NGC 3810. Source: ESA/Hubble, NASA

NGC 3810. Source: ESA/Hubble, NASA

Lamiya

Mowla

লামীয়া মওলা

Assistant professor at wellesley college

Observational Astronomer

Galaxy Formation and Evolution; Hubble; JWST; Simulations

I am an observational astronomer studying the structural evolution of astronomical objects in the early Universe. I want to understand how the first stars, star clusters, galaxies, and galaxy clusters formed in the infant Universe and how they changed as the Universe got older. For my research, I use space telescopes such as the Hubble and JWST, ground-based telescopes such as Dragonfly, as well as cosmological hydrodynamical simulations. Check here for the news coverage of my research.

I am a Wellesley alum (green class of 2013) and I received my Ph.D. in 2020 from Yale University (Advisor: Prof. Pieter van Dokkum). Recently I was a Dunlap Post-doctoral Fellow at the Dunlap Institute for Astronomy and Astrophysics, University of Toronto, Canada.

I am from Dhaka, Bangladesh, where my family still lives. I advocate for equal opportunities in scientific research/education for students from countries with limited access to resources. I have taught in the Yale Young African Scholars program in Ghana and Rwanda. I have also founded several outreach programs in Bangladesh including Bangladesh Science Outreach (2013) and Durbin (2023).

 
 

Interested in Astronomy in Bangladesh? Join Dürbin.

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Interested in Astronomy in Bangladesh? Join Dürbin. 〰️

research

JWST

I am in several extragalactic teams analyzing the early data from JWST. In particular, I am studying the dawn of diversity in galaxy structure. Were all galaxies born with the same shape? Were they all born as disks or spheroids? Were Ultra Compact Dwarves born in a compact halo and Ultra Diffuse Galaxies born in diffuse ones? Or were they the same at birth? Did mergers and feedback result in them having such peculiar morphologies? How important is dark matter in shaping a galaxy? I will use surveys such as CANUCS, UNCOVER and other future programs to answer these questions.

The work has already started! In JWST's first deep field, we discovered a collection of compact red objects around a remarkable z=1.38 galaxy ("The Sparkler") being strongly lensed by the SMACS 0723 cluster. These compact sources are red and quiescent - ideal candidates for globular clusters forming at z>7. This discovery opens the possibility of studying the growth of galaxies and their parent halos by investigating quiescent globular cluster populations at high redshifts. Find out more at Mowla et al. 2022b.

NOOR

I am creating mock observations of simulated galaxies at different epochs to disentangle the effect of dust on the observed morphological evolution of galaxies since z~6. Using SIMBA cosmological hydrodynamical simulations (Dave et al. 2019), which has on-the-fly dust production, and the Powderday 3D radiative transfer package (Narayanan et al. 2021), we are creating realistic mock observations of simulated galaxies for any HST and JWST. This is an ongoing project - please contact if you’d like to find out more!

 

3DDASH MAST page. (Image credit: Ivelina Momcheva)

3D-DASH SURVEY (successor of cosmos-dash)

The 3D-Drift And SHift (3D-DASH) program is a Hubble Space Telescope WFC3 F160W imaging and G141 grism survey of the equatorial COSMOS field. 3D-DASH is the widest HST/WFC3 imaging survey in the F160W filter, subsuming the COSMOS-DASH pilot survey (Mowla et al. 2019b). 3D-DASH extends the legacy of HST near-infrared imaging and spectroscopy to degree-scale swaths of the sky, enabling the identification and study of distant galaxies (z > 2) that are rare or in short-lived phases of galaxy evolution at rest-frame optical wavelengths.

The unique Drift And SHift (DASH) observing mode forgoes inefficient guide-star acquisition per pointing by guiding with three gyros alone. With DASH we increased the imaging efficiency of WFC3 by eight times to observe a wide field medium depth survey. Multiple read-outs per pointing with extremely small drifts between 25-second exposures are then shifted and coadded to create a final undistorted deep image. For full details of the technique, see Momcheva et al. (2017) and Appendix A1 of Mowla et al. (2019b).

Mass Dependent size-mass relation since z~3 and comparison with halo-to-stellar mass relation

Armed with the wide area of the high-resolution COSMOS-DASH image, we were finally able to measure the structural parameters of over a thousand massive galaxies at 0.1<z<3.0 (the last 11.5 billion years) and extend the size-mass relation to the high mass end (Mowla et al. 2019b). We noticed that the sizes of the massive galaxies are larger than expected from an extrapolation of the low mass size — M∗ relation. Hence, we reassess the size — M∗ relation of all galaxies since z~3 and found it to be well described by a broken power law (than a single power law), with a clear change in slope at a pivot mass Mp, which increases with redshift. We compared the size — M∗ relation to the Mhalo — M∗ relation (dark matter halo mass — stellar mass relation) and find remarkable agreement between the pivot stellar masses and slopes of both relations (for the simple assumption R_vir ∝ r_star). This suggests that the same underlying physical mechanisms might be driving both the relations. The pivot mass may reflect a transition from dissipational to dissipationless galaxy growth in both the Mhalo − M∗ and the size − M∗ relation. More can be found in Mowla et al. 2019a.

anomalously narrow co(3-2) linewidths of compact star-forming massive galaxies: Possible inclination bias in the size-mass relation of galaxies

Compact, massive star forming galaxies at z ∼ 2.5 (11 billion years ago) are thought to be building the central regions of giant elliptical galaxies today. Hence, their centers are expected to extremely dense - similar to that of their suspected descendent elliptical galaxies (FWHM of 500-800 km/s). This was tested by measuring the dispersions of ionized gas from the Hα line widths, where a significant fraction of these objects showed much smaller Hα line widths than expected (FWHM(Hα)∼125-260 km s−1; see van Dokkum et al. 2015). A possible interpretation is that Hα emission from their central regions, where the highest velocities are expected, is typically obscured by dust. Hence we observed the dust unobscured CO(3-2) emission lines of three of these compact star-forming galaxies narrow Hα line widths to test this hypothesis. Surprisingly, in all three galaxies, the CO line width is even narrower than the Hα line width: we find FWHM(CO)∼165 km s−1 for all three galaxies whereas FWHM(CO)∼450-700 km s−1 was expected from a simple virial estimator. These results show that the narrow Hα linewidths of many compact massive star-forming galaxies are not due to preferential obscuration of the highest velocity gas. An alternative explanation for the narrow line widths is that the galaxies are disks that are viewed nearly face-on. We suggest that there may be an inclination bias in the size-mass plane, such that the apparent rest-frame optical sizes of face-on galaxies are smaller than those of edge-on galaxies. Although not conclusive, this hypothesis is supported by an observed anti-correlation between size and axis ratio of massive galaxies. More can be found in Mowla et al. 2019c.

teasing out low surface brightness features of ultra diffuse galaxies

In addition to global galaxy properties such as size and compactness, morphologies hold important clues about the dynamical state of galaxies. For example, tidal features on galaxies suggest that a galaxy is being overcome by tidal forces which can help constrain the dynamical mass of the galaxy. Detecting faint tidal features require deep imaging which are particularly hard for low surface brightness objects, such as ultra diffuse galaxies (galaxies with mu(g,0)>magarcsec−2 and r_e>1.5 kpc). I developed a technique of teasing out faint features in galaxy outskirts through stacking deep images of galaxies oriented along their major axis. Isophotal analysis of stacked mock images of galaxies with tidal features reveal circularization of light profile at r>2 r_e while stacked images of galaxies with no tidal features show no change in axis-ratio at large radii. Using this technique on deep Subaru images of UDGs in Coma cluster, I found that these galaxies have remarkably uniform light profile out to ~4 r_e. We infer that the average tidal radius of the Coma UDGs is >7 kpc and estimate that the average dark matter fraction within the tidal radius of the UDGs inhabiting the innermost 0.5 Mpc of the Coma cluster is >99%. More can be found in Mowla et al. 2017.


Selected publications

  1. Mowla, L. and Iyer, K., et al., The Sparkler: Evolved High-Redshift Globular Clusters Captured by JWST, ApJL.

  2. Mowla, L., et al., 3D-DASH: The Widest Near-infrared Hubble Space Telescope Survey, ApJ, 933, 129, (2022).

  3. Whitaker, K., Williams, C., Mowla, L. et al., Quenching of star formation from a lack of inflowing gas to galaxies, Nature, 597, 7877, 485-488 (2021).

  4. Strubbe, L. et al., The Pan-African School for Emerging Astronomers, Nature Astronomy, 5, 217-220 (2021).

  5. Cutler, S., Whitaker, K., Mowla, L. et al., Diagnosing DASH: A Catalog of Structural Properties for the COSMOS-DASH Survey, ApJ, 925, 34, (2022).

  6. Mowla, L., Nelson, E. J., van Dokkum, P., Tadaki, K., et al. Anomalously Narrow CO Linewidths of Compact Massive Star-Forming Galaxies at z ∼ 2.3: A Possible Inclination Bias In the Size-Mass Plane, ApJL (in press).

  7. Mowla, L., van der Wel, A., van Dokkum, P., Miller, T. et al., A mass-dependent slope of the galaxy size–mass relation out to z ∼ 3: further evidence for a direct relation between median galaxy size and median halo mass, ApJL, 872, 13 (2019).

  8. Mowla, L., van Dokkum, P, et al., Brammer, G., Momcheva, I., et al., COSMOS-DASH: The Evolution of the Galaxy Size─Mass Relation since z ∼ 3 from New Wide-field WFC3 Imaging Combined with CANDELS/3D-HST, ApJ, 868, 96 (2018).

  9. Van Dokkum, et al. including Mowla L., A Galaxy Lacking Dark Matter, Nature, 555, 629 (2018).

  10. Mowla, L., van Dokkum, P., Merritt, A., Abraham, R., Yagi, M., Koda, J., Evidence of Absence of Tidal Features in the Outskirts of Ultra Diffuse Galaxies in the Coma Cluster, ApJ, 851, 27 (2017).

For a full list of my publications please visit my ADS page.

In the News

sparkler

3D-DASH

 

teaching and Outreach

 

দূরবিন (Dürbin)

Dürbin (Dur Biswer Nagorik) is an observational astronomy program we are starting in Bangladesh in 2023. Citizen astronomers will do astrophotography and citizen science projects using Unistelar Equinox telescopes. The telescopes will also be used in the classroom of the first astronomy course with an observational lab in Bangladesh. If you are in Bangladesh and want to join Dürbin, please apply at durbin.cc.

 
 
Ghana 2018 session of YYAS at Tema International School, Tema, Ghana.

Ghana 2018 session of YYAS at Tema International School, Tema, Ghana.

yale young African scholars (Ghana & Rwanda)

This is an intensive academic and enrichment program designed for African secondary school students planning to pursue tertiary education and who wish to make a meaningful impact as young leaders on the continent. In 2018 I was an Instructor in the program and taught eight astronomy seminars in Ghana and Rwanda on topics ranging from exoplanet search to gravitational waves. I also mentored students with college application processes and with honing their leadership skills.

BSO Mentors holding a workshop at Jangalia Madrasa, Gazipur, Bangladesh.

BSO Mentors holding a workshop at Jangalia Madrasa, Gazipur, Bangladesh.

bangladesh science outreach

This is an after-school science program in Bangladesh that I founded and lead during my gap year between college and graduate school. BSO is one of the first secondary school science activity program that was designed specifically for rural schools of Dhaka, Bangladesh, with limited access to technology/electricity. It was run by volunteer undergraduate students from national universities. BSO focused on many schools with no science classes and reached over a thousand students over two years. Currently BSO is on hiatus and we are looking for avenues to restart the program. You can find out about our work here:

I have also been an instructor at Yale Young Global Scholar, organizer of annual Yuri’s Night @ Yale, and a cultural companion at Integrated Refugee and Immigrant Services in New Haven. These programs are always looking for new volunteers. If you are interested in joining any of them, please visit their website or contact me.

For a broader list of my teaching, services, and outreach activities, please visit my CV.

 

data products

COSMOS-DASH Cutout Request

The COSMOS-DASH is the largest contiguous extragalactic imaging survey with the Hubble Space Telescope/Wide Field Camera 3 in near-infrared (F160W) covering 0.49 deg2 of the COSMOS field (0.66 deg^2 including archival data). The imaging was performed using the novel Drift and Shift technique (Momcheva et al. 2017). The reduced COSMOS-DASH mosaic is now publicly available in our COSMOS-DASH MAST page. To request cutouts and colored images (with ACS-F814W) of the COSMOS-DASH mosaic, please send a text file containing the coordinates and cutout size.

Catalog of structural properties of the most massive galaxies in COSMOS-DASH

Catalog of structural properties of ultra diffuse galaxies in the coma cluster

AIP Departmental Self-assessment survey

The American Institute of Physics have created a departmental self-assessment rubric to suggest a way for physics and astronomy departments to evaluate their effectiveness in creating a healthy learning environment for Black students. The self-assessment rubric is modeled after one created by the New England Resource Center for Higher Education and a similar one created by the AAS Task Force on Diversity and Inclusion in Graduate Education (Appendix X of Agüeros et al. 2019).

This online survey is based on this rubric which you can edit to fit to your department’s needs.

To make a copy of the AIP Departmental Self-Assessment Form you have to first copy the spreadsheet to your Google Drive:

  1. Click on the button below which will take you to a Google Spreadsheet

  2. Sign in to your gmail account and make a copy of this spreadsheet in your Drive.

  3. Go to Google Forms

  4. A copy of this form should appear in your Google Forms which you can edit and share.

  5. The responses will be collected in this spreadsheet.

The online form is created by Claire Dickey and Lamiya Mowla.

Systemic Changes to Increase African Americans with Bachelor's (and Doctoral) Degrees in Astronomy Adapted from American Institute of Physics Team-Up Appendix 8: https://www.aip.org/sites/default/files/aipcorp/files/teamup-appendix8.pdf The findings and recommendations of this report suggest a way for physics and astronomy departments to evaluate their effectiveness in educating African American students.