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Caltech Authors (167.915 recursos)

Repository of works by Caltech published authors.

Group = Infrared Processing and Analysis Center (IPAC)

Mostrando recursos 1 - 20 de 2.525

  1. Spitzer Light Curves of the Young, Planetary-mass TW Hya Members 2MASS J11193254–1137466AB and WISEA J114724.10–204021.3

    Schneider, Adam C.; Hardegree-Ullman, Kevin K.; Cushing, Michael C.; Kirkpatrick, J. Davy; Shkolnik, Evgenya L.
    We present Spitzer Space Telescope time-series photometry at 3.6 and 4.5 μm of 2MASS J11193254−1137466AB and WISEA J114724.10−204021.3, two planetary-mass, late-type (~L7) brown dwarf members of the ~10 Myr old TW Hya Association. These observations were taken in order to investigate whether or not a tentative trend of increasing variability amplitude with decreasing surface gravity seen for L3–L5.5 dwarfs extends to later-L spectral types and to explore the angular momentum evolution of low-mass objects. We examine each light curve for variability and find a rotation period of 19.39^(+0.33)_(−0.28) hr and semi-amplitudes of 0.798^(+0.081)_(−0.083)% at 3.6 μm and 1.108^(+0.093)_(−0.094)% at 4.5...

  2. New Y and T Dwarfs from WISE Identified by Methane Imaging

    Tinney, C. J.; Kirkpatrick, J. Davy; Faherty, Jacqueline K.; Mace, Gregory N.; Cushing, Mike; Gelino, Christopher R.; Burgasser, Adam J.; Sheppard, Scott S.; Wright, Edward L.
    We identify new Y- and T-type brown dwarfs from the WISE All Sky data release using images obtained in filters that divide the traditional near-infrared H and J bands into two halves—specifically CH_(4s) and CH_4l in the H and J2, and J3 in the J. This proves to be very effective at identifying cool brown dwarfs via the detection of their methane absorption, as well as providing preliminary classification using methane colors and WISE -to-near-infrared colors. New and updated calibrations between T/Y spectral types and CH_(4s)–CH_4l J3–W2, and CH_(4s)–W2 colors are derived, producing classification estimates good to a few spectral...

  3. Dust Attenuation Curves in the Local Universe: Demographics and New Laws for Star-forming Galaxies and High-redshift Analogs

    Salim, Samir; Boquien, Médéric; Lee, Janice C.
    We study the dust attenuation curves of 230,000 individual galaxies in the local universe, ranging from quiescent to intensely star-forming systems, using GALEX, SDSS, and WISE photometry calibrated on the Herschel ATLAS. We use a new method of constraining SED fits with infrared luminosity (SED+LIR fitting), and parameterized attenuation curves determined with the CIGALE SED-fitting code. Attenuation curve slopes and UV bump strengths are reasonably well constrained independently from one another. We find that A_λ/A_V attenuation curves exhibit a very wide range of slopes that are on average as steep as the curve slope of the Small Magellanic Cloud (SMC)....

  4. OGLE-2016-BLG-1266: A Probable Brown Dwarf/Planet Binary at the Deuterium Fusion Limit

    Albrow, M. D.; Calchi Novati, S.; Carey, S.; Beichman, C.
    We report the discovery, via the microlensing method, of a new very low mass binary system. By combining measurements from Earth and from the Spitzer telescope in Earth-trailing orbit, we are able to measure the microlensing parallax of the event, and we find that the lens likely consists of a (12.0 ± 0.6)M_J + (15.7 ± 1.5)M_J super-Jupiter/brown dwarf pair. The binary is located at a distance of 3.08 ± 0.18 kpc in the Galactic plane, and the components have a projected separation of 0.43 ± 0.03 au. Two alternative solutions with much lower likelihoods are also discussed, an 8M...

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

    Wilman, R. J.; Fabian, A. C.; Cutri, R. M.; Crawford, C. S.; Brandt, W. N.
    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_(Bo)l ≃ 2.3 × 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.

  6. Cosmic clocks: a tight radius–velocity relationship for H i-selected galaxies

    Meurer, Gerhardt R.; Obreschkow, Danail; Wong, O. Ivy; Zheng, Zheng; Audcent-Ross, Fiona M.; Hanish, D. J.
    H I-selected galaxies obey a linear relationship between their maximum detected radius Rmax and rotational velocity. This result covers measurements in the optical, ultraviolet, and H I emission in galaxies spanning a factor of 30 in size and velocity, from small dwarf irregulars to the largest spirals. Hence, galaxies behave as clocks, rotating once a Gyr at the very outskirts of their discs. Observations of a large optically selected sample are consistent, implying this relationship is generic to disc galaxies in the low redshift Universe. A linear radius–velocity relationship is expected from simple models of galaxy formation and evolution. The total mass...

  7. The DEIMOS 10K Spectroscopic Survey Catalog of the COSMOS Field

    Hasinger, G.; Capak, P.; Salvato, M.; Barger, A. J.; Cowie, L. L.; Faisst, A.; Hemmati, S.; Kakazu, Y.; Kartaltepe, J.; Masters, D.; Mobasher, B.; Nayyeri, H.; Sanders, D. B.; Scoville, N. Z.; Suh, H.; Steinhardt, C.; Yang, Fengwei
    We present a catalog of 10,718 objects in the COSMOS field, observed through multi-slit spectroscopy with the Deep Imaging Multi-Object Spectrograph (DEIMOS) on the Keck II telescope in the wavelength range ~5500–9800 Å. The catalog contains 6617 objects with high-quality spectra (two or more spectral features), and 1798 objects with a single spectroscopic feature confirmed by the photometric redshift. For 2024 typically faint objects, we could not obtain reliable redshifts. The objects have been selected from a variety of input catalogs based on multi-wavelength observations in the field, and thus have a diverse selection function, which enables the study of...

  8. Near-Infrared Flux Limits for Sgr A* Based on NICMOS Data

    Stolovy, Susan; Melia, Fulvio; McCarthy, Donald; Yusef-Zadeh, Farhad
    Images of the central arcsec of the Galaxy at near‐infrared(IR) wavelengths reveal a tight stellar cluster, however, no point source exactly coincident with the radio source Sgr A* has been clearly detected in the near‐IR. “Contaminating” emission due to overlapping point spread functions (PSFs) from this stellar cluster as well as from the bright IRS16 sources 1‐3″ away from Sgr A* makes it difficult to assess directly the near‐IR characteristics of Sgr A*. Taking advantage of the stability of the PSF achieved by HST/NICMOS observations, we employ PSF subtraction techniques in order to investigate the true nature of the near‐IR...

  9. Searching for old neutron stars with ROSAT. I. Soft X-ray sources in molecular clouds at high galactic latitude

    Danner, R.
    This is the first in a series of three papers aiming to put strong observational constraints on the number of old accreting neutron stars in the Galaxy. Old neutron stars have been predicted to be visible as soft X-ray sources. The brightest sources are expected where the density of the interstellar medium is high. I present an X-ray survey of a complete sample of molecular clouds at high galactic latitudes based on the ROSAT All-Sky Survey. I detect 89 sources inside the projected contours of the molecular clouds and report on a comprehensive identification program. For all sources I searched...

  10. Searching for old neutron stars with ROSAT. II. Soft X-ray sources in galactic dark clouds

    Danner, R.
    This is the second in a series of three papers constraining the number of detectable old neutron stars in the Galaxy. Here, I present the statistical analysis of a sample of X-ray sources coincident with areas of dark clouds in the Galactic plane. I compare this sample with all sources in the ROSAT All-Sky Survey bright source catalog within 20° of the Galactic plane. I present the results of an identification program of a subset of sources that are compatible with a soft, thermal X-ray spectrum and an effective source temperature of less than 70 eV. The three brightest sources in...

  11. The Nature of Deeply Buried Ultraluminous Infrared Galaxies: A Unified Model for Highly Obscured Dusty Galaxy Emission

    Marshall, J. A.; Elitzur, M.; Armus, L.; Díaz-Santos, T.; Charmandaris, V.
    We present models of deeply buried ultraluminous infrared galaxy (ULIRG) spectral energy distributions (SEDs) and use them to construct a three-dimensional diagram for diagnosing the nature of observed ULIRGs. Our goal is to construct a suite of SEDs for a very simple model ULIRG structure, and to explore how well this simple model can (by itself) explain the full range of observed ULIRG properties. We use our diagnostic to analyze archival Spitzer Space Telescope Infrared Spectrograph data of ULIRGs and find that: (1) in general, our model does provide a comprehensive explanation of the distribution of mid-IR ULIRG properties; (2)...

  12. Three Small Planets Transiting the Bright Young Field Star K2-233

    David, Trevor J.; Crossfield, Ian J. M.; Benneke, Björn; Petigura, Erik A.; Gonzales, Erica J.; Schlieder, Joshua E.; Yu, Liang; Isaacson, Howard T.; Howard, Andrew W.; Ciardi, David R.; Mamajek, Eric E.; Hillenbrand, Lynne A.; Cody, Ann Marie; Riedel, Adric; Schwengeler, Hans Martin; Tanner, Christopher; Ende, Martin
    We report the detection of three small transiting planets around the young K3 dwarf K2-233 (2MASS J15215519−2013539) from observations during Campaign 15 of the K2 mission. The star is relatively nearby (d = 69 pc) and bright (V = 10.7 mag, K_s = 8.4 mag), making the planetary system an attractive target for radial velocity follow-up and atmospheric characterization with the James Webb Space Telescope. The inner two planets are hot super-Earths (R_b = 1.40 ± 0.06 R_⊕, R_c = 1.34 ± 0.08 R_⊕), while the outer planet is a warm sub-Neptune (R_d = 2.6 ± 0.1 R_⊕). We estimate...

  13. An Improved Transit Measurement for a 2.4 R⊕ Planet Orbiting A Bright Mid-M Dwarf K2–28

    Chen, Ge; Knutson, Heather A.; Dressing, Courtney D.; Morley, Caroline V.; Werner, Michael; Gorjian, Varoujan; Beichman, Charles; Benneke, Björn; Christiansen, Jessie L.; Ciardi, David; Crossfield, Ian; Howell, Steve B.; Krick, Jessica E.; Livingston, John; Morales, Farisa Y.; Schlieder, Joshua E.
    We present a new Spitzer transit observation of K2–28b, a sub-Neptune (Rp = 2.45 ± 0.28 R⊕) orbiting a relatively bright (V_(mag) = 16.06, K_(mag) = 10.75) metal-rich M4 dwarf (EPIC 206318379). This star is one of only seven with masses less than 0.2 M⊙ known to host transiting planets, and the planet appears to be a slightly smaller analogue of GJ 1214b (2.85 ± 0.20 R⊕). Our new Spitzerobservations were taken two years after the original K2 discovery data and have a significantly higher cadence, allowing us to derive improved estimates for this planet's radius, semimajor axis, and orbital...

  14. Testing a double AGN hypothesis for Mrk 273

    Iwasawa, K.; U, V.; Mazzarella, J. M.; Medling, A. M.; Sanders, D. B.; Evans, A. S.
    The ultra-luminous infrared galaxy (ULIRG) Mrk 273 contains two infrared nuclei, N and SW, separated by 1 arcsecond. A Chandraobservation has identified the SW nucleus as an absorbed X-ray source with N_H ~ 4 × 10^(23) cm^(−2) but also hinted at the possible presence of a Compton-thick AGN in the N nucleus, where a black hole of ~10^9 M⊙ is inferred from the ionized gas kinematics. The intrinsic X-ray spectral slope recently measured by NuSTAR is unusually hard (Γ ~ 1.3) for a Seyfert nucleus, for which we seek an alternative explanation. We hypothesize a strongly absorbed X-ray source in...

  15. A preliminary analysis of the Shangri-La Bolide on 2017 Oct 4

    Ye, Quan-Zhi
    At 12:07 UT (8:07 pm China Standard Time) on 2017 Oct 4, a bright bolide was widely observed in the Shangri-La region of the Province of Yunnan, China (Figure 1). The event was well observed by the general public as it took place on the night of the Mid Autumn Festival, which is associated with moon gazing. Sonic booms and ground shaking were reported in an area of about a thousand square kilometers northwest of Shangri-La City. Data from U.S. government sensors suggests that the impact energy of the event was approximately 0.54 kt TNT equivalent, with the terminus of...

  16. Molecular outflow and feedback in the obscured quasar XID2028 revealed by ALMA

    Brusa, M.; Scoville, N. Z.
    We imaged, with ALMA and ARGOS/LUCI, the molecular gas and dust and stellar continuum in XID2028, which is an obscured quasi-stellar object (QSO) at z = 1.593, where the presence of a massive outflow in the ionised gas component traced by the [OIII]5007 emission has been resolved up to 10 kpc. This target represents a unique test case to study QSO feedback in action at the peak epoch of AGN-galaxy co-evolution. The QSO was detected in the CO(5 − 4) transition and in the 1.3 mm continuum at ~30 and ~20σ significance, respectively; both emissions are confined in the central...

  17. Meteor showers from active asteroids and dormant comets in near-Earth space: A review

    Ye, Quan-Zhi
    Small bodies in the solar system are conventionally classified into asteroids and comets. However, it is recently found that a small number of objects can exhibit properties of both asteroids and comets. Some are more consistent with asteroids despite episodic ejections and are labeled as “active asteroids”, while some might be aging comets with depleting volatiles. Ejecta produced by active asteroids and/or dormant comets are potentially detectable as meteor showers at the Earth if they are in Earth-crossing orbits, allowing us to retrieve information about the historic activities of these objects. Meteor showers from small bodies with low and/or intermittent...

  18. The Stellar Populations of Two Ultra-diffuse Galaxies from Optical and Near-infrared Photometry

    Pandya, Viraj; Romanowsky, Aaron J.; Laine, Seppo; Brodie, Jean P.; Johnson, Benjamin D.; Glaccum, William; Villaume, Alexa; Cuillandre, Jean-Charles; Gwyn, Stephen; Krick, Jessica; Lasker, Ronald; Martín-Navarro, Ignacio; Martínez-Delgado, David; van Dokkum, Pieter
    We present observational constraints on the stellar populations of two ultra-diffuse galaxies (UDGs) using optical through near-infrared (NIR) spectral energy distribution (SED) fitting. Our analysis is enabled by new Spitzer-IRAC 3.6 and 4.5 μm imaging, archival optical imaging, and the prospectorfully Bayesian SED fitting framework. Our sample contains one field UDG (DGSAT I), one Virgo cluster UDG (VCC 1287), and one Virgo cluster dwarf elliptical for comparison (VCC 1122). We find that the optical–NIR colors of the three galaxies are significantly different from each other. We infer that VCC 1287 has an old (≳7.7 Gyr) and surprisingly metal-poor ([Z/Z⊙] ≾...

  19. Optimizing Workflow Data Footprint

    Singh, Gurmeet; Vahi, Karan; Ramakrishnan, Arun; Mehta, Gaurang; Deelman, Ewa; Zhao, Henan; Sakellariou, Rizos; Blackburn, Kent; Brown, Duncan; Fairhurst, Stephen; Meyers, David; Berriman, G. Bruce; Good, John; Katz, Daniel S.
    In this paper we examine the issue of optimizing disk usage and scheduling large-scale scientific workflows onto distributed resources where the workflows are data-intensive, requiring large amounts of data storage, and the resources have limited storage resources. Our approach is two-fold: we minimize the amount of space a workflow requires during execution by removing data files at runtime when they are no longer needed and we demonstrate that workflows may have to be restructured to reduce the overall data footprint of the workflow. We show the results of our data management and workflow restructuring solutions using a Laser Interferometer Gravitational-Wave...

  20. On the Limitations of the Anomalous Microwave Emission Emissivity

    Tibbs, Christopher T.; Paladini, Roberta; Dickinson, Clive
    Many studies of anomalous microwave emission (AME) have computed an AME emissivity to compare the strength of the AME detected in different regions. Such a value is usually defined as the ratio between the intensity of the AME at 1 cm and the thermal dust emission at 100 μm. However, as studies of Galactic dust emission have shown, the intensity of the thermal dust emission at 100 μm is strongly dependent on the dust temperature, which has severe implications for the AME emissivity defined in this way. In this work, we illustrate and quantify this effect and find that the AME emissivity decreases...

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