This paper traces the 37 years of my career dedicated to the development ofintegral field spectroscopy (IFS), highlighting significant milestones andadvancements. This extensive journey encompasses three generations of IFS: theinitial prototype TIGER at CFHT, the first generation including OASIS at CFHTand SAURON at WHT, the second generation with MUSE at VLT, and the potentialthird generation represented by the Wide-field Spectroscopic Telescope (WST)project. Throughout, I discuss the lessons learned at each stage and provide myperspective on the future of IFS.

Gas metallicity, ionization parameter, and gas pressure can affect theobserved ratios of specific strong emission lines within galaxies. While thetheoretical strong lines diagnostics for gas metallicity, ionizationparameters, and gas pressure in star-forming regions are well-established,theoretical diagnostics for active galactic nuclei (AGNs) narrow line regionsare still lacking. In Zhu et al. (2023), we presented a new AGN model thatprovides the best predictions for observations spanning the UV, optical, andinfrared wavelengths. This paper presents a suite of theoretical diagnosticsfor the gas metallicity, ionization parameter, gas pressure, and the peakenergy in AGN ionizing radiation field $E_{peak}$ for AGN narrow-line regionsspanning the UV and optical wavelengths. We investigate the model dependency onthe ionization parameter, gas pressure, $E_{peak}$, and the nitrogen scalingrelation and make recommendations on metallicity diagnostics that are mostrobust against these parameters. We test our new AGN metallicity diagnosticsusing optical galaxy spectra from Sloan Digital Sky Survey DR16. These testsshow that the metallicities measured from different diagnostics in this paperare consistent within $\sim0.3$ dex. We compare consistent HII and AGNdiagnostics and demonstrate that HII and AGN diagnostics should not be usedinterchangeably. With a wide wavelength coverage, we anticipate that these AGNdiagnostics will enable new metallicity studies of galaxies dominated by AGN.

his paper explores what kinds of questions are best served by the waygenerative AI (GenAI) using Large Language Models(LLMs) that aggregate andpackage knowledge, and when traditional curated web-sourced search resultsserve users better. An experiment compared product searches using ChatGPT, Google search engine,or both helped us understand more about the compelling nature of generatedresponses. The experiment showed GenAI can speed up some explorations anddecisions. We describe how search can deepen the testing of facts, logic, andcontext. We show where existing and emerging knowledge paradigms can helpknowledge exploration in different ways. Experimenting with searches, our probes showed the value for curated websearch provides for very specific, less popularly-known knowledge. GenAIexcelled at bringing together knowledge for broad, relatively well-knowntopics. The value of curated and aggregated knowledge for different kinds ofknowledge reflected in different user goals. We developed a taxonomy todistinguishing when users are best served by these two approaches.

The most massive early-type galaxies (ETGs) are known to form throughnumerous galaxy mergers. Thus, it is intriguing to study whether theirformation in low-density environments, where nearby companions are almostabsent, is associated with mergers, which are directly traced by tidalfeatures. Using the 436 most massive ETGs with$M_\mathrm{star}>10^{11.2}\,M_{\odot}$ at $z<0.04$, we determine the variationin the fraction of massive ETGs with tidal features ($f_T$) across differentenvironments and verify whether the most massive ETGs commonly have tidalfeatures in very low density environments. Our main discovery is that the mostmassive ETGs exhibit tidal features more frequently in lower-densityenvironments. In the highest-density environments, like galaxy clusters, $f_T$is $0.21\pm0.06$, while in the lowest-density environments it triples to$0.62\pm0.06$. This trend is stronger for more extremely massive ETGs, with$f_T$ reaching $0.92\pm0.08$ in the lowest-density environments. Oneexplanation for our finding is that the most massive ETGs in lower-densityenvironments have genuinely experienced recent mergers more frequently thantheir counterparts in higher-density environments, suggesting that they possessextended formation histories that continue into the present. Anotherpossibility is that tidal features last shorter in denser environments owing toexternal factors inherent in these environments. Our additional findings thatmassive ETGs with bluer $u-r$ colors are a more dominant driver of our maindiscovery and that dust lanes are more commonly observed in massive ETGs inlow-density environments imply that gas-abundant mergers primarily contributeto the increased rate of recent mergers in low-density environments.