The CatWISE Preliminary Catalog: Motions from WISE and NEOWISE Data

CatWISE is a program to catalog sources selected from combined WISE and NEOWISE all-sky survey data at 3.4 and 4.6 μm (W1 and W2). The CatWISE Preliminary Catalog consists of 900,849,014 sources measured in data collected from 2010 to 2016. This data set represents four times as many exposures and spans over 10 times as large a time baseline as that used for the AllWISE Catalog. CatWISE adapts AllWISE software to measure the sources in coadded images created from six-month subsets of these data, each representing one coverage of the inertial sky, or epoch. The catalog includes the measured motion of sources in eight epochs over the 6.5 yr span of the data. From comparison to Spitzer, signal-to-noise ratio = 5 limits in magnitudes in the Vega system are W1 = 17.67 and W2 = 16.47, compared to W1 = 16.96 and W2 = 16.02 for AllWISE. From comparison to Gaia, CatWISE positions have typical accuracies of 50 mas for stars at W1 = 10 mag and 275 mas for stars at W1 = 15.5 mag. Proper motions have typical accuracies of 10 mas yr⁻¹ and 30 mas yr⁻¹ for stars with these brightnesses, an order of magnitude better than from AllWISE. The catalog is available in the WISE/NEOWISE Enhanced and Contributed Products area of the NASA/IPAC Infrared Science Archive

Euclid: Estimation of the impact of correlated readout noise for flux measurements with the euclid NISP instrument

The Euclid satellite, to be launched by ESA in 2022, will be a major instrument for cosmology for the next decades. Euclid is composed of two instruments: the Visible instrument and the Near Infrared Spectrometer and Photometer (NISP). In this work, we estimate the implications of correlated readout noise in the NISP detectors for the final in-flight flux measurements. Considering the multiple accumulated readout mode, for which the UTR (Up The Ramp) exposure frames are averaged in groups, we derive an analytical expression for the noise covariance matrix between groups in the presence of correlated noise. We also characterize the correlated readout noise properties in the NISP engineering-grade detectors using long dark integrations. For this purpose, we assume a (1/f)α-like noise model and fit the model parameters to the data, obtaining typical values of $\sigma ={19.7}_{-0.8}^{+1.1}$ e− Hz−0.5, ${f}_{\mathrm{knee}}=({5.2}_{-1.3}^{+1.8})\times {10}^{-3}\,\mathrm{Hz}$ and $\alpha ={1.24}_{-0.21}^{+0.26}$. Furthermore, via realistic simulations and using a maximum likelihood flux estimator we derive the bias between the input flux and the recovered one. We find that using our analytical expression for the covariance matrix of the correlated readout noise we diminish this bias by up to a factor of four with respect to the white noise approximation for the covariance matrix. Finally, we conclude that the final bias on the in-flight NISP flux measurements should still be negligible even in the white readout noise approximation, which is taken as a baseline for the Euclid on-board processing to estimate the on-sky flux

Euclid preparation XLIII. Measuring detailed galaxy morphologies for Euclid with machine learning

The Euclid mission is expected to image millions of galaxies at high resolution, providing an extensive dataset with which to study galaxy evolution. Because galaxy morphology is both a fundamental parameter and one that is hard to determine for large samples, we investigate the application of deep learning in predicting the detailed morphologies of galaxies in Euclid using Zoobot, a convolutional neural network pretrained with 450000 galaxies from the Galaxy Zoo project. We adapted Zoobot for use with emulated Euclid images generated based on Hubble Space Telescope COSMOS images and with labels provided by volunteers in the Galaxy Zoo: Hubble project. We experimented with different numbers of galaxies and various magnitude cuts during the training process. We demonstrate that the trained Zoobot model successfully measures detailed galaxy morphology in emulated Euclid images. It effectively predicts whether a galaxy has features and identifies and characterises various features, such as spiral arms, clumps, bars, discs, and central bulges. When compared to volunteer classifications, Zoobot achieves mean vote fraction deviations of less than 12% and an accuracy of above 91% for the confident volunteer classifications across most morphology types. However, the performance varies depending on the specific morphological class. For the global classes, such as disc or smooth galaxies, the mean deviations are less than 10%, with only 1000 training galaxies necessary to reach this performance. On the other hand, for more detailed structures and complex tasks, such as detecting and counting spiral arms or clumps, the deviations are slightly higher, of namely around 12% with 60000 galaxies used for training. In order to enhance the performance on complex morphologies, we anticipate that a larger pool of labelled galaxies is needed, which could be obtained using crowd sourcing. We estimate that, with our model, the detailed morphology of approximately 800 million galaxies of the Euclid Wide Survey could be reliably measured and that approximately 230 million of these galaxies would display features. Finally, our findings imply that the model can be effectively adapted to new morphological labels. We demonstrate this adaptability by applying Zoobot to peculiar galaxies. In summary, our trained Zoobot CNN can readily predict morphological catalogues for Euclid images

A narrowband imaging search for [O III] emission from galaxies at z > 3

We present the results of a narrowband survey of quasi-stellar-object (QSO) fields at redshifts that place the [O III] (5007 Å) emission line in the Δλ/λ ∼ 1% 2.16 μm filter. We have observed 3 arcmin and detected one emission-line candidate object in the field around PC 1109 + 4642. We discuss the possibilities that this object is a star-forming galaxy at the QSO redshift, z = 3.313, or a Seyfert galaxy. In the former case, we infer a star formation rate of 170 M yr for this K′ = 21.3 object. The galaxy has a compact but resolved morphology, with an FWHM = 0″.6 or 4.2 kpc at z = 3.313 (H = 50 km s Mpc and q = 0.5). The comoving density of such objects in QSO environments appears to be 0.0033 Mpc , marginally lower (≤ 3 σ) than the density observed for Hoα-emitters in absorption-line fields at z ∼ 2.5 but similar to the density of Lyman-break galaxies at z ∼ 3. If, on the other hand, most of the line emission is [O III] from a Seyfert 2 nucleus at z = 3.31, then the high inferred volume density could imply a large evolution in the Seyfert 2 luminosity function from the current epoch. We find the field containing the object to also contain many faint extended objects in the K′ image but little significant excess over the expected number-magnitude relation. We discuss the implication of the emission line being a longer wavelength line at a lower redshift. 2 -1 -1 -1 -3 em ⊙ 0

The counterarc to MS 1512-cB58 and a companion galaxy

We present near-infrared spectra of "A2," the primary counterarc to the gravitationally lensed galaxy MS 1512-cB58. The spectra show redshifted Hα, [N II], [O III], and Hβ at z = 2.729 ± 0.001. We observe the same Hα/[O III] ratio as cB58, which together with the redshift confirms that A2 is indeed another image of a single background galaxy. Published lensing reconstruction reports that A2 is a magnification of the entire source, while cB58 is an image of only a part. At marginal significance, A2 shows higher line-to-continuum ratios than cB58 (by a factor of ∼2), suggesting a nonuniform ratio of young to old stars across the galaxy. We observe a second emission-line source in the slit. This object, "W5," is predicted to be a lensed image of another galaxy at a redshift similar to cB58. W5 is blueshifted from cB58 by ∼400 km s-1 and has a significantly lower Hα/[0 III] ratio, confirming that it is an image of a different background galaxy in a group with cB58. The Hα emission line in W5 implies a star formation rate of 6 M⊙ yr-1 (H 0 = 70 km s-1 Mpc-1, ΩM = 0.3, ΩΛ = 0.7), after correcting for lensing magnification

A Spitzer-IRS search for the galaxies that re-ionized the Universe

We describe an observation designed to find H emission from galaxies at z712 made using the InfraRed spectrograph (IRS) on the Spitzer Space Telescope. © 2007 International Astronomical Union

Star formation in emission-line galaxies between redshifts of 0.8 and 1.6

Optical spectra of 14 emission-line galaxies representative of the 1999 NICMOS parallel grism Hα survey of McCarthy et al. are presented. Of the 14, 9 have emission lines confirming the redshifts found in the grism survey. The higher resolution of our optical spectra improves the redshift accuracy by a factor of 5. The [O II]/Hα values of our sample are found to be more than 2 times lower than expected from Jansen et al. This [O II]/Hα ratio discrepancy is most likely explained by additional reddening in our Hα-selected sample [on average, as much as an extra E(B- V) = 0.6], as well as by a possible stronger dependence of the [O II]/Hα ratio on galaxy luminosity than is found in local galaxies. The result is that star formation rates (SFRs) calculated from [O II] λ3727 emission, uncorrected for extinction, are found to be on average 4 ± 2 times lower than the SFRs calculated from Ha emission. Classification of emission-line galaxies as starburst or Seyfert galaxies based on comparison of the ratios [O II]/Hβ and [Ne III] λ3869/Hβ is discussed. New Seyfert 1 diagnostics using the Ha line luminosity, H-band absolute magnitude, and Hα equivalent widths are also presented. One galaxy is classified as a Seyfert 1 based on its broad emission lines, implying a comoving number density for Seyfert 1 galaxies of 2.5-2.1+5.9 × 10-5 Mpc-3. This comoving number density is a factor of 2.4-2.0+5.5times higher than estimated by other surveys

1-1.4 micron spectral atlas of stars

We present a catalog of J-band (1.08 to 1.35 μm) stellar spectra at low resolution (R ∼ 400). The targets consist of 105 stars ranging in spectral type from O9.5 to M7 and luminosity classes I through V. The relatively featureless spectra of hot stars, earlier than A4, can be used to remove the atmospheric features which dominate ground-based J-band spectroscopy. We measure equivalent widths for three absorption lines and nine blended features which we identify in the spectra. Using detailed comparison with higher resolution spectra, we demonstrate that low-resolution data can be used for stellar classification, since several features depend on the effective temperature and gravity. For example, the CN index (1.096-1.104 μm) decreases with temperature, but the strength of a blended feature at 1.28 μm (consisting of primarily Pβ) increases. The slope of a star's spectrum can also be used to estimate its effective temperature. The luminosity class of a star correlates with the ratio of the Mg I (1.1831 μm) line to a blend of several species at 1.16 μm. Using these indicators, a star can be classified to within several subclasses. Fifteen stars with particularly high and low metal abundances are included in the catalog, and some spectral dependence on metal abundance is also found

A search for lyman break galaxies at z > 8 in the NICMOS Parallel Imaging Survey

We have selected 14 J-dropout Lyman break galaxy (LBG) candidates with J110 - H160 ≥ 2.5 from the NICMOS Parallel Imaging Survey. This survey consists of 135 arcmin2 of imaging in 228 independent sight lines, reaching average 5 σ sensitivities of J 110 = 25.8 and H160 = 25.6 (AB). Distinguishing these candidates from dust-reddened star-forming galaxies at z ∼ 2-3 is difficult and will require longer wavelength observations. We consider the likelihood that any J-dropout LBGs exist in this survey and find that if L*z= 9.5 is significantly brighter than L*z=6 (a factor of 4), then a few J-dropout LBGs are likely. A similar increase in luminosity has been suggested by Eyles et al. and Yan et al., but the magnitude of this increase is uncertain. © 2007. The American Astronomical Society. All rights reserved