair. UGC 3995B is a foreground face-on spiral and UGC 3995A a bright background spiral with an AGN. We present analysis of the dust in the disc of UGC 3995B based on archival Hubble Space Telescope (HST) WFPC2 and PPAK IFU data from the CALIFA survey’s first data release. From the HST F606W image, we construct an extinction map by modeling the isophotes of the background galaxy UGC 3995A and the resulting transmission through UGC 3995B. This extinction map of UGC 3995B shows several distinct spiral extinction features. The radial distribution of AV values declines slowly with peaks corresponding to the spiral structures. The distribution of AV values in the HST extinction map peaks near AV = 0.3–0.4. Beyond this point, the distribution of AV values drops like an exponential: N(AV) = N0 × e(−AV/0.5). The 0.5 value is higher than typical for a spiral galaxy. The outer arms may be tidally distended; the extinction in the corresponding interarm regions is small to an unusually small radius. To analyze the PPAK IFU data, we take the ratio of a fibre spectrum in the overlap region and the corresponding background fiber spectrum to construct an extinction curve. We fit the Cardelli, Clayton and Mathis (CCM) curve to the extinction curve of each fiber element in the overlap region. A map of the extinction constructed from PPEX IFU data-cubes shows the same spiral structure of the HST extinction map but the some differences in the distribution of the normalization of the CCM fits (AV). The inferred extinction slopes (RV) maps do not display any structure and a range of values partly due to the sampling effects of the disc by fibers, sometimes due to bad fits, and possibly partly due to some reprocessing of dust grains in the interacting disc. We compare these findings to our other analysis of an occulting pair with HST and IFU data. In both cases the canonical RV = 3.1 is not recovered even though there is enough signal in the extinction curve. We attribute this to mixing opaque and more transparent sections of the disc in each resolution element (~3′′ or 0.9 kpc). To illustrate the difficulty of imposing a RV = 3.1 law over a section of a spiral disc, we average all spectra and show how a fully gray extinction curve is recovered

The Loneliest Galaxies in the Universe: A GAMA and GalaxyZoo Study on Void Galaxy Morphology

The large-scale structure (LSS) of the universe is comprised of galaxy filaments, tendrils, and voids. The majority of the universe’s volume is taken up by these voids, which exist as underdense, but not empty, regions. The galaxies found inside voids are void galaxies and expected to be some of the most isolated objects in the universe. However, their standard morphology remains poorly studied. This study, using the Galaxy and Mass Assembly (GAMA) survey and Galaxy Zoo’s SDSS survey, aims to remedy this. To do so, survey results from GAMA have been plotted using the Sérsic index (n) to analyze morphology, while data from Galaxy Zoo’s crowdsourced study supplies a second analysis. For completeness purposes, we only include void galaxies identified by Alpaslan et al. 2014 with a redshift (z) between .08 and .215 and stellar mass (M*) between 109.35 and 1011.5. We then utilize Kolmogorov-Smirnov (KS) testing for significance. As a result, we conclude that, as supported by previous literature (Kreckel et al. 2014, Beygu et al. 2015, Beygu et al. 2016, Fraser-McKelvie et al. 2016, Pustilnik et al. 2019) , most void galaxies have a disky morphology with Sérsic index

Automating the Synthetic Field Method:Application to Sextans A

We have automated the ``Synthetic Field Method'' developed by Gonzalez et al.(1998) and used it to measure the opacity of the ISM in the Local Group dwarf galaxy Sextans A by using the changes in counts of background galaxies seen through the foreground system. The Sextans A results are consistent with the observational relation found by Cuillandre et al. (2001) between dust opacity and HI column density in the outer parts of M31.Comment: 4 pages, 6 figures, submitted for the proceedings of The Dynamics, Structure and History of Galaxies: A Workshop in Honour of Prof. Ken Freema

Total Opacity of Local Group Galaxies and Large Scale Structure behind the Galactic Bulge

Recently, we have developed and calibrated the Synthetic Field Method to derive total extinction through disk galaxies. The method is based on the number counts and colors of distant background field galaxies that can be seen through the foreground object. Here, we investigate how large (10-m) and very large (20 to 30-m), diffraction-limited, optical and infrared telescopes in space would improve the detection of background galaxies behind Local Group objects, including the Galactic bulge. We find that, besides and perhaps more important than telescope size, a well-behaved, well-characterized PSF would facilitate in general the detection of faint objects in crowded fields, and greatly benefit several other important research areas, like the search for extrasolar planets, the study of quasar hosts and, most relevant for this meeting, the surveying of nearby large scale structure in the Zone of Avoidance, in particular behind the Galactic bulge.Comment: 9 pages, 4 figures, 1 table, uses asp2004.sty. To appear in ``Nearby Large-Scale Structures and the Zone of Avoidance,'' eds. A.P. Fairall, P. Woudt, ASP Conf. Series, in press, San Francisco: Astronomical Society of the Pacifi

The Sizes of Candidate z∼9−10z\sim9-10 Galaxies: confirmation of the bright CANDELS sample and relation with luminosity and mass

Recently, a small sample of six $z\sim9-10$ candidates was discovered in CANDELS that are $\sim10-20\times$ more luminous than any of the previous $z\sim9-10$ galaxies identified over the HUDF/XDF and CLASH fields. We measure the sizes of these candidates to map out the size evolution of galaxies from the earliest observable times. Their sizes are also used to provide a valuable constraint on whether these unusual galaxy candidates are at high redshift. Using galfit to derive sizes from the CANDELS F160W images of these candidates, we find a mean size of 0.13$\pm$0.02" (or 0.5$\pm$0.1 kpc at $z\sim9-10$). This handsomely matches the 0.6 kpc size expected extrapolating lower redshift measurements to $z\sim9-10$, while being much smaller than the 0.59" mean size for lower-redshift interlopers to $z\sim9-10$ photometric selections lacking the blue IRAC color criterion. This suggests that source size may be an effective constraint on contaminants from $z\sim9-10$ selections lacking IRAC data. Assuming on the basis of the strong photometric evidence that the Oesch et al. 2014 sample is entirely at $z\sim9-10$, we can use this sample to extend current constraints on the size-luminosity, size-mass relation, and size evolution of galaxies to $z\sim10$. We find that the $z\sim9-10$ candidate galaxies have broadly similar sizes and luminosities as $z\sim6$-8 counterparts with star-formation-rate surface densities in the range of $\rm \Sigma_{SFR}=1-20\, M_\odot~ yr^{-1}\, kpc^{-2}$. The stellar mass-size relation is uncertain, but shallower than those inferred for lower-redshift galaxies. In combination with previous size measurements at z=4-7, we find a size evolution of $(1+z)^{-m}$ with $m=1.0\pm0.1$ for $>0.3L^*_{z=3}$ galaxies, consistent with the evolution previously derived from $2 < z < 8$ galaxies.Comment: 9 figures, 5 tables, accepted by Ap

The onset of warps in Spitzer observations of edge-on spiral galaxies.

We analyse warps in the nearby edge-on spiral galaxies observed in the Spitzer/Infrared Array Camera (IRAC )4.5-μm band. In our sample of 24 galaxies, we find evidence of warp in 14 galaxies. We estimate the observed onset radii for the warps in a subsample of 10 galaxies. The dark matter distribution in each of these galaxies are calculated using the mass distribution derived from the observed light distribution and the observed rotation curves. The theoretical predictions of the onset radii for the warps are then derived by applying a self-consistent linear response theory to the obtained mass models for six galaxies with rotation curves in the literature. By comparing the observed onset radii to the theoretical ones, we find that discs with constant thickness can not explain the observations; moderately flaring discs are needed. The required flaring is consistent with the observations. Our analysis shows that the onset of warp is not symmetric in our sample of galaxies. We define a new quantity called the onsetasymmetry index and study its dependence on galaxy properties. The onset asymmetries in warps tend to be larger in galaxies with smaller disc scalelengths. We also define and quantify the global asymmetry in the stellar light distribution, that we call the edge-on asymmetry in edge-on galaxies. It is shown that in most cases the onset asymmetry in warp is actually anticorrelated with the measured edge-on asymmetry in our sample of edge-on galaxies and this could plausibly indicate that the surrounding dark matter distribution is asymmetric

TESS as a Low-surface-brightness Observatory: Cutouts from Wide-area Coadded Images

We present a mosaic of those co-added Full Frame Images acquired by the TESS satellite that had been released in 2020 April. The mosaic shows substantial stray light over the sky. Yet over spatial scales of a few degrees, the background appears uniform. This result indicates that TESS has considerable potential as a Low Surface Brightness Observatory. The co-added images are freely available as a High Level Science Product (HLSP) at MAST and accessible through a Jupyter Notebook