Thomas A. Kuchar

MIPSGAL: A Survey of the Inner Galactic Plane at 24 and 70 μm

MIPSGAL is a 278 deg^2 survey of the inner Galactic plane using the Multiband Infrared Photometer for Spitzer aboard the Spitzer Space Telescope. The survey field was imaged in two passbands, 24 and 70 μm with resolutions of 6″ and 18″, respectively. The survey was designed to provide a uniform, well-calibrated and well-characterized data set for general inquiry of the inner Galactic plane and as a longer-wavelength complement to the shorter-wavelength Spitzer survey of the Galactic plane: Galactic Plane Infrared Mapping Survey Extraordinaire. The primary science drivers of the current survey are to identify all high-mass (M > 5 M⊙) protostars in the inner Galactic disk and to probe the distribution, energetics, and properties of interstellar dust in the Galactic disk. The observations were planned to minimize data artifacts due to image latents at 24 μm and to provide full coverage at 70 μm. Observations at ecliptic latitudes within 15° of the ecliptic plane were taken at multiple epochs to help reject asteroids. The data for the survey were collected in three epochs, 2005 September–October, 2006 April, and 2006 October with all of the data available to the public. The estimated point-source sensitivities of the survey are 2 and 75 mJy (3 σ) at 24 and 70 μm, respectively. Additional data processing was needed to mitigate image artifacts due to bright sources at 24 μm and detector responsivity variations at 70 μm due to the large dynamic range of the Galactic plane. Enhanced data products including artifact-mitigated mosaics and point-source catalogs are being produced with the 24 μm mosaics already publicly available from the NASA/IPAC Infrared Science Archive. Some preliminary results using the enhanced data products are described.

The Physical Properties of the Midcourse Space Experiment Galactic Infrared-dark Clouds

The SPIRIT III infrared telescope on the Midcourse Space Experiment (MSX) satellite has provided an unprecedented view of the mid-infrared emission (8-25 μm) of the Galactic plane. An initial analysis of images from MSX Galactic plane survey data reveals dark clouds seen in silhouette against the bright emission from the Galactic plane (Egan et al.). These clouds have mid-infrared extinctions in excess of 2 mag at 8 μm. We probed the physical properties of 10 of these MSX dark clouds using millimeter-wave molecular rotational lines as an indicator of dense molecular gas. All 10 clouds were detected in millimeter spectral lines of H2CO, which confirms the presence of dense gas. The distances to these clouds range from 1 to 8 kiloparsecs and their diameters from 0.4 to 15.0 pc. Excitation analysis of the observed lines indicates that the clouds are cold (T 105 cm-3]. Some of the clouds have nearby H II regions, H2O masers, and other tracers of star formation at comparable spectral line velocities; however, only one cloud contains embedded centimeter or infrared sources. The lack of mid- to far-infrared emission associated with these clouds suggests that they are not currently forming high-mass stars. If star formation is present in these clouds, it is clearly protostellar class 0 or earlier.

Tracking a major interplanetary disturbance with SMEI

[1] We present the first clear observations of an Earth-directed interplanetary disturbance tracked by the Solar Mass Ejection Imager (SMEI). We find that this event can be related to two halo CMEs seen at the Sun about 2 days earlier, and which merged in transit to 1 AU. The disturbance was seen about 16 hours before it reached Earth, and caused a severe geomagnetic storm at the time which would have been predicted had SMEI been operating as a real-time monitor. It is concluded that SMEI is capable of giving many hours advance warning of the possible arrival of interplanetary disturbances.

Analysis of Plasma-Tail Motions for Comets C/2001 Q4 (NEAT) and C/2002 T7 (LINEAR) Using Observations from SMEI

Comets C/2001 Q4 (NEAT) and C/2002 T7 (LINEAR) passed within � 0.3 AU of Earth in April and May of 2004. Their tails were observed by the Earth-orbiting Solar Mass Ejection Imager (SMEI) during this period. A time series of photometric SMEI sky maps displays the motions and frequent disruptions of the comet plasma tails. Ephemerides are used to unfold the observing geometry; the tails are often seen to extend � 0.5 AU from the comet nuclei. Having selected 12 of the more prominent motions as ‘‘events’’ for further study, we introduce a new method for determining solar wind radial velocities from these SMEI observations. We find little correlation between these and the changing solar wind parameters as measured close to Earth, or with coarse three-dimensional reconstructions using interplanetary scintillation data. A likely explanation is that the transverse sizes of the solar wind perturbations responsible for these disruptions are small, P0.05 AU. We determine the radial velocities of these events during the disruptions,usingatechniqueonlypossiblewhentheobservedcomettailsextendoverasignificantfractionof anAU. We find typical radial velocities during these events of 50Y100 km s � 1 lower than before or afterward. Time durations of such events vary, typically from 3 to 8 hr, and correspond to comet traversal distances � 10 6 km (0.007 AU). We conclude that these large disturbances are primarily due to ubiquitous solar wind flow variations, of which these measured events are a subset. Subject headingg comets: individual (C/2001 Q4 (NEAT), C/2002 T7 (LINEAR), C/2004 F4 (Bradfield)) — solar wind — Sun: coronal mass ejections (CMEs)

3.6 YEARS OF DIRBE NEAR-INFRARED STELLAR LIGHT CURVES

The weekly averaged near-infrared fluxes for 2652 stars were extracted from the cold and warm era all-sky maps of the Diffuse Infrared Background Experiment (DIRBE). Since the DIRBE program only archived the individual Calibrated Infrared Observations for the 10 month cold era mission, the weekly averaged fluxes were all that were available for the warm era. The steps required to extract stellar fluxes are described as are the adjustments that were necessary to correct the results for several systematic effects. The observations are at a cadence of once a week for 3.6 years (~1300 days), providing continuous sampling on variable stars that span the entire period for the longest fundamental pulsators. The stars are divided into three categories: those with large amplitude of variability, smaller amplitude variables, and sources whose near-infrared brightness do not vary according to our classification criteria. We show examples of the results and the value of the added baseline in determining the phase lag between the visible and infrared.

Processing for the MIPSGAL 24 μm Survey of the Inner Galactic Plane

We describe improvements to the data processing pipeline for the Spitzer MIPSGAL survey of the Galactic plane. These involve both improvements to the processing of the 24 μm data, in particular the handling of saturations and near-saturated data, and mitigation of various artifacts not corrected in the basic calibration pipeline. The artifacts addressed postpipeline are typically caused by passage across bright point sources very common in the Galactic plane, and include column-to-column “jailbar” striping, latency effects resulting in both short-duration afterimages and long-duration responsivity depressions, scattered light, and background-level mismatches. We describe the artifacts phenomenologically and present in detail the algorithms developed to correct them.

DISCOVERY OF HIGHLY OBSCURED GALAXIES IN THE ZONE OF AVOIDANCE

We report the discovery of 25 previously unknown galaxies in the zone of avoidance (ZoA). Our systematic search for extended extragalactic sources in the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) and MIPS Galactic Plane Survey (MIPSGAL) mid-infrared surveys of the Galactic plane has revealed two overdensities of these sources, located around l ~ 47° and 55° and |b| ≾ 1° in the Sagitta-Aquila region. These overdensities are consistent with the local large-scale structure found at similar Galactic longitude and extending from |b| ~ 4 to 40°. We show that the infrared spectral energy distribution of these sources is indeed consistent with those of normal galaxies. Photometric estimates of their redshift indicate that the majority of these galaxies are found in the redshift range z ≃ 0.01-0.05, with one source located at z ≃ 0.07. Comparison with known sources in the local universe reveals that these galaxies are located at similar overdensities in redshift space. These new galaxies are the first evidence of a bridge linking the large-scale structure between both sides of the Galactic plane at very low Galactic latitude and clearly demonstrate the feasibility of detecting galaxies in the ZoA using mid-to-far infrared surveys.

Global Solar Magnetic Field Evolution Over 4 Solar Cycles: Use of the McIntosh Archive

The McIntosh Archive consists of a set of hand-drawn solar Carrington maps created by Patrick McIntosh from 1964 to 2009. McIntosh used mainly H, He-I 10830A and photospheric magnetic measurements from both ground-based and NASA satellite observations. With these he traced polarity inversion lines (PILs), filaments, sunspots and plage and, later, coronal holes over a ~45-year period. This yielded a unique record of synoptic maps of features associated with the large-scale solar magnetic field over four complete solar cycles. We first discuss how these and similar maps have been used in the past to investigate long-term solar variability. Then we describe our work in preserving and digitizing this archive, developing a digital, searchable format, and creating a website and an archival repository at NOAA’s National Centers for Environmental Information (NCEI). Next we show examples of how the data base can be utilized for scientific applications. Finally, we present some preliminary results on the solar-cycle evolution of the solar magnetic field, including the polar field reversal process, the evolution of active longitudes, and the role of differential solar rotation.

Imaging coronal mass ejections and other heliospheric phenomena: six years of observations and implications for future capabilities

January 2009 marked the 6th anniversary of the launch of the Air Force Research Laboratory Solar Mass Ejection Imager (SMEI) instrument on the Coriolis spacecraft. Originally planned as a three year mission, SMEI has amassed an unprecedented dataset of ~25,000 full-sky images since 2003 with a 102-minute cadence, 1° spatial resolution, and better than 8th magnitude sensitivity. SMEI, with its Sun/Earth line views, has been joined by the twin STEREO spacecraft, launched in October 2006, whose heliospheric Imagers (HIs) image along the ecliptic with opposing, off-axis views, 70° in diameter. These two data sets are complementary and several events observed by both SMEI and STEREO are being analyzed. But SMEI is nearing its end of life and the STEREO spacecraft continue to drift apart by 45°/year with decreasing telemetry coverage. What would be the characteristics of the next generation instrument in heliospheric imaging? What would the differences be for an operational instrument vs. a research instrument? What are the advantages of staring vs. composite imaging, views from the Sun/Earth line vs. other views, L1 position vs. low Earth orbit, etc? What are the engineering lessons learned from SMEI and STEREO and the environment through which such an instrument operates? In this presentation we discuss these issues and some possible future mission concepts.

Observations of Coronal Mass Ejections from the Solar Mass Ejection Imager and Space Weather Implications

The Solar Mass Ejection Imager (SMEI) was launched into a Sun-synchronous orbit in January 2003. Its mission objective is to detect and track coronal mass ejections (CMEs) from the Sun in order to improve space weather forecasts. In the three years since launch, over 200 CMEs, about 30 of which were Earth-directed, have been observed by SMEI. We have been able to track several of these CMEs from the SOHO LASCO coronagraphs ( 20◦) out to 0.5 AU and beyond, and to observe the morphology and evolution of distinctive features over this wide distance range. We report on comparisons of measurements of CME parameters made in the inner heliosphere with the more typical measurements made nearer the Sun with coronagraphs. We illustrate SMEI’s capabilities and present key statistical results on basic CME parameters and the use of SMEI-type data in space weather forecasting models. For example, timely observations by SMEI of CMEs en route to Earth could be input to DoD’s operational Hakamada-Akasofu-Fry solar wind model to correct or refine its real-time forecasts of approaching disturbances.