We obtained follow-up HST observations of the seven low surface brightnessgalaxies discovered with the Dragonfly Telephoto Array in the field of themassive spiral galaxy M101. Out of the seven galaxies, only three were resolvedinto stars and are potentially associated with the M101 group at $D=7\text{Mpc}$. Based on HST ACS photometry in the broad F606W and F814W filters, we usea maximum likelihood algorithm to locate the Tip of the Red Giant Branch (TRGB)in galaxy color-magnitude diagrams. Distances are $6.38^{+0.35}_{-0.35},6.87^{+0.21}_{-0.30}$ and $6.52^{+0.25}_{-0.27} \text{ Mpc}$ and we confirmthat they are members of the M101 group. Combining the three confirmed lowluminosity satellites with previous results for brighter group members, we findthe M101 galaxy group to be a sparsely populated galaxy group consisting ofseven group members, down to $M_V = -9.2 \text{ mag}$. We compare the M101cumulative luminosity function to that of the Milky Way and M31. We find thatthey are remarkably similar; In fact, the cumulative luminosity function of theM101 group gets even flatter for fainter magnitudes, and we show that the M101group might exhibit the two known small-scale flaws in the$\Lambda\textrm{CDM}$ model, namely `the missing satellite' problem and the`too big to fail' problem. Kinematic measurements of M101$'$s satellitegalaxies are required to determine whether the `too big to fail' problem doesin fact exist in the M101 group.

We report the discovery of a mysterious giant $H_{\alpha}$ blob that is $\sim8$ kpc away from the main MaNGA target 1-24145, one component of a dry galaxymerger, identified in the first-year SDSS-IV MaNGA data. The size of the$H_{\alpha}$ blob is $\sim$ 3-4 kpc in radius, and the $H_{\alpha}$distribution is centrally concentrated. However, there is no optical continuumcounterpart in deep broadband images reaching $\sim$26.9 mag arcsec$^{-2}$ insurface brightness. We estimate that the masses of ionized and cold gases are$3.3 \times 10^{5}$ $\rm M_{\odot}$ and $< 1.3 \times 10^{9}$ $\rm M_{\odot}$,respectively. The emission-line ratios indicate that the $H_{\alpha}$ blob isphotoionized by a combination of massive young stars and AGN. Furthermore, theionization line ratio decreases from MaNGA 1-24145 to the $H_{\alpha}$ blob,suggesting that the primary ionizing source may come from MaNGA 1-24145, likelya low-activity AGN. Possible explanations of this $H_{\alpha}$ blob include AGNoutflow, the gas remnant being tidally or ram-pressure stripped from MaNGA1-24145, or an extremely low surface brightness (LSB) galaxy. However, thestripping scenario is less favoured according to galaxy merger simulations andthe morphology of the $H_{\alpha}$ blob. With the current data, we can notdistinguish whether this $H_{\alpha}$ blob is ejected gas due to a past AGNoutburst, or a special category of `ultra-diffuse galaxy' (UDG) interactingwith MaNGA 1-24145 that further induces the gas inflow to fuel the AGN in MaNGA1-24145.

ALMA observations of the long wavelength dust continuum are used to estimatethe interstellar medium (ISM) masses in a sample of 708 galaxies at z = 0.3 to4.5 in the COSMOS field. The galaxy sample has known far-infrared luminositiesand, hence, star formation rates (SFRs), and stellar masses (M$_{\rm *}$) fromthe optical-infrared spectrum fitting. The galaxies sample SFRs from the mainsequence (MS) to 50 times above the MS. The derived ISM masses are used todetermine the dependence of gas mass on redshift, M$_{\rm *}$, and specific SFR(sSFR) relative to the MS. The ISM masses increase approximately 0.63 power ofthe rate of increase in SFRs with redshift and the 0.32 power of thesSFR/sSFR$_MS$. The SF efficiencies also increase as the 0.36 power of the SFRredshift evolutionary and the 0.7 power of the elevation above the MS; thus theincreased activities at early epochs are driven by both increased ISM massesand SF efficiency. Using the derived ISM mass function we estimate theaccretion rates of gas required to maintain continuity of the MS evolution($>100$ \msun yr$^{-1}$ at z $>$ 2.5). Simple power-law dependences aresimilarly derived for the gas accretion rates. We argue that the overallevolution of galaxies is driven by the rates of gas accretion. The cosmicevolution of total ISM mass is estimated and linked to the evolution of SF andAGN activity at early epochs.

We present ALMA observations of the [CII] fine structure line and theunderlying far-infrared (FIR) dust continuum emission in J1120+0641, the mostdistant quasar currently known (z=7.1). We also present observations targetingthe CO(2-1), CO(7-6) and [CI] 369 micron lines in the same source obtained atthe VLA and PdBI. We find a [CII] line flux of F_[CII]=1.11+/-0.10 Jy km/s anda continuum flux density of S_227GHz=0.53+/-0.04 mJy/beam, consistent withprevious unresolved measurements. No other source is detected in continuum or[CII] emission in the field covered by ALMA (~25"). At the resolution of ourALMA observations (0.23", or 1.2 kpc, a factor ~70 smaller beam area comparedto previous measurements), we find that the majority of the emission is verycompact: a high fraction (~80%) of the total line and continuum flux isassociated with a region 1-1.5 kpc in diameter. The remaining ~20% of theemission is distributed over a larger area with radius <4 kpc. The [CII]emission does not exhibit ordered motion on kpc-scales: applying the virialtheorem yields an upper limit on the dynamical mass of the host galaxy of(4.3+/-0.9)x10^10 M_sun, only ~20x higher than the central black hole. Theother targeted lines (CO(2-1), CO(7-6) and [CI]) are not detected, but thelimits of the line ratios with respect to the [CII] emission imply that theheating in the quasar host is dominated by star formation, and not by theaccreting black hole. The star-formation rate implied by the FIR continuum is105-340 M_sun/yr, with a resulting star-formation rate surface density of~100-350 M_sun/yr/kpc^2, well below the value for Eddington-accretion-limitedstar formation.

We present the results of a pilot near-infrared (NIR) spectroscopic campaignof five very massive galaxies ($\log(\text{M}_\star/\text{M}_\odot)>11.45$) inthe range of $1.7<z<2.7$. We measure an absorption feature redshift for onegalaxy at $z_\text{spec}=2.000\pm0.006$. For the remaining galaxies, we combinethe photometry with the continuum from the spectra to estimate continuumredshifts and stellar population properties. We define a continuum redshift($z_{\rm cont}$ ) as one in which the redshift is estimated probabilisticallyusing EAZY from the combination of catalog photometry and the observedspectrum. We derive the uncertainties on the stellar population synthesisproperties using a Monte Carlo simulation and examine the correlations betweenthe parameters with and without the use of the spectrum in the modeling of thespectral energy distributions (SEDs). The spectroscopic constraints confirm theextreme stellar masses of the galaxies in our sample. We find that three out offive galaxies are quiescent (star formation rate of $\lesssim 1M_\odot~yr^{-1}$) with low levels of dust obscuration ($A_{\rm V} < 1$) , thatone galaxy displays both high levels of star formation and dust obscuration(${\rm SFR} \approx 300 M_\odot~{\rm yr}^{-1}$, $A_{\rm V} \approx 1.7$~mag),and that the remaining galaxy has properties that are intermediate between thequiescent and star-forming populations.