RELIABLE COMPREHENSIVE ATOMIC DATA ARE NEEDED TO QUANTIFY THE TEMPERATURE AND HEAVY-ELEMENT CONTENT OF THE STARS AND GALAXIES THAT GIVE RISE TO OBSERVED FLUXES AND SPECTRA. CURRENTLY FE I LABORATORY MEASUREMENTS OF THE ENERGIES OF ITS HIGH-LYING LEVELS ARE WOEFULLY INCOMPLETE. THE RESULT IS A LARGE NUMBER OF UNIDENTIFIED ABSORPTION LINES IN THE UV AND THE INFRARED. IN THE RED AND INFRARED LINES OF OTHER NEUTRAL ELEMENTS SUCH AS CALCIUM AND SILICON HAVE A SIGNIFICANT PRESENCE AS WELL. WE HAVE MADE SIGNIFICANT PROGRESS ON FE I LINE IDENTIFICATION BY USING HIGH-RESOLUTION HIGH-QUALITY ARCHIVAL ULTRAVIOLET AND OPTICAL SPECTRA OF A DOZEN WARM AND COOL STARS AS THE FE I LABORATORY SOURCE RELYING ON THE WARMER TEMPERATURES OF THESE STARS TO POPULATE HIGHER EXCITATION LEVELS THAN IS POSSIBLE WITH THE NIST LABORATORY FURNACE. WE ESTABLISHED THE IDENTIFICATION AND ENERGY OF 124 PREVIOUSLY UNKNOWN FE I LEVELS BY DEMANDING AN EXACT MATCH OF THE POSITIONS OF AT LEAST FOUR KURUCZ PREDICTED LINES OF EACH UNKNOWN LEVEL TO OBSERVED BUT UNIDENTIFIED STELLAR ABSORPTION FEATURES (PETERSON&KURUCZ 2015; PETERSON KURUCZ &AYRES 2017). FOR EACH NEWLY-IDENTIFIED LINE THAT WAS SUFFICIENTLY STRONG AND UNBLENDED WE DETERMINED A SEMI-EMPIRICAL GF-VALUE BY FORCING ITS OBSERVED STRENGTH TO AGREE WITH THAT PREDICTED BY THE SPECTRAL CALCULATIONS FOR EACH RELEVANT STAR. LEVEL IDENTIFICATIONS THEIR ENERGY LEVELS AND THESE GF-VALUES ARE ALL PART OF EACH PUBLICATION AND THE COMPLETE FE I LINE LIST WITH THEORETICAL GF-VALUES IS MADE AVAILABLE ON THE KURUCZ WEB SITE AT THE SAME TIME. HERE WE PROPOSE TO ADD STELLAR INFRARED SPECTRAL COMPARISONS TO OUR ARSENAL TO EXPAND THE ENERGY RANGE OF THE SEARCH FOR LINES OF AN INDIVIDUAL LEVEL. THIS SHOULD ADD ENOUGH LINES TO IDENTIFY A SIZABLE NUMBER OF OTHERWISE INTRACTABLE LEVELS REFINE THE ENERGIES OF OUR PREVIOUS DETERMINATIONS AND CONTRIBUTE RELIABLE GF-VALUES FOR ALL SUFFICIENTLY UNBLENDED INFRARED LINES. OUR GOAL IS TO DOUBLE THE NUMBER OF OUR FE I LEVEL IDENTIFICATIONS WHICH SHOULD ADD IDENTIFICATIONS FOR NEARLY 2000 FEATURES THAT ARE POTENTIALLY DETECTABLE IN SPECTRA FROM THE UV TO THE MID-IR IN THE SUN AND RED GIANTS. WE PLAN TO ADD IDENTIFICATIONS FOR OTHER NEUTRAL SPECIES WHERE FEASIBLE. OUR PROGRAM IS HIGHLY RELEVANT TO THE LABORATORY ASTROPHYSICS SOLICITATION OF APRA. IT IS A SEMI-EMPIRICAL STUDY DESIGNED TO IMPROVE THE QUANTITATIVE UNDERSTANDING OF THE FE I ATOM BY INTERPRETING OBSERVED SOLAR AND STELLAR SPECTRA AS THE "LABORATORY" SOURCE OF FE I FEATURES IN ABSORPTION WITH THEORETICAL MODELING OF THE FE I ATOM AND OF THE SPECTRA THEMSELVES OVER A PANCHROMATIC WAVELENGTH RANGE FROM THE ULTRAVIOLET TO THE PROPOSED INFRARED. OUR INFRARED SPECTRAL OBSERVATIONS AND ANALYSIS TECHNIQUES ARE ALREADY WELL SUITED TO THIS TASK. FIG. 1 OF PETERSON ET AL. (2017) SHOWED THAT OUR ANALYSIS REPRODUCES VERY WELL THE HIGH-QUALITY HIGH-RESOLUTION SPECTRA IN THE H BAND OBTAINED BY OTHERS FOR THREE STARS SPANNING A TEMPERATURE RANGE OF 1500K. IT ALSO ILLUSTRATES HOW THE INFRARED SPECTRA PINPOINT THE POSITIONS OF NEWLY-IDENTIFIED FE I LINES WHICH MORE TIGHTLY CONSTRAINS THE ENERGIES FOR THE CORRESPONDING LEVELS. INFRARED LINE IDENTIFICATIONS ARE PARTICULARLY TIMELY FOR CLARIFICATIONS OF FLUX DISTRIBUTIONS OF INFRARED SOURCES AT VIRTUALLY ALL REDSHIFTS SUCH AS THOSE TO BE CHARACTERIZED WITH SPECTROSCOPY FROM JWST NIRCAM NIRSPEC AND MIRI AND KECK NIRES. IN HIGH-RESOLUTION ECHELLE SPECTRA SUCH AS THOSE FROM HST STIS AND KECK HIRES OUR FINDINGS WILL IMPROVE SUBSTANTIALLY THE MODELING OF INDIVIDUAL STELLAR UV SPECTRAL FEATURES AND THE DEFINITION OF THE UV CONTINUUM ESSENTIALS FOR DERIVING RELIABLE ELEMENTAL ABUNDANCES.
$475,769FY2020National Aeronautics and Space AdministrationNASA
Seti Institute, Mountain View CA