arXiv subjects

R. M. Cutri

Publications and source records attributed to R. M. Cutri.

46 records · Page 3Linked to original sources

arXiv2002

Detection of small scale fluctuations in the near-IR cosmic infrared background from long exposure 2MASS fields

We report first results for the cosmic infrared background (CIB) fluctuations at 1.25, 1.65 and 2.17 micron obtained from long exposures constructed from 2MASS standard star fields. We have co-added and analyzed scans from one such field with a total exposure time > 1 hour, and removed sources and other artifacts. The stars and galaxies were clipped out to K_s~19^m leaving only high-z galaxies (or possibly local low-surface-brightness systems). The residual component of the diffuse emission on scales from a few arc-sec to a few arc-min has a power-law slope consistent with emission produced by clustered galaxies. The noise (and residual artifacts) contribution to the signal is small and the colors of the signal are very different from Galactic stars or air-glow. We therefore identify the signal as CIB fluctuations from the faint unresolved galaxies. We show that the present-day galaxies with no evolution would produce a significant deficit in the observed CIB fluctuations. Thus the dominant contribution to the observed signal must come from high z and may indicate high rates of star formation at those epochs.

astro-ph↗

arXiv2002

Analysis of the diffuse near-IR emission from 2MASS deep integration data: foregrounds vs the cosmic infrared background

This is one of two papers in which we report the detection of structure in the cosmic infrared background (CIB) between 1.25 - 2.2 micron through the use of data from the Two Micron Sky Survey (2MASS). This paper concentrates on data assembly, analysis and the estimate of the various foreground contributions; the companion paper (Kashlinsky, Odenwald, Mather, Skrutskie, Cutri 2002, hereafter KOMSC) presents the cosmological results for the CIB fluctuations and their implications. By using repeated observations of a specific calibration star field, we were able to achieve integration times in excess of 3900 seconds compared to the 7.8 seconds in the standard 2MASS data product. This yielded a point source detection limit (3 σ) of +18.5^m in K_s band. The resulting co-added images were processed to remove point sources to a limiting surface brightness of +20^m/arcsec$^2 or 40 nW/m^2/sr. The remaining maps contained over 90% of the pixels and were Fourier transformed to study the spatial structure of the diffuse background light. After removing resolved sources and other artifacts, we find that the power spectrum of the final images has a power-law distribution consistent with clustering by distant galaxies. We estimate here the contributions to this signal from Galactic foregrounds, atmospheric OH-glow, zodiacal light and instrument noise, all of which are small and of different slopes. Hence, this supports the KOMSC identification of the signal as coming from the CIB fluctuations produced by distant clustered galaxies.

astro-ph↗

arXiv2002

Extinction with 2MASS: star counts and reddening toward the North America and the Pelican Nebulae

We propose a general method for mapping the extinction in dense molecular clouds using 2MASS near-infrared data. The technique is based on the simultaneous utilization of star counts and colors. These two techniques provide independent estimations of the extinction and each method reacts differently to foreground star contamination and to star clustering. We take advantage of both methods to build a large scale extinction map (2.5 x 2.5 degrees) of the North America-Pelican nebulae complex. With Ks star counts and H-Ks color analysis the visual extinction is mapped up to 35 mag. Regions with visual extinction greater than 20 mag account for less than 3% of the total mass of the cloud. Color is generally a better estimator for the extinction than star counts. Nine star clusters are identified in the area, seven of which were previously unknown.

astro-ph↗

arXiv2001

The Optical Polarization of Near-Infrared Selected QSOs

Optical broad-band polarimetry is presented for near-infrared color-selected AGN classified QSOs based on their K-band luminosity. More than 10% of a sample of 70 QSOs discovered in the Two Micron All Sky Survey (2MASS) with J-K > 2 and M_K < -23 show high broad-band linear polarization (P > 3%), and values range to a maximum of P = 11%. High polarization tends to be associated with the most luminous objects at K, and with QSOs having the highest near-IR-to-optical flux ratios. The 2MASS QSO sample includes objects possessing a wide range of optical spectral types. High polarization is seen in two of 22 broad emission-line (Type 1) objects, but 1/4 of the QSOs of intermediate spectral type (Type 1.5-1.9) are highly polarized. None of the nine QSOs classified as Type 2 exhibit P > 3%. It is likely that the unavoidable inclusion of unpolarized starlight from the host galaxy within the observation aperture results in reduced polarization for the narrow emission-line objects. The high polarization of 2MASS-discovered QSOs supports the conclusion inferred from their near-IR and optical colors, that the nuclei of many of these objects are obscured to some degree by dust. The 2MASS QSO sample is compared to other, predominantly radio-quiet, QSOs and is found to be consistent with the idea that the orientation of AGN to the line of sight plays a major role in determining their observed properties.

astro-ph↗

arXiv2000

Near-infrared Imaging and [O~I] spectroscopy of IC 443 using 2MASS and ISO

We present near-infrared J (1.25um), H (1.65um), and Ks (2.17um) imaging of the entire supernova remnant IC 443 from the Two Micron All Sky Survey (2MASS), and Infrared Space Observatory (ISO) LWS observations of [O I]. Near-infrared emission from IC 443 was detected in all three bands from most of the optically bright parts of the remnant, revealing a shell-like morphology, with bright Ks band emission along the southern ridge and bright J and H along the northeastern rim. The color and morphological structure are very different between the northeastern and southern parts. J and H band emission from the northeast rim is comparably bright and can be explained mostly by [Fe~II] line emission. The southern ridge is dominated by Ks band light exhibiting a clumped and knotty structure. Molecular hydrogen lines can explain most of K$_s$ band and at least half of J and H band emission in the south. Hence, the prominent broad-band color differences arise from physically different mechanisms: atomic fine structure lines along the northeastern rim and molecular ro-vibrational lines along the southern ridge. Shock models imply a fast J-shock with vs~100 km/s and 10<n<10^3 cm^-3 for the northeastern rim and a slow C-shock with vs \~30 km/s and n~10^{4} cm^{-3} for the southern ridge, respectively.

astro-ph↗

arXiv2000

Two Highly Polarized QSOs Discovered by 2MASS

We present optical observations of two remarkable new AGN discovered by the Two-Micron All Sky Survey. Both are classified as QSOs based on their optical spectra, near-IR colors, and near-IR and [O III]5007 luminosities, but their optical polarizations are among the highest seen for non-blazar AGN; approaching 15% for 2MASSI J151653.2+190048. The polarized light spectrum for each object exhibits broad Balmer emission lines, but lacks the narrow lines that are evident in the total light spectrum. This is most pronounced for the Type-1.5 object 2MASSI J165939.7+183436, where broad lines dominate only in polarized light. The polarization properties of these AGN suggest that dust near the nucleus at least partially obscures the AGN and that material probably intermixed with the narrow line-emitting gas scatters nuclear light into our line of sight. These QSOs illustrate the variety of highly polarized AGN that have been missed by traditional optical search techniques, and demonstrate that such objects are exposed by surveys in the near-IR.

astro-ph↗

arXiv2000

Discovery of a Brown Dwarf Companion to Gliese 570ABC: A 2MASS T Dwarf Significantly Cooler than Gliese 229B

We report the discovery of a widely separated (258$\farcs3\pm0\farcs$4) T dwarf companion to the Gl 570ABC system. This new component, Gl 570D, was initially identified from the Two Micron All Sky Survey (2MASS). Its near-infrared spectrum shows the 1.6 and 2.2 $\micron$ CH$_4$ absorption bands characteristic of T dwarfs, while its common proper motion with the Gl 570ABC system confirms companionship. Gl 570D (M$_J$ = 16.47$\pm$0.07) is nearly a full magnitude dimmer than the only other known T dwarf companion, Gl 229B, and estimates of L = (2.8$\pm$0.3)x10$^{-6}$ L$_{\sun}$ and T$_{eff}$ = 750$\pm$50 K make it significantly cooler and less luminous than any other known brown dwarf companion. Using evolutionary models by Burrows et al. and an adopted age of 2-10 Gyr, we derive a mass estimate of 50$\pm$20 M$_{Jup}$ for this object.

astro-ph↗

arXiv1999

Discovery of Four Field Methane (T-type) Dwarfs with 2MASS

We report the discovery of four field methane (T-type) brown dwarfs using 2MASS survey data. One additional methane dwarf, previously discovered by SDSS, was also identified. Near-infrared spectra clearly show the 1.6 and 2.2 um CH4 absorption bands characteristic of objects with T_eff < 1300 K, as well as broadened H2O bands at 1.4 and 1.9 um. Comparing the spectra of these objects with Gl 229B, we propose that all new 2MASS T dwarfs are warmer than 950 K, in order from warmest to coolest: 2MASS J1217-03, J1225-27, J1047+21 and J1237+65. Based on this preliminary sample, we find a warm T dwarf surface density of 0.0022 T dwarfs/sq. deg., or ~ 90 warm T dwarfs over the whole sky detectable to J < 16. The resulting space density upper limit, 0.01 T dwarfs/pc^3, is comparable to that of the L dwarf sample from Kirkpatrick et al. (1999).

astro-ph↗

arXiv1998

Limits on the X-ray emission from several hyperluminous IRAS galaxies

We report long, pointed ROSAT HRI observations of the hyperluminous galaxies IRAS F00235+1024, F12514+1027, F14481+4454 and F14537+1950. Two of them are optically classified as Seyfert-like. No X-ray sources are detected at the positions of any of the objects, with a mean upper limit L(X)/L(Bol) of 2.3 times 10^-4. This indicates that any active nuclei are either atypically weak at X-ray wavelengths or obscured by column densities N(H)>10^23 cm^-2. They differ markedly from `ordinary' Seyfert 2 galaxies, bearing a closer resemblance in the soft X-ray band to composite Seyfert 2 galaxies or to some types of starburst.

astro-ph↗

arXiv1998

NIR Spectroscopy and a Search for CO Emission in Three Extremely Luminous IRAS Sources; IR 09105+4108, IR 15307+3252, and PG 1634+706

Rest-frame 0.48-1.1 micron emission line strengths and molecular gas mass (H_2) upper limits for 3 luminous infrared sources - the hyperluminous infrared galaxies IR F09105+4108 (z=0.44), IR F15307+3252 (z=0.93), and the optically-selected QSO PG 1634+706 (z=1.3) - are presented. Diagnostic emission-line ratios indicate a Seyfert 2-like spectrum for both infrared galaxies, consistent with previously published work. The upper limits of molecular gas mass for all 3 sources are M(H_2) < 1-3x10^10 h^-2 M_sun (q=0.5, H=100h km/s/Mpc), less than that of the most gas-rich infrared galaxies in the local Universe. All 3 sources have L_ir/L'_CO = 1300-2000, and thus are the extragalactic sources with the most extreme L_ir/L'_CO values measured to date. Given the relatively warm far-infrared colors for all 3 objects, much of their infrared luminosity may emanate from a relatively modest amount of warm dust (e.g. M_d = 10^5-7 M_sun, T_d = 200-100 K) near the AGN...

astro-ph↗