CSO Science Seminars

CSO science seminars are held occasionally in the conference room at the CSO office in Hilo. Please join us!

CCAT
Dr. Steve Padin (Caltech)
Monday, 2012 June 27 at 4:00 pm

CCAT will be a 25 m diameter telescope equipped with cameras and spectrometers operating in the 0.2-2 mm wavelength range. CCAT will be large enough to resolve essentially all the submillimeter background at 350 µm, and its small beam will yield source positions with arcsecond accuracy to support follow-up observations. CCAT will be located on Cerro Chajnantor in northern Chile. The combination of an efficient telescope, an excellent site, and wide-field cameras and spectrometers will make CCAT a uniquely powerful survey instrument.

ZEUS-2: A Grating Spectrometer Optimized For Observations of High-Z Galaxies and Warm Molecular Gas In Nearby Galaxies
Dr. Thomas Nikola (Cornell University)
Thursday, 2011 June 9 at 4:00 pm

Observation of far-infrared line emission that is redshifted into the submillimeter regime provides a unique glimpse at the star-formation and nuclear activity of high-z galaxies. For example, the [CII] 158 micron and [OI] emission probe the properties of gas heated by recent star formation, while the [OIII] 88 micron and [NII] lines trace ionized gas that is excited either by star formation or nuclear activity. These observations require the most sensitive and state-of-the-art instruments.

Warm molecular gas is intimately linked to kinematic and radiative processes in galaxies, like shock excitation in cloud-cloud collisions, star formation, or nuclear activity. These processes also drive galaxy evolution. Since each of the mechanisms (e.g. PDR, XDR, shocks) that heat the molecular gas imprints a distinct signature on the mid- and high-J CO transitions these lines are excellent tools to study the interplay between global and local galactic properties, hence the evolution of galaxies.

ZEUS-2 is a submillimeter grating spectrometer optimized for these observations. It can observe multiple lines simultaneously and also provides spatial information in extended objects. In this presentation I will give an overview of the instrument, its current status, and the science cases that drive the requirements of ZEUS-2.

Protostellar Outflows and Clustered Star Formation: The Case of Serpens South
Dr. Fumitaka Nakamura (National Astronomical Observatory of Japan)
Monday, 2011 May 16 at 3:00 pm

I will briefly present some recent results of our numerical simulations of cluster formation including protostellar outflow feedback, discussing the importance of outflow feedback in clustered star formation. Then, as an example, I will present some recent results of our CO J = 3 － 2 observations toward a nearby embedded cluster, Serpens South, newly discovered by Spitzer legacy survey as an infrared dark cloud. Our CO J = 3 － 2 map reveals that many outflows are crowded in the dense cluster-forming clump. I will discuss how the outflow feedback influences the dynamics of the cluster-forming region.

The Multiwavelength Submillimeter Inductance Camera (MUSIC): A New Facility Instrument at the CSO
Nicole Czakon (Caltech)
Friday, 2011 May 9 at 4:00 pm

An insatiable appetite for large-format, kilo-pixel arrays in the millimeter/submillimeter astrophysics community has motivated the development of a novel detecting element–the millimeter-wave kinetic inductance detector (MKID). Our team is in the final stages of constructing an MKID camera called MUSIC. The camera will have 576 spatial pixels, each simultaneously sensitive to four wavelengths: .87, 1.0, 1.3, and 2.0 mm. An MKID uses a low gap-energy superconducting film to provide the inductive contribution to a resonant LC circuit. As the superconductor absorbs photons, its kinetic inductance changes, and detection occurs by monitoring the resulting shift in resonant frequency. By tuning each detector to a different frequency, hundreds of MKIDs can be coupled to a single microwave transmission line. Readout complexity is thus transferred to room temperature, where we have developed an FPGA-based readout, thanks, in part, to hardware and software from the CASPER-ROACH collaboration. Commissioning at the CSO is expected to begin in Winter 2011/2012. I will review the principles of MKID theory and design, how we read them out, and give an update on the current status of the instrument.

SMA and CSO Observations of Magnetic Fields in Star-forming Regions
Dr. Shih-Ping Lai (National Tsing Hua University)
Wednesday, 2011 May 27 at 11:00 am

In this talk, we will present the SMA and CSO polarization projects we have been working on: (1) Evolution of Magnetic Fields from Class 0 to Class II Stage, (2) Toroidal Magnetic Field Revealed in the Protostellar Disk of NGC1333 IRAS 4A, and (3) Constructing the Magnetic Field Geometry along line of sight with Multi-wavelength Polarization Observations. The main goal of these projects is to investigate the role magnetic field plays during star formation.

Observational Determination of the Turbulent Ambipolar Diffusion Scale in Molecular Clouds
Prof. Martin Houde (The University of Western Ontario)
Monday, 2008 December 8at 11:00 am

I will present a study of the turbulent velocity dispersion spectra (versus length scale) for the coexistent HCN and HCO+ molecular species in the M17 star-forming molecular cloud. I will show that the observed downward shift of the ion's spectrum relative to that of the neutral is readily explained by the existence of an ambipolar diffusion scale below which the motions of the ion and neutral components of the gas decouple from one another. For M17, this decoupling scale is measured to be 1.8 mpc; this is the first time that this fundamental quantity is determined observationally. Moreover, this result is in excellent agreement with previous theoretical predictions. I will also demonstrate how these observations can be used to estimate the strength of the plane-of-the-sky component of the embedded magnetic field in a completely novel way.

ZEUS on the CSO: Probing the Gas in Active Regions in ULIRGs and High-Redshift Galaxies
Dr. Thomas Nikola (The Cornell University)
2008 December 1 at 11:00 am

The star formation rate per unit volume shows strong evolution over the history of the Universe. This suggests a change of the gas properties in star formation regions or a variation of their size or both. We have built a grating spectrometer, ZEUS, for the submillimeter wavelength regime to investigate the physical properties of the gas in regions of enhanced star formation in ULIRGs and distant galaxies. With our instrument we observe redshifted far-infrared fine structure lines, especially the 158 micron [CII] line, mid-J CO lines, and the [CI] 371 micron fine structure line to trace the gas properties in the star forming regions. In this presentation I will introduce our grating spectrometer, ZEUS, and give an overview of the results that we have obtained using our instrument on the CSO.

Hydrogen Isocyanide in the ISM and Comets
Dr. Darek Lis (California Institute of Technology)
2008 July 18 at 3:00 pm

I discuss the current understanding of the origin of hydrogen isocyanide in the interstellar medium and comets. HNC, first detected in comet Hyakutake by means of submillimeter spectroscopy, has now been observed in a dozen moderately bright comets, not including the very active comets Hale-Bopp and McNaught. The existing data suggest that HNC production has to be efficient in the inner coma, just as the material leaves the nucleus. The process has to be temperature dependent to explain the observed variation in the HNC/HCN abundance ratio with the heliocentric distance. Thermal degradation of macromolecules or polymers produced from ammonia and carbon compounds, such as acetylene, methane, or ethane appears to be a process consistent with the existing observational data, including the very low HNC/HCN ratio measured recently in comet 73P/Schwassmann- Wachmann 3.

Evolution and Astrophysics of Distant Ultraluminous Galaxies
Prof. Andrew Blain (California Institute of Technology)
2008 April 28 at 11:00

The most luminous high-redshift galaxies are dominated by energy production at far-infrared wavelengths. Selected with poor angular resolution using ground-based submillimeter and space-borne far-infrared telescopes, they are a crucial component of our understanding of galaxy formation. However, understanding their properties requires arduous follow-up observations from radio to X-ray. I will describe progress with understanding the evolution and astrophysics of these galaxies, which trace the top end of the galaxy luminosity function, and highlight some forthcoming opportunities using NASA's WISE, and ALMA.

Extragalactic Science with APEX and SHARCII/CSO
Dr. Attila Kovacs (Max Planck Institute for Radio Astronomy)
2008 February 15 at 3:00 pm

I will provide a brief overview of the extragalactic science projects currently under way at the APEX telescope in Chile, with special focus on the early extragalactic results from the new 295-pixel bolometer camera LABOCA. In the second part, for a more local flavor, I will present the results from a follow-up study of submillimeter galaxies with the SHARCII camera at the CSO. The SHARCII data allows the first firm constraints of the dust-temperatures and bolometric luminosities for this population of high-z galaxies. They also allow the testing of the radio to far-infrared correlation at the higher redshifts.

Hydrogenated/Deuterated Species; Observations and Models
Dr. Evelyne Roueff (Observatoire de Paris)
2007 October 12 at 11:00 am

Thirty interstellar and circumstellar molecules containing deuterium have been detected to date, with several doubly- and triply-deuterated isotopologues. The fractionation ratio, defined as the ratio of the column density of a deuterated molecule to its hydrogen counterpart, is often found to be orders of magnitude higher than the elemental abundance ratio, which is typically from 1.5 × 10⁻⁵ to 2.3 × 10⁻⁵. This deuterium enhancement results from chemical processes, which may involve both gas-phase [1,2] and surface reactions [3]. Observational data and detailed gas-phase models will be reviewed. Particular emphasis will be put on ortho/ para chemistry and on the role of deuterated hydrocarbons as vectors for deuteration. We also discuss the consequences of local elemental deuterium enhancements on molecular fractionation ratios [4].

[1] Roberts, H., Herbst, E., Millar, T.J., 2003, ApJ 591, L41,
Roberts, H., Herbst, E., Millar, T.J., 2004, A&A 424, 905
[2] Roueff, E. Lis, D., van der Tak, F.F.S., Gerin, M., Goldsmith, P., 2005, A&A 438, 585
[3] Lishat, A., Biham, O., Herbst, E., 2004, MNRAS 348, 1055
[4] Roueff, E., Herbst, E., Lis, D., Phillips, T., 2007, ApJL in press.

Update to the CSO Submillimeter Active Optics System
Melanie Leong (Caltech Submillimeter Observatory)
2007 October 4 at 4:00 pm

The Caltech Submillimeter Observatory's (CSO's) Submillimeter Active Optics System is an open loop real time system that corrects the dish surface figure for imperfections and gravitational deformations as the dish moves in elevation during observations. This improvement in the telescope's aperture efficiency aids observations in the shorter wavelengths, specifically in the 350-µm-wavelength range. Simplicity, attention to detail, and perseverance were the keys to the success of this unique system.

The CSO's primary is part of a Robert Leighton telescope design, consisting of 84 hexagonal panels forming a 10.4-meter primary dish. There are 99 steel rod standoffs that interface the backing structure to the back of the primary. It is on these standoffs where heating and cooling assemblies are mounted and implemented to lengthen or shorten the standoffs to desired lengths.

Holography maps were used to build a correction table to determine the amount of length and location of change on the primary. Implementation of thermal electric devices enables the adjustability for each standoff.

The CSO's Submillimeter Active Optics System has been in use since February 2003. Since then, new discoveries of distant galaxies or sharper detail of known objects have been obtained. These will be presented during this talk.

By holography, the smoothness of the dish is better than 10 microns RMS from zenith angles of 5 to 63 degrees. The present percent improvement to the primary's surface is as high as 74%, with an average of 60% improvement.

Preliminary performance improvements have been found to compensate for SHARCII's new mounting location, from the Cassegrain focus to a second Nasmyth location, N2. SHARCII is an 384 pixel submillimeter high angular resolution camera.

Star Formation: From Cores to Disks
Prof. Neal J. EVANS II (The Univeristy of Texas at Austin)
2007 July 20 at 11 am

I will highlight recent developments in the early stages of star formation. Observations with the Spitzer Space Telescope and complementary data at other wavelengths have provided more complete samples of star-forming regions. These provide constraints on theoretical models of the origin of the initial mass function and evolutionary stages. The early stages of star formation include the separation of dense cores from the background molecular cloud, the evolution before point source formation, the infall onto the central source, and the formation of the disk. These events are usually associated with changes in the SED associated with the Class System. The large sample available from the Cores to Disks (c2d) program provides good statistics on the numbers of objects in various stages, and these can be used to estimate timescales.

H₃⁺, a new astrophysical probe, and revelation of warm and diffuse gas near the Galactic center
Prof. Takeshi OKA (University of Chicago)
2007 June 27 at 11:00 am

With a super-massive black hole at the core, the region near the Galactic center is the hub of activity. Emissions from radio to X-rays and the densities of stars and gas all peak in the region. It also harbors the Central Molecular Zone (CMZ), a region of radius ~ 200 pc which has the highest concentration of molecules in the Galaxy. Our infrared spectroscopic observations in the last five years have shown that sightlines toward the CMZ have H₃⁺ column densities that are ~ 10 times higher than the highest observed in the Galactic disk.

Using this richness of H₃⁺ with its unique characteristics as an astrophysical probe, a new category of gas with high temperature (~ 250 K) and low density (~< 100 cm^-3) has been revealed in the CMZ. Our observations of 8 sightlines toward bright infrared YSOs by the UKIRT, Subaru, Gemini South, and VLT and their analyses suggest that the gas is ubiquitous and has a high volume filling factor in the CMZ. The relation between this newly found gas and previously known, i. e., the cold (~ 50 K) and high density (~> 10⁴) cm^-3) gas observed by radio emission of CO, CS, HCN and other molecules, the hot (10^4-6 K) gas with high electron densities (~ 10 cm^-3) inferred from hyper-strong radio-wave scattering, and the ultra-hot (10^7-8K) gas emitting X-rays is speculated.

Does the Galactic Magnetic Field Anchor in Turbulent Giant Molecular Clouds?
Dr. Huabai LI (Harvard-Smithsonian Center for Astrophysics)
2007 June 7 at 11:00 am

Various mechanisms of supporting self-gravitating interstellar clouds and regulating star formation have been invoked. Among which, the relative importance between turbulence and magnetic fields has been long under debated, largely owing to the lack of observational constraints on cloud formation theories. The recent development of Submillimeter polarimetry offers a chance to map the field morphology from the bulk volume of a molecular cloud. By comparing the observed morphology with those from MHD simulations, we can estimate magnetic field strength relative to turbulence. I will present the data collected so far, and future observation plans with CSO and SMA, along with an introduction of the polarimeters used in these two observatories.