arXiv subjects

R. Cutri

Publications and source records attributed to R. Cutri.

16 recordsLinked to original sources

arXiv2012

Characterizing the Mid-IR Extragalactic Sky with WISE and SDSS

The Wide-field Infrared Survey Explorer (WISE) has completed its all-sky survey at 3.4-22 micron. We merge the WISE data with optical SDSS data and provide a phenomenological characterization of mid-IR, extragalactic sources. WISE is most sensitive at 3.4micron(W1) and least at 22micron(W4). The W1 band probes massive early-type galaxies out to z\gtrsim1. This is more distant than SDSS identified early-type galaxies, consistent with the fact that 28% of 3.4micron sources have faint or no r-band counterparts (r>22.2). In contrast, 92-95% of 12 and 22micron sources have SDSS optical counterparts with r<22.2. WISE 3.4micron detects 89.8% of the entire SDSS QSO catalog at SNR(W1)>7, but only 18.9% at 22micron with SNR(W4)>5. We show that WISE colors alone are effective in isolating stars (or local early-type galaxies), star-forming galaxies and strong AGN/QSOs at z<3. We highlight three major applications of WISE colors: (1) Selection of strong AGN/QSOs at z<3 using W1-W2>0.8 and W2<15.2 criteria, producing a census of this population. The surface density of these strong AGN/QSO candidates is 67.5+-0.14/deg^2. (2) Selection of dust-obscured, type-2 AGN/QSO candidates. We show that WISE W1-W2>0.8, W2<15.2 combined with r-W2>6 (Vega) colors can be used to identify type-2 AGN candidates. The fraction of these type-2 AGN candidates is 1/3rd of all WISE color-selected AGNs. (3) Selection of ULIRGs at z\sim2 with extremely red colors, r-W4>14 or well-detected 22micron sources lacking detections in the 3.4 and 4.6micron bands. The surface density of z~2 r-W4>14 ULIRGs is 0.9+-0.07/deg^2 at SNR(W4)>5 (flux(W4)>=2.5mJy), which is consistent with that inferred from smaller area Spitzer surveys. Optical spectroscopy of a small number of these high-redshift ULIRGs confirms our selection, and reveals a possible trend that optically fainter or r-W4 redder candidates are at higher redshifts.

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arXiv2012

Wide-Field InfraRed Survey Telescope (WFIRST) Final Report

In December 2010, NASA created a Science Definition Team (SDT) for WFIRST, the Wide Field Infra-Red Survey Telescope, recommended by the Astro 2010 Decadal Survey as the highest priority for a large space mission. The SDT was chartered to work with the WFIRST Project Office at GSFC and the Program Office at JPL to produce a Design Reference Mission (DRM) for WFIRST. Part of the original charge was to produce an interim design reference mission by mid-2011. That document was delivered to NASA and widely circulated within the astronomical community. In late 2011 the Astrophysics Division augmented its original charge, asking for two design reference missions. The first of these, DRM1, was to be a finalized version of the interim DRM, reducing overall mission costs where possible. The second of these, DRM2, was to identify and eliminate capabilities that overlapped with those of NASA's James Webb Space Telescope (henceforth JWST), ESA's Euclid mission, and the NSF's ground-based Large Synoptic Survey Telescope (henceforth LSST), and again to reduce overall mission cost, while staying faithful to NWNH. This report presents both DRM1 and DRM2.

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arXiv2011

WISE/NEOWISE Observations of the Jovian Trojans: Preliminary Results

We present the preliminary analysis of over 1739 known and 349 candidate Jovian Trojans observed by the NEOWISE component of the Wide-field Infrared Survey Explorer (WISE). With this survey the available diameters, albedos and beaming parameters for the Jovian Trojans have been increased by more than an order of magnitude compared to previous surveys. We find that the Jovian Trojan population is very homogenous for sizes larger than $\sim10$km (close to the detection limit of WISE for these objects). The observed sample consists almost exclusively of low albedo objects, having a mean albedo value of $0.07\pm0.03$. The beaming parameter was also derived for a large fraction of the observed sample, and it is also very homogenous with an observed mean value of $0.88\pm0.13$. Preliminary debiasing of the survey shows our observed sample is consistent with the leading cloud containing more objects than the trailing cloud. We estimate the fraction to be N(leading)/N(trailing) $\sim 1.4 \pm 0.2$, lower than the $1.6 \pm 0.1$ value derived by others.

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arXiv2011

WISE/NEOWISE Observations of the Hilda Population: Preliminary Results

We present the preliminary analysis of 1023 known asteroids in the Hilda region of the Solar System observed by the NEOWISE component of the Wide-field Infrared Survey Explorer (WISE). The sizes of the Hildas observed range from $\sim 3 - 200$km. We find no size - albedo dependency as reported by other projects. The albedos of our sample are low, with a weighted mean value $p_V = 0.055\pm0.018$, for all sizes sampled by the NEOWISE survey. We observed a significant fraction of the objects in the two known collisional families in the Hilda population. It is found that the Hilda collisional family is brighter, with weighted mean albedo of $p_V = 0.061\pm0.011$, than the general population and dominated by D-type asteroids, while the Schubart collisional family is darker, with weighted mean albedo of ($p_V = 0.039\pm0.013$). Using the reflected sunlight in the two shortest WISE bandpasses we are able to derive a method for taxonomic classification of $\sim 10%$ of the Hildas detected in the NEOWISE survey. For the Hildas with diameter larger than 30km there are $67^{+7}_{-15}%$ D-type asteroids and $26^{+17}_{-5}%$ C-/P-type asteroids (with the majority of these being P-types).

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arXiv2007

The reddest ISO-2MASS quasar

In the course of the NIR/MIR AGN search combining the 6.7 mu ISOCAM Parallel Survey and 2MASS we have discovered 24 type-1 quasars about a third of which are too red to be discriminated by optical/UV search techniques. Here we report on a detailed case study of the reddest type-1 quasar of our sample (J2341) at redshift z=0.236 with M_K=-25.8 and J-K=1.95. We performed spectroscopy in the optical with VLT/FORS1 and in the MIR with Spitzer as well as NIR imaging with ISPI at CTIO. The optical and NIR observations reveal a star forming emission-line galaxy at the same redshift as the quasar with a projected linear separation of 1.8 arcsec (6.7 kpc). The quasar and its companion are embedded in diffuse extended continuum emission. Compared with its companion the quasar exhibits redder optical-NIR colours, which we attribute to hot nuclear dust. The MIR spectrum shows only few emission lines superimposed on a power-law spectral energy distribution. However, the lack of strong FIR emission suggests that our potentially interacting object contains much less gas and dust and is in a stage different from dust reddened ULIRG-AGN like Mrk 231. The optical spectrum shows signatures for reddening in the emission-lines and no post-starburst stellar population is detected in the host galaxy of the quasar. The optical continuum emission of the active nucleus appears absorbed and diluted. Even the combination of absorption and host dilution is not able to match J2341 with standard quasar templates. While the BLR shows only a rather moderate absorption of E_(B-V)=0.3, the continuum shorter than 4500 AA requires strong obscuration with E_(B-V)=0.7, exceeding the constraints from the low upper limit on the 9.7 mu silicate absorption. This leads us to conclude that the continuum of J2341 is intrinsically redder than that of typical quasars.

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arXiv2007

Narrow-line AGN in the ISO-2MASS Survey

Context: A long-standing challenge of observational AGN research is to find type 2 quasars, the luminous analogues of Seyfert-2 galaxies. Aims: We search for luminous narrow-line type 2 AGN, characterise their properties, and compare them with broad-line type 1 AGN. Methods: Combining the ISOCAM parallel survey at 6.7 mu with 2MASS, we have selected AGN via near-mid-infrared colours caused by the hot nuclear dust emission. We performed spectroscopy in the optical and, for a subset of the sample, also in the mid-infrared with Spitzer. Results: We find nine type 2 AGN at redshift 0.1 0.5 we did not find type 2 AGN, probably because the hottest dust emission, still covered by the NIR filters, is obscured. The optical spectra of the type 2 host galaxies show young and old stellar populations. Only one object is an ultraluminous infrared galaxy with starburst. The 5-38 mu spectra of the two type 2 sources observed show a strong continuum with PAH emission in one case and silicate absorption in the other case. Conclusions: The near-mid-infrared selection is a successful strategy to find luminous type 2 AGN at low z. The objects exhibit a large range of properties so that it is difficult to infer details by means of popular SED fitting with simple average templates.

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arXiv2005

Preliminary Design of The Wide-Field Infrared Survey Explorer (WISE)

The Wide-field Infrared Survey Explorer (WISE), a NASA MIDEX mission, will survey the entire sky in four bands from 3.3 to 23 microns with a sensitivity 1000 times greater than the IRAS survey. The WISE survey will extend the Two Micron All Sky Survey into the thermal infrared and will provide an important catalog for the James Webb Space Telescope. Using 1024x1024 HgCdTe and Si:As arrays at 3.3, 4.7, 12 and 23 microns, WISE will find the most luminous galaxies in the universe, the closest stars to the Sun, and it will detect most of the main belt asteroids larger than 3 km. The single WISE instrument consists of a 40 cm diamond-turned aluminum afocal telescope, a two-stage solid hydrogen cryostat, a scan mirror mechanism, and reimaging optics giving 5" resolution (full-width-half-maximum). The use of dichroics and beamsplitters allows four color images of a 47'x47' field of view to be taken every 8.8 seconds, synchronized with the orbital motion to provide total sky coverage with overlap between revolutions. WISE will be placed into a Sun-synchronous polar orbit on a Delta 7320-10 launch vehicle. The WISE survey approach is simple and efficient. The three-axis-stabilized spacecraft rotates at a constant rate while the scan mirror freezes the telescope line of sight during each exposure. WISE is currently in its Preliminary Design Phase, with the mission Preliminary Design Review scheduled for July, 2005. WISE is scheduled to launch in mid 2009; the project web site can be found at www.wise.ssl.berkeley.edu.

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arXiv2005

The ISO-2MASS AGN survey: On the type-1 sources

We combined the ISOCAM Parallel Mode Survey at 6.7 micron (LW2 filter) with the Two Micron All Sky Survey in order to obtain a powerful tool to search for AGN independent of dust extinction. Using moderate colour criteria H-K>0.5 and K-LW2>2.7 we have selected a sample of 77 AGN candidates in an effective area of about 10 square degrees. By means of optical spectroscopy we find 24 (30%) type-1 QSOs at redshifts 0.1 0.8. About one third of the ISO-2MASS QSOs show so red optical colours, that they are missed in optical and UV AGN surveys like SDSS, 2DF, or HES. With a surface density of about 2 deg^(-2) down to R<18 mag the ISO-2MASS QSOs outnumber the 1.35 deg^(-2) of the SDSS quasar survey by 50%; we find a combined optical-IR QSO surface density of 2.7 deg^(-2). Since only two of the ISO-2MASS QSOs have also J-K>2, the inclusion of the ISO mid-infrared photometry significantly extends the capabilities of the pure 2MASS red AGN survey. We suggest that the newly found red AGN resemble young members of the quasar population, and that quasars spend much of their lifetime in a dust enshrouded phase.

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arXiv2005

Chandra Deep X-ray Observation of a Typical Galactic Plane Region and Near-Infrared Identification

Using the Chandra Advanced CCD Imaging Spectrometer Imaging array (ACIS-I), we have carried out a deep hard X-ray observation of the Galactic plane region at (l,b) ~ (28.5, 0.0), where no discrete X-ray source had been reported previously. We have detected 274 new point X-ray sources (4 sigma confidence) as well as strong Galactic diffuse emission within two partially overlapping ACIS-I fields (~250 arcmin^2in total). Sum of all the detected point source fluxes accounts for only ~ 10 % of the total X-ray flux in the field of view. Even hypothesizing a new population of much dimmer and numerous Galactic point sources, the total observed X-ray flux cannot be explained. Therefore, we conclude that X-ray emission from the Galactic plane has truly diffuse origin. Only 26 point sources were detected both in the soft and hard bands, indicating that there are two distinct classes of the X-ray sources distinguished by the spectral hardness ratio. Surface number density of the hard sources is only slightly higher than that measured at the high Galactic latitude regions, indicating that majority of the hard sources are background AGNs. Following up the Chandra observation, we have performed a near-infrared (NIR) survey with SOFI at ESO/NTT. Almost all the soft X-ray sources have been identified in NIR and their spectral types are consistent with main-sequence stars, suggesting most of them are nearby X-ray active stars. On the other hand, only 22 % of the hard sources had NIR counterparts, which are presumably Galactic. From X-ray and NIR spectral study, they are most likely to be quiescent cataclysmic variables. We have also carried out a precise spectral study of the Galactic diffuse X-ray emission excluding the point sources.

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arXiv2004

A Chandra Deep X-ray Exposure on the Galactic Plane and Near Infrared Identification

Using the Chandra ACIS-I instruments, we have carried out a deep X-ray observation on the Galactic plane region at (l,b) ~ (28.5, 0.0), where no discrete X-ray sources have been known previously. We have detected, as well as strong diffuse emission, 274 new point X-ray sources (4 sigma confidence) within two partially overlapping fields (~250 arcmin^2 in total) down to the flux limit ~3 x 10^{-15} $ erg s^{-1} cm^{-2} (2 -- 10 keV) and ~ 7 x 10^{-16} erg s^{-1} cm^{-2} (0.5 -- 2 keV). We clearly resolved point sources and the Galactic diffuse emission, and found that ~ 90 % of the flux observed in our field of view originates from diffuse emission. Many point sources are detected either in the soft X-ray band (below 2 keV) or in the hard band (above 2 keV), and only a small number of sources are detected in both energy bands. On the other hand, most soft X-ray sources are considered to be nearby X-ray active stars. We have carried out a follow-up near-infrared (NIR) observation using SOFI at ESO/NTT. Most of the soft X-ray sources were identified, whereas only a small number of hard X-ray sources had counterparts in NIR. Using both X-ray and NIR information, we can efficiently classify the point X-ray sources detected in the Galactic plane. We conclude that most of the hard X-ray sources are background Active Galactic Nuclei seen through the Milky Way, whereas majority of the soft X-ray sources are nearby X-ray active stars.

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arXiv2000

The K-Band Galaxy Luminosity Function

We measured the K-band luminosity function using a complete sample of 4192 morphologically-typed 2MASS galaxies with 7 < K < 11.25 mag spread over 2.12 str. Early-type (T < -0.5) and late-type (T > -0.5) galaxies have similarly shaped luminosity functions, alpha_e=-0.92+/-0.10 and alpha_l=-0.87+/-0.09. The early-type galaxies are brighter, M_*e=-23.53+/-0.06 mag compared to M_*l=-22.98\pm0.06 mag, but less numerous, n_*e=(0.0045+/-0.0006)h^3/Mpc^3 compared to n_*l=(0.0101+/-0.0013)h^3/Mpc^3 for H_0=100h km/s Mpc, such that the late-type galaxies slightly dominate the K-band luminosity density, j_late/j_early=1.17+/-0.12. Our morphological classifications are internally consistent, consistent with previous classifications and lead to luminosity functions unaffected by the estimated uncertainties in the classifications. These luminosity functions accurately predict the K-band number counts and redshift distributions for K < 18 mag, beyond which the results depend on galaxy evolution and merger histories.

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arXiv2000

A New Complete Sample of Sub-millijansky Radio Sources: An Optical and Near-Infrared Study

The Very Large Array (VLA) has been used in C-configuration to map an area \~0.3 square degrees at 1.4 GHz with 5sigma sensitivities of 0.305, 0.325, 0.380 and 0.450 mJy/beam over four equal subareas. Radio properties are presented for 62 detected sources. Deep optical imaging to Gunn r~25 mag using the Hale 5-m telescope covering ~0.21 square degrees is reported for a subset of 43 sources. This optical follow-up is much deeper than that of existing larger area radio surveys of similar radio sensitivity. Archival J, H and K-band photometry from the Two-Micron All Sky Survey (2MASS) is also presented. Using a robust likelihood-ratio technique, we optically identified 26 radio sources with probabilities >80%. Nine are uncertain/ambiguous detections and eight are empty fields. Comparisons with a stellar synthesis model that includes radio emission and dust reddening suggests that the near-infrared--to--optical emission in a small, bright sub-sample is reddened by `optically-thin' dust with absorption A_V ~ 2-2.5 mag, regardless of morphological type. This is consistent with other, more direct determinations of absorption. The radio--to--optical(--near-infrared) flux ratios of early-type galaxies require significant contamination in the radio by an active galactic nucleus (AGN), consistent with the current paradigm. Using our simple modeling approach, we also discuss a potential diagnostic for selecting Ultraluminous Infrared Galaxies (ULIGS) to z~1.6 from microJansky radio surveys.

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arXiv2000

A Global Photometric Analysis of 2MASS Calibration Data

We present results from the application of a global photometric calibration (GPC) procedure to calibration data from the first 2 years of The Two Micron All Sky Survey (2MASS). The GPC algorithm uses photometry of both primary standards and moderately bright `tracer' stars in 35 2MASS calibration fields. During the first two years of the Survey, each standard was observed on approximately 50 nights, with about 900 individual measurements. Based on the photometry of primary standard stars and secondary tracer stars and under the assumption that the nightly zeropoint drift is linear, GPC ties together all calibration fields and all survey nights simultaneously, producing a globally optimized solution. Calibration solutions for the Northern and Southern hemisphere observatories are found separately, and are tested for global consistency based on common fields near the celestial equator. Several results from the GPC are presented, including establishing candidate secondary standards, monitoring of near-infrared atmospheric extinction coefficients, and verification of global validity of the standards. The solution gives long-term averages of the atmospheric extinction coefficients, A_J=0.096, A_H=0.026, A_{K_s}=0.066 (North) and A_J=0.092, A_H=0.031, A_{K_s}=0.065 (South), with formal error of 0.001. The residuals show small seasonal variations, most likely due to changing atmospheric content of water vapor. Extension of the GPC to approximately 100 field stars in each of the 35 calibration fields yields a catalog of more than two thousand photometric standards ranging from 10th to 14th magnitude, with photometry that is globally consistent to $\sim 1%$.

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arXiv2000

2MASS Extended Sources in the Zone of Avoidance

The Two Micron All Sky Survey (2MASS) is now underway and will provide a complete census of galaxies as faint as 13.5 mag (3 mJy) at 2.2 microns for most of the sky, and ~12.1 mag (10 mJy) for regions veiled by the Milky Way. This census has already discovered nearby galaxies previously hidden behind our Galaxy, and will allow delineation of large-scale structures in the distribution of galaxies across the whole sky. Here we report the detection and discovery of new extended sources from this survey for fields incorporating the Galactic plane at longitudes between 40 and 70 deg. The area-normalized detection rate is ~1-2 galaxies per deg^2 brighter than 12.1 mag (10 mJy), roughly constant with Galactic latitude throughout the "Zone of Avoidance", of which 85-95% are newly discovered sources. In conjunction with the deep HI surveys, 2MASS will greatly increase the current census of galaxies hidden behind the Milky Way.

astro-ph↗

arXiv2000

2MASS Extended Source Catalog: Overview and Algorithms

The 2 Micron All-Sky Survey (2MASS) will observe over one-million galaxies and extended Galactic sources covering the entire sky at wavelengths between 1 and 2 microns. The survey catalog will have both high completeness and reliability down to J = 15.0 and Ks = 13.5 mag, equivalent to 1.6 mJy and 2.9 mJy, respectively. This paper describes the basic algorithms used to detect and characterize extended sources in the 2MASS database and catalog. Critical procedures include tracking the point spread function, image background removal, artifact removal, photometry and basic parameterization, star-galaxy discrimination and object classification using a decision tree technique. Examples of extended sources encountered in 2MASS are given.

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arXiv1999

L Dwarfs and the Substellar Mass Function

Analysis of initial observations from near-infrared sky surveys has shown that the resulting photometric catalogues, combined with far-red optical data, provide an extremely effective method of finding isolated, very low-temperature objects in the general field. Follow-up observations have already identified more than 25 sources with temperatures cooler than the latest M dwarfs. A comparison with detailed model predictions (Burrows & Sharp) indicates that these L dwarfs have effective temperatures between ~2000\pm100 K and 1500\pm100 K, while the available trigonometric parallax data place their luminosities at between 10^{-3.5} and 10^{-4.3} L_solar. Those properties, together with the detection of lithium in one-third of the objects, are consistent with the majority having substellar masses. The mass function cannot be derived directly, since only near-infrared photometry and spectral types are available for most sources, but we can incorporate VLM/brown dwarf models in simulations of the Solar Neighbourhood population and constrain Psi(M) by comparing the predicted L-dwarf surface densities and temperature distributions against observations from the DENIS and 2MASS surveys. The data, although sparse, can be represented by a power-law mass function, Psi(M) ~ M^{-alpha}, with 1 < alpha < 2. Current results favour a value nearer the lower limit. If alpha = 1.3, then the local space density of 0.075 > M/M_solar > 0.01 brown dwarfs is 0.10 systems pc^{-3}. In that case brown dwarfs are twice as common as main-sequence stars, but contribute no more than ~15% of the total mass of the disk.

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