The Cosmic Ultraviolet Baryon Survey (CUBS) is a large HST Cycle 25 GO

program designed to map 'dark' baryonic structures in the crucial but

unconstrained epoch between redshift z = 0.4 and z ~ 2.  The CUBS

program aims to combine absorption-line spectroscopy of 15 UV-bright

QSOs at z > 0.8 with matching deep galaxy survey data.  This legacy

sample enables systematic studies of the co-evolution of galaxies and

diffuse circumgalactic and intergalactic gas at a time when the star

formation rate density undergoes its most dramatic changes, and

provide key insights into how galaxy growth is regulated by accretion

and outflows.  In this talk, I will show some of the first results

from the CUBS program.

The AGN STORM (space telescope optical reverberation mapping) was an intense multi-wavelength campaign that observed NGC 5548, a type I Seyfert galaxy (z = 0.01717), for 180 months during 2014. The main goal was to determine the geometry and mass of the object through the reverberation mapping method, using 6 space-based and 21 ground-based telescopes.

NGC 5548 exhibited unusual behavior during the campaign: First, a strong soft X-ray absorption was present due to the appearance of a line of sight (LOS) obscurer between the central source and the observer. Then, it was discovered that broad emission lines and the UV continuum (emission-line holiday) decorrelated for 2 months during the observations. Finally, it was discovered that the same decorrelation happened between the narrow absorption lines and the continuum (absorption-line holiday).

We joined the campaign in 2017 to understand the behavior of NGC 5548 during the time of obscuration and holiday. We showed that LOS obscurer is the upper part of a symmetric continues disk-wind launched from the accretion disk. The base of this wind is called the equatorial obscurer and it persistently shields the BLR.  Based on Cloudy’s prediction, the variations of the covering factor of the LOS obscurer explains the absorption-line holiday, while changes in the column density/density of the equatorial obscurer explain the emission-line holiday.

Recently, we found out that the base of the wind has significant optical depth to electron scattering and must be a contributor to the Compton reflector. This reflector acts as a mirror and would reflect BLR emission. The wind’s optical depth explains why the far sides of the BLR are unexpectedly faint. During this talk, I will explain how our modeling resulted in this discovery, and also how the disk-wind model scenario fits into observations. 

I will report on the most recent discoveries by the NASA Neil Gehrels Swift mission of Active Galactic Nuclei (AGN) with high amplitude variabilities. While AGN typically vary with factors of 3 on times scales of days to years, some AGN exhibit outbursts or dramatic drops in the X-ray fluxes by factors of even more than 100. Among the most extreme cases are the Narrow-Line Seyfert 1 galaxy WPVS 007 which appears to be extremely X-ray faint, and the Seyfert 1.9 galaxy IC 3599 which has shown repeated X-ray flaring, most likely due to accretion disk instabilities. Swift capability of following objects for more than a decade with simultaneous X-ray and UV observations has allowed us to discover several of these extreme AGN.  Recent examples are IRAS 23226-3843, RX J2317-4422 and repeatedly Mkn 335 on which we triggered XMM/NuSTAR and HST observations several times in 2018 and 2019. In particular IRAS 23226-3843 is a so called changing look AGN that has changed its optical spectroscopic type several times. In most recent Swift observations IRAS 23226-3843 was found to be flaring again.

Diffuse Ionized Gas (DIG) is prevalent in star-forming galaxies. Using a sample of 365 nearly face-on star-forming galaxies observed by MaNGA, we demonstrate how DIG in star-forming galaxies impacts the measurements of emission line ratios, hence the interpretation of diagnostic diagrams and gas-phase metallicity measurements. At fixed metallicity, low ΣHα regions display enhanced [S ii]/Hα, [N ii]/Hα, [O ii]/Hβ, and [Oi]/Hα. [Sii]/Hα is determined by metallicity gradient and ΣHα. In line ratio diagnostic diagrams, contamination by DIG moves H ii regions towards composite or LI(N)ER-like regions. A harder spectrum is needed to explain DIG line ratios. Leaky H ii region fails to explain the composite/LI(N)ER line ratios. Our result favors ionization by evolved stars as a major ionization source for DIG with LI(N)ER-like emission. DIG can significantly bias the measurement of gas metallicity and metallicity gradient derived using strong line methods. Metallicities derived using N2O2 is optimal because it exhibits the smallest bias and error. Using O3N2, R23, N2=[Nii]/Hα, and N2S2Hα (Dopita et al. 2015) to derive metallicities will introduce a bias the metallicity gradient as large as the metallicity gradient itself. IZI (Blanc et al. 2015) can not be applied to DIG to get accurate metallicity because it currently contains only H ii region models fail to describe DIG.

I will first talk about the discovery of a pair of gigantic bubbles in our Galaxy 
using data from Fermi Gamma-ray Space Telescope, and the multi-wavelength
 observations on this so called "Fermi bubble" structure. Our numerical simulation 
demonstrates that the bubble structure could be evidence for past accretion events 
of the central supermassive black hole. I will then summarize the current state of dark 
matter search with Fermi data, with the focus on gamma-ray line searching from the 
Galactic center, galaxy clusters, and dwarf galaxies. I will explain why we got extremely 
excited in 2012 with a tentative gamma-ray line signal from the Galactic center. We have 
recently proposed to change the survey strategy of Fermi to increase the exposure at 
the Galactic center by more than a factor of 2. This new survey strategy has been 
initiated since December 2013 and will last for at least one year. I will end up with a 
discussion of future gamma-ray space missions.

Gamma-ray bursts are the most powerful known explosions in the universe.  These enigmatic events are thought to the be due to the collapse of a massive star, which radiates energy roughly equivalent to the rest mass energy of the Sun in the matter of seconds.  The launch of the Fermi spacecraft in 2008 has opened a new window into the ultra high energy properties from these events.  I will review some of the recent discoveries made through Fermi observations of GRBs, ranging from limits to quantum gravity models to the recent detection of the brightest GRB ever observed, GRB 130427A.  The emission from this exceptional event was of sufficient energy and duration that it has challenged the fundamental assumptions regarding the particle acceleration and emission mechanisms thought to produce the high-energy gamma-ray from GRBs.

A fundamental challenge in cosmology and galaxy evolution is to understand how dark matter (DM) haloes influence the galaxies that form inside them.  Unfortunately, the parts of this process that we can simulate well --- the growth of DM structures under the influence of gravity --- cannot be observed directly, while the observable stars and gas are difficult to simulate over large scales because of the complicated physics involved.  My past research has focused on connecting the star formation histories of passive galaxies to their observed dynamical structure.  Here, I will present two projects that tackle different aspects of the larger problem of galaxy evolution.  The first is a new method for measuring weak gravitational lensing.  This method uses a photometry-only analog to the Fundamental Plane of early type galaxies in order to measure magnification due to weak lensing.  Combined with existing techniques based on gravitational shear, this method will produce the most direct measurements of dark matter haloes around ordinary galaxies, allowing us to connect observed galaxies with the dark matter haloes that host them.  The second project uses detailed, resolved galaxy kinematics and stellar population gradients in local massive galaxies to trace their assembly history.  The goal is to isolate contributions from in situ star formation, major versus minor mergers, and the possible large-scale stripping of globular clusters.  I will present a pilot study of M87, which is the first of several dozen local galaxies we ultimately aim to analyze.