89 research outputs found

    Multi-band Optical and Near-infrared Properties of Faint Submillimeter Galaxies with Serendipitous ALMA Detections

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    We present a catalog of 26 faint submillimeter galaxies (SMGs) in the XMM-LSS field identified by cross-matching serendipitously detected sources in archival ALMA Band 6 and 7 data with multi-band near-infrared (NIR) and optical data from the Spitzer Extragalactic Representative Volume Survey, the VISTA Deep Extragalactic Survey, the Canada-France-Hawaii Telescope Legacy Large Survey, and the Hyper Suprime-Cam Subaru Strategic Program. Of the 26 SMGs in our sample, 15 are identified here for the first time. The majority of the sources in our sample (16/26) have faint submm fluxes (0.1mJy<S1mm<1mJy0.1\,{\rm mJy} < S_{\rm 1\,mm} < 1\,{\rm mJy}). In addition to the 26 SMGs with multi-band optical and NIR detections, there are 60 highly-reliable (>5σ>5\sigma) ALMA sources with no counterpart in any other band down to an IRAC [4.5] ABAB magnitude of 23.7\approx 23.7. To further characterize the 26 galaxies with both ALMA and optical/NIR counterparts, we provide 13-band forced photometry for the entire catalog using the Tractor and calculate photometric redshifts and rest-frame colors. The median redshift of our sample is z=2.66\langle z \rangle = 2.66. We find that our sample galaxies have bluer colors compared to bright SMGs, and the UVJ color plot indicates that their colors are consistent with main sequence star-forming galaxies. Our results provide new insights into the nature of the faint population of SMGs, and also highlight opportunities for galaxy evolution studies based on archival ALMA data.Comment: Accepted for publication in ApJ, 32 pages, 11 figures, 4 table

    Quasars in the 2MASS Second Incremental Data Release

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    Using the 2MASS Second Incremental Data Release, we have searched for near infrared counterparts to 13214 quasars from the Veron-Cetty & Veron(2000) catalog. We have detected counterparts within 4 arcsec for 2277 of the approximately 6320 quasars within the area covered by the 2MASS Second Incremental Data Release. Only 1.6% of these are expected to be chance coincidences. Though this sample is heterogeneous, we find that known radio-loud quasars are more likely to have large near-infrared-to-optical luminosity ratios than radio-quiet quasars are, at a statistically significant level. This is consistent with dust-reddened quasars being more common in radio-selected samples than in optically-selected samples, due to stronger selection effects against dust-reddened quasars in the latter. We also find a statistically significant dearth of optically luminous quasars with large near-infrared-to-optical luminosity ratios. This can be explained in a dust obscuration model but not in a model where synchrotron emission extends from the radio into the near-infrared and creates such large ratios. We also find that selection of quasar candidates from the B-J/J-K color-color diagram, modelled on the V-J/J-K selection method of Warren, Hewett & Foltz (2000), is likely to be more sensitive to dust-obscured quasars than selection using only infrared-infrared colors.Comment: To be published in May issue of Astronomical Journal (26 pages, 8 figures, 2 tables) Replaced Figure 6 and

    The Galaxy Population of Low-Redshift Abell Clusters

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    We present a study of the luminosity and color properties of galaxies selected from a sample of 57 low-redshift Abell clusters. We utilize the non-parametric dwarf-to-giant ratio (DGR) and the blue galaxy fraction (fb) to investigate the clustercentric radial-dependent changes in the cluster galaxy population. Composite cluster samples are combined by scaling the counting radius by r200 to minimize radius selection bias. The separation of galaxies into a red and blue population was achieved by selecting galaxies relative to the cluster color-magnitude relation. The DGR of the red and blue galaxies is found to be independent of cluster richness (Bgc), although the DGR is larger for the blue population at all measured radii. A decrease in the DGR for the red and red+blue galaxies is detected in the cluster core region, while the blue galaxy DGR is nearly independent of radius. The fb is found not to correlate with Bgc; however, a steady decline toward the inner-cluster region is observed for the giant galaxies. The dwarf galaxy fb is approximately constant with clustercentric radius except for the inner cluster core region where fb decreases. The clustercentric radial dependence of the DGR and the galaxy blue fraction, indicates that it is unlikely that a simple scenario based on either pure disruption or pure fading/reddening can describe the evolution of infalling dwarf galaxies; both outcomes are produced by the cluster environment.Comment: 28 pages, 6 figures, accepted for publication in Ap

    The North Dakota Dual Aurora Camera (NoDDAC), a student-led citizen science project: one-year retrospective, future developments, and scientific potential

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    The North Dakota Dual Aurora Camera (NoDDAC) is a student-led project operated in conjunction with the University of North Dakota (UND), the LiveAuroraNetwork, and Aurorasaurus citizen science. Aurora cameras are valuable tools for aurora chasers, and scientists, providing ground-truth visual data to gauge auroral activity, yet at midlatitudes, these facilities are few in number. Deploying aurora cameras in these areas provides a valuable resource for aurora-chasing communities, but also demonstrates scientific merit as the analysis of rare phenomena, such as STEVEs, benefit from multiple geographic observations. What makes this project unique is the student initiative being based at a university observatory, the focus on dual cameras with COTS equipment, and, the emphasis on open data, a responsive community resource, and citizen science. NoDDAC employs the Sony a7s ii camera and Sony 24mm f/1.4 GM lens as a north-facing aurora video camera. A less expensive all-sky Canon T6 camera paired with a Sigma 4.5mm f/2.8 circular fisheye lens continuously captures 60-second images every two minutes. The cameras are stationed at the Martens Observatory operated by the department of physics and astrophysics at UND (48.1oN). Specialized housings from the LiveAuroraNetwork weatherproof both cameras and proprietary IPTimelapse software allows images to be uploaded to a web server and analyzed. The LiveAuroraNetwork hosts the image streams from both cameras on their website and mobile app. When aurora is detected by the IPTimelapse software, the NoDDAC twitter account will post a short clip of the display to alert aurora chasers. These cameras will be shown on the Aurorasaurus auroral oval map along with other citizen scientist observations. Image data are archived and made open source, abiding by the FAIR data use principles. The north-facing camera records video, which will allow for small auroral features to be studied using Zooniverse-style image analysis citizen science efforts. In the first half of 2021, the cameras successfully detected aurora on over 20 occasions, including overhead aurora and STEVE, and rare noctilucent clouds. This presentation will reflect on the first year of NoDDAC, outline a timeline for NoDDAC’s future, and open the floor for collaborations with other citizen science efforts.https://commons.und.edu/as-showcase/1007/thumbnail.jp

    Globular cluster population of the HST frontier fields galaxy J07173724+3744224

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    We present the first measurement of the globular cluster population surrounding the elliptical galaxy J07173724+3744224 (z=0.1546). This galaxy is located in the foreground in the field-of-view of the Hubble Space Telescope (HST) Frontier Fields observations of galaxy cluster MACS J0717.5+3745 (z=0.5458). Based on deep HST ACS F435W, F606W, and F814W images, we find a total globular cluster population of N_tot = 3441 +/- 1416. Applying the appropriate extinction correction and filter transformation from ACS F814W to the Johnson V-band, we determine that the host galaxy has an absolute magnitude of M_V = -22.2. The specific frequency was found to be S_N = 4.5 +/- 1.8. The radial profile of the globular cluster system was best fit using a powerlaw of the form σR0.6\sigma\sim R^{-0.6}, with the globular cluster population found to be more extended than the halo light of the host galaxy (σhaloR1.7\sigma_{halo}\sim R^{-1.7}). The F435W-F814W colour distribution suggests a bimodal population, with red globular clusters 1-3x more abundant than blue clusters. These results are consistent with the host elliptical galaxy J07173724+3744224 having formed its red metal-rich GCs in situ, with the blue metal-poor globular clusters accreted from low-mass galaxies.Comment: 21 pages, 14 figures, 2 tables, revised following peer-review, accepted for publication in MNRA

    U-band Measurement of Star Formation in Cluster Galaxies

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    We propose to obtain deep U-band observations of 14 low-redshift (z ≤ 0.06) galaxy clusters using the WIYN 0.9m+HDI telescope/detector to complete our survey to probe star formation of galaxies in high-density environments. These observations, combined with previously obtained data of 11 clusters observed using the same telescope+detector, will give us a statistically significant sample for the Ph.D. dissertation of co-I Gihan Gamage. Clusters are selected from 57 clusters in which we have obtained deep B- and R-band data using the KPNO 0.9m+MOSA. U-band data will allow us to explore relative changes in the luminosity function for the U- and R-band as a function of cluster-centric radius. The large field-of-view of the telescope+detector will permit us to map out the spatial distribution of star forming galaxies from the core region to the outskirts. Comparing U-band observations with our R-band data will provide the necessary leverage to look for enhancements/quenching of star formation as galaxies fall into the cluster. These observations allow us to probe ~ 2 mag fainter than SDSS

    Mapping Star Formation from the Core to the Outskirts of Galaxy Clusters

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    We propose for time to complete our u- and r-band imaging program of 30 low-redshift (z ≤ 0.03) galaxy clusters using the CTIO Blanco 4m+DECam telescope/detector combination. These data will allow us to probe star formation from the cluster core to the infall region, and complete the acquisition of observations for the Ph.D. dissertation of Gihan Gamage (University of North Dakota). The deep u- and r-band data will allow us to explore relative changes in the luminosity function, dwarf-to-giant ratio, blue fraction, and galaxy morphological type as a function of cluster-centric radius for a statistically significant sample of 30 clusters. The large field-of-view of the telescope+detector will permit us to not only map star formation out to the infall region, but also to probe dwarf galaxies using a reasonable exposure time due to the low redshift of our target sample. The comparison of u- and r-band observations will provide the necessary leverage to look for enhancements/quenching of star formation as galaxies fall into the cluster environment from the low density field region

    Multi-Band Optical and Near-Infrared Properties of Faint Submillimeter Galaxies with Serendipitous ALMA Detections

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    We present a catalog of 26 faint submillimeter galaxies (SMGs) in the XMM Large Scale Structure (XMM-LSS) field identified by cross-matching serendipitously detected sources in archival pre–Atacama Large Millimeter Array (ALMA) band 6 and 7 data with multiband near-infrared (NIR) and optical data from the Spitzer Extragalactic Representative Volume Survey, the VISTA Deep Extragalactic Survey, the Canada–France–Hawaii Telescope Legacy Large Survey, and the Hyper Suprime-Cam Subaru Strategic Program. Of the 26 SMGs in our sample, 15 are identified here for the first time. The majority of the sources in our sample (16/26) have faint submillimeter fluxes (0.1 mJy \u3c S 1mm \u3c 1 mJy). In addition to the 26 SMGs with multiband optical and NIR detections, there are 60 highly reliable (\u3e5σ) ALMA sources with no counterpart in any other band down to an Infrared Array Camera (IRAC) [4.5] AB magnitude of ≈23.7. To further characterize the 26 galaxies with both ALMA and optical/NIR counterparts, we provide 13-band forced photometry for the entire catalog using the Tractor and calculate photometric redshifts and rest-frame colors. The median redshift of our sample is . We find that our sample galaxies have bluer colors compared to bright SMGs, and the UVJ color plot indicates that their colors are consistent with main-sequence star-forming galaxies. Our results provide new insights into the nature of the faint population of SMGs and also highlight opportunities for galaxy evolution studies based on archival ALMA data
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