Dust and PAHs
The interstellar medium is pervaded by dust. Dust grains are solid particles with sizes of 1μm that obscure the optical and ultraviolet light emitted from stars and reradiate the energy in the infrared, thereby modifying our view of galaxies. Moreover, dust plays important roles in physics and chemistry of the interstellar medium: dust grains are catalysts for the formation of certain molecules in the ISM and they are important in the heating of the interstellar gas, ISM gas dynamics (through, e.g., radiation pressure), and the influence of magnetic fields on the ISM.
I study the properties of dust in distant galaxies by looking at the emission and absorption features that are produced by dust particles.
Shivaei2022
Dust Emission
Using the Spitzer infrared space telescope I study the mid-infrared aromatic bands that are often attributed to Polycyclic Aromatic Hydrocarbon (PAH) molecules. PAHs are one of the important components of dust, they are abundant, substantially contribute to dust attenuation, and play a critical role in the physics and chemistry of the interstellar medium.
Moreover, I use images of the Herschel infrared space observatory to trace far-infrared dust emission of galaxies to determine total dust emission and obscured star formation.
In ALMA cycle 7, I was the PI of a successful 38-hour ALMA program (ranked A) to study the cold dust emission of *typical* z~2 galaxies as a function of metallicity. The data is being taken currently. Stay tuned for cool results!
Dust Absorption
In order to recover the intrinsic optical and ultraviolet emission of galaxies, we need to correct the observed light for dust obscuration. This requires knowledge of the amount of dust attenuation as a function of wavelength, called dust extinction/attenuation curve. Using Hubble space telescope data in addition to spectroscopic data from Keck telescopes, I constrain the dust attenuation curve and its variations as a function of galaxy properties at intermediate redshifts. My preliminary results indicate a significant change in the shape of the UV-optical attenuation curve of high-z galaxies with metallicity of the galaxy.
I study the properties of dust in distant galaxies by looking at the emission and absorption features that are produced by dust particles.
Shivaei2022
Dust Emission
Using the Spitzer infrared space telescope I study the mid-infrared aromatic bands that are often attributed to Polycyclic Aromatic Hydrocarbon (PAH) molecules. PAHs are one of the important components of dust, they are abundant, substantially contribute to dust attenuation, and play a critical role in the physics and chemistry of the interstellar medium.
Moreover, I use images of the Herschel infrared space observatory to trace far-infrared dust emission of galaxies to determine total dust emission and obscured star formation.
In ALMA cycle 7, I was the PI of a successful 38-hour ALMA program (ranked A) to study the cold dust emission of *typical* z~2 galaxies as a function of metallicity. The data is being taken currently. Stay tuned for cool results!
Dust Absorption
In order to recover the intrinsic optical and ultraviolet emission of galaxies, we need to correct the observed light for dust obscuration. This requires knowledge of the amount of dust attenuation as a function of wavelength, called dust extinction/attenuation curve. Using Hubble space telescope data in addition to spectroscopic data from Keck telescopes, I constrain the dust attenuation curve and its variations as a function of galaxy properties at intermediate redshifts. My preliminary results indicate a significant change in the shape of the UV-optical attenuation curve of high-z galaxies with metallicity of the galaxy.
My papers on this topic:
- Dependence of the IRX-β dust attenuation relation on metallicity and environment PDF
Shivaei, I., Darvish, B., Sattari, Z., et al. 2020, ApJL, 903, L28 - The MOSDEF Survey: the Variation of the Dust Attenuation Curve with Metallicity PDF
Shivaei, I., Reddy, N., Rieke, G., et al. 2020, ApJ, 899, 117 - The MOSDEF Survey: Metallicity Dependence of the PAH Emission at High Redshift and Implications for 24μm-inferred IR Luminosities and Star Formation Rates at z ∼ 2 PDF
Shivaei, I., Reddy, N., Shapley, A., et al., 2017, ApJ, 837, 157
Also featured in: UCR Today, Phys.org, Science Daily, EurekAlert, Space Daily - The MOSDEF Survey: The Strong Agreement Between Hα and UV-to-FIR Star Formation Rates for z ∼ 2 Star-Forming Galaxies PDF
Shivaei, I., Kriek, M., Reddy, N., et al., 2016, ApJL, 820, L23
Also featured in: Astronomy UCR, UCR Today, Keck Observatory, Phys.org, Science Daily, EurekAlert, Space Daily, Astronomy Now - Investigating Hα, UV, and IR Star-formation Rate Diagnostics for a Large Sample of z ∼ 2 Galaxies PDF
Shivaei, I., Reddy, N. A., Steidel, C. C., & Shapley, A. E., 2015a, ApJ, 804, 10
