Posters
Intensity Mapping of the [CII] Fine Structure Line during the Epoch of Reionization
Yan Gong (UC Irvine)
The atomic CII fine-structure line is one of the brightest lines in a typical star-forming galaxy spectrum with a luminosity ~ 0.1% to 1% of the bolometric luminosity. It is potentially a reliable tracer of the dense gas distribution at high redshifts and could provide an additional probe to the era of reionization. By taking into account of the spontaneous, stimulated and collisional emission of the CII line, we calculate the spin temperature and the mean intensity as a function of the redshift. When averaged over a cosmologically large volume, we find that the CII emission from ionized carbon in individual galaxies is larger than the signal generated by carbon in the intergalactic medium (IGM). Assuming that the CII luminosity is proportional to the carbon mass in dark matter halos, we also compute the power spectrum of the CII line intensity at various redshifts. In order to avoid the contamination from CO rotational lines at low redshift when targeting a CII survey at high redshifts, we propose the cross-correlation of CII and 21-cm line emission from high redshifts. To explore the detectability of the CII signal from reionization, we also evaluate the expected errors on the CII power spectrum and CII-21 cm cross power spectrum based on the design of the future milimeter surveys. We note that the CII-21 cm cross power spectrum contains interesting features that captures physics during reionization, including the ionized bubble sizes and the mean ionization fraction, which are challenging to measure from 21-cm data alone. We propose an instrumental concept for the reionization CII experiment targeting the frequency range of ~200 to 300 GHz with 1, 3 and 10 meter apertures and a bolometric spectrometer array with 64 independent spectral pixels with about 20,000 bolometers.
Observation of near-infrared background with MIRIS and SPICA/FPC-S
Woong-Seob Jeong (KASI, Korea), T. Matsumoto, D.-H. Lee, Y. Park, C.H. Ree, U.-W. Nam, B. Moon, S.-J. Park, J. Pyo, D. Lee, J.-H. Park, S.-W. Rhee, J.-O. Park, H. M. Lee, and W. Han
The MIRIS (Multipurpose Infra-Red Imaging System) is a small infrared space telescope which is being developed by Korea Astronomy and Space Science Institute (KASI), as the main payload of Science and Technology Satellite 3 (STSAT-3). In addition to the current space project, we are proposing the near-infrared instrument (FPC-S, Focal Plane Camera - Science) in order to participate the future space project, SPICA. One of the main sciences proposed in two instruments is to study the cosmic infrared background (CIB). The MIRIS has two wide spectral bands (I and H band) and one blank filter is allotted for the calibration of dark level. The primary target is the North Ecliptic Pole (NEP) region where AKARI has already observed, but only for the small central regions (~ 6 sq. deg.). Other low background regions are also under the consideration. The MIRIS is to measure the absolute brightness of CIB and to detect a large-scale fluctuation of CIB up to several degree scale observed by IRTS (Infrared Telescope in Space). Both two ecliptic pole regions will be monitored to subtract accurately the foreground and model the interplanetary dust cloud. After the integration into STSAT-3 and the final environmental test, it will be launched in 2012 by a Russian rocket. The FPC-S has the capabilities of a wide-band imaging and a low resolution imaging spectroscopy in the near-infrared range (0.7 - 5.2um). Due to larger field of view and higher throughput than JWST, the FPC-S has an advantage of the detailed study of the CIB. The accurate spectral and spatial information of CIB enable us to probe the epoch of formation and clustering properties of CIB.
Can the Near-IR Background Fluctuations Arise from Known Galaxy Populations?
Kari Helgason (Univ. of Maryland)
Significant anisotropies have been measured in the Cosmic Infrared Background (CIB) after removing foreground sources down to faint levels. We consider the possibility of these fluctuations arising from local and intermediate redshift galaxies beyond the detection threshold of current NIR observatories. We use over 230 luminosity functions in the literature obtained in a variety of surveys probing rest-frame UV, optical and near-IR to predict the projected fluctuations arising anywhere in the redshift cone. Providing fitting formulae for the multi-band evolution of the luminosity functions, we calculate the total emission redshifted into the near-IR bands in the observer frame and recover the galaxy number counts in the 0.45-4.5 micron range. Our empirically based calculations indicate that known galaxy populations, extrapolated to faint levels, are unable to account for the bulk of the measured clustering signal seen by Spitzer/IRAC and AKARI/IRC out to several arcmin.
The CIBER Narrow Band Spectrometer: An instrument for direct measurements of Zodiacal Light Intensity
Phil Korngut (Caltech/JPL)
Direct measurements of the Extragalactic Background Light (EBL) in the near infrared are complicated by the subtraction of the Zodiacal foreground. Traditionally, this has relied heavily on geometric modeling of the interplanetary dust cloud. The Narrow Band Spectrometer (NBS) aboard the Cosmic Infrared Background ExpeRiment (CIBER) is designed to directly measure the amplitude of the Zodiacal foreground via a Fraunhofer absorption line at 854.2 nm. By observing the same fields as DIRBE and working in concert with CIBER's wide band low resolution spectrometer (LRS) to extrapolate to 1250 nm, these measurements provide a stringent test on existing Zodiacal models which have been applied to EBL measurements. This poster will describe the design and calibration techniques used for the NBS. The preliminary detection of the Fraunhofer line in flight data will also be presented.
The 3.4 μm Infrared Background as Measured Using the Galaxy Luminosity Function from WISE
Sean Lake (UCLA)
We address the central controversy of this workshop on the mid-IR extragalactic background by calculating the contribution of galaxies to the 3.4 micron background using the galaxy luminosity function. We measure the 3.4 micron luminosity function in the redshift range [0.05, 1.0] using a combination of the WISE source database, the zCOSMOS data release 2, and a small redshift survey described in previous work (Lake et al. 2012). We find that the background produced by galaxies is at least 1.5 kJy sr$^{-1}$ ( 1.3 nW m$^{-2}$ sr$^{-1}$ ). On top of not being stronger than previous measurements, this result comes with heavy caveats. Addressing them will require further investigation and possible rethinking of our chosen data processing techniques.
The first dwarf galaxies: assembly of disks and the start of reionization
Andreas Pawlik (UT Austin)
The first galaxies are thought to have started the reionization of the Universe, that is the transformation of the cosmic hydrogen from its initial neutral to its present ionized state that occurred during the first few hundred million years after the Big Bang. Reionization is a watershed event in the history of galaxy formation and evolution. A number of observational projects are therefore underway to unravel the astrophysics at these early times. Prominently amongst them is the James Webb Space Telescopes (JWST), which will hunt for the light from the first galaxies. Cosmological simulations are the most powerful tools for gaining theoretical insight into the properties of the first galaxies that is urgently needed to interpret the upcoming observations. I will present results from zoomed cosmological simulations of the assembly of galaxies in halos reaching masses as large as one billion solar as early as five hundred million years after the Big Bang. These so-called first dwarf galaxies are thought to be amongst the main drivers of reionization. A characteristic outcome of the simulations is the assembly of rotationally supported galactic disks. I will address the impact of feedback from star formation on the disk assembly and discuss the prospects for observations of the first galaxies with the JWST.
Fluctuations in Lyman-Alpha Line Emission as a Reionization Signature
Anthony Pullen (Caltech/JPL)
Lyman-alpha line emission from sources in the reionization epoch should contribute to the extragalactic background light at around 1-2 microns. We determine the prospects for measuring spatial fluctuations in this line emission.
Spectrum of the Cosmic Infrared Background at 2-5um with AKARI IRC
Kouji Tsumura (ISAS/JAXA)
The spectral data of the interstellar diffuse emission obtained with the low-resolution prism spectroscopy mode on the AKARI Infra-Red Camera (IRC) NIR channel (2.0-5.0 um) was analyzed. After careful removal of the zodiacal light and diffuse Galactic light, the spectrum of the cosmic infrared background was obtained, which is consistent with previous results with IRTS and DIRBE without the DIRBE 4.9um band.
Absolute Photometry of the EBL and Reionization from the Outer Solar System
Michael Zemcov (Caltech/JPL), James Bock, Charles Beichman, Asantha Cooray, William Reach, Ranga-Ram Chary, and Michael Werner
Absolute photometric measurements of the Extragalactic Background Light (EBL) provide unique contraints on models of galaxy formation and evolution and provide an anchor connecting global radiation energy density to star formation, metal production, and gas consumption. From vantage points near the earth, the Zodical Light (ZL) is the dominant foreground to photometric measurements of the EBL. However, the dust which is responsible for the ZL is present in a thin disk coincident with the plane of the ecliptic and drops in density steeply with heliocentric distance so that the ZL foreground is significantly reduced away from the Earth. Our team is investigating the possibility of placing a small instrument package on a trajectory which would send it to the outer solar system, or high above the plane of the ecliptic, thereby reducing the ZL foreground brightness by factors of 10-100. From these vantage points, the ZL is so faint that the EBL becomes the brightest source of sky brightness and it becomes possible to measure the spectral energy distribution of the EBL due to the sources responsible for reionization directly. This paper will detail the case for EBL measurements from the outer solar system, and present the Zodiacal light, Extragalactic Background and Reionization Apparatus (ZEBRA) concept, a small instrument package optimized for absolute surface brightness photometry from a host outer solar system mission.