Matching Items (3)

155509-Thumbnail Image.png

H-alpha emitting galaxies at z ~0.6 in the deep and wide narrowband survey

Description

New measurements of the Hα luminosity function (LF) and star formation rate

(SFR) volume density are presented for galaxies at z∼0.62 in the COSMOS field.

These results are part of the Dee

New measurements of the Hα luminosity function (LF) and star formation rate

(SFR) volume density are presented for galaxies at z∼0.62 in the COSMOS field.

These results are part of the Deep And Wide Narrowband Survey (DAWN), a unique

infrared imaging program with large areal coverage (∼1.1 deg 2 over 5 fields) and

sensitivity (9.9 × 10 −18 erg/cm 2 /s at 5σ).

The present sample, based on a single DAWN field, contains 116 Hα emission-

line candidates at z∼0.62, 25% of which have spectroscopic confirmations. These

candidates have been selected through comparison of narrow and broad-band images

in the infrared and through matching with existing catalogs in the COSMOS field.

The dust-corrected LF is well described by a Schechter function with L* = 10 42.64±0.92

erg s −1 , Φ* = 10 −3.32±0.93 Mpc −3 (L* Φ* = 10 39.40±0.15 ), and α = −1.75 ± 0.09. From

this LF, a SFR density of ρ SF R =10 −1.37±0.08 M○ yr −1 Mpc −3 was calculated. An

additional cosmic variance uncertainty of ∼ 20% is also expected. Both the faint

end slope and luminosity density that are derived are consistent with prior results at

similar redshifts, with reduced uncertainties.

An analysis of these Hα emitters’ sizes is also presented, showing a direct corre-

lation between the galaxies’ sizes and their Hα emission.

Contributors

Agent

Created

Date Created
  • 2017

155787-Thumbnail Image.png

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

Description

Galaxy formation is a complex process with aspects that are still very uncertain or unknown. A mechanism that has been utilized in simulations to successfully resolve several of these outstanding

Galaxy formation is a complex process with aspects that are still very uncertain or unknown. A mechanism that has been utilized in simulations to successfully resolve several of these outstanding issues is active galactic nucleus (AGN) feedback. Recent work has shown that a promising method for directly measuring this energy is by looking at small increases in the energy of cosmic microwave background (CMB) photons as they pass through ionized gas, known as the thermal Sunyaev-Zel’dovich (tSZ) effect.

In this work, I present stacked CMB measurements of a large number of elliptical galaxies never before measured using this method. I split the galaxies into two redshift groups, "low-z" for z=0.5-1.0 and “high-z” for z=1.0-1.5. I make two independent sets of CMB measurements using data from the South Pole Telescope (SPT) and the Atacama Cosmology Telescope (ACT), respectively, and I use data from the Planck telescope to account for contamination from dust emission. With SPT I find average thermal energies of 7.6(+3.0/−2.3) × 10^60 erg for 937 low-z galaxies, and 6.0(+7.7/−6.3) × 10^60 erg for 240 high-z galaxies. With ACT I find average thermal energies of 5.6(+5.9/−5.6) × 10^60 erg for 227 low-z galaxies, and 7.0(+4.7/−4.4) × 10^60 erg for 529 high-z galaxies.

I then attempt to further interpret the physical meaning of my observational results by incorporating two large-scale cosmological hydrodynamical simulations, one with (Horizon-AGN) and one without (Horizon-NoAGN) AGN feedback. I extract simulated tSZ measurements around a population of galaxies equivalent to those used in my observational work, with matching mass distributions, and compare the results. I find that the SPT measurements are consistent with Horizon-AGN, falling within 0.4σ at low-z and 0.5σ at high-z, while the ACT measurements are very different from Horizon-AGN, off by 6.9σ at low-z and 14.6σ at high-z. Additionally, the SPT measurements are loosely inconsistent with Horizon-NoAGN, off by 1.8σ at low-z but within 0.6σ at high-z, while the ACT measurements are loosely consistent with Horizon-NoAGN (at least much more so than with Horizon-AGN), falling within 0.8σ at low-z but off by 1.9σ at high-z.

Contributors

Agent

Created

Date Created
  • 2017

157637-Thumbnail Image.png

Galaxy overdensities and emission line galaxies in the faint infrared grism survey

Description

Learning how properties of galaxies such as star formation, galaxy interactions, chemical composition, and others evolve to produce the modern universe has long been a goal of extragalactic astronomy. In

Learning how properties of galaxies such as star formation, galaxy interactions, chemical composition, and others evolve to produce the modern universe has long been a goal of extragalactic astronomy. In recent years, grism spectroscopy from the Hubble Space Telescope (HST) has provided a means to study these properties with spectroscopy while avoiding the limitations of ground-based observation. In this dissertation, I present several studies wherein I used HST G102 grism spectroscopy from the Faint Infrared Grism Survey (FIGS) to investigate these fundamental properties of galaxies and how they interact and evolve. In the first study, I combined the grism spectra with broadband photometry to produce a catalog of redshifts with improved accuracy, reducing the median redshift error from 3\% to 2\%. With this redshift catalog, I conducted a systematic search for galaxy overdensities in the FIGS fields, producing a list of 24 significant candidates. In the second study, I developed a method for identifying emission line galaxy (ELG) candidates from continuum-subtracted 1D spectra, and identified 71 ELGs in one FIGS field. In matching MUSE/VLT spectra, I measured the [OIII]$\lambda$4363 emission line for 14 FIGS ELGs, and used this to measure their $T_e$-based gas-phase metallicities. These ELGs show a low-metallicity offset on the Mass-Metallicity Relation, and I demonstrated that this offset can be explained by recent star formation. In the third study, I expanded the ELG search to all four FIGS fields, identifying 208 H$\alpha$, [OIII]$\lambda\lambda$4959,5007, and [OII]$\lambda\lambda$3727,3729 line emitters. I compiled a catalog of line fluxes, redshifts, and equivalent widths. I combined this catalog with the overdensity study to investigate a possible relationship between line luminosity, star formation, and an ELG's environment. In the fourth study, I usde 15 FIGS H$\alpha$ emitters and 49 ``green pea'' line emitters to compare H$\alpha$ and the far-UV continuum as tracers of star formation. I explored a correlation between the H$\alpha$-FUV ratio and the ratio of [OIII]$\lambda\lambda$4959,5007 to [OII]$\lambda\lambda$3727,3729 and its implications for star formation history.

Contributors

Agent

Created

Date Created
  • 2019