Recursos de colección

Caltech Authors (163.728 recursos)

Repository of works by Caltech published authors.

Group = Infrared Processing and Analysis Center (IPAC)

Mostrando recursos 1 - 20 de 2.411

  1. Low-excitation atomic gas around evolved stars. II. ISO observations of O-rich nebulae

    Castro-Carrizo, A.; Bujarrabal, V.; Fong, D.; Meixner, M.; Tielens, A. G. G. M.; Latter, W. B.; Barlow, M. J.
    We have observed atomic fine-structure lines in the far-infrared (FIR) from 12 oxygen-rich evolved stars. The sample is composed of mostly proto-planetary nebulae (PPNe) and some planetary nebulae (PNe) and asymptotic giant branch (AGB) stars. ISO LWS and SWS observations of [O i], [C ii], [N ii], [Si i], [Si ii], [S i], [Fe i], and [Fe ii] lines were obtained. Taking into account also the sample presented by Fong et al. (Paper I) of carbon-rich evolved stars, we find that PPNe emit in these low-excitation atomic transitions only when the central star is hotter than ∼10 000 K. This...

  2. A molecular-line study of clumps with embedded high-mass protostar candidates

    Brand, J.; Cesaroni, R.; Palla, F.; Molinari, S.
    We present molecular line observations made with the IRAM 30-m telecopes of the immediate surroundings of a sample of 11 candidate high-mass protostars. These observations are part of an effort to clarify the evolutionary status of a set of objects which we consider to be precursors of UC HII regions. In a preceding series of papers we have studied a sample of objects, which on the basis of their IR colours are likely to be associated with compact molecular clouds. The original sample of 260 objects was divided approximately evenly into a High group, with IR colour indices [25-12] ≥...

  3. ISOPHOT – Photometric calibration of point sources

    Schulz, B.; Huth, S.; Laureijs, R. J.; Acosta-Pulido, J. A.; Braun, M.; Castañeda, H. O.; Cohen, M.; Cornwall, L.; Gabriel, C.; Hammersley, P.; Heinrichsen, I.; Klaas, U.; Lemke, D.; Müller, T.; Osip, D.; Román-Fernández, P.; Telesco, C.
    All observations by the aperture photometer (PHT-P) and the far-infrared (FIR) camera section of ISOPHOT included reference measurements against stable internal fine calibration sources (FCS) to correct for temporal drifts in detector responsivities. The FCSs were absolutely calibrated in-orbit against stars, asteroids and planets, covering wavelengths from 3.2 to 240 μm. We present the calibration concept for point sources within a flux-range from 60 mJy up to 4500 Jy for staring and raster observations in standard configurations and discuss the requisite measurements and the uncertainties involved. In this process we correct for instrumental effects like nonlinearities, signal transients, time variable...

  4. Spitzer Observations of the North Ecliptic Pole

    Nayyeri, H.; Ghotbi, N.; Cooray, A.; Bock, J.; Clements, D. L.; Im, M.; Kim, M. G.; Korngut, P.; Lanz, A.; Lee, H. M.; Lee, D. H.; Malkan, M.; Matsuhara, H.; Matsumoto, T.; Matsuura, S.; Nam, U. W.; Pearson, C.; Serjeant, S.; Smidt, J.; Tsumura, K.; Wada, T.; Zemcov, M.
    We present a photometric catalog for Spitzer Space Telescope warm mission observations of the North Ecliptic Pole (NEP; centered at R.A. = 18^h00^m00^s, decl. = 66^d33^m38^s.552). The observations are conducted with IRAC in the 3.6 and 4.5 μm bands over an area of 7.04 deg^2, reaching 1σ depths of 1.29 μJy and 0.79 μJy in the 3.6 μm and 4.5 μm bands, respectively. The photometric catalog contains 380,858 sources with 3.6 and 4.5 μm band photometry over the full-depth NEP mosaic. Point-source completeness simulations show that the catalog is 80% complete down to 19.7 AB. The accompanying catalog can be...

  5. iPTF Archival Search for Fast Optical Transients

    Ho, Anna Y. Q.; Kulkarni, S. R.; Nugent, Peter E.; Zhao, Weijie; Rusu, Florin; Cenko, S. Bradley; Ravi, Vikram; Kasliwal, Mansi M.; Perley, Daniel A.; Adams, Scott M.; Bellm, Eric C.; Brady, Patrick R.; Fremling, Christoffer; Gal-Yam, Avishay; Kann, David Alexander; Kaplan, David; Laher, Russ R.; Masci, Frank; Ofek, Eran O.; Sollerman, Jesper; Urban, Alex
    There has been speculation about a class of relativistic explosions with an initial Lorentz factor Γ_(init) smaller than that of classical gamma-ray bursts (GRBs). These "dirty fireballs" would lack prompt GRB emission but could be pursued via their optical afterglow, appearing as transients that fade overnight. Here we report a search for such transients (that fade by 5-σ in magnitude overnight) in four years of archival photometric data from the intermediate Palomar Transient Factory (iPTF). Our search criteria yielded 50 candidates. Of these, two were afterglows to GRBs that had been found in dedicated follow-up observations to triggers from the...

  6. An Ultra-short Period Rocky Super-Earth with a Secondary Eclipse and a Neptune-like Companion around K2-141

    Malavolta, Luca; Ciardi, David R.
    Ultra-short period (USP) planets are a class of low-mass planets with periods shorter than one day. Their origin is still unknown, with photo-evaporation of mini-Neptunes and in situ formation being the most credited hypotheses. Formation scenarios differ radically in the predicted composition of USP planets, and it is therefore extremely important to increase the still limited sample of USP planets with precise and accurate mass and density measurements. We report here the characterization of a USP planet with a period of 0.28 days around K2-141 (EPIC 246393474), and the validation of an outer planet with a period of 7.7 days...

  7. The shroud around the twin radio jets in NGC 1052

    Vermeulen, R. C.; Ros, E.; Kellermann, K. I.; Cohen, M. H.; Zensus, J. A.; van Langevelde, H. J.
    We discuss multiple Very Long Baseline Interferometry (VLBI) continuum and spectral line imaging observations and Westerbork Synthesis Radio Telescope spectroscopy of the compact variable nuclear radio jet source in the elliptical galaxy NGC 1052. Absorption and emission signatures reveal ionised, atomic, and molecular components of the surrounding medium.
Ten epochs of Very Long Baseline Array (VLBA) data at 15 GHz, spanning almost six years, show bi-symmetric jets, in which multiple sub-parsec scale features display outward motions of typically v_(app) ~ 0.26c(H_0km s^(-1) Mpc^(-1)) on each side. The jets are most likely oriented near the plane of the sky.
Multi-frequency VLBA observations at...

  8. The nature of the TRAPPIST-1 exoplanets

    Grimm, Simon L.; Carey, Sean; Ingalls, James G.
    Context. The TRAPPIST-1 system hosts seven Earth-sized, temperate exoplanets orbiting an ultra-cool dwarf star. As such, it represents a remarkable setting to study the formation and evolution of terrestrial planets that formed in the same protoplanetary disk. While the sizes of the TRAPPIST-1 planets are all known to better than 5% precision, their densities have significant uncertainties (between 28% and 95%) because of poor constraints on the planet’s masses. Aims. The goal of this paper is to improve our knowledge of the TRAPPIST-1 planetary masses and densities using transit-timing variations (TTV). The complexity of the TTV inversion problem is known to be particularly acute in...

  9. Far-infrared dust opacity and visible extinction

    Cambrésy, L.; Boulanger, F.; Lagache, G.; Stepnik, B.
    We present an extinction map of the Polaris molecular cirrus cloud derived from star counts and compare it with the Schlegel et al. [13] extinction map derived from the far-infrared dust opacity. We find that, within the Polaris cloud, the Schlegel et al. [13] AV values are, on average, a factor 2 higher than the star count values. We propose that this discrepancy results from a difference in τ_(FIR)/A_V between the diffuse atomic medium and the Polaris cloud. We use the difference in spectral energy distribution, warm for the diffuse atomic medium, cold for the Polaris cloud, to separate their...

  10. The Carnegie Supernova Project I. Photometry data release of low-redshift stripped-envelope supernovae

    Stritzinger, M. D.; Madore, B. F.
    The first phase of the Carnegie Supernova Project (CSP-I) was a dedicated supernova follow-up program based at the Las Campanas Observatory that collected science data of young, low-redshift supernovae between 2004 and 2009. Presented in this paper is the CSP-I photometric data release of low-redshift stripped-envelope core-collapse supernovae. The data consist of optical (uBgVri) photometry of 34 objects, with a subset of 26 having near-infrared (YJH) photometry. Twenty objects have optical pre-maximum coverage with a subset of 12 beginning at least five days prior to the epoch of B-band maximum brightness. In the near-infrared, 17 objects have pre-maximum observations with...

  11. iPTF Survey for Cool Transients

    Adams, S. M.; Blagorodnova, N.; Kasliwal, M. M.; Barlow, T.; Cook, D. O.; Ho, A. Y. Q.; Kulkarni, S. R.; Kupfer, T.; Neill, J. D.; Walters, R.; Laher, R. R.; Masci, F.
    We performed a wide-area (2000 deg^2) g and I band experiment as part of a two month extension to the Intermediate Palomar Transient Factory. We discovered 36 extragalactic transients including iPTF17lf, a highly reddened local SN Ia, iPTF17bkj, a new member of the rare class of transitional Ibn/IIn supernovae, and iPTF17be, a candidate luminous blue variable outburst. We do not detect any luminous red novae and place an upper limit on their rate. We show that adding a slow-cadence I band component to upcoming surveys such as the Zwicky Transient Facility will improve the photometric selection of cool and dusty...

  12. The Star Formation in Radio Survey: Jansky Very Large Array 33 GHz Observations of Nearby Galaxy Nuclei and Extranuclear Star-forming Regions

    Murphy, E. J.; Dong, Dillon; Momjian, E.; Linden, S.; Kennicutt, R. C., Jr.; Meier, D. S.; Schinnerer, E.; Turner, J. L.
    We present 33 GHz imaging for 112 pointings toward galaxy nuclei and extranuclear star-forming regions at ≈2" resolution using the Karl G. Jansky Very Large Array (VLA) as part of the Star Formation in Radio Survey. A comparison with 33 GHz Robert C. Byrd Green Bank Telescope single-dish observations indicates that the interferometric VLA observations recover 78% ± 4% of the total flux density over 25" regions (≈kpc scales) among all fields. On these scales, the emission being resolved out is most likely diffuse non-thermal synchrotron emission. Consequently, on the ≈30–300 pc scales sampled by our VLA observations, the bulk...

  13. Type Ia Supernova Distances at Redshift >1.5 from the Hubble Space Telescope Multi-cycle Treasury Programs: The Early Expansion Rate

    Riess, Adam G.; Hemmati, Shoubaneh
    We present an analysis of 15 Type Ia supernovae (SNe Ia) at redshift z 〉 1 (9 at 1.5 〈 z 〈 2.3) recently discovered in the CANDELS and CLASH Multi-Cycle Treasury programs using WFC3 on the Hubble Space Telescope. We combine these SNe Ia with a new compilation of ~1050 SNe Ia, jointly calibrated and corrected for simulated survey biases to produce accurate distance measurements. We present unbiased constraints on the expansion rate at six redshifts in the range 0.07 〈 z 〈 1.5 based only on this combined SN Ia sample. The added leverage of our new sample...

  14. Revisiting the Extended Schmidt Law: The Important Role of Existing Stars in Regulating Star Formation

    Shi, Yong; Yan, Lin; Armus, Lee; Gu, Qiusheng; Helou, George; Qiu, Keping; Gwyn, Stephen; Stierwalt, Sabrina; Fang, Min; Chen, Yanmei; Zhou, Luwenjia; Wu, Jingwen; Zheng, Xianzhong; Zhang, Zhi-Yu; Gao, Yu; Wang, Junzhi
    We revisit the proposed extended Schmidt law, which posits that the star formation efficiency in galaxies depends on the stellar mass surface density, by investigating spatially resolved star formation rates (SFRs), gas masses, and stellar masses of star formation regions in a vast range of galactic environments, from the outer disks of dwarf galaxies, to spiral disks and to merging galaxies, as well as individual molecular clouds in M33. We find that these regions are distributed in a tight power law as Σ _SFR ∝ (Σ_(star)^0.5 Σ__gas)^(1.09), which is also valid for the integrated measurements of disk and merging galaxies...

  15. YSOVAR: Mid-infrared Variability among YSOs in the Star Formation Region Serpens South

    Wolk, Scott J.; Günther, H. Moritz; Poppenhaeger, Katja; Winston, E.; Rebull, L. M.; Stauffer, J. R.; Gutermuth, R. A.; Cody, A. M.; Hillenbrand, L. A.; Plavchan, P.; Covey, K. R.; Song, Inseok
    We present a time-variability study of young stellar objects (YSOs) in the Serpens South cluster performed at 3.6 and 4.5 μm with the Spitzer Space Telescope; this study is part of the Young Stellar Object VARiability project. We have collected light curves for more than 1500 sources, including 85 cluster members, over 38 days. This includes 44 class I sources, 19 sources with flat spectral energy distributions (SEDs), 17 class II sources, and five diskless YSO candidates. We find a high variability fraction among embedded cluster members of ~70%, whereas young stars without a detectable disk display no variability. We...

  16. The Intrinsic Characteristics of Galaxies on the SFR–M_∗ Plane at 1.2 < z < 4: I. The Correlation between Stellar Age, Central Density, and Position Relative to the Main Sequence

    Lee, Bomee; Giavalisco, Mauro; Whitaker, Katherine; Williams, Christina C.; Ferguson, Henry C.; Acquaviva, Viviana; Koekemoer, Anton M.; Straughn, Amber N.; Guo, Yicheng; Kartaltepe, Jeyhan S.; Lotz, Jennifer; Pacifici, Camilla; Croton, Darren J.; Somerville, Rachel S.; Lu, Yu
    We use the deep CANDELS observations in the GOODS North and South fields to revisit the correlations between stellar mass (M_*), star formation rate (SFR) and morphology, and to introduce a fourth dimension, the mass-weighted stellar age, in galaxies at 1.2 < z < 4. We do this by making new measures of M_*, SFR, and stellar age thanks to an improved SED fitting procedure that allows various star formation history for each galaxy. Like others, we find that the slope of the main sequence (MS) of star formation in the M_*; SFR plane bends at high mass. We observe...

  17. The WISE AGN Catalog

    Assef, R. J.; Stern, D.; Noirot, G.; Jun, H. D.; Cutri, R. M.; Eisenhardt, P. R. M.
    We present two large catalogs of active galactic nucleus (AGN) candidates identified across 30,093 deg^2 of extragalactic sky from the Wide-field Infrared Survey Explorer's AllWISE Data Release. Both catalogs are selected purely using the Wide-field Infrared Survey Explorer (WISE) W1 and W2 bands. The R90 catalog consists of 4,543,530 AGN candidates with 90% reliability, while the C75 catalog consists of 20,907,127 AGN candidates with 75% completeness. These reliability and completeness figures were determined from a detailed analysis of UV- to near-IR spectral energy distributions of ~ 10^5 sources in the 9 deg^2 Boötes field. The AGN selection criteria are based...

  18. Combining Spitzer Parallax and Keck II Adaptive Optics Imaging to Measure the Mass of a Solar-like Star Orbited by a Cold Gaseous Planet Discovered by Microlensing

    Beaulieu, J.-P.; Batista, V.; Bennett, D. P.; Marquette, J.-B.; Blackman, J. W.; Cole, A. A.; Coutures, C.; Danielski, C.; Prester, D. Dominis; Donatowicz, J.; Fukui, A.; Koshimoto, N.; Lončarić, K.; Morales, J. C.; Sumi, T.; Suzuki, D.; Henderson, C.; Shvartzvald, Y.; Beichman, C.
    To obtain accurate mass measurements for cold planets discovered by microlensing, it is usually necessary to combine light curve modeling with at least two lens mass–distance relations. The physical parameters of the planetary system OGLE-2014-BLG-0124L have been constrained thanks to accurate parallax effect between ground-based and simultaneous space-based Spitzer observations. Here, we resolved the source+lens star from sub-arcsecond blends in H-band using adaptive optics (AO) observations with NIRC2 mounted on Keck II telescope. We identify additional flux, coincident with the source to within 160 mas. We estimate the potential contributions to this blended light (chance-aligned star, additional companion to the...

  19. Discovery of a Possible Early-T Thick-disk Subdwarf from the AllWISE2 Motion Survey

    Kellogg, Kendra; Kirkpatrick, J. Davy; Metchev, Stanimir; Gagné, Jonathan; Faherty, Jacqueline K.
    We have discovered a potential T0 ± 1 subdwarf from a search for sources in the AllWISE2 Motion Survey that do not have counterparts in surveys at shorter wavelengths. With a tangential velocity of ~170 km s^(-1), this object—WISE J071121.36–573634.2—has kinematics that are consistent with the thick-disk population of the Milky Way. Spectral fits suggest a low-metallicity for this object but also allow for the possibility of unresolved multiplicity. If WISE J0711–5736 is indeed an sdT0 dwarf, it would be only the second early-T subdwarf discovered to date.

  20. OGLE-2014-BLG-0289: Precise Characterization of a Quintuple-peak Gravitational Microlensing Event

    Udalski, A.; Beichman, C.; Carey, S.; Calchi Novati, S.
    We present the analysis of the binary-microlensing event OGLE-2014-BLG-0289. The event light curve exhibits five very unusual peaks, four of which were produced by caustic crossings and the other by a cusp approach. It is found that the quintuple-peak features of the light curve provide tight constraints on the source trajectory, enabling us to precisely and accurately measure the microlensing parallax π_E. Furthermore, the three resolved caustics allow us to measure the angular Einstein radius θ_E. From the combination of π_E and θ_E, the physical lens parameters are uniquely determined. It is found that the lens is a binary composed...

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