High Galactic Latitude Fields Research Articles

New Horizons Observations of the Cosmic Optical Background

Abstract We used existing data from the New Horizons Long-range Reconnaissance Imager (LORRI) to measure the optical-band (0.4 ≲ λ ≲ 0.9 μm) sky brightness within seven high–Galactic latitude fields. The average raw level measured while New Horizons was 42–45 au from the Sun is 33.2 ± 0.5 nW m−2 sr−1. This is ∼10× as dark as the darkest sky accessible to the Hubble Space Telescope, highlighting the utility of New Horizons for detecting the cosmic optical background (COB). Isolating the COB contribution to the raw total required subtracting scattered light from bright stars and galaxies, faint stars below the photometric detection limit within the fields, and diffuse Milky Way light scattered by infrared cirrus. We removed newly identified residual zodiacal light from the IRIS 100 μm all-sky maps to generate two different estimates for the diffuse Galactic light. Using these yielded a highly significant detection of the COB in the range 15.9 ± 4.2 (1.8 stat., 3.7 sys.) nW m−2 sr−1 to 18.7 ± 3.8 (1.8 stat., 3.3 sys.) nW m−2 sr−1 at the LORRI pivot wavelength of 0.608 μm. Subtraction of the integrated light of galaxies fainter than the photometric detection limit from the total COB level left a diffuse flux component of unknown origin in the range 8.8 ± 4.9 (1.8 stat., 4.5 sys.) nW m−2 sr−1 to 11.9 ± 4.6 (1.8 stat., 4.2 sys.) nW m−2 sr−1. Explaining it with undetected galaxies requires the assumption that the galaxy count faint-end slope steepens markedly at V > 24 or that existing surveys are missing half the galaxies with V < 30.

Mapping the Stellar Halo with the H3 Spectroscopic Survey

Abstract Modern theories of galaxy formation predict that the Galactic stellar halo was hierarchically assembled from the accretion and disruption of smaller systems. This hierarchical assembly is expected to produce a high degree of structure in the combined phase and chemistry space; this structure should provide a relatively direct probe of the accretion history of our Galaxy. Revealing this structure requires precise 3D positions (including distances), 3D velocities, and chemistry for large samples of stars. The Gaia satellite is delivering proper motions and parallaxes for >1 billion stars to G ≈ 20. However, radial velocities and metallicities will only be available to G ≈ 15, which is insufficient to probe the outer stellar halo (≳10 kpc). Moreover, parallaxes will not be precise enough to deliver high-quality distances for stars beyond ∼10 kpc. Identifying accreted systems throughout the stellar halo therefore requires a large ground-based spectroscopic survey to complement Gaia. Here we provide an overview of the H3 Stellar Spectroscopic Survey, which will deliver precise stellar parameters and spectrophotometric distances for ≈200,000 stars to r = 18. Spectra are obtained with the Hectochelle instrument at the MMT, which is configured for the H3 Survey to deliver resolution R ≈ 23,000 spectra covering the wavelength range 5150–5300 Å. The survey is optimized for stellar halo science and therefore focuses on high Galactic latitude fields ( ), sparsely sampling 15,000 sq. degrees. Targets are selected on the basis of Gaia parallaxes, enabling very efficient selection of bona fide halo stars. The survey began in the fall of 2017 and has collected 88,000 spectra to-date. All of the data, including the derived stellar parameters, will eventually be made publicly available via the survey website: h3survey.rc.fas.harvard.edu.

A Code for Robust Astrometric Solution of Astronomical Images

I present a software tool for solving the astrometry of astronomical images. The code puts emphasis on robustness against failures for correctly matching the sources in the image to a reference catalog, and on the stability of the solutions over the field of view (e.g., using orthogonal polynomials for the fitted transformation). The code was tested on over 5 × 104 images from various sources, including the Palomar Transient Factory (PTF) and the Zwicky Transient Facility (ZTF). The tested images equally represent low and high Galactic latitude fields and exhibit failure/bad-solution rate of ≲2 × 10−5. Running on PTF 60-s integration images, and using the GAIA-DR2 as a reference catalog, the typical two-axes-combined astrometric root-mean square (rms) is 14 mas at the bright end, presumably due to astrometric scintillation noise and systematic errors. I discuss the effects of seeing, airmass, and the order of the transformation on the astrometric accuracy. The software, available online, is developed in MATLAB as part of an astronomical image processing environment and it can be run also as a stand-alone code.

A MILLISECOND INTERFEROMETRIC SEARCH FOR FAST RADIO BURSTS WITH THE VERY LARGE ARRAY

A MILLISECOND INTERFEROMETRIC SEARCH FOR FAST RADIO BURSTS WITH THE VERY LARGE ARRAY

The stellar activity‐rotation relationship

AbstractUsing a new catalog of 824 solar and late‐type stars with measured X‐ray luminosities and rotation periods we have studied the relationship between rotation and stellar activity that is believed to be a probe of the underlying stellar dynamo. Using an unbiased subset of the sample we calculate the power law slope of the unsaturated regime of the activity‐rotation relationship as LX/Lbol α Roβ, where β = –2.70 ± 0.13. Notably this is inconsistent with the canonical β = –2 slope to a confidence of 5σ are argues for an interface‐type dynamo. Super‐saturation is observed for the fastest rotators in our sample and its parametric dependencies are explored. Significant correlations are found with both the corotation radius and the excess polar updraft, the latter theory being preferred as it is supported by other observations. We also present a new X‐ray population synthesis model of the mature stellar component of our Galaxy and use it to reproduce deep observations of a high Galactic latitude field. The model, XStar, can be used to test models of stellar spin‐down and dynamo decay, as well as for estimating stellar X‐ray contamination rates for non‐stellar studies. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The bright end of thez ~ 7UVluminosity function from a wide and deep HAWK-I survey

(Abridged) We present here the second half of an ESO Large Programme, which exploits the unique combination of area and sensitivity provided in the near-IR by the camera Hawk-I at the VLT. We have obtained - 30 observing hours with Hawk-I in the Y-band of two high galactic latitude fields. We combined the Y-band data with deep J and K Hawk-I observations, and with FORS1/FORS2 U, B, V, R, I, and Z observations to select z-drop galaxies having Z - Y > 1, no optical detection and flat Y - J and Y - K colour terms. We detect 8 high-quality candidates in the magnitude range Y = 25.5 - 26.5 that we add to the z-drop candidates selected in two Hawk-I pointings over the GOODS-South field. We use this full sample of 15 objects found in -161 arcmin^2 of our survey to constrain the average physical properties and the evolution of the number density of z ~ 7 LBGs. A stacking analysis yields a best-fit SED with photometric redshift z= 6.85 +0.20 -0.15 and an E(B-V)=0.05 +0.15 -0.05. We compute a binned estimate of the z ~ 7 LF and explore the effects of photometric scatter and model uncertainties on the statistical constraints. After accounting for the expected incompleteness through MonteCarlo simulations, we strengthen our previous finding that a Schechter luminosity function constant from z=6 to z=7 is ruled out at a >99% confidence level, even including the effects of cosmic variance. For galaxies brighter than M_1500= -19.0, we derive a luminosity density rho_UV = 1.5^{+2.1}{-0.8} x 10^25 erg/s/Hz/Mpc^3, implying a decrease by a factor 3.5 from z=6 to z=6.8. We find that, under standard assumptions, the emission rate of ionizing photons coming from UV bright galaxies is lower by at least a factor of two than the value required for reionization. Finally, we exploit deep Hawk-I J and K band observations to derive an upper limit on the number density of M1500<~ -22.0 LBGs at z-8 (Y-dropouts).

Metallicities and ages of stellar populations at a high Galactic latitude field

We present an analysis of $UBVRI$ data from the Selected Area SA 141. By applying recalibrated methods of measuring ultraviolet excess (UVX), we approximate abundances and absolute magnitudes for 368 stars over 1.3 square degrees out to distances over 10 kpc. With the density distribution constrained from our previous photometric parallax investigations and with sufficient accounting for the metallicity bias in the UVX method, we are able to compare the vertical abundance distribution to those measured in previous studies. We find that the abundance distribution has an underlying uniform component consistent with previous spectroscopic results that posit a monometallic thick disk and halo with abundances of $[Fe/H]$ = $-$0.8 and $-$1.4, respectively. However, there are a number of outlying data points that may indicate contamination by more metal-rich halo streams. The absence of vertical abundance gradients in the Galactic stellar populations and the possible presence of interloping halo streams would be consistent with expectations from merger models of Galaxy formation. We find that our UVX method has limited sensitivity in exploring the metallicity distribution of the distant Galactic halo, owing to the poor constraint on the $UBV$ properties of very metal-poor stars. The derivation of metallicities from broadband $UBV$ photometry remains fundamentally sound for the exploration of the halo but is in need of both improved calibration and superior data.

Faint Objects at High Galactic Latitudes in the Sloan Digital Sky Survey

ABSTRACTWe derive an empirical conversion of SDSS point sources to J magnitudes, in addition to resulting estimates of guide stars available to JWST. We also discuss high Galactic latitude fields in the SDSS in terms of completeness limits and populations of stars, galaxies, and QSOs.

Faint quasar candidates from Hubble Space Telescope imaging: number counts from 31 new high-latitude fields

Quasars representative of the populous faint end of the luminosity function are dim with m ∼ 24 at intermediate redshift, and traditional ground-based surveys for such faint quasars often suffer from severe contamination by compact faint galaxies. In order to limit the latter morphological contamination, we are conducting a combined multicolour and morphological survey for faint quasars, to B < 24.5 and z < 2.1, using archival Hubble Space Telescope (HST) images. Our previous work provided a similar survey of the Groth-Westphal Strip. Here, we extend our survey to an additional 31 high galactic latitude (pure parallel) fields that cover another 0.04 deg 2 of sky, imaged with the superb 0.1 -arcsec spatial resolution of the Wide Field Planetary Camera 2 aboard HST. In our expanded survey, we identify an additional 19 high-likelihood ultraviolet-excess quasar candidates having stellar or unresolved nucleus plus host-galaxy morphology, and yielding a cumulative quasar surface density of 511 +142 -113 deg -2 to B < 24.5 and z < 2.1. Our results are in reasonable agreement both with our own earlier survey of the Groth-Westphal Strip and with other faint quasar surveys that utilize very different selection approaches.

ESO imaging survey: optical follow-up of 12 selected XMM-Newton fields

This paper presents the data recently released for the XMM-Newton/WFI survey carried out as part of the ESO Imaging Survey (EIS) project. The aim of this survey is to provide optical imaging follow-up data in BVRI for identification of serendipitously detected X-ray sources in selected XMM-Newton fields. In this paper, fully calibrated individual and stacked images of 12 fields as well as science-grade catalogs for the 8 fields located at high-galactic latitude are presented. These products were created, calibrated and released using the infrastructure provided by the EIS Data Reduction system and its associated EIS/MVM image processing engine, both of which are briefly described here. The data covers an area of ∼3 square degrees for each of the four passbands. The median seeing as measured in the final stacked images is 0. �� 94, ranging from 0. �� 60 and 1. �� 51. The median limiting magnitudes (AB system, 2 �� aperture, 5σ detection limit) are 25.20, 24.92, 24.66, and 24.39 mag for B-, V-, R-, and I-band, respectively. When only the 8 high-galactic latitude fields are included these become 25.33, 25.05, 25.36, and 24.58 mag, in good agreement with the planned depth of the survey. Visual inspection of images and catalogs, comparison of statistics derived from the present data with those obtained by other authors and model predictions, as well as direct comparison of the results obtained from independent reductions of the same data, demonstrate the science-grade quality of the automatically produced final images and catalogs. These survey products, together with their logs, are available to the community for science exploitation in conjunction with their X-ray counterparts. Preliminary results from the X-ray/optical cross-correlation analysis show that about 61% of the detected X-ray point sources in deep XMM-Newton exposures have at least one optical counterpart within 2 �� radius down to R � 25 mag, 50% of which are so faint as to require VLT observations thereby meeting one of the top requirements of the survey, namely to produce large samples for spectroscopic follow-up with the VLT, whereas only 15% of the objects have counterparts down to the DSS limiting magnitude.

VGCF detection of galaxy systems at intermediate redshifts

We continue the development of our Voronoi Galaxy Cluster Finder (VGCF) technique by applying it to galaxy catalogs obtained with B and R band observations of four high galactic latitude fields of square degrees each. These fields are deep (, ) and partially overlap the Palomar Distant Cluster (PDCS) fields at 0 and 2. We run the VGCF also on the original V and I band PDCS galaxy catalogs. We identify a total of 48 clusters that are particularly reliable, being detected in at least two bands. The analysis of color–magnitude diagrams and, in a few cases, spectroscopic observations allow us to further increase the reliability of 25 of the 48 clusters. For these 26 clusters we also estimate redshifts that fall in the approximate range . We detect 41 VGCF clusters within the strict limits of the PDCS fields at 0 and 2. The PDCS catalog for the same regions consists of 28 clusters. The two catalogs have 20 clusters in common. These clusters together with the remaining PDCS and VGCF clusters lead to a total number of 46 “independent” clusters. The total number of clusters is therefore 20% larger than the number of VGCF clusters and more than 60% larger than the number of PDCS clusters. These results confirm a) that the VGCF is a competitive algorithm for the identification of optical clusters, and b) that a combined catalog of matched-filter and VGCF clusters constitutes a significant progress toward a more complete selection of clusters from bidimensional optical data.

TheHubble Space TelescopeACS Grism Parallel Survey. II. First Results and a Catalog of Faint Emission-Line Galaxies atz ≤ 1.6

We present the first results from the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) Grism Parallel Survey, a large program obtaining deep, slitless ACS grism spectroscopy of high-latitude HST parallel fields. We report on 11 high Galactic latitude fields here, each with grism integration times of more than 12 ks. We identify 601 compact emission-line galaxies at z ≤ 1.6, reaching emission lines to a flux limit of ≳5 × 10-18 ergs cm-2 s-1 (3 σ). We determine redshifts by cross-correlation of the target spectra with template spectra, followed by visual inspection. We measure star formation rates from the observed [O II] λ3727, [O III] λ5007, and Hα line fluxes. Follow-up observations with the Keck telescope of one of the survey fields confirms our classification and redshifts with σ(z) ≃ 0.02. This is one of the deepest emission-line surveys to date, covering a total area of 121 arcmin2. The rough estimate of the comoving number density of emission-line galaxies in our survey at 0.3 < z < 1.3 is ∼4.5 × 10-3 h Mpc-3. We reach deeper into the emission-line luminosity function than either the STIS or NICMOS grism parallel surveys, finding an apparent space density of emission-line galaxies several times higher than those surveys. Because of the ACS high spatial resolution, our survey is very sensitive to faint, compact galaxies with strong emission lines and weak continua. The ACS grism survey provides the comoving star formation density at z ≤ 1.6 at a high level of completeness.

Faint Blue Objects at High Galactic Latitude. VIII. Performance Characteristics of the US Survey

The US survey has cataloged 3987 objects in seven high Galactic latitude fields according to their optical colors, magnitudes, and morphologies using photographic techniques. This paper analyzes the effectiveness of the survey at producing finding lists for complete samples of hot stars and quasars that exhibit blue and/or ultraviolet excess (B-UVX) relative to the colors of halo F and G subdwarf stars. A table of 599 spectroscopic identifications summarizes the spectroscopic coverage of the US objects that has been accomplished to date. In addition, some of the survey plates have been reexamined for objects missed during the original selection, and the literature has been searched for all other spectroscopically identified blue stars and quasars with z < 2.2 that have been selected by other surveys within the US survey areas. These results are used to estimate empirically both the accuracy of the US survey selection boundaries (in color, morphology, and brightness) and the completeness of the resulting samples of B-UVX US objects within those boundaries. In particular, it is shown that the reliability of the US color classifications is high and that the previously derived US morphological boundary for the complete selection of unresolved quasars is accurate. The contribution of color and morphological classification errors to B-UVX sample incompleteness is therefore correspondingly small. The empirical tests indicate high levels of completeness (95%) for the samples of US quasars and hot stars isolated within the stated survey selection limits. Errata and improvements to some of the published catalog data are presented in Appendices.

Star Counts and Galactic Structure

We use a model of theGalactic stellar distribution to analyse the BATC star count datatoward two high Galactic latitude fields. Since star counts athigh Galactic latitudes are not strongly related to the radialdistribution, they are very suitable for the study of the verticaldistribution of the Galaxy. The vertical density distribution ofthe stars shows the contribution of the thin disc, the thick discand the stellar halo of the Galaxy. We give quantitativedescriptions of these components in terms of exponential discs anda de Vaucouleurs halo. We find that the observed counts support anaxial ratio of c/a~0.5, implying a more flattened halo. Weconsider that it is possible that the halo has twosubpopulations, i.e. a flattened inner halo and a spherical outer haloin the Milky Way.

The VIRMOS deep imaging survey

This paper describes the CFH12K-VIRMOS survey: a deep imaging survey in four fields totalling more than , conducted with the arcmin2 field CFH-12K camera. The survey is intended to be a multi-purpose survey used for a variety of science goals, including surveys of very high redshift galaxies and weak lensing studies. Four high galactic latitude fields, each deg2, have been selected along the celestial equator: 0226-04, 1003+01, 1400+05, and 2217+00. The 16 deg2 of the “wide” survey are covered with exposure times of 2 hr, 1.5 hr, 1 hr, 1 hr, respectively while the deg2 area of the “deep” survey at the center of the 0226-04 field is covered with exposure times of 7 h, 4.5 h, 3 h, 3 h, in respectively. An additional area ~2 deg2 has been imaged in the 0226-04 field corresponding to the area surveyed by the XMM-LSS program [CITE]. The data is pipeline processed at the Terapix facility at the Institut d'Astrophysique de Paris to produce large mosaic images. The catalogs produced contain the positions, shapes, total and aperture magnitudes for 2.175 million objects measured in the four areas. The limiting magnitudes, measured as a measurement in a 3 arcsec diameter aperture is in the “Wide” areas, and in the deep area. Careful quality control has been applied on the data to ensure internal consistency and assess the photometric and astrometric accuracy as described in a joint paper [CITE]. These catalogs are used to select targets for the VIRMOS-VLT Deep Survey, a large spectroscopic survey of the distant universe (Le Fèvre et al. 2003). First results from the CFH12K-VIRMOS survey have been published on weak lensing (e.g. van Waerbeke & Mellier 2003). Catalogs and images are available through the VIRMOS database environment under Oracle (http://www.oamp.fr/cencos). They are open for general use since July 1st, 2003.

Lyman Break Galaxies at Redshiftz∼ 3: Survey Description and Full Data Set

We present the basic data for a large ground-based spectroscopic survey for z ~ 3 Lyman break galaxies (LBGs), photometrically selected using rest-UV colors from very deep images in 17 high Galactic latitude fields. The total survey covers an area of 0.38 deg2 and includes 2347 photometrically selected candidate LBGs to an apparent AB magnitude limit of 25.5. Approximately half of these objects have been observed spectroscopically using the Keck telescopes, yielding 940 redshifts with z = 2.96 ± 0.29. We discuss the images, photometry, target selection, and spectroscopic program in some detail and present catalogs of the photometric and spectroscopic data, made available in electronic form. We discuss the general utility of conducting nearly volume-limited redshift surveys in prescribed redshift intervals using judicious application of photometric preselection.

Ultradeep Near-Infrared ISAAC Observations of the Hubble Deep Field South: Observations, Reduction, Multicolor Catalog, and Photometric Redshifts

We present deep near-infrared (NIR) Js-, H-, and Ks-band ISAAC imaging of the Wide Field Planetary Camera 2 (WFPC2) field of the Hubble Deep Field South (HDF-S). The 25 × 25 high Galactic latitude field was observed with the Very Large Telescope under the best seeing conditions, with integration times amounting to 33.6 hr in Js, 32.3 hr in H, and 35.6 hr in Ks. We reach total AB magnitudes for point sources of 26.8, 26.2, and 26.2, respectively (3 σ), which make it the deepest ground-based NIR observation to date and the deepest Ks-band data in any field. The effective seeing of the co-added images is ≈045 in Js, ≈048 in H, and ≈046 in Ks. Using published WFPC2 optical data, we constructed a Ks-limited multicolor catalog containing 833 sources down to K 26, of which 624 have seven-band optical-to-NIR photometry. These data allow us to select normal galaxies from their rest-frame optical properties to high redshift (z 4). The observations, data reduction, and properties of the final images are discussed, and we address the detection and photometry procedures that were used in making the catalog. In addition, we present deep number counts, color distributions, and photometric redshifts of the HDF-S galaxies. We find that our faint Ks-band number counts are flatter than published counts in other deep fields, which might reflect cosmic variations or different analysis techniques. Compared to the HDF-N, we find many galaxies with very red V-H colors at photometric redshifts 1.95 2.3 (in Johnson magnitudes). Because they are extremely faint in the observed optical, they would be missed by ultraviolet–optical selection techniques, such as the U-dropout method.

Unlocking the potential of the XMM Serendipitous Survey via multi‐colour broad band imaging

The XMM-Newton Serendipitous Survey has been detecting X-ray sources at a rate of 50,000 per year. As part of the XMM serendipitous source identification programme (XID) of the XMM Science Survey Center (Watson et al. 2001), we have been obtaining optical multi-colour CCD imaging data for a large number of XMM fields. The multi-colour CCD imaging data for high Galactic latitude fields is currently being obtained with the wide field CCD mosaic cameras at the 2.5m Isaac Newton Telescope in La Palma and the 2.2m MPG/ESO Telescope in Chile. The scientific goals are: to provide optical/IR counterparts for the need of the XID spectroscopic identification programme (e.g. Barcons et al. 2002) and photometric identification of XMM sources for which spectroscopic data are not available; to explore in a statistical manner various topics such as hard X-ray sources, the CXB, objects at high redshifts, and AGN evolution.

Constraining the LogN-LogSRelation of Far-Infrared Unresolved Sources Using aP(D)Analysis; Application to FIRBACK Maps Obtained by ISO

The FIRBACK survey is a deep imaging survey carried out with ISOPHOT on board ISO, at 170 μ m. The survey covers ≈4 sq deg in three high galactic latitude fields (FIRBACK South Marano, FIRBACK North 1 and FIRBACK/ELAIS North 2). In these fields, fluctuations due to unresolved extra-galactic sources were isolated for the first time [1]. We are using a P(D) (probability distribution of fluctuations) analysis to gain information about the N(≥S) curve of the unresolved sources which make up the background. Many planned surveys ( e.g. SIRTF, FIRST, PLANCK...) will pose the same analysis challenges and we hope that the outcome of this study will be useful in that context. As a preparation to the analysis of the FIRBACK maps we analyze simulated sky maps. We create histograms of number of pixels per flux bin. The histograms are binned such that there are enough pixels per bin to allow us to apply Gaussian estimates for the errors. We then calculate the expected number of pixels within the relevant flux ranges and evaluate the χ 2 statistic. We will use a maximum likelihood algorithm to find the parameters of N(≥S) .

A deep ISOCAM survey in the SSA13

We present initial results of a deep mid-infrared survey conducted in the high galactic latitude field SSA13 with ISO. We have surveyed through the broad band filter LW2 (5-8.5 μm) of the mid-infrared camera ISOCAM to probe the near-infrared light at high redshift. The 80% completeness limit for point sources in the central 6 arcmin2 reaches 10 μJy at 6.7 μm. 65 sources are detected down to 6 μJy in 16 arcmin2. The integral galaxy number counts are 1.4 × 104 deg-2 at 10 μJy with the slope of -1.5. The integrated 6.7 μm light down to 6 μJy is estimated as 0.43 nWm-2sr-1. Our counts are consistent with the results in the HDF and the model prediction based on the K band local luminosity function. It suggests that the majority of the detected sources are E/S0 galaxies at z>1.