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Register a new userSHELS: Complete Redshift Surveys of Two Widely Separated Fields
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The SHELS (Smithsonian Hectospec Lensing Survey) is a complete redshift survey covering two well-separated fields (F1 and F2) of the Deep Lens Survey. Both fields are more than 94% complete to a Galactic extinction corrected R0 = 20.2. Here we describe the redshift survey of the F1 field centered at R.A. = 00h53m25.3s and Decl = 12d33m55s; like F2, the F1 field covers 4 sq deg. The redshift survey of the F1 field includes 9426 new galaxy redshifts measured with Hectospec on the MMT (published here). As a guide to future uses of the combined survey we compare the mass metallicity relation and the distributions of D4000 as a function of stellar mass and redshift for the two fields. The mass-metallicity relations differ by an insignificant 1.6 sigma. For galaxies in the stellar mass range 1.e10 to 1.e11 MSun, the increase in the star-forming fraction with redshift is remarkably similar in the two fields. The seemingly surprising 31-38% difference in the overall galaxy counts in F1 and F2 is probably consistent with the expected cosmic variance given the subtleties of the relative systematics in the two surveys. We also review the Deep Lens Survey cluster detections in the two fields: poorer photometric data for F1 precluded secure detection of the single massive cluster at z = 0.35 that we find in SHELS. Taken together the two fields include 16,055 redshifts for galaxies with R0 <= 20.2 and 20,754 redshifts for galaxies with R <= 20.6. These dense surveys in two well-separated fields provide a basis for future investigations of galaxy properties and large-scale structure.
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The SHELS (Smithsonian Hectospec Lensing Survey) is a complete redshift survey covering two well-separated fields (F1 and F2) of the Deep Lens Survey to a limiting R = 20.6. Here we describe the redshift survey of the F2 field (R.A.$_{2000}$ = 09$^h$19$^m$32.4$^s$ and Decl.$_{2000}$ = +30$^{circ}$00$^{prime}$00$^{primeprime}$). The survey includes 16,294 new redshifts measured with the Hectospec on the MMT. The resulting survey of the 4 deg$^2$ F2 field is 95% complete to R = 20.6, currently the densest survey to this magnitude limit. The median survey redshift is $ z = 0.3$; the survey provides a view of structure in the range 0.1 $ lesssim z lesssim 0.6$. A movie displays the large-scale structure in the survey region. We provide a redshift, spectral index D$_n$4000, and stellar mass for each galaxy in the survey. We also provide a metallicity for each galaxy in the range 0.2 $< z <0. 38$. To demonstrate potential applications of the survey, we examine the behavior of the index D$_n$4000 as a function of galaxy luminosity, stellar mass, and redshift. The known evolutionary and stellar mass dependent properties of the galaxy population are cleanly evident in the data. We also show that the mass-metallicity relation previously determined from these data is robust to the analysis approach.
Weak lensing surveys are emerging as an important tool for the construction of mass selected clusters of galaxies. We evaluate both the efficiency and completeness of a weak lensing selection by combining a dense, complete redshift survey, the Smithsonian Hectospec Lensing Survey (SHELS), with a weak lensing map from the Deep Lens Survey (DLS). SHELS includes 11,692 redshifts for galaxies with R < 20.6 in the four square degree DLS field; the survey is a solid basis for identifying massive clusters of galaxies with redshift z < 0.55. The range of sensitivity of the redshift survey is similar to the range for the DLS convergence map. Only four the twelve convergence peaks with signal-to-noise > 3.5 correspond to clusters of galaxies with M > 1.7 x 10^14 solar masses. Four of the eight massive clusters in SHELS are detected in the weak lensing map yielding a completeness of roughly 50%. We examine the seven known extended cluster x-ray sources in the DLS field: three can be detected in the weak lensing map, three should not be detected without boosting from superposed large-scale structure, and one is mysteriously undetected even though its optical properties suggest that it should produce a detectable lensing signal. Taken together, these results underscore the need for more extensive comparisons among different methods of massive cluster identification.
The mutually complementary Euclid and Roman galaxy redshift surveys will use Halpha- and [OIII]-selected emission line galaxies as tracers of the large scale structure at $0.9 lesssim z lesssim 1.9$ (Halpha) and $1.5 lesssim z lesssim 2.7$ ([OIII]). It is essential to have a reliable and sufficiently precise knowledge of the expected numbers of Halpha-emitting galaxies in the survey volume in order to optimize these redshift surveys for the study of dark energy. Additionally, these future samples of emission-line galaxies will, like all slitless spectroscopy surveys, be affected by a complex selection function that depends on galaxy size and luminosity, line equivalent width, and redshift errors arising from the misidentification of single emission-line galaxies. Focusing on the specifics of the Euclid survey, we combine two slitless spectroscopic WFC3-IR datasets -- 3D-HST+AGHAST and the WISP survey -- to construct a Euclid-like sample that covers an area of 0.56 deg$^2$ and includes 1277 emission line galaxies. We detect 1091 ($sim$3270 deg$^{-2}$) Halpha+[NII]-emitting galaxies in the range $0.9leq z leq 1.6$ and 162 ($sim$440 deg$^{-2}$) [OIII]$lambda$5007-emitters over $1.5leq z leq 2.3$ with line fluxes $geq 2 times 10^{-16}$ erg s$^{-1}$ cm$^{-2}$. The median of the Halpha+[NII] equivalent width distribution is $sim$250r{A}, and the effective radii of the continuum and Halpha+[NII] emission are correlated with a median of $sim$0.38 and significant scatter ($sigma sim $0.2$-$0.35). Finally, we explore the prevalence of redshift misidentification in future Euclid samples, finding potential contamination rates of $sim$14-20% and $sim$6% down to $2times 10^{-16}$ and $6 times 10^{-17}$ erg s$^{-1}$ cm$^{-2}$, respectively, though with increased wavelength coverage these percentages drop to nearly zero.
A multipath mechanism similar to that used in Australia sixty years ago by the Sea-cliff Interferometer is shown to generate correlations between the periods of oscillations observed by two distant radio telescopes pointed to the Sun. The oscillations are the result of interferences between the direct wave detected in the main antenna lobe and its reflection on ground detected in a side lobe. A model is made of such oscillations in the case of two observatories located at equal longitudes and opposite tropical latitudes, respectively in Ha Noi (Viet Nam) and Learmonth (Australia), where similar radio telescopes are operated at 1.4 GHz. Simple specular reflection from ground is found to give a good description of the observed oscillations and to explain correlations that had been previously observed and for which no satisfactory interpretation, instrumental or other, had been found.
The IRAC mapping of the NMBS-II fields program is an imaging survey at 3.6 and 4.5$mu$m with the Spitzer Infrared Array Camera (IRAC). The observations cover three Canada-France-Hawaii Telescope Legacy Survey Deep (CFHTLS-D) fields, including one also imaged by AEGIS, and two MUSYC fields. These are then combined with archival data from all previous programs into deep mosaics. The resulting imaging covers a combined area of about 3 $deg^2$, with at least $sim$2 hr integration time for each field. In this work, we present our data reduction techniques and document the resulting coverage maps at 3.6 and 4.5$mu$m. All of the images are W-registered to the reference image, which is either the z-band stack image of the 25% best seeing images from the CFHTLS-D for CFHTLS-D1, CFHTLS-D3, and CFHTLS-D4, or the K-band images obtained at the Blanco 4-m telescope at CTIO for MUSYC1030 and MUSYC1255. We make all images and coverage maps described herein publicly available via the Spitzer Science Center.
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