...
| term | definition | links |
|---|---|---|
| BA | (burst advocate) BAs are LAT team members who keep an eye on gamma-ray burst (GRB) activity. The GRB group has automatic software to check if the LAT detected statistically significant emission from GRBs. The BA's job is to check the output from the software and alert the rest of the group. BAs are on duty for a week at a time. | BA Confluence page |
| back | The back half of the LAT is the 4 layers of thicker tungsten (which converts the photons into electron-positron pairs) that are at the bottom of the LAT. Photons that convert in this region tend to not be as well reconstructed as photons that convert in the front. It is possible to only use the front or back events on their own in an analyses, but generally, the fact that events are either front- or back-converting is automatically accounted for in the analysis software and instrument response functions. | Cicerone |
| back-converting | Back-converting events are photons that are converted into electron-positron pairs in the bottom portion of the LAT (see back). | |
| backsplash | In the LAT, upward-moving secondary particles and photons resulting from high-energy particles or photons interacting in the instrument (primarily in the calorimeter). Backsplash secondaries can trigger the ACD, causing self-veto of LAT triggers. | Cicerone |
| batch / batch farm | SLACs workload management platform, and job scheduler. Uses the LSF (load sharing facility) product. Allows queuing and scheduling of batch jobs on the non-interactive slac computers. Basically, the batch farm is useful if you have code that takes a while to run / needs to run on a lot of data. | LSF at SLAC presentation from 2012 Info on using the farm |
| BGO | (bismuth germanate detector) | |
| blazar | ||
| BL Lac | ||
| BLR | ||
| boresight | The boresight is the line of sight pointing out from the center of the LAT that is perpendicular to the surface of the LAT. (Essentially, it's "straight up" from the center of the LAT.) |
C
| term | definition | links |
|---|---|---|
| C&A (group) | (Calibration and Analysis) | C&A group page |
| CAL | (Calorimeter) The calorimeter is the part of the LAT that records stops each electron-positron pair and records its energy, after the tracker has converted the photons into these pairs. The main purpose of the calorimeter is to record the energy, but the CAL is also able to roughly track the trajectories. Physically, it is located at the bottom of the LAT. It is made of cesium iodide (CsI) crystals. | §2.2.2 |
| cat. / Cat. | (category) Papers written by the LAT collaboration are assigned a category out of I, II, and III. | category explanation |
| catalog | A catalog is a paper that contains information on all of a certain type of object that the LAT has observed. Catalogs can be more general ("all objects in the sky that emit gamma rays") or more specific ("all pulsars"). | LAT catalogs |
| Catalog (group) | Catalog group page | |
| clean (event class) | ||
| CR | (cosmic ray) Cosmic rays are charged, high energy particles from outer space. Mostly consisting of protons, some electrons and heavier elements, they range from a few MeV to EeV. Cosmic rays are the main source of background that the LAT detects. | |
| CTB | (Classification Tree Bill/Best) |
D
| term | definition | link |
|---|---|---|
| dec | (declination) | |
| diffuse (group) | Diffuse group page | |
| diffuse (event class) | In previous versions of the LAT data, the diffuse event class was the event class with the most stringent cuts on background. However, the "diffuse" name is no longer used. | |
| DM (group) | (Dark Matter) | DM group link |
| DQM | (Data Quality Monitor) Also known as "datamon." A DQM is the LAT member whose duty it is to monitor the spacecraft's automatic plots and diagnostics to make sure all is well. If all is not well, the DQM's task is to alert the experts, who can take a closer look. DQM shifts last for one week at a time. | DQM information page |
| ds9 | (Deep Space 9 (seriously)) ds9 is a piece of software that is used for data visualization and imaging. For instance, someone analyzing Fermi data might use ds9 to look at a counts map (a map of where the photons that Fermi observed came from). | http://ds9.si.edu/site/Home.html |
| DRP | ||
| dSph | (dwarf spheroidal galaxy) |
E
| A sub-class of Active Galactic Nuclei (AGN) in which a jet of particles and photons is directly nearly along the line of sight to the Earth. Flat Spectrum Radio Quasars (FSRQs) and BL Lacertae objects (BL Lacs) are blazars, the principal type of AGN seen by the LAT. | ||
| BL Lac | BL Lacertae objects are one of the two types of Active Galactic Nuclei in the blazar sub-class, the other being Flat Spectrum Radio Quasars (FSRQs). | |
| BLR | (Broad Line Region) In an Active Galactic Nucleus, a region within about a parsec of the core containing gas clouds whose rapid motions produce broadened spectral lines in the optical, hence the name. | |
| boresight | The boresight is the line of sight pointing out from the center of the LAT that is perpendicular to the surface of the LAT. (Essentially, it's "straight up" from the center of the LAT.) |
C
| term | definition | links |
|---|---|---|
| C&A (group) | (Calibration and Analysis) | C&A group page |
| CAL | (Calorimeter) The calorimeter is the part of the LAT that records stops each electron-positron pair and records its energy, after the tracker has converted the photons into these pairs. The main purpose of the calorimeter is to record the energy, but the CAL is also able to roughly track the trajectories. Physically, it is located at the bottom of the LAT. It is made of cesium iodide (CsI) crystals. | §2.2.2 |
| cat. / Cat. | (category) Papers written by the LAT collaboration are assigned a category out of I, II, and III. | category explanation |
| catalog | A catalog is a paper that contains information on all of a certain type of object that the LAT has observed. Catalogs can be more general ("all objects in the sky that emit gamma rays") or more specific ("all pulsars"). | LAT catalogs |
| Catalog (group) | Catalog group page | |
| clean (event class) | ||
| CR | (cosmic ray) Cosmic rays are charged, high energy particles from outer space. Mostly consisting of protons, some electrons and heavier elements, they range from a few MeV to EeV. Cosmic rays are the main source of background that the LAT detects. | |
| CTB | (Classification Tree Bill/Best) |
D
| term | definition | link |
|---|---|---|
| dec | (declination) | |
| diffuse (group) | Diffuse group page | |
| diffuse (event class) | In previous versions of the LAT data, the diffuse event class was the event class with the most stringent cuts on background. However, the "diffuse" name is no longer used. | |
| DM (group) | (Dark Matter) | DM group link |
| DQM | (Data Quality Monitor) Also known as "datamon." A DQM is the LAT member whose duty it is to monitor the spacecraft's automatic plots and diagnostics to make sure all is well. If all is not well, the DQM's task is to alert the experts, who can take a closer look. DQM shifts last for one week at a time. | DQM information page |
| ds9 | (Deep Space 9 (seriously)) ds9 is a piece of software that is used for data visualization and imaging. For instance, someone analyzing Fermi data might use ds9 to look at a counts map (a map of where the photons that Fermi observed came from). | http://ds9.si.edu/site/Home.html |
| DRP | ||
| dSph | (dwarf spheroidal galaxy) dSphs are small satellite galaxies of our Milky Way Galaxy. They are thought to contain a large fraction of Dark Matter, because the light from their stars indicates that stars make up only a small fraction of their total mass. |
E
| term | definition | link |
|---|---|---|
| Earth limb / Earth's limb | The Earth is a bright emitter of gamma rays, due to cosmic rays interacting with the atmosphere. | |
| EBL | (Extragalactic Background Light). When used in gamma-ray astrophysics, EBL usually means the infrared-optical-ultraviolet light that fills intergalactic space, coming from all the stars that ever existed. Gamma rays can be absorbed by the EBL through the process of photon-photon pair production, in which a high-energy gamma ray collides with a low-energy IR-optical-UV photon to produce an electron-positron particle pair. | |
| term | definition | link |
| Earth limb / Earth's limb | The Earth is a bright emitter of gamma rays, due to cosmic rays interacting with the atmosphere. | |
| EBL | (Extragalactic Background Light) | |
| effective area | The number of photons detected divided by the source flux. The LAT effective area is a function of photon energy and inclination angle. | |
| EPO (group) | (Education and Public Outreach) | EPO group link |
| event | An "event" is a catch-all name for "things that the LAT detects" (although sometimes it is used specifically to mean photons). In practice, these are either photons or cosmic rays. | |
| event class | Events that are detected by the LAT are sorted into different classes based on how confident we are that the event is a photon. | Cicerone |
| Evo | Video conferencing software that has now been superseded by SeeVogh. | |
| exposure |
...
| term | definition | link |
|---|---|---|
| FA | (flare advocate) Flare Advocates are volunteers who watch the LAT gamma-ray sky on one-week shifts, looking for flares of known or unknown gamma-ray sources. | Flare Advocates Confluence Main Page |
| FITS / fits / .fits / fit (file type) | (Flexible Image Transport System) FITS files are often used in astronomy, and are made of one or more HDUs (Header and Data Unit). Each HDU has a header with general information about the file, the instrument, etc., as well as a table or image. Public LAT data is always (?) distributed as FITS files. | FITS Support Office |
| FltOps | (Flight Operations) | |
| FOT | (Flight Operations Team) The FOT is the staff at the Mission Operations Center (at NASA Goddard), which controls the spacecraft. The FOT is responsible for, among other things, inputting special maneuvers such as TOOs. | |
| FOV / FoV | (field of view) | |
| front | The front half of the LAT is the 12 layers of thinner tungsten (which converts the photons into electron-positron pairs) that are at the top of the LAT. Photons that convert in this region tend to better reconstructed than photons that convert in the back (or bottom). It is possible to only use the front or back events on their own in an analyses, but generally, the fact that events are either front- or back-converting is automatically accounted for in the analysis software and instrument response functions. | |
| front-converting | Front-converting events are photons that are converted into electron-positron pairs in the top portion of the LAT (see front). | |
| FSRQ | (Flat Spectrum Radio Quasar) FSRQs, along with BL Lac objects, make up the sub-class of Active Galactic Nuclei called blazars, the most common type of extragalactic source seen by the LAT. | |
| FSSC | (Fermi Science Support Center) | Fermi Science Support Center |
| FSW | (Flight Software) | |
| FT1 (file) | FT1 files are the LAT public data files with information on each individual photon. | |
| FT2 (file) | FT2 files are the LAT public data files with information on the spacecraft (where it is, where it's pointing, etc.). | |
| FTOOLS | A package of tools to manipulate FITS files. | FTOOLS main page |
| fv | (Fits Viewer) fv is a program to view FITS files. | fv main page |
...
| term | definition | link | |||
|---|---|---|---|---|---|
| GALPROP | |||||
| GBM | (Gamma-ray Burst Monitor) The GBM is the other instrument on Fermi. It is made of 12 NaI (sodium iodide) and 2 BGO (bismuth germanate) detectors. The GBM detects emission from gamma-ray bursts, solar flares, terrestrial gamma-ray flashes ... | ||||
| GCN | (Gamma-ray Coordinates Network) GCN is the primary way the gamma-ray-burst (GRB) community shares information.. | GCN | (Gamma-ray Coordinates Network) GCN Notices and Reports are sent out by essentially all GRB observers. Some AGN flares from the LAT also trigger GCN Notices to inform multiwavelength observers that something interesting is happening in the gamma-ray sky. | ||
| GEANT | |||||
| ghosts | Ghosts are events where two particles enter the LAT in a small enough time frame that the LAT considers the interactions a single event. A typical example would be a gamma ray and proton entering the LAT near simultaneously. This caused a fraction of gamma-ray events to be vetoed. This problem was first addressed in Pass7 and substantial improvements have been made in Pass8 to recover gamma-ray data from these ghost events. | ||||
| GI | (Guest Investigator) | ||||
| GLAST | (Gamma-ray Large Area Space Telescope) GLAST is the name that Fermi was referred to before it was launched. It is tradition to give NASA missions a different name after launch, as a good-luck superstition. | ||||
| GlastRelease | |||||
| GLEAM | |||||
| GRB (group) | (Gamma-Ray Burst) The LAT has detected high-energy emission (>100 MeV) from ~80 GRBs since launch. In some cases, it detects the prompt emission (the short "burst" of photons lasting anywhere from less than a second to hundreds of seconds), and in the majority of cases it detects the afterglow (the long lasting, slowly fading emission). The Gamma-ray Burst Monitor has detected keV-MeV emission from over 1000 GRBs. | GRB group page | |||
| gt_____ | The standard set of software used to analyze LAT data is called the Science Tools. Each individual tool has a specific function. The names all start with "gt", for "GLAST", which was the original pre-launch name of Fermi. | Science Tools references |
...
| term | definition | link |
|---|---|---|
| L1Proc | (Level 1 Processing) | |
| LAT | (Large Area Telescope) The LAT is the main instrument on Fermi. The parts of the LAT are the Tracker, Calorimeter, and ACD. | |
| light curve | A light curve is generally a plot of the photon flux versus time. | |
| likelihood | Maximum likelihood analysis, likelihood for short, is the principal statistical analysis tool used in LAT analysis to evaluate significance of any signal. | |
| livetime | ||
| LLE | (LAT Low Energy) LLE is a loose event selection that starts at 30 MeV (while the standard LAT event classes start at 100 MeV). The LLE is background-dominated, so it is only appropriate for short, transient events such as gamma-ray bursts or solar flares. | |
| LMC | (Large Magellanic Cloud) | |
| LPA |
...
| term | definition | link |
|---|---|---|
| MC | (Monte Carlo) | |
| merit / merit file | ||
| MET | (Mission Elapsed Time) Many missions record times in MET, which is the number of seconds since January 1, 2001. | A tool for converting from MET to dates |
| MIP | (minimum ionizing particle) | |
| MOC | (Mission Operations Center) | |
| MSP | (millisecond pulsar) | |
| MSP | (millisecond pulsar) | |
| MSPs are generally considered to be "recycled" pulsars, neutron stars in binary systems, spun up by accretion from their companion star. As the name implies, MSPs have rotation periods in the millisecond range. Think kitchen blender speed, only on an object the size of the Washington Beltway having a mass 1.5 times that of our Sun. | ||
| multimessenger | Multimessenger studies include data from instruments that detect things other than light. For instance, one might combine LAT data (photons) with neutrinos, cosmic rays, gravitational waves, etc. | |
| MW | (multiwavelength) Multiwavelength studies are conducted across different wavelengths and energies. For instance, one might combine LAT data (MeV-GeV) with optical, radio, IR, TeV, etc. data. |
...
| term | definition | link | |
|---|---|---|---|
| Pass #, version # | |||
| Pgwave | |||
| phi | |||
| pipeline | |||
| pointed observations | more info | ||
| pole pointing | |||
| PSF | (point-spread function) | ||
| pointed observations | more info | ||
| pole pointing | |||
| PSF | (point-spread function) | ||
| PSR | (pulsar) | Pulsar group page | |
| PWN | (pulsar wind nebula) |
Q
...
| PSR | (pulsar) | Pulsar group page |
| PWN | (pulsar wind nebula) |
Q
R
| term | definition | link |
|---|---|---|
| RA | (right ascension) | |
| ROI | (region of interest) The ROI is the region of space that is being analyzed. A typical ROI for an individual source (such as a pulsar or a gamma-ray burst) is 10 or 12 degrees, although the exact size can differ and depends on the many factors. | |
| ROOT, .root file | ROOT is an object oriented software package built on C++ by particle physicists at CERN to analyze large amounts of data. The Merit files are root files and require ROOT to read the data from said file. | http://root.cern.ch/drupal/ |
S
| term | definition | link | RA
|---|---|---|
| SAA | ( | right ascension)|
| ROI | (region of interest) The ROI is the region of space that is being analyzed. A typical ROI for an individual source (such as a pulsar or a gamma-ray burst) is 10 or 12 degrees, although the exact size can differ and depends on the many factors. | |
| ROOT, .root file | ROOT is an object oriented software package built on C++ by particle physicists at CERN to analyze large amounts of data. The Merit files are root files and require ROOT to read the data from said file. | http://root.cern.ch/drupal/ |
S
South Atlantic Anomaly) | ||
| Science Tools | ||
| SeeVogh | SeeVogh is the video conferencing software that is used by the LAT collaboration. | SeeVogh Research Network |
| selection | ||
| Senior Review | NASA has a policy that every operating mission must be reviewed for scientific productivity every two years. These Senior Reviews are conducted by senior scientists, hence the name. Missions that fare poorly in a Senior Review are terminated. The Fermi Project has to write a Senior Review Proposal each time to explain what Fermi has accomplished and what it will do in the coming years. The Project Scientist and the head of the Fermi Users Group (FUG) do a presentation to the Senior Review Panel. | |
| term | definition | link |
|---|---|---|
| SAA | (South Atlantic Anomaly) | |
| Science Tools | ||
| SeeVogh | SeeVogh is the video conferencing software that is used by the LAT collaboration. | SeeVogh Research Network |
| selection | ||
| senior review | ||
| SMC | (Small Magellanic Cloud) | |
| SNR | (supernova remnant) | SNR group page |
| source (event class) | ||
| survey mode | ||
| star trackers |
...
| term | definition | link | ||
|---|---|---|---|---|
| TDRSS | (Tracking and Data Relay Satellite System) | ). TDRSS is an array of satellites in geosynchronous orbit. These satellites relay data from missions like Fermi to ground stations. | ||
| TGFs | (terrestrial gamma-ray flashes) TGFs are very short (less than 1 millisecond) flashes of low-energy gamma rays produced near thunderstorms on Earth. The large electric fields of thunderstorms accelerate electrons to high enough energies that they can produce gamma rays as they interact with air molecules. | TGFs | (terrestrial gamma-ray flashes) | |
| theta | ||||
| ToO | (Target of Opportunity) | more info | ||
| transient | ||||
| transient (event class) | ||||
| TRK | (Tracker) The Tracker is a part of the LAT whose purpose is twofold: 1) To convert gamma rays into electron-positron pairs, and 2) To track these pairs of charged particles through the instrument in order to figure out where the original gamma ray came from. The Tracker is made of alternating layers of tungsten foils (to convert the gamma rays) and silicon strip detectors (to track the pairs), arranged in 64 columns (8 by 8). | §2.2.1 | ||
| Trunc64 | ||||
| TS | (test statistic) |
...
| term | definition | link |
|---|---|---|
| walkthrough | Part of the internal review process for any LAT publication is that the material is presented at a Weekly Analysis Meeting by having the authors walk the team through the paper. | |
| WAM | (Weekly Analysis Meeting) An online collaboration-wide meeting held every Friday at 8 am PST / 11 am EST / 5 pm CST. The WAMs are held over SeeVogh, which can be downloaded at this website. Topics discussed during WAMs include collaboration-wide items of interest (such as newly released Fermi data), detections of GRBs (gamma-ray bursts) and flaring AGN (active galactic nuclei), and walkthroughs (short summaries) of upcoming papers within the LAT collaboration. | WAM agenda page |
| white paper |
...