First Direct Carbon Abundance Measured at <i>z</i> > 10 in the Lensed Galaxy MACS0647-JD
Tiger Yu-Yang Hsiao, Michael W. Topping, Dan Coe, John Chisholm, Danielle A. Berg, Abdurrouf, Javier Álvarez-Márquez, R. Maiolino, Pratika Dayal, Lukas J. Furtak
Abstract
Abstract Investigating the metal enrichment in the early Universe helps us constrain theories about the first stars and study the ages of galaxies. The lensed galaxy MACS0647−JD at z = 10.17 is the brightest galaxy known at z > 10. Previous work analyzing JWST NIRSpec and MIRI data yielded a direct metallicity <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>12</mml:mn> <mml:mo>+</mml:mo> <mml:mi mathvariant="normal">log</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mi mathvariant="normal">O</mml:mi> <mml:mo>/</mml:mo> <mml:mi mathvariant="normal">H</mml:mi> <mml:mo stretchy="false">)</mml:mo> <mml:mspace width="0.14em"/> <mml:mo>=</mml:mo> <mml:mn>7.79</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.09</mml:mn> </mml:math> (∼0.13 Z ⊙ ) and electron density <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="normal">log</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi>n</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>e</mml:mi> </mml:mrow> </mml:msub> <mml:mo>/</mml:mo> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">cm</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>3</mml:mn> </mml:mrow> </mml:msup> <mml:mo stretchy="false">)</mml:mo> <mml:mo>=</mml:mo> <mml:mn>2.9</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.5</mml:mn> </mml:math> , the most distant such measurements to date. Here we estimate the direct C/O abundance for the first time at z > 10, finding a subsolar <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="normal">log</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mi mathvariant="normal">C</mml:mi> <mml:mo>/</mml:mo> <mml:mi mathvariant="normal">O</mml:mi> <mml:mo stretchy="false">)</mml:mo> <mml:mspace width="0.14em"/> <mml:mo>=</mml:mo> <mml:mo>−</mml:mo> <mml:mn>0.4</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>4</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.07</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.06</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> . This is higher than other z > 6 galaxies with direct C/O measurements, likely due to higher metallicity. It is also slightly higher than galaxies in the local Universe with similar metallicity. This may suggest a very efficient and rapid burst of star formation, a low effective oxygen abundance yield, or the presence of unusual stellar populations, including supermassive stars. Alternatively, the strong C iii ] λλ 1907,1909 emission (14 ± 3 Å rest-frame equivalent width may originate from just one of the two component star clusters JDB ( r ∼ 20 pc). Future NIRSpec integral field unit spectroscopic observations of MACS0647−JD will be promising for disentangling C/O in the two components to constrain the chemistry of individual star clusters just 460 Myr after the Big Bang.