15 research outputs found
The Effect of Dust Evolution and Traps on Inner Disk Water Enrichment
Substructures in protoplanetary disks can act as dust traps that shape the
radial distribution of pebbles. By blocking the passage of pebbles, the
presence of gaps in disks may have a profound effect on pebble delivery into
the inner disk, crucial for the formation of inner planets via pebble
accretion. This process can also affect the delivery of volatiles (such as
HO) and their abundance within the water snow line region (within a few
au). In this study, we aim to understand what effect the presence of gaps in
the outer gas disk may have on water vapor enrichment in the inner disk.
Building on previous work, we employ a volatile-inclusive multi-Myr disk
evolution model that considers an evolving ice-bearing drifting dust
population, sensitive to dust-traps, which loses its icy content to sublimation
upon reaching the snow line. We find that vapor abundance in the inner disk is
strongly affected by fragmentation velocity (v) and turbulence, which
control how intense vapor enrichment from pebble delivery is, if present, and
how long it may last. Generally, for disks with low to moderate turbulence
( 1 10) and for a range of v, radial
location, and gap depth (especially that of the innermost gaps), can
significantly alter enrichment. Shallow inner gaps may continuously leak
material from beyond it, despite the presence of additional deep outer gaps. We
finally find that the for realistic v ( 10 m s), presence
of gaps is more important than planetesimal formation beyond the snow line in
regulating pebble and volatile delivery into the inner disk.Comment: 24 Pages, 15 Figures, Accepted to Ap
The Effect of Dust Evolution and Traps on Inner Disk Water Enrichment
Substructures in protoplanetary disks can act as dust traps that shape the radial distribution of pebbles. By blocking the passage of pebbles, the presence of gaps in disks may have a profound effect on pebble delivery into the inner disk, crucial for the formation of inner planets via pebble accretion. This process can also affect the delivery of volatiles (such as H2O) and their abundance within the water snow line region (within a few au). In this study, we aim to understand what effect the presence of gaps in the outer gas disk may have on water vapor enrichment in the inner disk. Building on previous work, we employ a volatile-inclusive disk evolution model that considers an evolving ice-bearing drifting dust population, sensitive to dust traps, which loses its icy content to sublimation upon reaching the snow line. We find that the vapor abundance in the inner disk is strongly affected by the fragmentation velocity (vf) and turbulence, which control how intense vapor enrichment from pebble delivery is, if present, and how long it may last. Generally, for disks with low to moderate turbulence (α ≤ 1 × 10−3) and a range of vf, radial locations and gap depths (especially those of the innermost gaps) can significantly alter enrichment. Shallow inner gaps may continuously leak material from beyond it, despite the presence of additional deep outer gaps. We finally find that for realistic vf (≤10 m s−1), the presence of gaps is more important than planetesimal formation beyond the snow line in regulating pebble and volatile delivery into the inner disk
JWST reveals excess cool water near the snowline in compact disks, consistent with pebble drift
Previous analyses of mid-infrared water spectra from young protoplanetary
disks observed with the Spitzer-IRS found an anti-correlation between water
luminosity and the millimeter dust disk radius observed with ALMA. This trend
was suggested to be evidence for a fundamental process of inner disk water
enrichment, used to explain properties of the Solar System 40 years ago, in
which icy pebbles drift inward from the outer disk and sublimate after crossing
the snowline. Previous analyses of IRS water spectra, however, were very
uncertain due to the low spectral resolution that blended lines together. We
present new JWST-MIRI spectra of four disks, two compact and two large with
multiple radial gaps, selected to test the scenario that water vapor inside the
snowline is regulated by pebble drift. The higher spectral resolving power of
MIRI-MRS now yields water spectra that separate individual lines, tracing upper
level energies from 900 K to 10,000 K. These spectra clearly reveal excess
emission in the low-energy lines in compact disks, compared to the large disks,
establishing the presence of a cooler component with 170-400 K and
equivalent emitting radius 1-10 au. We interpret the cool
water emission as ice sublimation and vapor diffusion near the snowline,
suggesting that there is indeed a higher inwards mass flux of icy pebbles in
compact disks. Observation of this process opens up multiple exciting prospects
to study planet formation chemistry in inner disks with JWST.Comment: Posted as submitted to ApJ Letters; feedback and input from the
community is welcom
Water-Rich Disks around Late M-stars Unveiled: Exploring the Remarkable Case of Sz114
We present an analysis of the JDISC JWST/MIRI-MRS spectrum of Sz~114, an
accreting M5 star surrounded by a large dust disk with a shallow gap at au. The spectrum is molecular-rich: we report the detection of water, CO,
CO, HCN, CH, and H. The only identified atomic/ionic transition
is from [NeII] at 12.81 micron. A distinct feature of this spectrum is the
forest of water lines with the 17.22 micron emission surpassing that of most
mid-to-late M-star disks by an order of magnitude in flux and aligning instead
with disks of earlier-type stars. Moreover, flux ratios of CH/HO
and HCN/HO in Sz~114 also resemble those of earlier-type disks, with a
slightly elevated CO/HO ratio. While accretional heating can boost all
infrared lines, the unusual properties of Sz~114 could be explained by the
young age of the source, its formation under unusual initial conditions (a
large massive disk), and the presence of dust substructures. The latter delays
the inward drift of icy pebbles and help preserve a lower C/O ratio over an
extended period. In contrast, mid-to-late M-star disks--which are typically
faint, small in size, and likely lack significant substructures--may have more
quickly depleted the outer icy reservoir and already evolved out of a
water-rich inner disk phase. Our findings underscore the unexpected diversity
within mid-infrared spectra of mid-to-late M-star disks, highlighting the need
to expand the observational sample for a comprehensive understanding of their
variations and thoroughly test pebble drift and planet formation models.Comment: 16 pages, 8 figures, accepted by ApJ
JWST Reveals Excess Cool Water near the Snow Line in Compact Disks, Consistent with Pebble Drift
Previous analyses of mid-infrared water spectra from young protoplanetary disks observed with the Spitzer-IRS found an anticorrelation between water luminosity and the millimeter dust disk radius observed with ALMA. This trend was suggested to be evidence for a fundamental process of inner disk water enrichment proposed decades ago to explain some properties of the solar system, in which icy pebbles drift inward from the outer disk and sublimate after crossing the snow line. Previous analyses of IRS water spectra, however, were uncertain due to the low spectral resolution that blended lines together. We present new JWST-MIRI spectra of four disks, two compact and two large with multiple radial gaps, selected to test the scenario that water vapor inside the snow line is regulated by pebble drift. The higher spectral resolving power of MIRI-MRS now yields water spectra that separate individual lines, tracing upper level energies from 900 to 10,000 K. These spectra clearly reveal excess emission in the low-energy lines in compact disks compared to large disks, demonstrating an enhanced cool component with T ≈ 170–400 K and equivalent emitting radius R
eq ≈ 1–10 au. We interpret the cool water emission as ice sublimation and vapor diffusion near the snow line, suggesting that there is indeed a higher inward mass flux of icy pebbles in compact disks. Observation of this process opens up multiple exciting prospects to study planet formation chemistry in inner disks with JWST