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Register a new userIntroducing the FLAMINGOS-2 Split-K Medium Band Filters: The Impact on Photometric Selection of High-z Galaxies in the FENIKS-pilot survey
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Deep near-infrared photometric surveys are efficient in identifying high-redshift galaxies, however they can be prone to systematic errors in photometric redshift. This is particularly salient when there is limited sampling of key spectral features of a galaxys spectral energy distribution (SED), such as for quiescent galaxies where the expected age-sensitive Balmer/4000 A break enter the $K$-band at $z>4$. With single filter sampling of this spectral feature, degeneracies between SED models and redshift emerge. A potential solution to this comes from splitting the $K$-band into multiple filters. We use simulations to show an optimal solution is to add two medium-band filters, $K_mathrm{blue}$ ($lambda_mathrm{cen}$=2.06 $mu$m, $Deltalambda$=0.25 $mu$m) and $K_mathrm{red}$ ($lambda_mathrm{cen}$=2.31 $mu$m, $Deltalambda$=0.27 $mu$m), that are complementary to the existing $K_mathrm{s}$ filter. We test the impact of the $K$-band filters with simulated catalogues comprised of galaxies with varying ages and signal-to-noise. The results suggest that the $K$-band filters do improve photometric redshift constraints on $z>4$ quiescent galaxies, increasing precision and reducing outliers by up to 90$%$. We find that the impact from the $K$-band filters depends on the signal-to-noise, the redshift and the SED of the galaxy. The filters we designed were built and used to conduct a pilot of the FLAMINGOS-2 Extra-galactic Near-Infrared $K$-band Split (FENIKS) survey. While no new $z>4$ quiescent galaxies are identified in the limited area pilot, the $K_mathrm{blue}$ and $K_mathrm{red}$ filters indicate strong Balmer/4000 A breaks in existing candidates. Additionally we identify galaxies with strong nebular emission lines, for which the $K$-band filters increase photometric redshift precision and in some cases indicate extreme star-formation.
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Multiple color selection techniques have been successful in identifying quasars from wide-field broad-band imaging survey data. Among the quasars that have been discovered so far, however, there is a redshift gap at $5 lesssim {rm z} lesssim 5.7$ due to the limitations of filter sets in previous studies. In this work, we present a new selection technique of high redshift quasars using a sequence of medium-band filters: nine filters with central wavelengths from 625 to 1025 nm and bandwidths of 50 nm. Photometry with these medium-bands traces the spectral energy distribution (SED) of a source, similar to spectroscopy with resolution R $sim$ 15. By conducting medium-band observations of high redshift quasars at 4.7 $leq$ z $leq$ 6.0 and brown dwarfs (the main contaminants in high redshift quasar selection) using the SED camera for QUasars in EArly uNiverse (SQUEAN) on the 2.1-m telescope at the McDonald Observatory, we show that these medium-band filters are superior to multi-color broad-band color section in separating high redshift quasars from brown dwarfs. In addition, we show that redshifts of high redshift quasars can be determined to an accuracy of $Delta{rm z}/(1+{rm z}) = 0.002$ -- $0.026$. The selection technique can be extended to z $sim$ 7, suggesting that the medium-band observation can be powerful in identifying quasars even at the re-ionization epoch.
We describe the selection of a sample of photometrically-defined Lyman break galaxies (LBGs) at z~5 using the multi-wavelength imaging data of the ESO Remote Galaxy Survey (ERGS). The data is drawn from ten widely-separated fields covering a total sky area of 275 arcmin squared. Starting with a simple colour (R-I>1.3) and magnitude (I<26.3) cut to isolate the Lyman break and then refining the sample by applying further optical and near-infrared photometric criteria we identify a sample of 253 LBG candidates. We carefully model the completeness of this sample and the factors that affect its reliability. There is considerable overlap between this sample and a spectroscopically-confirmed sample drawn from the same survey and this allows us to determine the reliability of the optical photometric selection (~60 per cent) and to show that the reliability can be significantly improved (to ~80 per cent) by applying near-infrared waveband criteria to exclude very red contaminants. Even this high level of reliability may compromise some statistical studies of LBG properties. We show that over 30 per cent of the highest reliability candidates have multiple UV-luminous components and/or disturbed morphology in HST imaging, though it is unclear whether this represents multiple interacting/merging sources or individual large sources with multiple UV bright regions. Using this sample we confirm that the normalisation of the bright end of the z=5 UV luminosity function (down to M*) is lower than the same at z=4 by a factor of 3. Using a Schechter fit we determine M*uv=-20.9+/-0.2. We discuss whether it is reasonable to expect the UV luminosity function to follow a Schechter function, given the UV emission is short-lived and stochastic, and does not necessarily trace the underlying mass of the galaxy.
Upon commissioning on Gemini South, FLAMINGOS-2 will be one of the most powerful wide-field near-infrared imagers and multi-object spectrographs ever built for use on 8-meter-class telescopes. In order to take best advantage of the strengths of FLAMINGOS-2 early in its life cycle, the instrument team has proposed to use 21 nights of Gemini guaranteed time in 3 surveys -- the FLAMINGOS-2 Early Science Surveys (F2ESS). The F2ESS will encompass 3 corresponding science themes -- the Galactic Center, galaxy evolution, and star formation. In this paper, I review the design performance and status of FLAMINGOS-2, and describe the planned FLAMINGOS-2 Galactic Center Survey.
We present the first measurements of the projected clustering and intrinsic alignments (IA) of galaxies observed by the Physics of the Accelerating Universe Survey (PAUS). With photometry in 40 narrow optical passbands ($450rm{nm}-850rm{nm}$), the quality of photometric redshift estimation is $sigma_{z} sim 0.01(1 + z)$ for galaxies in the $19,rm{deg}^{2}$ Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) W3 field, allowing us to measure the projected 3D clustering and IA for flux-limited, faint galaxies ($i < 22.5$) out to $zsim0.8$. To measure two-point statistics, we developed, and tested with mock photometric redshift samples, `cloned random galaxy catalogues which can reproduce data selection functions in 3D and account for photometric redshift errors. In our fiducial colour-split analysis, we made robust null detections of IA for blue galaxies and tentative detections of radial alignments for red galaxies ($sim1-3sigma$), over scales of $0.1-18,h^{-1}rm{Mpc}$. The galaxy clustering correlation functions in the PAUS samples are comparable to their counterparts in a spectroscopic population from the Galaxy and Mass Assembly survey, modulo the impact of photometric redshift uncertainty which tends to flatten the blue galaxy correlation function, whilst steepening that of red galaxies. We investigate the sensitivity of our correlation function measurements to choices in the random catalogue creation and the galaxy pair-binning along the line of sight, in preparation for an optimised analysis over the full PAUS area.
The determination of galaxy redshifts in James Webb Space Telescope (JWST)s blank-field surveys will mostly rely on photometric estimates, based on the data provided by JWSTs Near-Infrared Camera (NIRCam) at 0.6-5.0 {mu}m and Mid Infrared Instrument (MIRI) at {lambda}>5.0 {mu}m. In this work we analyse the impact of choosing different combinations of NIRCam and MIRI broad-band filters (F070W to F770W), as well as having ancillary data at {lambda}<0.6 {mu}m, on the derived photometric redshifts (zphot) of a total of 5921 real and simulated galaxies, with known input redshifts z=0-10. We found that observations at {lambda}<0.6 {mu}m are necessary to control the contamination of high-z samples by low-z interlopers. Adding MIRI (F560W and F770W) photometry to the NIRCam data mitigates the absence of ancillary observations at {lambda}<0.6 {mu}m and improves the redshift estimation. At z=7-10, accurate zphot can be obtained with the NIRCam broad bands alone when S/N>=10, but the zphot quality significantly degrades at S/N<=5. Adding MIRI photometry with one magnitude brighter depth than the NIRCam depth allows for a redshift recovery of 83-99%, depending on SED type, and its effect is particularly noteworthy for galaxies with nebular emission. The vast majority of NIRCam galaxies with [F150W]=29 AB mag at z=7-10 will be detected with MIRI at [F560W, F770W]<28 mag if these sources are at least mildly evolved or have spectra with emission lines boosting the mid-infrared fluxes.
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