AS5_random

short, unrelated, randomly ordered ideas for the After Sloan 5 Blue Skies process

Instructions to authors:

Fork this repository, add a bullet point to the list of ideas below, and add your name to the author list, and generate a pull request. If you add an idea, you must add your name, and vice versa.

Style notes:

Keep it brief, but specific. Boldface a phrase or sentence that serves as the "title" for your idea.

Authors:

• Joel Brownstein (University of Utah)
• Joe Burchett (New Mexico State University)
• Andy Casey (Monash University)
• Jamey Eriksen (Apache Point Observatory)
• Carrie Filion (Flatiron Institute)
• David W. Hogg (Flatiron Institute)
• Ilija Medan (Vanderbilt University)
• Sean Morrison (University of Illinois Urbana-Champaign)
• Moire Prescott (New Mexico State University)
• José Sánchez-Gallego (University of Washington)
• Andrew Saydjari (Princeton University)
• Zach Way (Georgia State University)

Ideas:

• Create a live auction for spectra. The interface is: Choose your instrument, your observing conditions, exposure time, time constraints, and so on, and a maximum amount you are willing to pay for one spectrum (the bid). At every interval (15 minutes, say), we find the telescope pointing and field configurations that maximize revenue. We charge a discounted rate to the bids, which is discounted because we bill a total amount to all the winning bids that delivers to us a total revenue that is halfway between the best field's total of bids and the second-best field's total of bids (I believe there is research about this structure). — Hogg

• Follow the LSST footprint, by some algorithm (choices are required, because LSST does many pointings per any reasonable 2.5-m pointing). Operate a time-domain survey that is always pointing at a field that was observed by LSST within the last N minutes. Permits all-sky survey targets and also LSST-triggered target-of-opportunity targets in the same program. Could be combined with the live auction idea above. — Hogg

• Fill out the binary system parameter space. There will be many binary systems where Gaia DR4 will be unable to solve the complete orbit. Some will be too faint, particularly for stars in the dusty disk. Other systems might be multi-modal: two or more likely regions of binary parameter space. In these situations, a (possibly) well-timed RV precise (~100 m/s) RV measurement from APOGEE will resolve the orbit. — Casey

• A noisier expansion of Galactic Genesis. APOGEE is the only current or planned spectrograph that can survey the Galactic plane at scale. GALAH, 4MOST, and WEAVE either avoid the plane entirely, or produce shallow samples. A low S/N spectrum (~20) for millions more Galactic Genesis targets would be sufficient to measure a radial velocity, to measure interstellar dust along the line of sight. — Casey

• Narrow-band photometry yields abundance indicators for stellar litmus tests. There are stellar astrophysics questions where competing physical explanations might be differentiated by the measurement of a single absorption line. For example, is this star lithium-rich? Is there also high berylium, or high chromospheric activity in the helium lines? Is the lead abundance in this star very high (indicating one nucleosynthetic process), or very low (indicating the other)? With good models of stellar spectra, an extremely narrow-band photometric filter can be sufficient to perform these litmus tests for large numbers of stars, where high-resolution spectroscopy would otherwise be too expensive. — Casey

• Bridging the gap between low- and high-resolution spectroscopy for low-luminosity stars. Low-luminosity stars are ubiquitous across the sky and are observed in large numbers in surveys like Gaia. Notably in Gaia DR3, a large number of these stars have low-resolution Gaia XP spectra. In SDSS however, 99% of APOGEE spectra are of targets with M_G < 10.5 mag, meaning the vast majority of these low-luminosity objects haven't been systematically targeted in higher resolution spectroscopic surveys. We propose to make these targets a high priority in a future iteration of SDSS. This would require the creation of a new APOGEE observing mode with extended exposure times that achieve sufficient signal-to-noise for these fainter objects. Specifically, APOGEE fibers could be parked on low-luminosity (and other faint) objects for long exposure times, while BOSS fibers are reconfigured at the typical 15 minute exposure time cadence. This would be the first time a large number of these low-luminosity objects are systematically observed with high resolution spectroscopy, which would deepen our understanding of low-mass stars and expand our overlap with other surveys. — Medan and Way

• LVM in the North for M31 and Friends LVM is doing incredible work in the Southern hemisphere; why not add a second LVM and extend the footprint to include the Northern hemisphere, too? In addition to the Milky Way science that LVM can do in the North, it would also be able to provide exquisite observations of M31 and M33. LVM North data for the disks and haloes of M31 and M33 (and the bridge between them!) would allow us to create unique maps of the kinematics and chemistry of our nearest spiral galaxy neighbors, ultimately better contextualizing our own Galaxy. — Filion

• A MaNGA-style approach to studying AGN with extended emission line regions tracing outflows or ionization echoes. This would presumably have to be restricted to lower z cases (e.g., the Voorwerpje) due to the typical angular sizes and surface brightnesses, but it would allow for detailed studies of AGN outflows and would also probe extremely long time-baselines in the case of ionization echoes (i.e., 10,000-50,000 years). One would need to think about the available sample sizes, whether this would be feasible in terms of sensitivities, and what we could learn beyond what was done using AGN hosts in the original MaNGA sample. — Moire

• Mapping Spiral Arms in Dust APOGEE is now achieving velocity resolution with DIBs comparable to CO gas studies of Galactic structure. This capability is unrivaled and provides a unique opportunity to SEE the spiral arm structure of our own Milky Way, because DIBs have the advantage of partial distance information that admits a 4D reconstruction of Galactic structure. Observations in the Galactic Plane, targeted off of DECaPS2, VVV, and Roman GPS will provide a denser spectroscopic sampling of lines-of-sight necessary to constrain these reconstructions. This project can be carried out synergistically with other stellar proposals in the plane, but its optimization benefits from volume, uniformity, and "dustiness" of the targets. Additional fibers, increasing the multiplexing of APOGEE, would be a benefit, but this can be carried out with current software and hardware. — Saydjari

• A comprehensive scan of the sky for signatures of strong gravitational lenses. In the AS5 era, the availability of advanced instruments for followup confirmation make the SDSS BOSS spectograph, at redshifts between 0.3 -- 1.0, and MaNGA IFU instrument, at resdhifts less than 0.3, ideal tools to scan the sky for multiple redshifts in the same line-of-sight. This type of spectrographic detection has provided the most successful method of detecting strong galaxy-galaxy gravitational lenses (e.g. SLACS and SWELLS for SDSS-II, BELLS for SDSS-III, and SILO for SDSS-IV with CASIGLO providing machine learning deep-learning neural network). The extension of the search for strong gravitational lenses into the FPS era for AS5 would allow multiple visits, or long exposure times, in order to generate sufficient S/N to better resolve the emission-lines and velocity dispersion measurements used by the detection algorithms that have been steadily improved since the original Burles and Bolton code. In addition the extension to include QSO lenses would enable the transient detections related to the (second-order) time-delay effect, which has not been spectroscopically observed. A comprehensive scan of the sky for gravitational lenses including followup imaging to allow lens models is extremely valuable, because gravitational lenses provide a direct probe into the effect of dark matter at the galaxy's Einstein radius, in principle allowing the mathematical dissection into luminous and dark components. The opportunity to create a collaboration of many non-SDSS folks from the gravitational lensing community could also provide individual "slots" for the AS5 budget, if such a proposal were to be made attractive to faculty and postdocs that strongly depend on these rare (approximately one in a thousand) astronomical targets, with significant research impact following 2 years of AS5 observing time, or 4 more years to include transient phenomena, such as the time delay effect. — Brownstein

• Modernisation and revamping of APO BOSS hardware. The BOSS spectrographs will be over 15 years old by the end of SDSS-V, with some hardware dating back to the original SDSS spectrograph. While one of the spectrographs (sp2) received significant maintenance prior to be moved to LCO for SDSS-V observations, the sp1 hardware (the BOSS spectrograph that stayed at APO) has not seen significant modifications since it was originally assembled. In case of an SDSS-VI project that would continue making use of the BOSS spectrographs, significant maintenance would be required. We propose an overhaul of BOSS sp1 similar to the one carried out for sp2. This overhaul would include replacing the camera and readout electronics with an STA Archon controller, replacing the mechanical hardware (shutter and Hartmann door pneumatics, collimator motors), data acquisition software, and potentially the LN2 auto-fill system. The experience gained with sp2 at LCO would make this overhaul significantly simpler and it could be carried out with little downtime and with only a fraction of the development and troubleshooting effort. — Sánchez-Gallego, Morrison, Eriksen

• Capitalize on up-the-ramp to diversify targets and observing strategies. The APOGEE detectors are up-the-ramp. Thus it is possible to read out sub-exposures of subframes of the detector, after the fact (ie, no need to do this in real time, provided that we preserve enough up-the-ramp samples in the readout). Thus it is possible to look at stellar variability (say) within an exposure, or on timescales shorter than an individual exposure. Thus it is also possible that we could re-assign a fiber (from a bright target, say) mid-exposure to another target. Then, at data-analysis time, these multiple targets could be separately extracted by performing custom extractions in the up-the-ramp data. This project might not have good science cases: Maybe we don't have enough target diversity in any field to make use of this? Also, this program would be very highly dependent on fully understanding any persistence effects in the APOGEE detectors, especially if we are observing stars of very different brightnesses through the same fibers. Finally, this project would require a substantial overhaul not just to the pipelines but to the data model, since now a fiber-exposure no longer corresponds to a unique target! But this capability could be made to work, I believe, if there is a good use case. — Hogg

• Extend Local Volume Mapper to The Circumgalactic Mapper. The inescapable facts that a) galaxies do not have enough cold, dense gas to form stars at their current rates and b) these same galaxies exhibit ubiquitous outflows beg us track galaxy fueling and feedback vis a vis their vast gas reservoirs in the circumgalactic medium (CGM). Recent IFU surveys have made great strides in detecting extended CGM emission from optical [OII], [OIII], and Hbeta lines out to 20-30 kpc around relatively distant galaxies (z=0.01-0.5; e.g., Nielsen et al. 2023, Rupke et al. 2019) to those proposed for future LVM extragalactic mapping (see Blue Skies White Paper by Egorov et al.). While the aforementioned CGM emission was mapped with Keck/KCWI, the surface brightness limits of those data are commensurate with those planned for LVM (few x 10^-18 erg/s/cm²/arcsec²). Piggybacking on the proposed LVM extensions, extending these observations to larger galactocentric radii would enable an unprecedented, but critical, characterization of the circumgalactic environs around Local Group galaxies (and possibly those beyond).