Cover Page. Project Title: Probing Dark Matter, Cosmology, Black Holes and Fundamental Physics with VERITAS

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1 Cover Page Project Title: Probing Dark Matter, Cosmology, Black Holes and Fundamental Physics with VERITAS Applicant / Institution: Smithsonian Astrophysical Observatory Street Address: 60 Garden St Cambridge, MA USA Postal Address: 60 Garden St, MS-23 Cambridge, MA USA Lead PI: Dr. Wystan Benbow wbenbow@cfa.harvard.edu Administrative Point of Contact: Michael Griffith mgriffith@cfa.harvard.edu Funding Opportunity FOA Number: DE-FOA DOE / Office of Science Program Office: Office of High Energy Physics DOE / Office of Science Program Office Technical Contact: Kathy Turner kathy.turner@science.doe.gov PAMS Letter of Intent or Pre-Proposal Tracking Number: None Research Area: Experimental Research at the Cosmic Frontier in High Energy Physics

2 Probing Dark Matter, Cosmology, Black Holes and Fundamental Physics with VERITAS 1. General Background This proposal requests continued support for the research efforts of the very high energy (VHE; E>100 GeV) γ-ray astrophysics group at the Smithsonian Astrophysical Observatory (SAO) during a 3-year period from Aug. 1, 2014 until July 31, SAO has been involved in VHE astrophysics for the past ~46 years. The current leader of this group, and PI of this proposal, is Dr. Wystan Benbow. The PI is a federal employee at SAO and is the VERITAS Project Scientist. SAO is responsible for the day-to-day operations of the Very Energetic Radiation Imaging Telescope Array System (VERITAS), and it hosts both the project and the VERITAS Project Office (VPO) at the F. L. Whipple Observatory (FLWO). The PI is also the director of the VPO, which consists of consists of the 8 employees, including 2 scientists. Support for the VPO and VERITAS site-operations comes from separate grants to the PI from SAO, the National Science Foundation and the Department of Energy (DOE) Office of Science. The DOE is the primary source of external support for the SAO group s research since Dr. Benbow is the PI for two current DOE grants: Expanding the Discovery Potential of VERITAS via Moonlight Observations (#DE-FG02-09ER41619) which will be terminated on July 31, 2014, and the aforementioned VERITAS site-operations grant ( The Application of Two Dimensional Imaging to Very-High-Energy Gamma-Ray Astronomy, #DE-FG02-91ER40635) which expires on April 30, No funding for the base-research efforts of the SAO group, aside from the PI s entire salary and some overhead waivers, is provided by SAO. This proposal will be the SAO group s the primary source of support for the forthcoming 3-year period ( ). The PI will also continue to try to augment his group s funding via smaller awards from NASA Guest Investigator (GI) programs. As a federal employee, Dr. Benbow was never eligible for the DOE Early Career Research or Junior Investigator Programs. Since Dr. Benbow became the group leader in 2008, the SAO VHE γ-ray astrophysics group s research efforts were supported by the Moonlight grant ($285,000 total; ), several smaller NASA grants (Fermi GI and Swift GI), and the prior group leader s DOE base grant ( ; Dr. Benbow was PI after Dr. Trevor Weekes retired in 2008). Overall, these funds supported 4 post-doctoral researchers and 2 PhD students full-time for their VERITAS research, and several 3-month stipends enabling visits to VERITAS by students working on research programs led by the PI. The two fully-supported PhD students completed their degrees. The scientists currently in the SAO group are Dr. Benbow (PI), Dr. Weekes, Dr. Matteo Cerruit (post-doc), Dr. Anna Barnacka (post-doc), Dr. Pascal Fortin (Observatory Manager) and Dr. Nicola Galante (Deputy Observatory Manager). The latter two scientists actively participate in VERITAS research, but focus on operations and are 100% supported by the site-operations grants. The two post-docs are largely supported via NASA GI channels, the last of which expires in This proposal requests a new 3-year base grant for the PI (~$506k), and will support the group s VERITAS research efforts. The funding will pay for the stipend / healthinsurance for one post-doc and and one new student, support the group s travel expenses, purchase materials required for VERITAS research, and cover all publication/printing expenses. 2. VERITAS Overview VERITAS [56] is an array of four 12-meter atmospheric-cherenkov Telescopes (ACTs). It is the most-sensitive VHE γ-ray observatory in the Northern Hemisphere, and is the only fullyoperational US facility for these studies. VERITAS was commissioned in 2006 and began fullscale operations in September It was a high-priority experiment in DOE sponsored reports. The DOE contributed to the development of VERITAS and funded ~42% of its ~$17.6 million construction cost. VERITAS is operated by a collaboration of ~100 scientists from 19 institutions in 4 countries, and its site operations are fully funded through VERITAS is used to study VHE γ-rays from astrophysical sources. These VHE γ-rays are observed via the Cherenkov light produced as they interact in the Earth s atmosphere. The data are taken with high-speed systems similar to those used in other particle physics experiments, and reduced using custom software employing CERN packages. VERITAS is

3 operating well and routinely observes for >1100 good-weather hours each year. All promised performance metrics of the experiment are achieved or exceeded [56]. These include an energy threshold of ~60 GeV, an energy resolution of ~15%, an angular resolution of ~0.1º, and a sensitivity of <1% of the Crab Nebula flux in 25 hours. In Summer 2012, a major upgrade of VERITAS was completed, improving the its sensitivity and decreasing its energy threshold. The experiment now detects sources ~2.5 times faster than in 2007 [57]. Due to its unprecedented sensitivity, VERITAS will continue to make major contributions to the field of astrophysics. While a next-generation VHE observatory is in the R&D phase, VERITAS will remain the premier VHE facility in at least the Northern Hemisphere beyond the length of this proposal. Further upgrades of VERITAS hardware are being studied, and new analysis techniques are nearly complete; we expect these techniques to result in a factor of sensitivity increase [58]. Figure 1: The VERITAS array of imaging atmospheric-chereknov telescopes (IACTs) at FLWO in AZ. 3. Moonlight Observation Capabilities Data taking during periods of moonlight is not universal to all VHE observatories. However, several methods that enable VERITAS to operate during all levels of moonlight were developed. These methods include running with higher pixel-level triggers, running with reduced pixel gains, and/or running with custom filters that preferentially pass the UV/blue Cherenkov light. SAO led the deployment, testing, performance evaluation of these methods, and the development of their user protocol. This development required special instrument simulations, calibration settings, etc. These new methods enable VERITAS to run every night of the year, albeit with reduced sensitivity at lower energies. VERITAS can now respond to transient phenomena accessible to no other IACTs (e.g., during the full moon). In addition, the observation yield of VERITAS is increased by 60% from ~850 hours per year to ~1350 hours. Moonlight data-taking is now routine and these data are both scientifically useful and regularly published. Clearly the project s capabilities are increased, as promised in our previous DOE research grant Expanding the Discovery Potential of VERITAS via Moonlight Observations. 4. VERITAS Science Introduction VERITAS seeks to both identify new sources of VHE γ-rays, and to perform in-depth studies of the known sources to better understand their underlying fundamental processes. Since VHE γ-ray sources emit radiation over ~20 orders of magnitude in energy, these studies often involve collaboration with experiments at lower energies (e.g., radio, optical, X-ray, and MeV-GeV γ-ray). Currently >150 VHE γ-ray sources are known [59]. The primary targets of VERITAS Galactic observations are supernova remnants, pulsars, binary systems, and known VHE sources whose (likely Galactic) classification is unknown. The extragalactic targets observed by VERITAS include active galactic nuclei, radio galaxies, starburst galaxies, galaxy clusters, globular clusters and gamma-ray bursts. Local Group galaxies, the Galactic Center and dwarf galaxies are targets of VERITAS observations focused on the indirect detection of cold dark matter. The results of these studies often have broad implications beyond the physics of the objects. Other topics addressed include fundamental physics (e.g., the energy dependence of the speed of light), the origin of cosmic rays, cosmology and dark matter. The VHE observation programs also have multi-messenger implications; e.g. for wide-acceptance

4 particle telescopes such as IceCube (neutrinos, [60]) and the Pierre Auger Observatory (UHE cosmic rays, [61]). The emission from objects detected by the Fermi γ-ray Space Telescope [62] extends from ~300 MeV to ~300 GeV, overlapping the >60 GeV regime covered by VERITAS. Results from both experiments are highly complementary, and both benefit from the simultaneous coverage of the entire γ-ray spectra of non-thermal emitters. In particular, the 10 5 times larger effective area of VERITAS enables time-resolved measurements of flux and spectral variability for transient sources not possible with Fermi alone, and continuation of the γ- ray spectra to TeV energies is critical for measuring the extragalactic background light and intergalactic magnetic field. Such a unique MeV-TeV viewing window is unprecedented, and it may be decades before another such opportunity due to the limited lifetime of Fermi. In addition new facilities in the X-ray (NuStar [63], Astro-H [64]) and VHE bands (HESS-II [65], HAWC [66]) have, or will soon, come online providing new opportunities. The LHC is providing new constraints that will guide the dark-matter search strategy. Indeed the growing number of upper limits on physics beyond the standard mode (up to TeV energies) may already suggest the scale for new physics is beyond the reach of terrestrial experiments, requiring TeV γ-ray observations. 5. VERITAS Science Plans for In 2011, the VERITAS Sceince Board (VSB) organized the development a long-term observation program assuming operation through at least This long-term plan (LTP) was developed by members of VERITAS, with input from the scientific community, and was written by the PI. It was strongly endorsed by the VERITAS External Science Advisory Committee (ESAC), and subsequently delivered to the three agencies that fund VERITAS site operations. The VERITAS science program will continue to follow the guidelines outlined in this longterm plan, which is based on the projected ultimate accomplishments of VERITAS. During the planning, strong consideration was given to creating a balanced program in fundamental physics and astrophysics. The plan is based on 4 major scientific themes: Particle Physics and Fundamental Laws, Cosmology, Black Holes, and Galactic Tevatrons / Pevatrons. The full plan is public [67] and the 3 themes of most importance to the SAO group are highlighted below. Proposals for all VERITAS observations are organized annually by Sceince Working Groups (SWGs), and are evaluated in an open competition. The VSB mandates that the planned program strongly reflects the LTP science drivers, and the time allocations be within ~15% of the goals detailed in the LTP. SAO scientists lead two of the four major non-technical SWGs: Dr. Benbow (the PI) leads the Blazar SWG, and Dr. Galante co-leads the Dark Matter, Astroparticle, Extragalactic Non-blazar (DM-AsPEN) SWG. 5.1 Particle Physics and Fundamental Laws: The origin of dark matter (DM) is one of the most compelling mysteries facing 21 st century physics and astronomy. In the standard scenario, where DM is comprised of weakly interacting massive particles (WIMPs), DM annihilation in astrophysical regions with a large concentration of DM would produce a clearly recognizable signal of VHE γ-rays. This indirect detection technique provides an important complement to direct-detection experiments underground and to searches for new particle physics at the LHC. Even if the LHC detects evidence for super-symmetry, only astrophysical VHE γ-ray measurements can reveal the distribution of dark matter in haloes. In addition, the characteristic shape of the VHE spectrum provides crucial information on the particle mass and branching ratios beyond the capabilities of direct-detection experiments and the LHC. As one of the world s premier VHE detectors, VERITAS will make the most-sensitive searches for dark matter in the mass region above 200 GeV. Since the predicted signal for DM sources outside the Galactic Center are predicted to be very weak, long, dedicated exposures on the most promising dark matter targets are required. In addition to dark matter searches, VERITAS has significant sensitivity to other aspects of particle physics, including searches for axion-like particles and primordial black holes that could be created in the early universe. The detection of fast VHE γ-ray flares from a GRB or a blazar will allow VERITAS to make the most sensitive tests to date of Lorentz-invariance violation, especially for quadratic (~E 2 ) and higher-order terms in the electromagnetic dispersion relation.

5 5.2 Cosmology: VHE observations of blazars, and possibly GRBs, are useful for cosmological measurements. Their γ-ray spectra are modified by interactions with inter-galactic radiation fields through pair-production (γγ to e + e - ) and subsequent cascade processes, and thus contain imprints of the extragalactic background light (EBL) and the intergalactic magnetic field (IGMF). The EBL is the combined flux of all extragalactic sources integrated over the entire history of the universe, and its calorimetric information carries unique information regarding the epochs of galaxy formation and the history of galaxy evolution. Detailed measurements by VERITAS of a number of blazars at different redshifts enable the first reliable determination of the density and spectrum of the EBL in the optical-ir band, which is also sensitive to the dark matter content of the universe and its evolution. Since VERITAS has a catalog of 25 blazars extending to redshifts of >0.6, a multi-year observing program makes an EBL-measurement possible [76]. Currently there are only weak constraints on the IGMF and no direct measurements. The γ-ray beams from AGN / GRBs provide a measurement of the IGMF strength not accessible to other techniques. A measurement of the IGMF would have profound cosmological implications because it implies a primordial field produced in the early universe. Even a good constraint on the IGMF has high value, and recent work [68,69] combining Fermi-LAT and VHE blazar measurements already provide the first reliable lower bounds on the IGMF. Using multi-year blazar studies, VERITAS will use three different observables to constrain or determine the IGMF. The origin of cosmic rays is a 100-year old mystery. VERITAS observations of starburst galaxies (SBGs), supernova remnants (SNRs), and star-formation regions (SFRs) hold the key to ultimately solving this puzzle. By establishing SNRs and SFRs as hadronic particle accelerators, and demonstrating a hadronic origin of the VHE emission from SBGs (which have extremely high cosmic-ray densities), we will solve this puzzle (at least up to energies of ~10 15 ev). Indeed VERITAS results from the Tycho SNR [27] and the SBG M82 [14] already provide significant progress towards ending this mystery. VERITAS observations of SBGs, and similar ultra-luminous infrared galaxies (ULIRGS), also provide a new handle on studying the star formation in different galactic environments. These observations and those of galaxy clusters will yield information about the pressure content of cosmic rays on large scales, and indicate how random kinetic energy is distributed among the interstellar matter. 5.3 Black Holes: Active galactic nuclei (AGN) are believed to be powered by the accretion of matter onto a super-massive ( solar mass) black hole (SMBH). About 10% of all AGN have collimated, relativistic outflows of particles (jets), and blazars (the most numerous, identified source of VHE γ-rays) are a class of AGN where one jet is pointed directly towards Earth. The VHE γ-rays are believed to be created by these jets in a compact region near the SMBH event horizon. Thus VERITAS studies of AGN probe the innermost regions of these powerful particle accelerators, where the bulk of their luminosity is emitted, and are critical to understanding the process of astrophysical jet formation and evolution, the effect of the jet on the surrounding environment, as well as the process of matter accretion and magneto-hydrodynamics in the strong-gravity region near the central SMBH. Blazars are among the most variable objects in the universe, and the brightest and fastest variability is observed in the VHE band. During flaring episodes, it is possible for VERITAS to rapidly generate unprecedented statistics, particularly at >TeV energies, which when combined with multi-wavelength data (radio, optical, X-ray and Fermi) will conclusively address issues in source modeling, the EBL, the IGMF, and the origin of ultra-high-energy cosmic rays. Observing VHE flares is key for the program, but our goals can be accomplished without them, using deep exposures. Large flares are rare, so multiple years are needed to catch future events, and to acquire these deep data sets. In addition to detailed studies of a few sources for targeted scientific programs, we are amassing enough AGN detections that, for the first time, we will also be able perform population studies. 6. Science Results from Prior DOE Support VERITAS recently began its seventh year of operations. The experiment is running well and is well-understood. Results from the VERITAS science programs include the detections of at least 46 astrophysical sources of VHE γ-rays, including at least 20 not previously detected in the VHE band. More than half of these discoveries were initially reported by SAO scientists due

6 to their discovery in automated next-day and season-long analysis efforts the group maintains with DOE support. Figure 2 shows the public VERITAS catalog and its near exponential growth. Figure 2: Left) The VHE γ-ray sky as seen by VERITAS (visible area in blue). The different color points represent different astrophysical classes. Right) The number of objects detected by VERITAS vs. year. Numerous VERITAS results from the first six observation seasons have been published or submitted for publication, including 55 refereed journal articles. VERITAS results have appeared in academic literature such as the Astrophysical Journal, Nature, Science, Physical Review Letters, as well as in the mainstream media (e.g., National Geographic, New Scientist, Wired, and The USA Today). Approximately 35 other journal articles are in various stages of preparation. Many of these articles are joint publications with some combination of the Fermi- LAT, AGILE, MAGIC and HESS collaborations (gamma-rays), and a large fraction of these articles also contain data from major lower-energy observatories, including the Swift, Chandra, XMM, Suzaku and RXTE X-ray satellites. Since 2006, >40 graduate students have completed their PhD theses using VERITAS results, including 3 supervised by SAO. The VERITAS collaboration s refereed journal publications are listed in the references [1-55]. While the entire collaboration contributed to the development of these 55 manuscripts, SAO scientists were the primary author of 6 (11%) [6,10,14,15,20,53] and played a major role (e.g., provided analysis and / or significant text) in 14 (25%) [2,17,18,23,24,33,35,36,37,38,42,44,50,51]. By having led two of the four major SWGs for the past ~4 years, the SAO group has also directly coordinated 51% of the Collaboration s published output. Although no VERITAS result is possible without the efforts of the entire collaboration, it is hopefully clear that the SAO group is among the most productive. Four SAO-driven results are given below: VERITAS discovery [14] of gamma-ray emission from the starburst galaxy M 82: This new type of VHE emitter firmly connects high levels of star formation activity to the origin of cosmic rays. These data are a major component in solving the 100-year-old mystery of cosmic-ray origin, and provide key insights into the role of CRs in driving large-scale galactic winds and in the effects of star formation on galaxy structure. The SAO group led all aspects of this effort; the PI wrote the Nature article and the corresponding press releases. The 2010 [70] and 2013 [71] major VHE flares (factor of flux increases) from the blazar Mkn 421. The first flare shows variations on ~1 minute time scales which challenge blazar emission models, and generate the strongest blazar-related constraints on Lorentz-invariance violation to date. The latter flare triggered continuous measurements with NuStar, Fermi-LAT, Swift and numerous ground-based facilities and was reported by the BBC; the unprecedented follow-up efforts were initiated by the PI and enable definitive time-dependent modeling. A deep, multi-year observation of 1ES [53]: The VERITAS detection of VHE flux variability suggests that IGMF constraints derived from 1ES , which are the strongest, need to be reassessed. The VHE spectrum shows completion of the long-term plan, will enable the best EBL measurement in the mid- to far-ir band. The acquired simultaneous multi-wavelength data was modeled by SAO with a new technique. Rather than reporting one, degenerate model solution, we reported the range of acceptable parameters.

7 Figure 3 (SAO plots): Left: VHE light curve from Mkn 421 in The average flux is twice that from the Crab Nebula (the brightest steady VHE source) and on one night (inset with 2-minute time bins) averaged 7 Crab. Right: The SED of 1ES An SSC model successfully fit to the data is also shown, along with a contour plot showing the allowed parameter space for 2 physical quantities. VERITAS dwarf galaxy limits [23,38]: These are used to set limits on the velocity-weighted cross section and lifetime of dark matter (DM) particles versus particle mass, and limits on any boost to the potential DM-related VHE flux from substructure in the DM halo. Results from the deep observation with VERITAS of Segue 1 [38] also strongly disfavor the DM interpretation of the ATIC [72] and PAMELA [73,74] anomalies in the cosmic-ray lepton spectrum. Figure 4: VERITAS sark matter (DM) constraints from Segue 1 [38]; Left) Limits on the velocityweighted DM-annihilation cross section vs. particle mass (with and without Sommerfeld boosting). The dark band is theoretical expectations. Center) Lower-limits on the DM decay lifetime vs. particle mass. Right) Limits on the overall boost factor BF vs. the DM particle mass. 7. Statement of Work Since 1996, the PI has participated in 75% of the world s current major VHE γ-ray astrophysics collaborations; he is thus is familiar with all the experimental techniques and a majority of the researchers in the field. He has extensive hand s on experience with VHE observatories, and his work is extensively published (>135 refereed articles). He has given invited research talks at scientific meetings on five continents, and his collaboration as a visiting scientist was funded by several international institutions. The PI frequently serves as a referee for academic journals and for multi-million dollar funding proposals. The PI s research in VHE γ-ray astrophysics is broad-based, encompassing both galactic and extragalactic sources. However, he primarily focuses on observations of extragalactic VHE sources, especially Active Galactic Nuclei (AGN) -- Nature s most powerful and efficient particle accelerators, starburst galaxies, and dark matter (DM) dominated objects. A major focus of these programs is to explore and characterize the implications of the observational results beyond the physics of the sources themselves. In particular the PI leads efforts to address topics in fundamental physics, cosmology, indirect DM searches, and the origin of cosmic rays. Naturally that the SAO group s continued efforts will also focus on this science. Dr. Benbow will continue to lead the SAO VHE γ-ray group, and will continue to direct the VERITAS Project Office and act as Project Scientist. The PI will attend all important VERITAS meetings, and serve on the VERITAS Executive Committee (VEC) and the Science Board (VSB). The VEC is the ultimate authority for making decisions within VERITAS. The VSB

8 organizes the science program of VERITAS, and is responsible for the observing program and the scientific interactions of the collaboration with the outside world. Through the VSB, the PI will continue to develop the scientific program for VERITAS. The PI will continue to act as a leader of the Blazar Science Working Group (SWG). This includes organizing all the observation proposals, analysis and resulting publications, determining the scientific direction of the SWG, organizing meetings and stewarding the rapid analysis of the data (immediate, nextday and season-summary). The PI will organize the targets to be observed during each monthlong shift in conjunction with the approved observing program, and update the targets based on the latest information. In addition, he will ensure that simultaneous multi-wavelength data, in particular X-ray and optical, are taken for all high-value observations. The PI will also ensure the blazar observation program described in Section 7.1 is implemented within 20% of the targets, that all data are analyzed within 24 hours, and published in <2 years. He will actively participate in other SWGs, will continue to author observation proposals and publications, and also will continue to participate in the community planning process. SAO s Dr. Fortin & Dr. Galante will largely focus ensuring smooth operations of VERITAS and that the planned observing program is implemented. During their time for research, Dr. Fortin will lead the continued development and improved technical understanding of the moonlight observing efforts that yield 60% more data for the project. Dr. Galante will continue as co-coordinator of the DM-AsPEN SWG, which has similar duties to the PI s Blazar SWG responsibilities. The DM-AsPEN observing program is described in Sections 7.2 and 7.3. He will also remain as one of the major software developers of the standard VERITAS analysis package, with a focus on the codes that produce many of the quantitative, scientific results reported by the project (e.g. spectra, light curves). Dr. Galante will also manage the group s technical responsibility for the optical alignment of VERITAS. Through the successful implementation of the Blazar, Dark Matter, and AsPEN programs, the PI along with Dr. Fortin and Dr. Galante will ensure the VERITAS Long-term Science Plan s goals in Particle Physics and Fundamental Laws, Cosmology and Black Holes are achieved. These scientists will supervise any the SAO junior researchers to ensure these goals are met; the latter s statement of work is given in Section The Blazar Observation Program (440 h / yr): This program is largely focused on our goals in fundamental physics (i.e. Lorentz-invariance constraints and EBL/IGMF measurements), and one major flaring event could change our understanding of the Universe. We will regularly monitor 15 selected VHE blazars to maximize the chance of successfully detecting any VHE flares while simultaneously building deep, multi-year exposures. The selected targets consist of 7 EBL/IGMF-science focused blazars, 4 nearby, bright HBL for use in studies of Lorentz-invariance violation and UHECR acceleration, and 4 non-hbl blazars for studies to unravel the mechanisms behind the blazar sequence. Contemporaneous radio, optical/uv, X-ray and GeV monitoring will be organized to enable source modeling, and Target of Opportunity proposals in these wavebands will be submitted yearly to ensure coverage of flaring events. A Fermi-LAT-guided VHE discovery effort will be continued, and will focus on high-risk/reward endeavors, and will seek to expand the understanding of the blazar sequence, and find new blazars useful for EBL/IGMF studies. We will respond to flares from the long-term monitoring program and those seen at lower energy, and deepen exposures on new VHE discoveries. To aid this effort, optical and Swift X-ray monitoring of all VHE blazars and highvalue candidates is organized, in addition to several automatic LAT analysis/alert pipelines [75]. 7.2 Dark Matter (DM) Program (155 h / yr): We will probe the DM particle mass and constrain its annihilation cross section within an order of magnitude of generic predictions, and strongly constrain scenarios with Sommerfeld or astrophysical boosts. Dwarf galaxies have extremely high concentrations of DM and no astrophysical backgrounds that may confuse the origin of a VHE signal. They are the best VHE targets and we will acquire >100 h of data annually on promising dwarf galaxies. The use of multiple sources will average over systematic uncertainties in the DM distribution. A deeper stacked result will also be made, which could have fewer systematic issues than a single deep observation. We will also observe new

9 astrophysical sources with the potential for the discovery of a DM sub-halo. These targets are hard-spectrum, steady, high-galactic-latitude Fermi-LAT sources that are unidentified at other wavelengths. The Galactic Center has the highest local concentration of DM. Our observations are very sensitive above a few TeV and improve on the deep HESS result focused on lower energies. Only a modest astrophysical boost is needed for DM detection, and VERITAS limits on generic DM models at high mass (>few TeV) will complement the LHC. 7.4 Extragalactic Non-Blazar Program (85 h / yr): These rare VHE emitters rank amongst the most interesting sources detected by VERITAS, yielding papers in both Nature and Science. The radio galaxy M87 will be monitored to build up the deepest-ever exposure and to identify flaring states. The latter will trigger intense high-spatial-resolution Chandra X-ray and radio observations, to correlate any morphological changes with the VHE flux to indicate the acceleration region of TeV photons in AGN. The starburst galaxy M82 will be observed to differentiate between various models for its VHE emission, which has significant implications for cosmic-ray origin and cosmology. Time will also be used for risky, often-lat-guided discovery observations of starburst/ultra-luminous galaxies, radio galaxies, globular clusters and galaxy clusters. The latter two classes can contain up to 85% dark matter. 8. Junior Researcher s Statement of Work The full salaries of the senior group members are covered by other sources. This funding request is to largely support a post-doc and a new PhD student to assist them in the implementation of their programs, particularly with data analysis. Due to the staff s siteoperations responsibilities, this support is critical, and the researchers are given considerable freedom the program s implementation. Much of the work focuses on regularly using/improving existing machinery for the staff s key efforts. The work program has four areas of organization: Acquiring the necessary data: The post-doc will annually prepare several (>3) observation proposals for VERITAS, and will operate the experiment during at least one shift. They will upgrade / maintain data-quality-monitoring (DQM) software for VERITAS to ensure there are no high-level issues in the data; the DQM software will run daily. The post-doc will also maintain and improve the existing automatic analysis pipelines for reducing public Fermi-LAT (MeV-GeV) data to alert VERITAS for flaring events in blazars / AGN; this pipeline will update daily. In addition, the post-doc will coordinate the optical observing program of the SAO group using the FLWO 48 telescope, whose data are automatically reduced and provide flaring alerts; this pipeline will update daily. The post-doc will maintain the program which checks for scheduled X-ray observations on a daily basis and automatically alerts the VERITAS observers to observe simultaneously in a pre-approved program; these data, along with public Fermi-LAT data, provide comprehensive measurements for modeling. The post-doc will take measurements to confirm the optical alignment of VERITAS exceeds specifications, and will ensure the moonlight observation program continues. Reducing the good-quality data: The post-doc will also focus on analyzing and publishing results from VERITAS observations of AGN / blazars, all starburst galaxies and all dark-matter dominated objects. Specifically, the post-doc will work with the DOE-funded VERITAS group at Iowa State University (ISU; PI: Krennrich) to ensure all data from the EBL / IGMF blazar program are comprehensively reduced with publication-ready analyses annually. They will also work with the DOE-funded VERITAS groups at Washington University (PI: Buckley) and Argonne National Lab (ANL; PI: Byrum) to ensure that all targets for Indirect Dark Matter detection are all comprehensively reduced with publication-ready analyses annually. The postdoc will upgrade, maintain and run the VERITAS next-day / season-summary analyses on all these targets, and the results will be updated daily and immediately reported. These analyses are key for identifying AGN flares, as well as new source phenomena that require follow-up. Interpreting and presenting the data: The post-doc will attend >90% of all Blazar and DM- AsPEN teleconferences. The post-doc will model new VERITAS blazar detections with the new software that provides the range of acceptable parameters instead of one degenerate solution. Understanding the underlying processes and demonstrating that they are not

10 unusual is key to strengthening the EBL / IGMF conclusions, in addition to providing the basis for the blazar sequence efforts. The post-doc will reduce all major VHE flare data (>5 Crab) from blazars, and processes the photon lists through the statistical codes / simultations (written by SAO) to assess if there are any energy-dependent time-delays useful for Lorentzinvariance constraints, and work with the ANL group to publish these results within 1 year. The post-doc will work with the ISU group to generate an EBL measurement by combining Fermi-LAT and VERITAS spectra from multiple sources. A near-final draft of this manuscript will exist by 2017, noting the result already is significantly improved from the HESS result [76] (particularly in the mid-far IR bands). The post-doc will work with the Washington University and ANL groups to convert the dark matter observations (e.g. VERITAS flux limits) into limits on dark matter quantities, and to stack the individual dwarf galaxy analyses (including systematic tests) to gain a more sensitive result. A comprehensive stacked DM result will be published by The post-doc will present their scientific work at the twice annual collaboration meetings, and annually present new results to the general community. The PI expects the post-doc to publish at least one journal article per year and hopefully more. Independent Projects: The post-doc will have 20% time to pursue PI-approved, VERITAS related independent projects. These currently include searches for primordial black holes, searches for gamma-rays from lensed galaxies, and developing AGN modeling codes. In the first year, the student will be trained in the methods of particle astrophysics, the analysis techniques of VERITAS (e.g. Root, C++, shell-scripting, UNIX), and the experiment s science drivers. In the second year, the student will contribute to VERITAS observation proposals, be trained in analysis techniques for satellite data, and perform advanced studies with reduced VERITAS data. In the third year, the student will lead proposals for further thesis data, prepare VERITAS and satellite analyses, and potentially complete their thesis. The student will perform VERITAS shifts, and present at all domestic collaboration meetings, and present at a conference in the latter two years. The student is expected to publish at least one journal article. The post-doc will help mentor the graduate student. 8. Concluding Remarks The SAO VHE γ-ray astrophysics research group has long been a leader in this field of particle astrophysics, and has received DOE Office of Science funding since In many senses the field of TeV γ-ray astronomy was founded largely through the efforts of the SAO group, previously led by Dr. Trevor Weekes, and it is not unreasonable to say the field might not exist were it not for long-standing DOE support. We are extremely grateful for this past support. We believe we have produced a particularly large number of significant results in both fundamental physics and astrophysics to reward DOE for its investment, and sincerely hope we have motivated future support. Given the recent dramatic increase in the numbers and types of astrophysical VHE γ-ray sources, it is truly a golden age for the field and by extension the science to be drawn from it. VHE γ-ray sources are Nature s most powerful particle accelerators (i.e. naturally occurring Tevatrons). Understanding these unique objects not only provides insight into how such efficient accelerators can be built, but the results from their VHE γ-ray observation provides key information regarding physics topics such as the nature and distribution of dark matter, large scale neutrino production, the origin of cosmic rays, cosmology (the EBL density and IGMF strength) and potential Lorentz-invariance violation. As such the results from γ-ray astrophysics have clear applicability to the DOE HEP program s mission to explore and to discover the laws of nature as they apply to the basic constituents of matter, and the forces between them. It should also be noted that many of the researchers trained in this relatively inexpensive field of research go on to have careers (academic and industry) in both particle and nuclear physics, because the techniques and methodology of this field are identical to those used in these fields. Finally, the PI is looking forward to the opportunity to continue to be a leader in the decades-long DOE research program in VHE γ-ray astrophysics.

11 Appendix 1: Biographical Sketch Wystan Benbow 60 Garden St, MS-20 Phone: (+1) Cambridge, MA Fax: (+1) USA Nationality: USA Education: Ph.D., Physics, University of California, Santa Cruz, 2002 Thesis: A Study of TeV Emission From the Crab Nebula and Selected AGN Using the Milagro Gamma-Ray Observatory M.S., Physics, University of California, Santa Cruz, 1998 B.S., Physics & Astronomy, with Distinction, University of Iowa, 1996 Awards & Fellowships: Observatoire de Paris-Meudon Fellow, 2008 & 2011 Max Planck fellowship to support EU-US scientific collaboration, IGPP Fellow, Chancellor's Outstanding Teaching Assistant Award, 2000 GAANN Fellow, University of California Regents' Fellow, James Van Allen Award, 1996 Phi Beta Kappa, 1996 Professional Experience: 2007-present: Astrophysicist - Federal GS-13 (VERITAS & CTA Collaborations) Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA : Visiting Scientist (H.E.S.S. Collaboration) Max Planck Institut für Kernphysik, Heidelberg, Germany : Research Assistant (Milagro Collaboration) Santa Cruz Institute for Particle Physics University of California, Santa Cruz, CA, USA : Teaching Assistant University of California, Santa Cruz, CA, USA : Learning Instructional Assistant Cabrillo Community College, Santa Cruz, CA, USA Leadership: VERITAS Project Scientist & PI of Site Operations: 7/2008 to present PI of the Smithsonian Astrophysical Observatory VERITAS Group: 7/2008 to present Chair of the VERITAS Blazar Science Working Group: 6/2009 to present Graduated Smithsonian s Palmer Leadership Development Program in 12/2012 Major Committees: Local Organizing Committee, 2004 International Gamma-ray Symposium (Heidelberg) H.E.S.S. Observation Committee: 4/2006 to 11/2007 VERITAS Time Allocation Committee: 7/2008 to 7/2010 VERITAS Science Board: 1/2008 to present VERITAS Executive Committee: 7/2008 to present VERITAS Building Construction Committee: Building delivered in 9/2011 CTA Speakers and Publications Committee: 10/2012 to present Smithsonian Astrophysical Observatory Library Committee: 10/2012 to present Smithsonian Astrophysical Observatory Hiring Committees: Several PhD Committees: Lucie Gerard (APC, 2010)

12 Public Presentations: Statistics as of Aug. 30, 2013 Invited talks: 20 long (~1 hr) & 6 intermediate (~30 min) Contributed Talks: 3 intermediate (~30 min) & 14 short (~15 min); Posters: 10 Five most-recent invited talks: TeV Jets: Astrophysical Particle Acceleration, Santa Fe, NM, USA; 8/ rd ICRC Highlight Talk, Rio de Janeiro, Brazil; 7/2013 Harvard Smithsonian CfA HEAD Seminar, Cambridge, MA, USA; 10/2011 AGN Physics in the CTA Era, Toulouse, France, 5/2011 APS Physics Meeting, Anaheim, CA, USA, 5/2011 Publications: Hirsch index = 54; Statistics as of Aug 30, articles in refereed journals (11 as primary author) 46 conference proceedings (18 as primary author) 5 miscellaneous publications (4 as primary author) Five relevant articles: E. Aliu et al., VERITAS deep observations of the dwarf spheroidal galaxy Segue 1, Physical Review D, 85, , 2012 V. Acciari et al., A connection between star formation activity and cosmic rays in the starburst galaxy M 82, Nature, 462, 770, 2009 F. Aharonian et al., Limits on an Energy Dependence of the Speed of Light from a Flare of the Active Galaxy PKS , Physical Review Letters, 101, , 2008 F. Aharonian et al., The energy spectrum of cosmic-ray electrons at TeV energies. Physical Review Letters, 101, 1104, 2008 F. Aharonian et al., A low level of extragalactic background light as revealed by γ- rays from blazars, Nature, 440, 1018, 2006 Conflicts of interest: Collaborators / Co-editors in past 48 months: Member of VERITAS Collaboration ( & the CTA Collaboration ( - all members are conflicts of interest Co-authored articles, but no likely conflicts of interest, with: Milagro Collaboration: HESS Collaboration: MAGIC collaboration: Fermi-LAT collaboration: AGILE collaboration: Graduate Advisor ( ): David Williams, University of California, Santa Cruz Post-doctoral Advisor ( ): Werner Hofmann, MPI for Nuclear Physics in Heidelberg, Germany Prior PhD students: Mark Theiling (now at Purdue), Victor Acciari (now in industry; Italy) Current PhD students: None Prior post-docs: Nicola Galante (still at SAO), Jeremy Perkins (now at NASA), Jonathan Kildea (now in industry; Canada), Martin Schroedter (teacher in WA) Current post-docs: Matteo Cerruti & Anna Barnacka

13 Appendix 2: Current & Pending Support PI: Wystan Benbow - Current and Pending Support Dr. Benbow is a Federal Scientist where 100% of his salary and benefits are received from the Federal Government. Dr. Benbow is named as PI on the following grants and proposals: ************************************************************************ Current VERITAS Operational Funding for FY13-FY16 (Renewal) DOE $1,425,000 5/1/13 4/30/16 ************************************************************************ Current Expanding the Discovery Potential of VERITAS via Moonlight Observations (Renewal) DOE $285,000 8/1/10 7/31/14 ************************************************************************ Current Joint VERITAS-FERMI Study of Extragalactic Star Formation Regions NASA Fermi Guest Investigator Cycle 4 $95,968 12/1/11 11/30/13 ************************************************************************ Current Collaborative Research: MRI Consortium: Development of a Novel Telescope for Very High- Energy Gamma-Ray Astrophysics. NSF - UCLA Sub-award to SAO $140,000 9/15/12 7/31/15 ************************************************************************ Pending Operations of VERITAS in the Epoch 2013 to 2016 NSF $1,425,000 10/1/13 9/30/16 ************************************************************************

14 Appendix 3: Bibliography & References Cited (1) V. Acciari et al., Observation of gamma-ray emission from the galaxy M87 above 250 GeV with VERITAS, Astrophysical Journal Letters, 679, 379, 2008 (2) V. Acciari et al., VERITAS Observations of the Gamma-ray Binary LS I , Astrophysical Journal Letters, 679, 1427, 2008 (3) V. Acciari et al., VERITAS Discovery of >200 GeV Gamma-ray Emission from the Intermediate-frequency-peaked BL Lac Object W Comae, Astrophysical Journal Letters, 684, L73, 2008 (4) V. Acciari et al., Discovery of Very High-Energy Gamma-Ray Radiation from the BL Lac 1ES , Astrophysical Journal Letters, 690, L126, 2009 (5) I. Donnarumma et al., The June 2008 Flare of Markarian 421 from Optical to TeV Energies, Astrophysical Journal Letters, 691, L13, 2009 (6) V. Acciari et al., VERITAS Observations of a Very High Energy Gamma-ray Flare from the Blazar 3C 66A, Astrophysical Journal Letters, 693, L104, 2009 (7) V. Acciari et al., VERITAS Observations of the BL Lac Object 1ES , Astrophysical Journal, 695, 1370, 2009 (8) V. Acciari et al., Evidence for long-term Gamma-ray and X-ray variability from the unidentified TeV source HESS J , Astrophysical Journal Letters, 698, L94, 2009 (9) V. Acciari et al., Observation of Extended VHE Emission from the Supernova Remnant IC 443 with VERITAS, Astrophysical Journal Letters, 698, L133, 2009 (10) V. Acciari et al., Multiwavelength Observations of LS I with VERITAS, Swift and RXTE, Astrophysical Journal, 700, 1034, 2009 (11) V. Acciari et al., Radio imaging of the very-high-energy gamma-ray emission region in the central engine of a radio galaxy, Science, 325, 444, 2009 (12) V. Acciari et al., Simultaneous Multiwavelength Observations of Markarian 421 During Outburst, Astrophysical Journal, 703, 169, 2009 (13) V. Acciari et al., Detection of Extended VHE Gamma Ray Emission from G with VERITAS, Astrophysical Journal Letters, 703, L6, 2009 (14) V. Acciari et al., A connection between star formation activity and cosmic rays in the starburst galaxy M 82, Nature, 462, 770, 2009 (15) V. Acciari et al., VERITAS Upper Limit on the VHE Emission from the Radio Galaxy NGC 1275, Astrophysical Journal Letters, 706, L275, 2009 (16) V. Acciari et al., Multiwavelength observations of a TeV-Flare from W Com, Astrophysical Journal, 707, 612, 2009 (17) V. Acciari et al., Discovery of very high energy gamma rays from PKS and multiwavelength constraints on its redshift, Astrophysical Journal Letters, 708, L100, 2010 (18) V. Acciari et al., Discovery of Variability in the Very High Energy Gamma-Ray Emission of 1ES with VERITAS, Astrophysical Journal Letters, 709, L163, 2010 (19) V. Acciari et al., Observations of the shell-type SNR Cassiopeia A at TeV energies with VERITAS, Astrophysical Journal, 714, 163, 2010 (20) V. Acciari et al., The Discovery of γ-ray emission from the Blazar RGB J , Astrophysical Journal Letters, 715, L49, 2010 (21) V. Acciari et al., VERITAS monitoring of the variable gamma-ray source M87, Astrophysical Journal, 716, 819, 2010 (22) V. Acciari et al., Discovery of VHE Gamma-ray Emission from the SNR G , Astrophysical Journal Letters, 719, L69, 2010 (23) V. Acciari et al., VERITAS Search for VHE Gamma-ray Emission from Dwarf Spheroidal Galaxies, Astrophysical Journal, 720, 1174, 2010 (24) A. Abdo et al., Multi-wavelength Observations of Flaring Gamma-ray Blazar 3C 66A in

15 October 2008, Astrophysical Journal, 726, 43, 2011 (25) A. Abdo et al., Insights Into the High-energy γ-ray Emission of Markarian 501 from Extensive Multifrequency Observations in the Fermi Era, Astrophysical Journal, 727, 129, 2011 (26) V. Acciari et al., Spectral Energy Distribution of Markarian 501: Quiescent State vs. Extreme Outburst, Astrophysical Journal, 729, 2, 2011 (27) V. Acciari et al., Discovery of TeV Gamma-ray Emission From Tycho's Supernova Remnant, Astrophysical Journal Letters, 730, L20, 2011 (28) V. Acciari et al., Gamma-ray observations of the Be/pulsar binary 1A during a giant X-ray outburst, Astrophysical Journal, 733, 96, 2011 (29) E. Aliu et al., VERITAS Observations of the Unusual Extragalactic Transient Swift J , Astrophysical Journal Letters, 738, L30, 2011 (30) V. Acciari et al., VERITAS Observations of the TeV Binary LSI during , Astrophysical Journal, 738, 3, 2011 (31) V. Acciari et al., TeV and Multi-wavelength Observations of Mrk 421 in , Astrophysical Journal, 738, 25, 2011 (32) V. Acciari et al., Multiwavelength Observations of the VHE Blazar 1ES , Astrophysical Journal, 738, 169, 2011 (33) E. Aliu et al., Detection of Pulsed Gamma Rays Above 100 GeV from the Crab Pulsar, Science, 334, 69, 2011 (34) E. Aliu et al., Multiwavelength Observations of the Previously Unidentified Blazar RXJ , Astrophysical Journal, 742, 127, 2011 (35) V. Acciari et al., VERITAS Observations of Gamma-ray Bursts Detected by Swift, Astrophysical Journal, 743, 62, 2011 (36) A. Abramowski et al., The 2010 VHE Flare & 10 Years of Multi-Wavelength Observations of M87 Astrophysical Journal, 746, 151, 2012 (37) E. Aliu et al., VERITAS observations of day-scale flaring of M87 in April 2010, Astrophysical Journal, 746, 141, 2012 (38) E. Aliu et al., VERITAS deep observations of the dwarf spheroidal galaxy Segue 1, Physical Review D, 85, , 2012 (39) E. Aliu et al., Discovery of High-energy and Very High Energy γ-ray Emission from the Blazar RBS 0413 Astrophysical Journal, 750, 94, 2012 (40) E. Aliu et al., VERITAS Observations of the Nova in V407 Cygni, Astrophysical Journal, 754, 77, 2012 (41) E. Aliu et al., Multiwavelength Observations of the AGN 1ES with VERITAS, Fermi-LAT, Swift-XRT, and MDM, Astrophysical Journal, 755, 118, 2012 (42) T. Arlen et al., Constraints on Cosmic Rays Magnetic Fields and Dark Matter from Gammaray Observations of the Coma Cluster of Galaxies with VERITAS and Fermi, Astrophysical Journal, 757, 123, 2012 (43) E. Aliu et al., VERITAS Observations of Six Bright Hard-Spectrum Fermi-LAT Blazars, Astrophysical Journal, 759, 102, 2012 (44) E. Aliu et al., Search for a correlation between very-high-energy gamma rays and giant radio pulses in the Crab pulsar, Astrophysical Journal, 760, 136, 2012 (45) T. Arlen et al., Rapid TeV Gamma-ray Flaring of BL Lacertae, Astrophysical Journal, 762, 92, 2013 (46) E. Aliu et al., Discovery of TeV Gamma-ray Emission from CTA 1 by VERITAS, Astrophysical Journal, 764, 38, 2013 (47) E. Aliu et al., Discovery of TeV Gamma-ray Emission Toward Supernova Remnant SNR G , Astrophysical Journal, 770, 93, 2013