GALAXY EVOLUTION EXPLORER (GALEX)
GUEST INVESTIGATOR PROGRAM - Cycle 4
1.Guest Investigator (GI) Program Description
1.1 Overview
1.2 Program Types
1.2.1 New Observations
1.2.2 Archival Investigations
1.2.3 Unscheduled Observing Time – Targets of Opportunity and Discretionary Time
1.3 Mission Capabilities and Constraints – Cycle 4
1.4 General Guidelines and Policies
1.4.1 Proposal Process
1.4.2 Who May Propose
1.4.3 Late Proposals
1.5 Data Rights and Distribution
1.7 Proposal Evaluation and Selection
1.8 Funding for US Investigators
1.9 Education and Public Outreach
2. Proposal Preparation and Submission
2.1 General Information on NASA Proposals
2.2 Notice of Intent
2.4 Cover Page
2.5 Proposal Format and Content
2.6 Proposal Template, Examples and Instructions
3.1 Mission Overview
3.3 Satellite Operations and Observation Planning
3.3.1 Observation Modes
3.3.2 Brightness Limits
3.4 Data Processing, Calibration, and Distribution
3.4.1 Pipeline Processing and Calibration
3.4.2 Data distribution
GALEX GUEST INVESTIGATOR PROGRAM - Cycle 4
1 Guest Investigator (GI) Program Description
This program element (D.5) of the 2007 ROSES solicits proposals for the acquisition and analysis of new scientific data from the Galaxy Evolution Explorer (GALEX). GALEX operates in two broad bands, Far-UV (FUV, 1350-1800 Å) and Near-UV (NUV, 1800-2800 Å), providing wide-field (1.2 degree) imaging and low resolution (R = 150-300) grism spectroscopy, with sufficient sensitivity to study a wide variety of objects within and outside of our Galaxy. GALEX was launched on April 28, 2003. The GALEX primary mission is scheduled for completion around September 2008.
During calendar year 2008, the scientific capabilities of GALEX will be available to the astronomical community for scientific investigations that do not duplicate the GALEX team investigations. This solicitation is for Cycle 4 of the GALEX Guest Investigator (GI) Program, to be carried out beginning on January 1, 2008, and lasting approximately 12 months. Section 2 contains instructions for proposal preparation. A brief description of the GALEX mission is in Section 3; a more detailed description can be found at http://galexgi.gsfc.nasa.gov/.
Proposals will be accepted for both new observations and for archival research. Proposed scientific investigations should not duplicate GALEX primary science investigations, which are listed on the GALEX GI website (http://galexgi.gsfc.nasa.gov/science/ ). GI investigations may be proposed for fields already observed by the GALEX science team, as long as the science investigation is clearly different. Many projects may be best addressed as archival investigations, using the data already collected for the primary mission; all publicly available GALEX data in the Multimission Archive at Space Telescope (MAST) will be available for archival investigations. Potential proposers are strongly encouraged to examine the descriptions of the GALEX primary science investigations and the contents of the GALEX existing and planned observations (http://galexgi.gsfc.nasa.gov/targets ) before proposing.
Proposals submitted in response to this program may be for new observations with GALEX, or for analysis of existing GALEX data. Approximately 1500 ksec (1/3 of the available observing time) is expected to be available to the community for new observations in Cycle 4. There are four proposal categories: 1) Standard, 2) Legacy, and 3) Snap proposals are for new observations; 4) Archival proposals are for investigations using the rich GALEX archival data set. Mixed proposals may be submitted that include some new observations and some archival work, provided the archival work is not expected to comprise more than ~1/3 of the investigation's effort; these should be submitted as the relevant type of observing proposal. If more than ~1/3 of a combined investigation is expected to comprise work with archival data, and the investigators wish to request funding for the archival work, then two separate proposals (one new observing, one archival) should be submitted and the connection noted in each proposal. More information on the different proposal types may be found in the following sections.
For the first three categories,
proposals submitted in response to this NRA constitute the first phase of the
GALEX GI proposal process. The following information is required: a
scientific justification, a description of the observations, a discussion of
the technical feasibility, astronomical target data, exposure time estimates,
and any special operational requirements (e.g., orientation constraints, timing
considerations, etc.). Section 1.3
describes important capabilities and constraints that affect how GI programs
will be evaluated and implemented in Cycle 4. After selection by NASA,
successful GI's will be required to submit a detailed observing plan (Phase 2
proposal) so that safety checks, assessments, feasibility assessment, and
observation scheduling can be performed. No Phase 2 submission will be required
for successful archival proposals.
There are two types of unscheduled observing time that can be made available, with the approval of the GALEX Mission Scientist. The first deals with major Targets of Opportunity (ToO), such as supernovae, novae, and comets. The second type, called Discretionary Observing Time (DOT), is intended for observations of an urgent nature requiring a small amount of observing time and of sufficiently high scientific priority that they should not be delayed to the next observing cycle (See Section 1.2.3 for more details).
1.2.1 New Observations: Program Categories and Time Allocation
GALEX observing time is allocated in orbital nights (orbits). Proposals should request only the time needed for scientific exposures. Observing Program Categories - Each GALEX observing proposal must be designated in one of three proposal categories at the time of submission - Standard, Legacy, or Snap - and this category must apply to all targets in the proposal. Approximately 1/3 of the available observing time during Cycle 4 (~ 1500ksec) is expected to be be available to the community for new observations.
1. Standard proposals provide the opportunity to observe targets specified by the proposer. These may include shallow or deep imaging, shallow or deep grism observations, repeated visits to observe time-variable phenomena, or mapping of regions of the sky not observed by the GALEX primary science surveys. NASA intends to execute all observations associated with accepted proposals.
2. Legacy proposals provide the
opportunity for large, coherent projects of general and lasting importance to a
wide astrophysical audience. These proposals are expected to request a
minimum of 100 orbits. Legacy proposals are expected to use GALEX to
perform major observing programs that will enhance significantly the overall
scientific contribution of the mission. NASA intends to execute all
observations associated with the allocated observing time for accepted
proposals. NASA anticipates that at least 25% of the GI observing time in
Cycle 4 will be allocated to Legacy proposals.
3. Snap proposals are intended to maximize
the science return of GALEX and to provide scheduling flexibility by providing
a large pool of targets to the mission schedulers; they will receive lower
priority in target scheduling. Snap programs provide the opportunity for
observations of a class of objects to be undertaken without the requiring that
any specific object in the class be observed. It is unlikely that all
targets in an accepted Snap program will be observed. Although there is no
assurance that any specific target in a Snap program will be observed, NASA
expects that data will be obtained for many targets in this category.
Following the evaluation of submitted proposals, some proposals submitted but not accepted by NASA under the Standard category may be recommended for inclusion in the Snap category. It will be the proposer's option to accept or reject such reprogramming of a submitted Standard proposal.
Observing Program Constraints – Standard and Snap proposals may only request observations using GALEX standard observing modes. These are described briefly in Section 3.3.1 and in more detail in the GALEX Observers Guide. In Cycle 4, Legacy proposals will be accepted for programs using non-standard GALEX observing or data-processing modes, IF the GI proposal team includes one or more GALEX team experts to be responsible for the non-standard operations as part of the proposed investigation (this should be explained in the feasibility section of the proposal).
Program Execution and Carryover - NASA intends that all observations for non-ToO Standard and Legacy observing programs will be performed. If necessary, observations not executed during the current cycle will be carried over into the following cyle. GIs do not need to repropose for these observations, and any such programs will be given priority for execution in the next cycle. ToO programs will not be carried over into the next Cycle. ToO programs that are not activated and executed within the nominal one-year observing cycle must be reproposed in order to be considered in the next observing year. Unobserved targets in Snap programs must also be reproposed each Cycle.
Proposals will be accepted for scientific investigations based on any data in the GALEX public archive at MAST (http://galex.stsci.edu). A list of completed and and planned non-AIS GALEX observations may be found at at http://galexgi.gsfc.nasa.gov/targets. Investigators considering an Archival proposal should pay close attention to the GALEX primary science investigations. Although Archival proposals may be based on any data released in the GALEX data releases, they may not duplicate the science goals of type 1 PI science team investigations.
1.2.3 Unscheduled Observing Time
Targets of
The lack of a real-time observing
capability constrains the speed with which a ToO observation can be
implemented. The GALEX ToO response time is expected to be no less than 7 days during Cycle 4. ToO
proposals must clearly state the required response time. An
accepted ToO proposal must submit a “dummy” Phase 2 proposal, and must
negotiate an agreement on what will constitute a “trigger” for the TOO with the
Discretionary Observing Time -- Discretionary Observing Time (DOT) is intended for observations of an urgent nature for which no approved observing program exists, and that are of sufficiently high scientific merit and priority that they should not be delayed to the next observing cycle. The total amount of DOT available during Cycle 4 is extremely limited. The GALEX Mission Scientist may approve DOT in those cases where the scientific timeliness of the project is such that it should be done quickly, the need for the observation could not have been foreseen and proposed for in the current observing cycle, and the observation does not duplicate or infringe on PI or approved GI programs. A proposal for DOT may be submitted to the Mission Scientist in the form of a letter (printed or electronic) and should describe the scientific objectives, reason(s) for requiring GALEX, the proposed observations and their feasibility, and should explain why DOT should be granted in lieu of consideration during the next proposal cycle. All requests for DOT will be reviewed for scientific merit and technical feasibility.
1.3 Mission Capabilities and Constraints During Cycle 4
This section summarizes GALEX capabilities that should be considered by all GALEX proposers. Complete information on the GALEX instrument and other topics is available from the GALEX Observer’s Guide and the Mission and Instrument Overview (both available from http://galexgi.gsfc.nasa.gov/Documents).
Sensitivity Limits – There are fundamental detector performance limitations which preclude observations of individual bright targets, of target fields containing bright stars, and of bright or crowded fields (section 3.3.2). Proposers should pay particular attention to this issue in the “Feasibility” section of their proposal. New observing techniques are being tested that may permit limited (FUV only) observations of objects at or near the bright limits cited here, if the observation poses no risk to the instrument (as determined in technical review by the GALEX operations team). Updated information about this option will be posted on the GALEX GI web site (http://galexgi.gsfc.nasa.gov/), as it becomes available. Further information on brightness limits may be found in Section 3.3.2 and in the detector section of the GALEX Observers Guide. Further information on the detectors may be found in the GALEX Detector Operations Guide.
Please note: For Cycle 4, brightness limits preclude Magellanic cloud observations within 3.75 degrees of the LMC center, or 2.0 degrees of the SMC center. Proposals for such observations will not be reviewed.
Observing Modes - GALEX has two observing modes, broad-band imaging and grism spectroscopy. The exposure time alone defines the achievable signal-to-noise ratio for a given image or spectrum. Imaging observations are typically done either “normal” mode (observe one field for one orbital night), or in “petal pattern mode” (observe several mostly-overlapping fields centered on the proposed field center – in this mode full exposure depth will be obtained for a region 1 degree in diameter, used for fields with containing stars very near the brightness limits). Grism spectroscopy is done in multiple orbits, with a different grism orientation used for each orbital night. Observations are generally obtained in both FUV and NUV bands simultaneously. Further information on observing modes may be found in Section 3.3.1 and in the GALEX Observers Guide.
Targets of
1.4 General Guidelines and Policies
Notices of Intent are strongly
encouraged, but are not required. Proposals should provide a strong scientific
justification and careful feasibility analysis, which will form the basis for
selection by NASA, and an overview of planned observations and targets.
Proposals that are awarded observing time based on the evaluation process
described in Section 1.7 subsequently will be required to
work with the GALEX Science Operations Center (SOC) to develop more detailed
observation specifications (Phase 2 proposals) following guidelines provided by
the GALEX Project. In addition, successful
Participation in the GALEX GI
Program is open to individuals associated with all categories of
Consistent with NASA policy, a late proposal may be considered only if it is judged to be in the best interests of the Government. However, a proposal submitted after the published deadline is unlikely to be considered of uniquely greater value to NASA than proposals submitted on time. A proposal is considered “on time” only if all necessary components, (Cover page, Target forms and Scientific Justification pdf file) are submitted by the proposal deadline. Finally, please note that processing delays due to (but not limited only to) network failures, denial-of-service attacks, hard disk crashes, power outages, Internet delays, or hungry dogs, do not excuse late submission of a proposal.
1.5 Data Rights and Distribution
GIs will be notified electronically when their data are available from the archive. Data rights for GALEX GI observations (Legacy, Standard and Snap programs) reside solely with each observing program's Principal Investigator for a period of six months following availability of the processed data at the GALEX data archive in MAST (http://galex.stsci.edu/). After this period, the data become available for public access through MAST. Investigators, particularly for Legacy Proposals, are encouraged to consider waiving the proprietary period for their data.
Observations of calibration targets/fields generally have no proprietary period and will be released through the GALEX archive as soon as the processed data products are available. The GALEX Project reserves the right to use any GALEX observation to assist in assessing the performance of the instrument, but the confidentiality of data obtained for scientific programs will be maintained.
The Cycle 4 observing opportunity primarily seeks to identify new targets for observation with the GALEX satellite or to obtain significantly deeper exposures of already-observed targets. Lists of all targets observed or planned for observation (excluding AIS fields, including previous cycle GI targets) may be found at (http://galexgi.gsfc.nasa.gov/targets ). Each target's name and celestial coordinates (right ascension and declination, epoch J2000) will be considered when judging any potential target duplications.
Target Duplication – By design, the GALEX prime mission will obtain moderate exposures of a large fraction of the sky in the All-Sky Imaging Survey (AIS), and somewhat deeper observations of a significant part of the sky observed by the Sloane Digital Sky Survey (SDSS) in the GALEX Medium-deep Imaging Survey (MIS). Many GI projects may be well suited to archival investigations using the data collected for the primary mission. Any target duplication between Cycle 4 GI observing programs and those observed (or expected to be observed) by the GALEX primary mission, or by previous cycle GIs, must be strongly justified in the proposal (e.g., expected variability, need for deeper exposures, etc.). Review panels will receive a summary of any perceived duplications between pending and existing observations and those proposed for Cycle 4. The panels will also receive a summary of target duplications between different Cycle 4 proposals. In general, a given pointing center will be allocated to only one observing program. Failure to provide accurate target data in the proposal may result in disallowing a target if a conflict with another program is discovered after proposal acceptance and the target conflict was missed as a result of the inaccurate target data.
Target List Modifications - After selection of Cycle 4 programs, small changes to a program's target list may be permitted only with the approval of the GALEX Mission Scientist. Any new target must be consistent with the program's scientific objectives and must not already be allocated to another program. Large-scale target list changes will not be accepted.
Calibration Targets - Astronomical targets are used for photometric and wavelength calibration. Most of the calibration objects (Appendix, In-Flight Calibration Guide) will be observed for calibration purposes. GI's are allowed to include calibration targets as scientific targets in their programs. The GALEX Project may continue to use these objects for calibration, even if the target is allocated to a GI program.
1.7 Proposal Evaluation and Selection Process
Proposals submitted to NASA in response to this opportunity will be evaluated in a competitive peer review conducted by NASA Headquarters, using review panels organized by scientific research area. Upon completion of the review by the individual panels, a final cross-discipline panel review chaired by a NASA HQ representative will synthesize the results of the individual panels. Legacy proposals will be reviewed with other GALEX proposals in the same scientific discipline as well as in other disciplines (e.g., stellar evolution, ISM, large scale structure, etc). Each scientific panel will have the option to forward a small number of Legacy proposals for final evaluation by the chairs of the GALEX peer panels; this panel of chairs will formulate the final recommendations to NASA for the Cycle 4 observing program. Based on these results, the GALEX Program Scientist will then develop a recommendation for the total program to be submitted to the Selection Official. The final proposal selection will be made by the director of the Astrophysics Division of NASA's Science Mission Directorate. The following factors, listed in descending order of importance, will be used in evaluating proposals for their scientific merit and technical feasibility for the GALEX Guest Investigator Program:
1. The overall scientific merit of the proposed investigation;
2. The suitability and feasibility of using the GALEX observatory or GALEX data for the proposed investigation;
3. The feasibility of accomplishing the objectives of the investigation;
4. The degree to which the investigation uses the unique capabilities of GALEX;
5. The feasibility and scope of the data analysis plans;
6. The relevance to NASA’s goals.
Legacy proposals will also be evaluated on:
7. Provisions to provide legacy data to the community in a timely fashion (possibly waiving the proprietary period) and/or plans to provide enhanced data products to the community.
Scientific review panels will be given an assessment of the technical feasibility of each proposal, determined by the GALEX operations team. After acceptance of an observing program by NASA, successful proposers must work with the Caltech SOC to prepare detailed (Phase 2) observing plans. These Phase 2 plans are required for scheduling purposes, and will be assessed again for feasibility. Should there be any question regarding the safety or feasibility of individual observations, the GALEX PI, in consultation with the GALEX Mission Scientist, will make the final decision as to whether or not to attempt or postpone a particular observation, based on the latest information available regarding the satellite’s on-orbit performance. NASA reserves the right to select only a portion of a proposed investigation, in which case the investigator will be given the opportunity to accept or decline such partial selection.
1.8 Funding for
Limited funds for awards under
this NRA are expected to be available to investigators at
1.9 Education and Public Outreach
The policy of NASA’s Science Mission Directorate (SMD) continues to encourage the participation by the space science community in education and public outreach activities, with the goal of enhancing the Nation’s formal education system and contributing to the broad public understanding of science, mathematics, and technology. A significant national program in space science education and outreach is now underway, and SMD’s demonstrated contributions to education and outreach have now become an important part of the broader justification for the public support of space science (for further details see the SMD’s “Education and Public Outreach” page (http://science.hq.nasa.gov/research/epo.htm). Guest Investigators selected for GALEX Cycle 4 will have an opportunity to submit a supplemental E/PO element to their research proposal in conjunction with the budget phase of the proposal process. E/PO proposals will be due 60 days after the date of the selection letter for the Cycle 4 science proposal. Information about and instructions for preparing and submitting E/PO proposals is available in Section (b) of the ROSES-2007 NRA Summary of Solicitation.
2. Proposal Preparation and Submission
General information on the preparation and submission of research proposals to NASA may be found in the 2007 NASA HQ NRA Proposers Guidebook (http://www.hq.nasa.gov/office/procurement/nraguidebook/). If you have questions about the general nature of NASA NRAs, or questions or problems with submitting NOIs or Phase 2 Budget proposals, please consult the NASA HQ Proposal Submission FAQ page, or send technical support questions to proposals@hq.nasa.gov.
Questions about the GALEX Guest Investigator Program, or about the GALEX Cycle 4 GI proposal submission process should be directed to the GALEX GI help desk (send email to galexhelp@galexgi.gsfc.nasa.gov).
In order to expedite the proposal review process and the timely selection of scientific peer review panels, investigators intending to submit proposals for participation in this program are encouraged to submit a Notice of Intent (NOI) to propose by
April 27, 2007
The NOI Web site will request the tentative title of the investigation, name and affiliation of the PI and any Co-I's, and a brief summary of the proposed investigation. Although NOI’s are encouraged, they are not required.
GALEX Cycle 4 proposal submission is all-electronic, and is done using the Remote Proposal Submission (RPS) system of the HEASARC. Proposers will need to establish an account with the Astrophysics Knowledge Base for Analysis and Reporting (AKBAR) to submit proposals. A proposal submission checklist can be found at http://galexgi.gsfc.nasa.gov/propforms/ProposalChecklist.html, with links to more detailed instructions. A complete proposal submission consists of the following steps:
1. Fill out the AKBAR cover sheet information and target form(s).
2. Verify the AKBAR form, using the “Verify” button.
3. Submit the AKBAR form (the “Submit” button will not appear until the form has passed verification. (An acknowledgment of receipt will be sent to the proposal submitter by return e-mail if requested in your AKBAR account setup.)
4. Upload the .pdf file of your Scientific Justification.
You may re-submit and re-upload if needed. All steps must be completed by
4:30 pm EDT on 22 June, 2007
in order to be included in the
proposal review for this cycle of the GALEX Guest Investigator program.
2.4 Cover Pages and Target Information.
Cover pages and Target information are submitted directly into RPS (Remote Proposal System) of the HEASARC, see Section 2.3).
Cover page information includes Title, PI information, Co-I’s and affiliations, and basic information about the proposal (type, science area, time requested etc.)
In all cases, including Archival Proposals, a target list must be submitted. More information on target submission can be found in the help file for the GALEX RPS forms.
2.5 Science Justification - Format and Content
Proposals must be written concisely, in English. The length of each section of the proposal should not exceed the page limits indicated below. Proposals must be printed with a font size no smaller than 11 points (about 6 characters per cm) throughout (References and figure captions may be 10pt). Margins should be 1 inch (2.54cm). Proposals should be single spaced on 8.5x11 or A4 paper. Reviewers will be instructed to base their review only on the portion of each proposal that complies with the page limits given below in this NRA; excess pages will be rejected before being sent to the reviewers. Illustrations contained in the printed proposal may be in black and white or color. Proposals will be sent to reviewers as .pdf files, and may be printed out on the reviewer’s printer, so proposers would be prudent to verify that any color entries are also legible in black and white.
A GALEX proposal Science Justification requires the following sections, which should be included in the order indicated. Page limits for each section are indicated below. Total page limits are: 8 pages for Standard or Snap observing proposals, 10 pages for Legacy proposals, 6 pages for Archival proposals (including figures, tables and references).
1. Scientific Justification (not to exceed 3 pages for Standard, Survey or Archival proposals, or 5 pages for Legacy proposals): Fully describe the scientific objectives of the proposed investigation, clearly stating its goals, its significance to astronomy, why GALEX data are essential to the investigation, and the relevance to NASA goals. The page limit includes all text, figures, tables, and references for this Section. The proposed scientific investigation should not duplicate GALEX primary science investigations or accepted GI programs (http://galexgi.gsfc.nasa.gov/science/); any cases where overlap might be perceived should be clearly justified. GI investigations may be proposed for targets or fields observed by the GALEX science team, as long as the science goals of the investigation are clearly different.
2. Description of Observations (no more than 1 page, not required for archival proposals): Describe the desired observations. All observing constraints (e.g., Time-Critical (coordinated observations, phase coverage, contiguous orbits etc.), Target of Opportunity, Low Zodiacal Light, Moving Target), and/or Special Requirements (non-standard data products, FUV-only observations, brightness waivers, specified grism orientation, etc.) must be explained and justified. Triggering events for Targets of Opportunity should be defined. Actual ephemeris data for Solar System targets are not required for this phase of the proposal process, but a discussion of when and where should be provided (Proposers wishing to observe moving targets should be aware that they will need to request receive time-tagged photon data and will need to reconstruct these into images themselves).
3. Feasibility (not to exceed 1 page, not required for archival proposals): Feasibility: The proposed program must justify the need for the requested exposure time for each target, noting the required signal-to-noise ratio (S/N) and spectral resolution, expected flux, and any other information relevant to the observation (e.g., wavelength, region of interest, spectral flux distribution, emission line intensities). This section forms the basis for technical assessment of the feasibility of the proposed observations. Safety. Although a safety check is not required for Cycle 4 Phase 1, proposers are strongly advised to verify that their targets can be safely observed and to explain any questionable cases in the Feasibility discussion. Proposers requesting time-critical observations are strongly advised to verify that their targets are visible to the GALEX spacecraft at the desired times. Safety concerns, as well as target visibility through the year, proximity to overbright objects, zodiacal light background, etc. may be checked using several tools available at http://galexgi.gsfc.nasa.gov/tools.; an exposure simulator is at the same site.
4. Additional Information (up to 1 page, required for archival proposals): This Section may be used to provide any relevant information concerning data analysis plans, modeling capabilities, corollary data from other telescopes, etc. A data analysis plan is required for Archival proposals or for mixed new observation & archival proposals.
2.6 Templates, Examples, and Instructions
GALEX proposal Scientific Justifications must be submitted as .pdf files, which are uploaded by AKBAR (after cover sheet and target information are entered). Proposals may be prepared using the proposer’s choice of word processor, so long as they follow the guidelines given in Section 2.5. GALEX proposal templates (LaTex or Word) may be used to format the final printed proposal in the desired format. A LaTeX proposal form and style file, a Word proposal form, more detailed instructions for preparing the proposal, a sample filled-in latex form, and sample proposals may be found at (http://galexgi.gsfc.nasa.gov/propforms). If a proposer does not wish to use the templates provided, s/he may use a text-editor of choice to provide a similarly formatted proposal (i.e. page limits, font sizes, required sections and summary information must be provided as shown in the sample proposals).
Submission procedures are described in Section 2.3.
3.1
GALEX is a NASA PI-class mission, developed
in collaboration by Caltech in
The GALEX PI is responsible for achieving the scientific objectives of the primary mission. GALEX’s primary objectives are to map the global history and probe the causes of star formation over the redshift range 0 < z < 2. This timespan traces 80% of the life of the universe, the period over which galaxies have evolved dramatically, and the time that most stars, elements, and galaxy disks had their origins. GALEX uses the space ultraviolet (l < 3000 Å) to simultaneously measure redshift (using emission lines and the Lyman Break), extinction (using the UV spectral slope), and star formation rate (using the UV luminosity, which is proportional to the instantaneous star formation rate). Other scientific objectives supporting this overarching goal are: 1) Determining the UV properties of local galaxies and how their rest-UV properties, measured at high redshift by other missions, relate to star formation rate, extinction, metallicity, and burst history; 2) Measuring the star formation and metal production history of galaxies over the redshift range 0 < z < 2; 3) Determining the time and location of the origins of the stars and elements we see today, and connecting this to the evolution between 0 < z < 2; and 4) Identifying the global (galaxy-wide) factors that drive star formation and evolution in galaxies.
The GALEX prime mission is addressing these objectives by performing omplementary imaging and spectroscopic surveys. Approximately 2000 orbits will be devoted to each survey. Details of the GALEX primary mission science plan, and how it will use these surveys, can be found on the GALEX GI Website. Approximately 70% of the survey data will be available for GI archival proposals in Cycle 4.
Five imaging surveys are being done in two bands (FUV (1350-1800 Å) and NUV (1800-2800 Å) ), with ~5 arcsec\ resolution, a 1.2 degree field-of-view, and <1 arcsec astrometric accuracy. These surveys will detect millions of galaxies in the local universe and many thousands in the more distant universe over the redshift range 0.5 < z < 2. More detailed information may be found in Table 1, or at http://galexgi.gsfc.nasa.gov/surveys/.
· AIS - All-sky Imaging Survey: ~80% of the sky, Galactic caps first, avoiding Galactic plane, typical exposure time 100 sec.
· MIS - Medium Imaging Survey: SDSS and 2df overlap, 1000 deg^2, typical exposure 1500sec.
· DIS - Deep Imaging Survey: Overlaps other deep surveys (see list of surveys included), total of 80 deg^2, typical exposure 30 ksec
· UDIS - Ultra Deep Imaging Survey: 4 degrees2, includes e.g., CDFS, Groth, NOAO Deep-Wide, others.
· NGS - Nearby Galaxy Survey: 150 nearby galaxies, with exposures of 1 or 2 orbits per galaxy (1500-3000sec) and mosaics of the nearest galaxies (LMC, SMC, M31).
Two spectroscopic surveys are using a slitless grism with spectral resolution of R=150-300. These surveys will measure approximately 100,000 galaxies over a wide range of luminosities and star formation rates, over the redshift range of 0 < z < 2.
· MSS - Medium-deep Spectroscopic Survey: Centers of DIS fields
· DSS - Deep Spectroscopic Survey: Chandra DFS, NOAO Deep-Wide Fields
Table 1 – Survey Summary – see also Survey Summary
SF History
Å ®Local Universe
|
|
Survey |
Survey Parameters |
Scientific objectives |
||||||
|
|
Area [deg2] |
Time [ |
Expos [ksec] |
Mag. Limit [mAB*] |
Flux Limit**_
|
# Gals (est.) |
Vol. [Gpc3] |
<z> |
|
|
|
All-sky Imaging (AIS) |
>30,000 |
4 |
0.1 |
20.5 |
1.5x10-16 |
107 |
1.5 |
0.2 |
|
|
Nearby Galaxies (NGS) |
--- |
0.5 |
1.5 |
27.5 [arcsec-2] |
3.8x10-19 |
100 |
--- |
-- |
|
|
Medium Imaging (MIS) |
1000 |
2 |
1.5 |
23.5 |
9.6x10-18 |
3 x 106 |
~1 |
0.6 |
|
|
Medium Spectroscopic (MSS) |
8 |
2 |
300 |
21.5 R=100] 23.3 [R=20] |
4.7x10-17 1.1x10-17 |
104-5 |
0.03 |
0.5 |
|
|
Deep Spectroscopic (DSS) |
2 |
4 |
1500 |
22.5 R=100] 24.3 [R=20] |
2.4x10-17 4.6x10-18 |
104-5 |
0.05 |
0.9 |
|
|
Deep Imaging (DIS) |
80 |
4 |
30 |
25 |
2.4x10-18 |
107 |
1.0 |
0.85 |
|
|
Ultra-Deep Imaging (UDIS) |
4 |
1 |
150 |
26 |
9.0x10-19 |
3x105 |
0.05 |
0.9 |
* mAB = m0 – 2.5 log (Flux / U), where
UFUV = 2.05 x 10-16 ergs cm-2 Å-1 s-1, UNUV = 1.40 x 10-15 ergs cm-2 Å–1 s -1
m0_FUV = 18.82 , m0_NUV = 20.18
**Flux limits are given for the NUV band, and are in ergs cm-2 Å–1 sec-1
Approximately 2/3 of the observing time during Cycle 4 will be used by the PI Team to complete these surveys.
The wide field-of-view and spectral bandpasses provided by GALEX permits the study of many important astrophysical subjects besides galaxy evolution. These include, but are not limited to: stellar winds and outflows, post-main-sequence stellar evolution, binary/multiple star evolution, globular cluster structure and evolution, massive stars, supernova remnants, reflection nebulae, interstellar dust, structure of the ISM / IGM, the UV background, nearby galaxy populations, galaxy clusters, intergalactic material, QSO evolution, and large scale structure.
More information on GALEX science objectives and further information on GALEX survey content and strategy may be found at http://galexgi.gsfc.nasa.gov/science/.
GALEX is a 50cm UV-optimized telescope that obtains images simultaneously in two bands: 1350-1800Å (far-UV, FUV) and 1800-2800Å (near-UV, NUV). The field of view is 1.2 degrees and the angular resolution is ~4.5 arcsec. GALEX can also obtain slitless spectroscopy (same field of view and spatial resolution) with spectral resolution of R=200-350 (FUV) and 80-150 (NUV). The telescope has one primary 50 cm mirror, which