LMT: Large Millimeter Telescope

Link to LMT Web site

I. General project/facility description

1. Overview of the facility/project
   The Large Millimeter Telescope (LMT) Project is the joint effort of the University of Massachusetts at Amherst and the Instituto Nacional de Astrofísica, Óptica, y Electrónica (INAOE) in Mexico. The LMT is a 50m diameter millimeter-wave telescope designed for principal operation at wavelengths between 1mm and 4mm. The telescope is being built atop Sierra Negra, a volcanic peak in the state of Puebla, Mexico. Site construction and fabrication of most of the major antenna parts is underway, with telescope construction expected to be complete in 2007.
   The Five College Radio Astronomy Observatory (FCRAO) is a Research Group in Radio Astronomy at the University of Massachusetts at Amherst. Its present telescope is the 14m millimeter wave antenna which has been in operation since 1976. The 50m Large Millimeter Telescope (LMT) will be the FCRAO's next telescope. In this report, past discussions report on the success of the 14m telescope.
   Located at a high (15000 ft) dry site in Mexico at latitude +19°, the LMT will be instrumented for continuum and spectroscopic mapping covering the wavelength range from from 4mm to 0.8mm. The Sierra Negra site was selected in 1997 following radiometric site tests at a number of potential mountain top sites in Mexico. The 19° latitude was a significant factor in the site selection, and the LMT's coverage of the southern sky will be very good, with the Galactic center culminating at an elevation of about 45°. The site is at a very high elevation (4600m). The atmospheric opacity, as measured by a 225 GHz tipping radiometer, is low for most of the year. Observations within the 3mm band are expected year round while 1mm measurements may be limited to the winter months.
   The 1.3 mm atmospheric window contains many important diagnostics of the physical conditions in the interstellar medium of galactic and extragalactic sources, and the LMT has been designed to work well in this wavelength band.

2. Managing institution and organization
   Between 1994 and 2004, the LMT construction was managed jointly by UMass and the INAOE. An Executive Management Team (EMT), comprised of three members from each institution, provided general oversight to the project. Institutional oversight was provided by a Principal Investigator for each country, while day-to-day operations were supervised by two Project Managers, one at UMass and one at INAOE. Two Project Scientists provided scientific oversight.
   In January 2005, the management responsibility transitioned from the separate construction project offices at UM-Amherst and INAOE to the Large Millimeter Telescope Observatory (LMTO). The LMTO is charged with the operation and maintenance of the the LMT. It is a Mexican Civil Association, formed by UM-Amherst and INAOE as partners. Detailed plans for the operation of the LMTO are still under development. It is foreseen that the LMTO will be an institutional collaboration between UM-Amherst and INAOE under a project agreement between the institutions which will covers the activities of collaboration and decides what counts as a contribution to the project.
   The LMTO will be governed by a board with membership determined according to the contributions of the partner institutions. The LMTO Board will provide oversight and advice to a director who will manage the staff and day-to-day activities.

3. Funding source(s)
   Current funding: University Radio Observatories (URO) Program in NSF-AST. Expected budget for 2005-6: $2.3M.

4. Construction history and cost
   LMT has expended or committed approximately $111M USD as of mid-2004. Project needs to raise an additional $15-20M to complete the basic telescope. This estimate of additional funding only counts telescope construction costs and does not include completion of instruments or commissioning.
   LMT Timeline:
   • 1997: Site Selection
   • 1997-2000: Antenna Design
   • 1999-2002: Site Preparation; Installation of Foundation
   • 2001: Factory Steel Fabrication and Trial Assembly
   • 2001-2003: Reflector Panel Design/Development
   • 2002-2005: Erection of Steel Structure at Site
   • 2005-2007: Reflector Panel Fabrication/ Installation
   • 2007: Commissioning Begins
5. Operational history and cost
   Future facility.
   It is anticipated that partial support for the LMT operations will come from NSF under the AST University Radio Observatories Program. Such funds will support:
   • the science program at UMass-Amherst including support for students and post-docs, travel for observations and professional meetings and publications.
   • Technical support for US Astronomers using LMT.
   • Technical Activities at UMass-Amherst
   • Science Instrument Development
   • Telescope Systems Development
   • Commissioning of Antenna Systems and Instrumentation
   • US Share of LMTO Operations Budget.

II. Technical details

1. Specifics of telescope/instrument
   
   • Antenna Design:
     • Antenna Designer: MAN Technologie
     • "Open Air" Design (no enclosure).
     • Active Surface of 180 trapezoidal surface segments with actuators at four corners of segments and an open-loop lookup table for positioning.
       Use of Active Surface eliminates gravitational distortion as major error source.
   • Science Instrumentation
     UMass Astronomy is building the initial complement of LMT's scientific instruments; funded primarily through grants outside of LMT Project funding.
     • SEQUOIA: 32 element focal plane array for 3mm spectroscopy (completed and in use)
     • Redshift Receiver: ultra-wideband 3mm receiver for spectroscopic measurements of redshifts
     • 1mm Receiver: spectroscopic receiver for 1mm band
     • BOLOCAM II: focal plane array for imaging in 1mm and 2mm wavelength bands
     • SPEED: multi-wavelength continuum instrument
     • Wideband Digital Correlator: flexible array of correlators for frontend heterodyne arrays
     • Monitor and Control System

   • New capabilities anticipated/planned in next 5-10 years
     Future facility. Expected instrumentation developments.
     Several future instruments are under consideration:
     • OMAR: 1mm heterodyne focal plane array -- 16-32 pixel SIS receiver system (proposal pending)
     • CIX: 64 element, multiwavelength continuum camera (proposal pending)
     • Large format continuum imaging system

III. User profile

1. % of "open skies" time
   Use of LMT by US Astronomers
   • Fractional time allocated on the LMT depends upon contributions to construction and instrument costs.
   • It is anticipated that the initial division of time will be approximately 55% Mexico and 45% UMass.
   • Over time, this division is expected to reach 50:50 as UMass contributes additional instrumentation packages
   • The U.S. Time will be allocated between UMass and the U.S. Community, consistent with past practice on the FCRAO 14m telescope.

2. Institutional affiliations of users
   Future facility: NYA.
   14m Telescope users during the period Nov03 to May04 came from 14 institutions plus U. Mass. In addition, there were users from 11 institutions in Canada, the U.K., France, Germany, Spain and Korea.

3. Student access, involvement, usage
   Students from UMass and elsewhere have been heavily involved in the operation and use of the 14m telescope. At least 55 PhDs have been awarded to U.Mass. radio astronomy graduate students.

IV. Science Overview

1. Current forefront scientific programs
   Future facility:NA
   On-going key projects/surveys with the 14m Telescope
   • BU-FCRAO Galactic Ring Survey (ongoing). See: http://www.bu.edu/galacticring/
   • Taurus Molecular Cloud Survey (ongoing). See: http://www.astro.umass.edu/~heyer/taurus.html
   • Cepheus Survey/Extended Outer Galaxy Survey -- ¹²CO and ¹³CO imaging survey to complement the International Galactic Plane Consortium (HI 21cm line and continuum)
     See: http://www.astro.umass.edu/~brunt/fcrao.galdisk.png
   • COMPLETE -- ancillary data to complement Spitzer Legacy "Cores to Disk" Program
   • CO Imaging Survey of Spitzer SINGS galaxies
   • CO Survey of Spitzer First Look Survey Field galaxies

2. Major discoveries (through 1999)
   Future facility:NA
   Science Highlights with the 14m Telescope:
   • The Relationship between Molecular Outflows and HH objects
   • Properties of Massive Molecular Cores
   • Monitoring Behavior of HCN in Halley's Comet
   • CO follows blue light and H-alpha
   • Star Formation Efficiency and Rate varies with environment
   • Star Formation Efficiency is independent of Hubble type
   • The Dynamics of Giant Molecular Clouds
   • Interstellar Chemistry
   • HCO+ distribution in Comet Hale-Bopp
   • Arm-Interarm Contrasts in Outer Galaxy
   Major Surveys with the 14m Telescope:
   • Massachusetts-Stony Brook Galactic Plane CO Survey
   • The Spectrum of Orion-KL at 2mm
   • FCRAO Extragalactic Survey
   • Surveys of Molecular Line Emission from GMC Cores and Dark Clouds
   • FCRAO Outer Galaxy Survey (see: http://www.astro.umass.edu/~fcrao/telescope/2quad.html
   • Survey of Molecular Gas in M31

3. Science highlights of last 5 years
   Future facility:NA
   Science Highlights with the 14m Telescope:
   • Universality of Turbulence in Galactic Molecular Clouds
   • Water in the ISM: many papers from Submillimeter-wave Astronomy Satellite (SWAS) with FCRAO supporting data
   • Equilibrium State of Molecular Clouds
   • Molecular Depletion in Dense Cores
   • Imaging Local Group Galaxies: M31
   • Imaging Local Group Galaxies: M33
   • CO Luminosity Function for galaxies
   • CO Imaging Survey of Virgo Cluster spiral galaxies

4. Main future science questions to be addressed
   
   • Determining the energy densities in the universe and growth of structure with S-Z bolometric surveys
     Measurement of the galaxy clusters masses and number density as a function of redshift can be used to constrain the matter density and the equation of state of the dark energy if a sufficiently large sample can be studied. Surveys of SZE clusters with Bolocam II on LMT can accomplish this. The high angular resolution and sensitivity of the LMT will play a particularly important role in understanding the underlying cluster physics and source confusion required to interpret such SZE measurements correctly.
   • Charting the dust obscured cosmic star formation history with wide field bolometric surveys and spectroscopic redshifts
     The substantial population of massive dusty starburst galaxies discovered by deep submm continuum surveys using SCUBA on JCMT may account for nearly entire FIR cosmic background and should account for a large majority of the cosmic star formation history. With its high sensitivity and angular resolution, LMT will be able to fully resolve the FIR cosmic background and map the cosmic evolution of this submm galaxy population by conducting large surveys to cover several 10's of square degrees (to overcome cosmic variance). LMT surveys will detect about 1000 sources per hour, and some 10⁵ sources will be detected and 1000s of spectroscopic redshifts obtained during the first year of operation. In comparison, a total of about 200 sources were detected by all existing telescopes during the past 6 years.
   • Unveiling the nature of gamma ray bursts
     The capability of the LMT to produce sensitive, wide field images on a short notice and obtain accurate photometry data on spectral and temporal variations at 75-300 GHz would make it an ideal tool for studying physics of Gamma ray bursts and their host galaxies. The peak flux density of a GRB afterglow is expected to occur at millimeter wavelengths, and the broadband spectral shape is a key discrimater among several competing models for the GRB energetics. The successful launch of SWIFT and future GLAST mission will set the stage for active new research in the GRB and related high energy phenomena, and LMT will provide important follow-up observations and important clues for understanding the underlying physics.
   • Resolving Structures around super-massive black holes with mm VLBI
     VLBI observations using large current and future telescopes such as the LMT at millimeter and submillimeter wavelengths will enable phase coherent VLBI observations with 20 micro-arcsec resolution. This resolution is sufficient to resolve an accretion disk around a massive black hole in the nearest quasars and is close to the expected Schwarzschild radius of the massive central black hole of the MW galaxy, Sgr A*. These observations should allow a unique test of relativistic GR theory and detailed mechanisms of matter inflow and energy output surrounding a black hole as well as the launch and collimation of relativistic jets. LMT is the second large telescope after the ALMA and is thus a critical component in such experiments.
   • Imaging of the dust and gas components for a large sample of galaxies to identify large scale processes that regulate star formation
     Imaging of the dust and gas components for a large sample of galaxies to identify large scale processes that regulate star formation: With unique, millimeter wave imaging instrumentation on the 50-meter, filled aperture telescope, the LMT will contribute to our understanding of galaxies by imposing critical observational constraints to prevailing paradigms and discovering new phenomena to be explained by the models. The LMTsystem will detect complexes of molecular gas and dust that are current or future sites of star formation within the disks of galaxies and rapidly survey these disks to generate an unbiased census. With high mapping speeds, scientists will gather important information on a large sample of galaxies to derive statistically robust scientific conclusions. The figure on the next slide demonstrates the imaging capability of the LMT to resolve the spatial and kinematic relationships of the molecular gas to dynamical features in a galaxy including spiral arms, stellar bars, and nuclei.
   • Scrutinize current descriptions of star formation in molecular clouds with accurate measurements of dynamics of protostellar regions
     Accurate descriptions of the dynamics of molecular clouds are essential to our understanding of the star formation process. The dynamics of a cloud plays a pivotal role in setting the time interval over which the cloud can produce stars and the mode (clustered or distributed) in which stars are generated. High resolution views of nearby molecular clouds reveal webs of filaments, shells, and high density cores that attest to a complex dynamical state. The observed complexity arises from expanding motions from HII regions and stellar winds and the interplay between magneto-turbulent pressures and the self-gravity of the cloud. Determining the relative roles of the magnetic field, turbulence, and wind driven shocks is a central goal of molecular cloud studies and the subject of a spirited debate amongst theorists within the astronomical community. LMT is poised to resolve this debate with observations that set meaningful constraints to theoretical descriptions of the molecular ISM and star formation. Wide field imaging of molecular line emission with the LMT provides a wealth of dynamical information beyond the capabilities of current millimeter wave single dish telescopes and interferometers as both small and large scale structure of the cloud are recovered. The spatial variations of velocity and column density are fossil records of the dynamics that can be compared to model predictions of cloud structure. With the dual polarization of the LMT frontend, heterodyne systems, one can detect and image the Zeeman Effect in molecular clouds to examine the spatial variations of the magnetic field.
   • Chemistry and dynamics of comets
     Cometary molecular constituents in almost all cases do not have transitions at optical wavelengths, but the sensitivity of current radio facilities allows their rotational transitions to be observed, just as in molecular clouds. In fact, of the 24 or so known cometary volatiles, 70% have been discovered at millimeter and sub-millimeter wavelengths. Spectroscopic and Continuum measurements at Millimeter wavelengths of a broad sample of comets covering a range of possible heliocentric distances allow astronomers to address several interesting questions: What is the range of volatile compositions in comets, and what can the composition tell us about gradients in conditions in the solar nebula? What is the relation between the composition of the nuclear ices and the observable gas in the cometary coma? What is the nature and abundance of large dust particles in the coma?

5. Synergies with other major forefront facilities
   
   • ALMA -- LMT wide field surveys provide targets for high resolution followup studies of distant galaxies. It also supplies short spacing data for studies of extended sources.
   • Large Optical/ IR Telescopes (ex. JWST, Keck, Gemini, VLT) -- LMT will probe the millimeter universe to identify the earliest epoch of galaxy formation and identify the relationship between galaxies contributing the the mm/submm background and Lyman Break Galaxies.
   • Spitzer Space Telescope -- mid and far-infrared emissions from dust are complemented by 1mm thermal dust emission from the LMT and molecular line spectroscopy to gather kinematic information and distances to photometric sources that include distant galaxies and star forming regions in the Milky Way
   • Herschel/SOFIA -- far infrared dust continuum and line emission are similarly complemented by counterparts within the 1-3mm bands. Physical interpretation of the fine structure C⁺ 158mm line is greatly aided by CO measurements.
   • VLA -- LMT mm bands provide important connection between VLA radio data and far-infrared to define spectral energy distributions of distant galaxies to estimate redshifts.
   • CARMA -- LMT will provide critical short spacing information on extended sources and environmental context beyond the mosaicked interferometer fields.
   • VLBI -- LMT contributes significant collecting area to the mm VLBI network.

6. Unique contributions
   
   • LMT will be the world's most sensitive single dish telescope for millimeter-wave astronomy.
   • LMT will exceed sensitivity of nearest University-based competitor (CARMA) by significant margin.
   • LMT will be competitive with ALMA: the major international undertaking in Millimeter-wave Astronomy

   	GBT	CARMA	LMT	ALMA	ALMA
   Year of Operation	2006	2006	2007	2008	2012
   Sensitivity to Point Sources Line (3mm) Continuum (1mm)	0.6 na	2.5 19	1.0 1.0	1.1 2.9	0.3 0.7
   Sensitivity to Extended Emission Line (3mm; 12" resolution) Continuum (1mm; 6" res.)	2.3 na	3.3 25	1.0 1.0	3.3 8.8	2.5 6.6
   Mapping Speed (Point Sources) Line (3mm) Continuum (1mm)	15 na	4.5 1108	1.0 1.0	1.1 34	0.1 2.2
   Mapping Speed (Extended Emission) Line (3mm) Continuum (1mm)	348 na	7.7 1908	1.0 1.0	10 324	5.8 182

   LMT compares favorably with ALMA and will compete with ALMA as the best place for certain experiments.

V. Education/Outreach activities

1. Visitor facility
   Significant community outreach activities already take place in Mexico with staff participation in local events and lectures. Planning is underway for a LMT Visitor Center. The "LMT Book" will be available in early 2005.

2. Student programs
   Training of graduate students and postdoctoral fellows
   Summer undergraduate research opportunities at FCRAO (typically 3-4 students/year)

3. Other (as apply)
   Bi-national collaboration between U.S. and Mexico that fosters scientific and technical exchange

VI. Documentation/website URLs

1. URL of facility website
   
   • FCRAO: http://www.astro.umass.edu/~fcrao
   • LMT: http://www.lmtgtm.org
   • LMTO: http://www.lmtgtm.org/lmto

2. URL of EPO website
   http://www.lmtgtm.org/outreach

3. URL(s) of any brief overviews of project/facility
   
   • Science: http://www.lmtgtm.org/overview/sci
   • Instrumentation: http://www.lmtgtm.org/overview/ins