Niusha Ahvazi

University of California, Riverside

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Trends

Author Order

Document Type

Co-Authors

Laura V. Sales

University of California, Riverside

Andrew Benson

Carnegie Observatories

Richard D’Souza

Vatican Secret Archives

Ignacio Trujillo

Instituto de Astrofísica de Canarias

Jessica E Doppel

University of California, Riverside

Javier Román

University of Groningen

Sachi Weerasooriya

Carnegie Observatories

A. Boselli

Laboratoire d’Astrophysique de Marseille

Mia Sauda Bovill

University of Maryland, College Park

R. Michael Rich

University of California, Los Angeles

Cooperative Institutions

Instituto de Astrofísica de Canarias

Universidad de La Laguna

Carnegie Observatories

Max Planck Society

Harvard University

Consejo Superior de Investigaciones Científicas

Max Planck Institute for Astronomy

University of California, Riverside

University of Groningen

Max Planck Institute for Astrophysics

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Field

A giant thin stellar stream in the Coma Galaxy Cluster

Astronomy and Astrophysics (2023)

Javier Román R. Michael Rich Niusha Ahvazi Laura V. Sales Chester Li

The study of dynamically cold stellar streams reveals information about the gravitational potential where they reside and provides important constraints on the properties of dark matter. However, the intrinsic faintness of these streams makes their detection beyond Local environments highly challenging. Here, we report the detection of an extremely faint stellar stream ( μ g , max = 29.5 mag arcsec −2 ) with an extraordinarily coherent and thin morphology in the Coma Galaxy Cluster. This Giant Coma Stream spans ∼510 kpc in length and appears as a free-floating structure located at a projected distance of 0.8 Mpc from the center of Coma. We do not identify any potential galaxy remnant or core, and the stream structure appears featureless in our data. We interpret the Giant Coma Stream as being a recently accreted, tidally disrupting passive dwarf. Using the Illustris-TNG50 simulation, we identify a case with similar characteristics, showing that, although rare, these types of streams are predicted to exist in Λ-CDM. Our work unveils the presence of free-floating, extremely faint and thin stellar streams in galaxy clusters, widening the environmental context in which these objects are found ahead of their promising future application in the study of the properties of dark matter.

Coma Cluster

Coma (optics)

Gravitational potential

10.1051/0004-6361/202346780

Cite

Citations (2)

A comprehensive model for the formation and evolution of the faintest Milky Way dwarf satellites

Monthly Notices of the Royal Astronomical Society (2024)

Niusha Ahvazi Andrew Benson Laura V. Sales Ethan O. Nadler Sachi Weerasooriya

ABSTRACT In this study, we modify the semi-analytic model galacticus in order to accurately reproduce the observed properties of dwarf galaxies in the Milky Way. We find that reproducing observational determinations of the halo occupation fraction and mass–metallicity relation for dwarf galaxies requires us to include H2 cooling, an updated ultraviolet background radiation model, and to introduce a model for the metal content of the intergalactic medium. By fine-tuning various model parameters and incorporating empirical constraints, we have tailored the model to match the statistical properties of Milky Way dwarf galaxies, such as their luminosity function and size–mass relation. We have validated our modified semi-analytic framework by undertaking a comparative analysis of the resulting galaxy–halo connection. We predict a total of $300 ^{+75} _{-99}$ satellites with an absolute V-band magnitude (MV) less than 0 within 300 kpc from our Milky Way analogues. The fraction of subhaloes that host a galaxy at least this bright drops to 50 per cent by a halo peak mass of ∼8.9 × 107 M⊙, consistent with the occupation fraction inferred from the latest observations of Milky Way satellite population.

10.1093/mnras/stae761

Cite

Citations (8)

A giant thin stellar stream in the Coma Galaxy Cluster

arXiv (Cornell University) (2023)

Javier Román R. Michael Rich Niusha Ahvazi Laura V. Sales Chester Li

The study of dynamically cold stellar streams reveals information about the gravitational potential where they reside and provides important constraints on dark matter properties. However, their intrinsic faintness makes detection beyond Local environments highly challenging. Here we report the detection of an extremely faint stellar stream ($\mu_{g,max}=$ 29.5 mag arcsec$^{-2}$) with an extraordinarily coherent and thin morphology in the Coma Galaxy Cluster. This Giant Coma Stream spans ~510 kpc in length and appears as a free-floating structure located at a projected distance of 0.8 Mpc from the centre of Coma. We do not identify any potential galaxy remnant or core, and the stream structure appears featureless in our data. We interpret the Giant Coma Stream as being a recently accreted, tidally disrupting passive dwarf. Using the Illustris-TNG50 simulation, we identify a case with similar characteristics, showing that, although rare, these types of streams are predicted to exist in $\Lambda$-CDM. Our work unveils the presence of free-floating, extremely faint and thin stellar streams in galaxy clusters, widening the environmental context for their promising future applications in the study of dark matter properties.

Coma Cluster

Coma (optics)

Gravitational potential

10.48550/arxiv.2305.03073

Cite

Citations (1)

How Many Bursts Does it Take to Form a Core at the Center of a Galaxy?

arXiv (Cornell University) (2024)

Olivia Mostow Paul Torrey Jonah C. Rose Alex M. Garcia Niusha Ahvazi

We present a novel method for systematically assessing the impact of central potential fluctuations associated with bursty outflows on the structure of dark matter halos for dwarf and ultra-faint galaxies. Specifically, we use dark-matter-only simulations augmented with a manually-added massive particle that modifies the central potential and approximately accounts for a centrally-concentrated baryon component. This approach enables precise control over the magnitude, frequency, and timing of when rapid outflow events occur. We demonstrate that this method can reproduce the established result of core formation for systems that undergo multiple episodes of bursty outflows. In contrast, we also find that equivalent models that undergo only a single (or small number of) burst episodes do not form cores with the same efficacy. This is important because many ultra-faint dwarf (UFD) galaxies in the local universe are observed to have tightly constrained star formation histories that are best described by a single, early burst of star formation. Using a suite of cosmological, zoom-in simulations, we identify the regimes in which single bursts can and cannot form a cored density profile, and therefore, can or cannot resolve the core-cusp problem.

Center (category theory)

10.48550/arxiv.2412.09566

Cite

Citations (0)

The progenitors of the intra-cluster light and intra-cluster globular clusters in galaxy groups and clusters

Monthly Notices of the Royal Astronomical Society (2024)

Niusha Ahvazi Laura V. Sales Jessica E Doppel Andrew Benson Richard D’Souza

ABSTRACT We use the TNG50 from the IllustrisTNG suite of cosmological hydrodynamical simulation, complemented by a catalogue of tagged globular clusters, to investigate the properties and build up of two extended luminous components: the intra-cluster light (ICL) and the intra-cluster globular clusters (ICGCs). We select the 39 most massive groups and clusters in the box, spanning the range of virial masses $5 \times 10^{12} \lt \rm M_{200}/\rm {\rm M}_{\odot } \lt 2 \times 10^{14}$. We find good agreement between predictions from the simulations and current observational estimates of the fraction of mass in the ICL and its radial extension. The stellar mass of the ICL is only $\sim 10~{{\ \rm per\ cent}}$–20 per cent of the stellar mass in the central galaxy but encodes useful information on the assembly history of the group or cluster. About half the ICL in all our systems is brought in by galaxies in a narrow stellar mass range, M* = 1010–1011 M⊙. However, the contribution of low-mass galaxies (M* < 1010 M⊙) to the build up of the ICL varies broadly from system to system, $\sim 5~{{\ \rm per\ cent}}-45~{{\ \rm per\ cent}}$, a feature that might be recovered from the observable properties of the ICL at z = 0. At fixed virial mass, systems where the accretion of dwarf galaxies plays an important role have shallower metallicity profiles, less metal content, and a lower stellar mass in the ICL than systems where the main contributors are more massive galaxies. We show that intra-cluster GCs are also good tracers of this history, representing a valuable alternative when diffuse light is not detectable.

10.1093/mnras/stae848

Cite

Citations (4)

Star formation beyond galaxies: widespread in-situ formation of intra-cluster stars

The Open Journal of Astrophysics (2024)

Niusha Ahvazi Laura V. Sales Julio F. Navarro Andrew Benson A. Boselli

We study the fraction of the intra-cluster light (ICL) formed in-situ in the three most massive clusters of the TNG50 simulation, with virial masses ∼1014. We find that a significant fraction of ICL stars ( 8%- 28%) are born in-situ. This amounts to a total stellar mass comparable to the central galaxy itself. Contrary to simple expectations, only a sub-dominant fraction of these in-situ ICL stars are born in the central regions and later re-distributed to more energetic orbits during mergers. Instead, many in-situ ICL stars form directly hundreds of kiloparsecs away from the central galaxy, in clouds condensing out of the circum-cluster medium. The simulations predict a present-date diffuse star formation rate of $$1 M⊙/yr, with higher rates at higher redshifts. The diffuse star forming component of the ICL is filamentary in nature, extends for hundreds of kiloparsecs and traces the distribution of neutral gas in the cluster host halo. We discuss briefly how numerical details of the baryonic treatment in the simulation, in particular the density threshold for star formation and the equation of state, may play a role in this result. We conclude that a sensitivity of 1.6×10−19−2.6×10−18 erg s −1 cm −2 arcsec −2 in H α flux (beyond current observational capabilities) would be necessary to detect this diffuse star-forming component in galaxy clusters.

10.33232/001c.127132

Cite

Citations (0)

A comprehensive model for the formation and evolution of the faintest Milky Way dwarf satellites

arXiv (Cornell University) (2023)

Niusha Ahvazi Andrew Benson Laura V. Sales Ethan O. Nadler Sachi Weerasooriya

In this study, we modify the semi-analytic model Galacticus in order to accurately reproduce the observed properties of dwarf galaxies in the Milky Way. We find that reproducing observational determinations of the halo occupation fraction and mass-metallicity relation for dwarf galaxies requires us to include H$_2$ cooling, an updated UV background radiation model, and to introduce a model for the metal content of the intergalactic medium. By fine-tuning various model parameters and incorporating empirical constraints, we have tailored the model to match the statistical properties of Milky Way dwarf galaxies, such as their luminosity function and size$-$mass relation. We have validated our modified semi-analytic framework by undertaking a comparative analysis of the resulting galaxy-halo connection. We predict a total of $300 ^{+75} _{-99}$ satellites with an absolute $V$-band magnitude (M$_{V}$) less than $0$ within $300$ kpc from our Milky Way-analogs. The fraction of subhalos that host a galaxy at least this bright drops to $50\%$ by a halo peak mass of $\sim 8.9 \times 10^{7}$ M$_{\odot}$, consistent with the occupation fraction inferred from the latest observations of Milky Way satellite population.

Dwarf galaxy problem

Dwarf spheroidal galaxy

Local Group

Satellite galaxy

10.48550/arxiv.2308.13599

Cite

Citations (0)

The progenitors of the intra-cluster light and intra-cluster globular clusters in galaxy groups and clusters

arXiv (Cornell University) (2023)

Niusha Ahvazi Laura V. Sales Jessica E Doppel Andrew Benson Richard D’Souza

We use the IllustrisTNG50 cosmological hydrodynamical simulation, complemented by a catalog of tagged globular clusters, to investigate the properties and build up of two extended luminous components: the intra-cluster light (ICL) and the intra-cluster globular clusters (ICGC). We select the 39 most massive groups and clusters in the box, spanning the range of virial masses $5 \times 10^{12} < \rm M_{200}/\rm M_{\odot} < 2 \times 10^{14}$. We find good agreement between predictions from the simulations and current observational estimates of the fraction of mass in the ICL and its radial extension. The stellar mass of the ICL is only $\sim10\%-20\%$ of the stellar mass in the central galaxy but encodes useful information on the assembly history of the group or cluster. About half the ICL in all our systems is brought in by galaxies in a narrow stellar mass range, $M_*=10^{10}-10^{11}$ $\rm M_{\odot}$. However, the contribution of low-mass galaxies ($M_*<10^{10}$ $\rm M_{\odot}$) to the build-up of the ICL varies broadly from system to system, $\sim 5\%-45\%$, a feature that might be recovered from the observable properties of the ICL at $z=0$. At fixed virial mass, systems where the accretion of dwarf galaxies plays an important role have shallower metallicity profiles, less metal content and a lower stellar mass in the ICL than systems where the main contributors are more massive galaxies. We show that intra-cluster GCs are also good tracers of this history, representing a valuable alternative when diffuse light is not detectable.

Virial mass

Stellar mass

Velocity dispersion

10.48550/arxiv.2308.12340

Cite

Citations (0)

Star formation beyond galaxies: widespread in-situ formation of intra-cluster stars in TNG50

arXiv (Cornell University) (2024)

Niusha Ahvazi Laura V. Sales Julio F. Navarro Andrew Benson A. Boselli

We study the fraction of the intra-cluster light (ICL) formed in-situ in the three most massive clusters of the TNG50 simulation, with virial masses $\sim 10^{14}$ M$_{\odot}$. We find that a significant fraction of ICL stars ($8\%$-$28\%$) are born in-situ. This amounts to a total stellar mass comparable to the central galaxy itself. Contrary to simple expectations, only a sub-dominant fraction of these in-situ ICL stars are born in the central regions and later re-distributed to more energetic orbits during mergers. Instead, many in-situ ICL stars form directly hundreds of kiloparsecs away from the central galaxy, in clouds condensing out of the circum-cluster medium. The simulations predict a present-date diffuse star formation rate of $\sim$1 $\mathrm{M}_{\odot}$/yr, with higher rates at higher redshifts. The diffuse star forming component of the ICL is filamentary in nature, extends for hundreds of kiloparsecs and traces the distribution of neutral gas in the cluster host halo. We discuss briefly how numerical details of the baryonic treatment in the simulation may play a role in this result and conclude that a sensitivity of $1.6 \times 10^{-19} - 2.6 \times 10^{-18}$ erg s$^{-1}$ cm$^{-2}$ arcsec$^{-2}$ in H$_\alpha$ flux (beyond current observational capabilities) would be necessary to detect this diffuse star-forming component in galaxy clusters.

10.48550/arxiv.2403.04839

Cite

Citations (1)