arXiv subjects

Alice Young

Publications and source records attributed to Alice Young.

3 recordsLinked to original sources

arXiv2026

A Single Line-Emitter Identified in an Unbiased Search with JWST/NIRSpec: Multi-Object Coronagraphy for Slitless Spectroscopy

We report the detection of a previously unknown object with a single emission line within the Hubble Ultra Deep Field, using a new JWST NIRSpec technique called Multi-Object Coronagraphy for Slitless Spectroscopy (MOCSS) with the G140M/F100LP observing mode. The MOCSS technique involves opening almost all the shutters on the NIRSpec microshutter array, while simultaneously closing the shutters that lie on top of known low redshift objects, facilitating a wide field slitless spectroscopic search without contamination from bright objects. This observational technique has enabled the detection of a strong emission line in four different dither positions and in two position angles, and thus cannot be artificial. This line is detected at 1.60 $\rm μm$ with a line flux of $[2.5\pm 0.3]\times10^{-18} \rm erg\ s^{-1} cm^{-2}$ and a FWHM of $13.2\pm2.0$Å, and does not correspond to any known source with some of the deepest HST and JWST imaging in existence. Based upon the absence of imaging detection, we place a lower limit on the observed frame equivalent width (EW) of 7620Å on this object, which strongly limits the number of possible lines that this line can be. Given the wavelength, an EW limit that is near the ceiling of expectation, and the lack of other lines in the bandpass, this line cannot be easily explained by [OII] at $z=3.29$, [OIII] at $z=2.20$, H$α$ at $z=1.44$, and Ly$α$ at $z=12.16$. We discuss possible AGN and transient phenomena that could explain the finding.

astro-ph.GA↗

arXiv2026

MOCSS: Multi-Object Coronagraphy for JWST/NIRSpec Slitless Spectroscopy

We present an experimental JWST/NIRSpec observational method to obtain $R\gtrsim1000$ G140M/F100LP slitless spectroscopic observations. This "Multi-Object Coronagraphy for Slitless Spectroscopy" (MOCSS) technique involves opening essentially all microshutters on NIRSpec simultaneously while closing shutters corresponding on-sky with known bright objects. Through observations of the Hubble Ultra Deep Field, we demonstrate the discovery potential of these deep, high resolution observations without the need for target pre-selection. We obtain a catalog of 22 secure multi-line emitters at $1.3<z<4.6$, with observations of [OII], [OIII], H$α$, H$β$ and [NII] lines, accounting for $\sim80\%$ of the emission lines identified directly in the dispersed images. The MOCSS survey provides first time spectroscopic redshifts for 18 of these sources. We also demonstrate that first order traces of the NIRSpec/G140M/F100LP observing mode extend substantially beyond the nominal $\sim1.89\rm μm$ red cutoff, as far as $2.94\rm μm$ in the most extreme case. Compared to existing NIRISS WFSS of similar exposure times, we find that the MOCSS technique can observe very faint lines while covering the full $1-2 \rm μm$ regime without gaps in wavelength coverage. This study describes the highest-resolution slitless spectroscopy campaign of the $1-2 \rm μm$ regime and emphasizes the discovery potential of this unorthodox observational technique.

astro-ph.GA↗

arXiv2022

The young stars in the Galactic Center

We present a large ${\sim 30" \times 30"}$ spectroscopic survey of the Galactic Center using the SINFONI IFU at the VLT. Combining observations of the last two decades we compile spectra of over $2800$ stars. Using the Bracket-$γ$ absorption lines we identify $195$ young stars, extending the list of known young stars by $79$. In order to explore the angular momentum distribution of the young stars, we introduce an isotropic cluster prior. This prior reproduces an isotropic cluster in a mathematically exact way, which we test through numerical simulations. We calculate the posterior angular momentum space as function of projected separation from Sgr~A*. We find that the observed young star distribution is substantially different from an isotropic cluster. We identify the previously reported feature of the clockwise disk and find that its angular momentum changes as function of separation from the black hole, and thus confirm a warp of the clockwise disk ($p \sim 99.2\%$). At large separations, we discover three prominent overdensities of angular momentum. One overdensity has been reported previously, the counter-clockwise disk. The other two are new. Determining the likely members of these structures, we find that as many as $75\%$ of stars can be associated with one of these features. Stars belonging to the warped clockwise-disk show a top heavy K-band luminosity function, while stars belonging to the larger separation features do not. Our observations are in good agreement with the predictions of simulations of in-situ star formation, and argue for common formation of these structures.

astro-ph.GA↗