Evidence for shock-heated gas in the Taffy Galaxies and Bridge from Optical Emission-Line IFU spectroscopy

We present optical IFU observations of the Taffy system (UGC 12914/15); named for the radio emission that stretches between the two galaxies. Given that these gas rich galaxies are believed to have recently collided head-on, the pair exhibits a surprisingly normal total (sub-LIRG) IR luminosity ($\mathrm{L_{FIR} \sim 4.5 \times 10^{10}}$ L$_\odot$). Previous observations have demonstrated that a large quantity of molecular and neutral gas have been drawn out of the galaxies into a massive multi-phase bridge. We present, for the first time, spatially resolved spectroscopy of the ionized gas in the system. The results show that the ionized gas is highly disturbed kinematically, with gas spread in two main filaments between the two galaxies. The line profiles exhibit widespread double components in both the bridge and parts of the disks of the galaxies. We investigate the spatial distribution of the excitation properties of the ionized gas using emission-line diagnostic diagrams, and conclude that large quantities (up to 40$\%$) of the emission from the entire system is consistent with gas heated in $\sim$200 \kms\ shocks. While the shocked gas is mainly associated with the bridge, there is a significant amount of shocked gas associated with both galaxies. Confirming other multi-wavelength indicators, the results suggest that the effects of shocks and turbulence can continue to be felt in a high-speed galaxy collision long after the collision has occurred. The persistence of shocks in the Taffy system may explain the relatively low current star formation rates in the system as a whole.Comment: 19 pages, 13 figures. Accepted for publication in Ap

FIGS -- Faint Infrared Grism Survey: Description and Data Reduction

The Faint Infrared Grism Survey (FIGS) is a deep Hubble Space Telescope (HST) WFC3/IR (Wide Field Camera 3 Infrared) slitless spectroscopic survey of four deep fields. Two fields are located in the Great Observatories Origins Deep Survey-North (GOODS-N) area and two fields are located in the Great Observatories Origins Deep Survey-South (GOODS-S) area. One of the southern fields selected is the Hubble Ultra Deep Field. Each of these four fields were observed using the WFC3/G102 grism (0.8$\mu m$-1.15$\mu m$ continuous coverage) with a total exposure time of 40 orbits (~ 100 kilo-seconds) per field. This reaches a 3 sigma continuum depth of ~26 AB magnitudes and probes emission lines to $\approx 10^{-17}\ erg\ s^{-1} \ cm^{-2}$. This paper details the four FIGS fields and the overall observational strategy of the project. A detailed description of the Simulation Based Extraction (SBE) method used to extract and combine over 10000 spectra of over 2000 distinct sources brighter than m_F105W=26.5 mag is provided. High fidelity simulations of the observations is shown to significantly improve the background subtraction process, the spectral contamination estimates, and the final flux calibration. This allows for the combination of multiple spectra to produce a final high quality, deep, 1D-spectra for each object in the survey.Comment: 21 Pages. 17 Figures. To appear in Ap

Evidence for Shock-heated Gas in the Taffy Galaxies and Bridge from Optical Emission-line IFU Spectroscopy

We present optical integral field unit observations of the Taffy system (UGC 12914/15), named for the radio emission that stretches between the two galaxies. Given that these gas-rich galaxies are believed to have recently collided head-on, the pair exhibits a surprisingly normal total (sub-LIRG) IR luminosity (L_(FIR) ~ 4.5 × 10^(10) L_⊙). Previous observations have demonstrated that a large quantity of molecular and neutral gas has been drawn out of the galaxies into a massive multiphase bridge. We present, for the first time, spatially resolved spectroscopy of the ionized gas in the system. The results show that the ionized gas is highly disturbed kinematically, with gas spread in two main filaments between the two galaxies. The line profiles exhibit widespread double components in both the bridge and parts of the disks of the galaxies. We investigate the spatial distribution of the excitation properties of the ionized gas using emission-line diagnostic diagrams and conclude that a large quantity (up to 40%) of the emission from the entire system is consistent with gas heated in ~200 km s^(−1) shocks. While the shocked gas is mainly associated with the bridge, there is a significant amount of shocked gas associated with both galaxies. Confirming other multiwavelength indicators, the results suggest that the effects of shocks and turbulence can continue to be felt in a high-speed galaxy collision long after the collision has occurred. The persistence of shocks in the Taffy system may explain the relatively low current star formation rates in the system as a whole

Science Impacts of the SPHEREx All-Sky Optical to Near-Infrared Spectral Survey: Report of a Community Workshop Examining Extragalactic, Galactic, Stellar and Planetary Science

SPHEREx is a proposed SMEX mission selected for Phase A. SPHEREx will carry out the first all-sky spectral survey and provide for every 6.2" pixel a spectra between 0.75 and 4.18 $\mu$m [with R$\sim$41.4] and 4.18 and 5.00 $\mu$m [with R$\sim$135]. The SPHEREx team has proposed three specific science investigations to be carried out with this unique data set: cosmic inflation, interstellar and circumstellar ices, and the extra-galactic background light. It is readily apparent, however, that many other questions in astrophysics and planetary sciences could be addressed with the SPHEREx data. The SPHEREx team convened a community workshop in February 2016, with the intent of enlisting the aid of a larger group of scientists in defining these questions. This paper summarizes the rich and varied menu of investigations that was laid out. It includes studies of the composition of main belt and Trojan/Greek asteroids; mapping the zodiacal light with unprecedented spatial and spectral resolution; identifying and studying very low-metallicity stars; improving stellar parameters in order to better characterize transiting exoplanets; studying aliphatic and aromatic carbon-bearing molecules in the interstellar medium; mapping star formation rates in nearby galaxies; determining the redshift of clusters of galaxies; identifying high redshift quasars over the full sky; and providing a NIR spectrum for most eROSITA X-ray sources. All of these investigations, and others not listed here, can be carried out with the nominal all-sky spectra to be produced by SPHEREx. In addition, the workshop defined enhanced data products and user tools which would facilitate some of these scientific studies. Finally, the workshop noted the high degrees of synergy between SPHEREx and a number of other current or forthcoming programs, including JWST, WFIRST, Euclid, GAIA, K2/Kepler, TESS, eROSITA and LSST.Comment: Report of the First SPHEREx Community Workshop, http://spherex.caltech.edu/Workshop.html , 84 pages, 28 figure

A comprehensive study of Hα\alpha emitters at z∼z \sim 0.62 in the DAWN survey: the need for deep and wide regions

We present new estimates of the luminosity function (LF) and star formation rate density (SFRD) for an H$\alpha$ selected sample at $z\sim0.62$ from the Deep And Wide Narrow-band (DAWN) survey. Our results are based on a new H$\alpha$ sample in the extended COSMOS region (compared to Coughlin et al. 2018) with the inclusion of flanking fields, resulting in a total area coverage of $\sim$1.5 deg$^2$. A total of 241 H$\alpha$ emitters were selected based on robust selection criteria using spectro-photometric redshifts and broadband color-color classification. We explore the effect of different dust correction prescriptions by calculating the LF and SFRD using a constant dust extinction correction, A{$_{\textrm{H}\alpha}=1$} mag, a luminosity-dependent correction, and a stellar-mass dependent correction. The resulting H$\alpha$ LFs are well fitted using Schechter functions with best-fit parameters: L$^*=10^{42.24}$ erg s$^{-1}$, $\phi^*=10^{-2.85}$ Mpc$^{-3}$, $\alpha = -1.62$ for constant dust correction, L$^*=10^{42.31}$ erg s$^{-1}$, $\phi^*=10^{-2.8}$ Mpc$^{-3}$, $\alpha=-1.39$ for luminosity-dependent dust correction, and L$^*=10^{42.36}$ erg s$^{-1}$, $\phi^*=10^{-2.91}$ Mpc$^{-3}$, $\alpha = -1.48$, for stellar mass-dependent dust correction. The deep and wide nature of the DAWN survey effectively samples H$\alpha$ emitters over a wide range of luminosities, thereby providing better constraints on both the faint and bright end of the LF. Also, the SFRD estimates $\rho_{\textrm{SFR}}=10^{-1.39}$ M$_{\odot}$yr$^{-1}$Mpc$^{-3}$ (constant dust correction), $\rho_{\textrm{SFR}}=10^{-1.47}$ M$_{\odot}$yr$^{-1}$Mpc$^{-3}$ (luminosity-dependent dust correction), and $\rho_{\textrm{SFR}}=10^{-1.49}$ M$_{\odot}$yr$^{-1}$Mpc$^{-3}$ (stellar mass-dependent dust correction) are in good agreement with the evolution of SFRD across redshifts ($0 < z < 2$) seen from previous H$\alpha$ surveys.Comment: 16 pages, 8 figures, Accepted for publication in Ap

Investigating Galaxy Evolution and Active Galactic Nucleus Feedback with the Sunyaev-Zel'dovich Effect

International audienceGalaxy formation is a complex process with aspects that are still very uncertain. A mechanism that has been used in simulations to successfully resolve several of these outstanding issues is active galactic nucleus (AGN) feedback, where a large amount of energy is driven outwards through a galaxy and the surrounding region by a central supermassive black hole. A promising method for directly measuring this energy is by looking at small increases in the energy of the cosmic microwave background (CMB) photons as they pass through hot gas, known as the thermal Sunyaev-Zel'dovich (tSZ) effect. I will present work done to measure the tSZ effect around a large number of 0.5 5x10^11 M_Sun), favor the Horizon-NoAGN results at more than a 6-sigma level. These results indicate that AGN feedback may be milder than often predicted, and they also highlight the promising nature of tSZ effect measurements and the need for further work using better data and more varied simulations

High-Precision Redshifts for Type Ia Supernovae with the Nancy Grace Roman Space Telescope P127 Prism

We present results from simulating slitless spectroscopic observations with the Nancy Grace Roman Space Telescope's (Roman) Wide-Field Instrument (WFI) P127 prism spanning 0.75 $\mu m$ to 1.8 $\mu m$. We quantify the efficiency of recovered Type Ia supernovae (SNe Ia) redshifts, as a function of P127 prism exposure time, to guide planning for future observing programs with the Roman prism. Generating the two-dimensional dispersed images and extracting one-dimensional spectra is done with the slitless spectroscopy package pyLINEAR along with custom-written software. From the analysis of 1698 simulated SN Ia P127 prism spectra, we show the efficiency of recovering SN redshifts to $z\lesssim3.0$, highlighting the exceptional sensitivity of the Roman P127 prism. Redshift recovery is assessed by setting a requirement of $\sigma_z = (\left|z - z_\mathrm{true} \right|)/(1+z) \leq 0.01$. We find that 3 hr exposures are sufficient for meeting this requirement, for $\gtrsim 50\%$ of the sample of mock SNe Ia at $z\approx2$ and within $\pm5$ days of rest-frame maximum light in the optical. We also show that a 1 hr integration of Roman can achieve the same precision in completeness to a depth of $24.4 \pm 0.06$ AB mag (or $z\lesssim 1$). Implications for cosmological studies with Roman P127 prism spectra of SNe Ia are also discussed.Comment: 17 pages, 10 figures. Submitted to AAS journals. Comments welcom

A Synthetic Roman Space Telescope High-Latitude Time-Domain Survey: Supernovae in the Deep Field

NASA will launch the Nancy Grace Roman Space Telescope (Roman) in the second half of this decade, which will allow for a generation-defining measurement of dark energy through multiple probes, including Type Ia supernovae (SNe Ia). To improve decisions on survey strategy, we have created the first simulations of realistic Roman images that include artificial SNe Ia injected as point sources in the images. Our analysis combines work done on Roman simulations for weak gravitational lensing studies as well as catalog-level simulations of SN samples. We have created a time series of images over two years containing $\sim$ 1,050 SNe Ia, covering a 1 square degree subarea of a planned 5 square degree deep survey. We have released these images publicly for community use along with input catalogs of all injected sources. We create secondary products from these images by generating coadded images and demonstrating recovery of transient sources using image subtraction. We perform first-use analyses on these images in order to measure galaxy-detection efficiency, point source-detection efficiency, and host-galaxy association biases. The simulated images can be found here: https://roman.ipac.caltech.edu/sims/SN_Survey_Image_sim.html.Comment: 12 pages, 12 figures. Submitted to MNRAS. For simulated images see https://roman.ipac.caltech.edu/sims/SN_Survey_Image_sim.htm