Galaxy Evolution and Dynamical Structures - GEDS 2018

Venue: Bhaskara 3, IUCAA

Date: Jan 22 - 24, 2018

Jan 22, 2018

9.25 - 9.30

Welcome by the director, IUCAA

Session 1 (Chair: Ralf-J. Dettmar)

9.30 - 10.15

Elena D’Onghia

Univ. of Wisconsin, USA

The nature of spiral arms in Disk Galaxies


10.15 - 10.45

Soumavo Ghosh

IISc, Bangalore

Role of interstellar gas on longevity of spiral structure in disk galaxies

We show inclusion of gas lowers the group velocity of the wave packet of density wave, thus helps the spiral arms to survive for the longer time-scale. Also, inclusion of gas is necessary to get stable density wave for the observed pattern speed

10.45 - 11.15

Tea break

11.15 - 12.00

Mousumi Das

IIA, Bangalore

Star Formation and Spiral Arms in the Extreme Outer Disks of Galaxies

We present UV observations of star formation in the Extended Ultraviolet Disks (XUV) of nearby galaxies. Such galaxies show filamentary or diffuse star formation in regions well beyond their optical disks. GALEX found that 30% of all nearby spiral galaxies have XUV disks. They can be classified into two broad classes, type 1 or 2, depending on their UV morphology. Type~1 XUV disks have spiral arms that extend into the outer disk and type~2 XUV disks have low surface brightness disks that are rich in UV emission. The XUV star formation maybe driven by gas accretion from the intergalactic medium, high altitude clouds or by interactions with neighboring galaxies. The nature of star formation in XUV disks is different from normal galaxies as the outer disk environment is metal poor and stellar surface density low. In this presentation we show UVIT observations of XUV disks and discuss their origin and the nature of their spiral structure.

12.00 - 12.30

Sarita Vig

IIST, Trivandrum

UVIT view of ring galaxies


12.30 - 13.00

Arunima Banerjee

IISER, Tirupati

Origin of low surface brightness galaxies: A dynamical study

Using the 2-component disc stability parameter Q_RW as proposed by Romeo \& Wiegert (2011), we show that LSBs have more stable discs than HSBs, which could explain their low star formation rates and, possibly, their low surface brightness nature.

13.00 - 14.00

Lunch Break

Session 2 (Chair: Mousumi Das)

14.00 - 14.30

Amitesh Omar

ARIES, Nainital

Chemical evolution and HI dynamics in nearby dwarf galaxies

An episode of star formation in dwarf galaxies can bring significant evolution in its chemical composition and dynamics. The present sensitivities of 2 to 4-m class optical telescopes equipped with integral field and slit spectrographs are adequate to study chemical evolution in several nearby galaxies. The radio interferometers such as GMRT are sensitive to study HI-based dynamics of galaxies. I will present some recent results on nearby dwarf galaxies with very recent (<10 Myr) active star formation as traced by Wolf-Rayet (WR) emission-line features. We could trace tidal interaction in majority of dwarf WR galaxies using optical and radio observations. The observed chemical (in)homogeneity in dwarf galaxies will also be addressed. The importance of the upcoming integral field spectrograph for the 3.6-m Devasthal Optical telescope will be highlighted for study of dwarf galaxies.

14.30 - 15.00

Sushma Kurapati


Angular momentum of dwarf galaxies

We present the measurements of baryonic mass (M) and the baryonic specific angular momentum (j) of 11 dwarf galaxies that lie in Lynx-Cancer void based on high-resolution HI observations and the stellar mass profiles. We find that the dwarf galaxies in the void show similar trend in j-M pane as that of the dwarf galaxies in average density environments. However, all the dwarf galaxies have significantly higher specific angular momentum than expected from the relation obtained for the larger spiral galaxies. We find a systematic trend with mass, in that dwarf galaxies with masses lower than 10$^{9.1}$ M$_{\odot}$ have significantly higher baryonic specific angular momentum than expected from the relation found for spiral galaxies . As the mass of the galaxy increases beyond 10$^{9.1}$ M$_{\odot}$, the baryonic specific angular momentum decreases and they tend to follow the relation obtained for the massive galaxies with zero bulge fraction. Interestingly, the mass threshold that we find, viz, 10$^9.1} M$_{\odot}$ is similar to the one at which galaxy disks begin to systematically thicken. We propose that both these effects, viz. the thickening of disks and the increase in specific angular momentum are due to stellar feedback processes. These preferentially remove the low angular momentum gas from the central parts of dwarfs (thus increasing the specific angular momentum of the system) and also inject mechanical energy into the system, leading to thicker discs.

15.00 - 15.30

Chayan Mondal

IIA, Bangalore

UVIT imaging of WLM : Understanding hot star forming regions in the nearby dwarf irregular galaxy

We present ultra-violet study of the nearby dwarf irregular galaxy WLM with UVIT multi band observation. The galaxy, having a distance 995 kpc, was observed in three UVIT filters F148W, N245M and N263M. We created two different color maps (F148W/N245M and F148W/N263M) for studying the temperature morphology of different star forming regions of the galaxy. We identified several star forming clumps with temperature $>$ 35000 K and size $\sim$ 10 - 50 pc. The detected high temperature regions also show good spatial correlation with the H$\alpha$ emitting regions of the galaxy. The hottest core of each star forming clumps are found to be enveloped by regions with gradually decreasing temperature. We also studied the FUV disk of the galaxy and identified two main star forming complexes in the galaxy. We further performed psf photometry to identify possible star clusters present in the galaxy and estimated their masses by using starburst99 SSP model.

15.30 - 16.30

Tea break + Poster session

16.30 - 17.00

Abhishek Paswan

ARIES, Nainital

A detailed mrophological study of Wolf-Rayet galaxies

The morphological study of stellar light, neutral and ionized gases in star-forming galaxies may provide insight to the mechanisms responsible for fuelling and triggering recent/ongoing star formation. With this aim, we present a detailed morphological structural analysis of a sample of nearby Wolf-Rayet galaxies known to harbour very recent (< 10 Myr) starburst events. In this analysis, we identified several star-forming regions widespread over the disk of galaxies. Morphologically, these galaxies showed the lopsided, barred, plump, multiple-nuclei, arc-like and cometary-type head-tail structures of the ionized gas and stellar light distributions. Some galaxies revealed the disturbed gas kinematics and HI clouds outside the optical extent. These features in galaxies, indicative of recent tidal interaction or merger scenario which is most likely responsible for availing the galaxies of their cold gas and triggering recent star formation. Overall, this study concludes that galaxies in the sample are undergoing a morphological evolution due to recent/ongoing star formation.

17.00 - 17.30

Somak Raychaudhury


Galaxy evolution on the outskirts of clusters


Jan 23, 2018

Session 3 (Chair: Sudhansu Barway)

9.30 - 10.15

Daniel Pfenniger

Geneva Observatory, Switzerland

The relationship between bar and disk thickening


10.15 - 10.45

Kanak Saha


Pinched and peanut bulges in spiral galaxies


10.45 - 11.15

Tea Break

11.15 - 12.00

Monica Valluri

Univ. of Michigan, USA

New insights into the orbital structure of bars and Box/Peanut bulges


12.00 - 12.30

Isha Pahwa


LSB galaxies and their structural properties


12.30 - 13.00

Sandeep Kumar Kataria

IIA, Bangalore

The Effect of Bulge Mass and Concentration on Bar Formation and Pattern Speed

We use N-body simulations of bar formation in an isolated galaxy to study the effect of bulge mass and bulge concentration on bar formation and bar pattern speed. Two sets of models are generated, one that has a dense bulge and high surface density disk and a second model that has a less concentrated bulge and a lighter disk. Simulations of both the models show that there is an upper cut-off in bulge to disk mass ratio Mb/Md above which bars cannot form; the cut-off is smaller for denser bulges( Mb/Md = 0.2) compared to less denser ones (Mb/Md = 0.5). We define a new criteria for bar formation in terms of bulge to disk radial force ratio (Fb/Fd) at the disk scale length above which bars cannot form and show that if Fb/Fd > 0.35, a disk is stable and a bar cannot form. The net decrease in pattern speed \Delta \Omega_p increase with bulge mass and the ratio of corotation radii to bar semi-major axis decreases from 1.85 to 1.63 as we go from bulgeless to bulge dominated galaxies.

13.00 - 14.00

Lunch break

Session 4 (Chair: Monica Valluri)

14.00 - 14.30

Arianna Cortesi

Univ. of Sao Paolo, Brazil

The S0 road: a network of routes to create lenticular galaxies


14.30 - 15.00

Sudhanshu Barway

IIA, Bangalore

Do bars in S0 galaxies prefer a bulge type?


15.00 - 16.00

Tea break + poster session

16.00 - 16.30

Preetish Kumar Mishra


Age bimodality in the central region of pseudobulges in S0 galaxies

We present evidence for bimodal stellar age distribution of pseudobulges of S0 galaxies as probed by the $D_n(4000)$ index. We do not observe any bimodality in age distribution for pseudobulges in spiral galaxies. Our sample is flux limited and contains 2067 S0 and 2630 spiral galaxies drawn from the Sloan Digital Sky Survey. We identify pseudobulges in S0 and spiral galaxies, based on the position of the bulge on the Kormendy diagram and their central velocity dispersion. Dividing the pseudobulges of S0 galaxies into old and young population, we study the connection between global star formation and pseudobulge age on the $u-r$ color-mass diagram. We find that most old pseudobulges are hosted by passive galaxies while majority of young bulges are hosted by galaxies which are star forming. Dividing our sample of S0 galaxies into early type S0s and S0/a galaxies, we find that old pseudo bulges are mainly hosted by early type S0 galaxies while most of the pseudo bulges in S0/a galaxies

16.30 - 17.00

Koshy George

IIA, Bangalore

Star forming blue early-type galaxies: Structure and stellar population analysis

The color map and structural analysis of 55 star forming blue early-type galaxies reveal features indicative of diverse star formation processes. The results in the context of the stellar mass growth in early-type galaxies will be discussed.

17.00 - 17.30

Omkar Bait


Outlying H alpha emitters in SDSS IV MaNGA


Special talk

17.30 - 18.00

Dipankar Bhattacharya


Science with AstroSat


19.00 -

Conference Dinner @ Akashganga 1

Jan 24, 2018

Session 5 (Chair: Daniel Pfenniger)

9.15 - 10.00

Young-Wook Lee

Yonsei University, South Korea

Building the Milky Way bulge from globular clusters: Evidence from the double red clump

The double red clump (RC) observed in the color magnitude diagram of the Milky Way bulge is widely accepted as evidence for an X-shaped structure originated from the bar instability. A drastically different interpretation was suggested, however, based on He-enhanced multiple stellar population phenomenon as is observed in globular clusters (GCs). Here we report our discovery that the stars in the two RCs show a significant difference in CN band strength, in stark contrast to the X-shaped bulge scenario. The difference is comparable to those observed in GCs between the first- and later generation stars. Since CN-strong stars trace a population with enhanced N, Na, and He abundances originated in GCs, this is direct evidence that the double RC is due to the multiple population phenomenon, and that a significant population of stars in the Milky Way bulge were provided by disrupted proto-GCs.

10.00 - 10.30

Tejpreet Kaur

Punjab Univ.

Chemical abundance evolution and radial migration in the Milky Way galaxy

The elemental abundance gradients of all the elements upto Zinc for the galactic disc of Milky Way galaxy are determined by simulating the galaxy in a realistic manner by evolving interstellar medium and numerous generations of stars. The galaxy is divided into eight concentric annular rings each with width of 2 kpc. The evolution of star formation rate(SFR), supernova rates, total surface mass density, and metallicity for each ring in the galactic disc over the galactic time scale is determined by incorporating the latest understanding of accretion history of galaxy, the star formation rate, the stellar initial mass function (IMF), supernova rates, the updated stellar nucleosynthetic yields, and the stellar evolutionary theories for different stellar masses and metallicities.

10.30 - 11.00

Tea break

11.00 - 11.45

Florent Renaud

Univ. of Sweden, Sweden

Retracing the assembly of the Milky Way from its star clusters


11.45 - 12.15

Devendra Ojha

TIFR, Mumbai

A Stellar Population Synthesis Model for the Study of Ultraviolet Star Counts of the Galaxy

We have upgraded the Besancon model of stellar population synthesis to predict star counts in the UV passbands of the Ultraviolet Imaging Telescope (UVIT) onboard Astrosat which will be very useful to separate out different stellar populations and to estimate the structural parameters of the Galaxy with better precision. The aim of our present study is to investigate in detail the observed UV star counts obtained by GALEX vis-à-vis the model simulated catalogues produced by the Besançon model in various Galactic directions, and to explore the potential for studying the structure of our Galaxy from images in multiple near-UV (NUV) and far-UV (FUV) filters of the UVIT.

12.15 - 12.45

Yogesh Joshi

ARIES, Nainital

Investigation of open clusters to probe the galactic structure in the solar neighbourhood

Significant progress has been made in recent years to understand the formation and evolution of Milky Way through various stellar populations. Open star clusters are one such example which are distributed throughout the Galactic disk and trace the spiral arms through their younger populations. In recent times a large number of open clusters are reported in the Milky Way using both optical and Infrared observations and a homogenous sample of more than 3000 open clusters has been constructed. Using such archival data on open clusters, one can not only understand the general properties of the open cluster system in the Galaxy but can also be used to probe the Galactic structure in the solar neighborhood. In this talk, I discuss Galactic open cluster systems in the context of understanding Galactic structure.

Special talk

12.45 - 13.15

Joydeep Bagchi


Saraswati Supercluster


13.15 - 14.15

Lunch break

Session 6 (Chair: Arianna Cortesi)

14.15 - 15.00

Ralf-J. Dettmar

Univ. of Bochum, Germany

Observational Evidence for CR-Driven Galactic Winds

CR-driven winds are currently considered as an important form of feedback in galaxy evolution. In this talk we will provide observational evidence from several recent radio-surveys supporting this theoretical concept.

15.00 - 15.30

Sonali Sachdeva


Bulges more compact and brighter than ellipticals at intermediate redshifts

Abstract: Examining bright disc galaxies at intermediate redshifts (0.4-1.0), in both optical and infrared using images from HST-ACS and WFC3, we have discovered a class of bulges (12%, 43 out of 358) which are more compact and brighter than elliptical galaxies. These bulges can not be classified as pseudo (which are dimmer and elongated) or classical (which are as bright and compact as ellipticals). Such bulges have not been reported in literature, even for local redshifts where there have been dense galaxy decomposition studies covering large samples. We denote them as "strange" bulges. Disc galaxies with strange bulges are intensely compact considering that they are about 1 kpc shorter in half light radius and disc scale length and about twice as massive as discs with pseudo bulges and 1.5 times more massive than those with classical bulges. These bulges are an anomaly is also reflected in the fact that the bulge accounts for more than 40% of total optical galaxy light which is a rarity at such high redshifts. Another interesting feature is that these galaxies have double the star formation rates and UV-luminosities than disc galaxies with pseudo and classical bulges which have comparable values of these two parameters. Analysing their evolution with the reference frame of 6413 bright local discs and elliptical galaxies, we examine if they are descendants of red nuggets and have recently acquired the disc through accretion.

15.30 - 16.00

Jonathan Freundlich

Racah Institute of Physics, Israel

Molecular gas reservoirs and morphology during the winding-down of star formation

Star formation in the Universe decreased by an order of magnitude in the last ten billion years, during which galaxies experienced morphological changes. The PHIBSS2 program at the IRAM NOEMA interferometer surveys the molecular gas properties of galaxies at different redshifts on and around the main sequence, where most of star formation occurs. At z=0.5-0.8, we observe the CO(2-1) line for 61 targets, from which we determine molecular gas masses, gas fractions and depletion times. Our results contribute to show that the cosmic evolution of the star formation rate is mainly driven by that of the molecular gas fraction, albeit with a small inflexion of the star formation efficiency. We further obtain disk sizes and bulge-to-total luminosity ratios, pointing towards little dependence of the molecular gas content and star formation with bulge size. This may suggest an ongoing supply of molecular gas to compensate for star formation and a contribution of disk stars to the growing bulge.


Rupjyoti Gogoi

Tezpur Univ., Assam

Probing the morphologies of very high redshift galaxies


16.30 - 17.00



Summary and Concluding remarks

17.00 -

High Tea

End of the meeting

Poster Presentation


Aditya K

IISER, Tirupati

Constraining  vertical stellar dispersion in superthin galaxy UGC7321 using scale height data



Ananda Hota

CBS, Mumbai

From spirals to Speca: Galactic structures and wind- and jet-feedbacks as drivers of galaxy evolution



Ankit Singh

IISER Mohali

Quenching of star formation : contribution of ram pressure



Ashok Mondal

Univ. of Calcutta, Kolkata

Fragmentation of interstellar clouds with negative polytropic indices




IIA, Bangalore

Study of stellar populations in disk of the Galaxy in the GAIA era



Geeta Rangwal

Kumaun Univ. Uttarakhand

Galactic disc structure in fourth Galactic quadrant

Open star clusters are irregular groups of dozen to thousand of population I metal rich stars which have a closer gravitational interaction than that of surrounding field stars. Open star clusters are concentrated towards the plane of Galaxy so the spatial distribution of these clusters defines the spiral arm structure of the Galaxy. We have investigated the galactic disc structure in the direction of l ∼ 270 ◦ to l ∼ 360 ◦ . For this study we have selected open star clusters from WEBDA database lying in this direction. We will present the results of this study in the poster.


Naseer Iqbal

Univ. of Kashmir, Kashmir

Cosmological Phase transitions in Galaxy Clusters



Priya Hasan

MANU Univ., Hyderabad

Morphology of AGN Host Galaxies



Rahul Rana

IISER Mohali

GAMA:Correlation with ALFALFA HI sources

Old galaxies are generally optically red and elliptical while young galaxies are star-forming, blue, spirals or irregular. This also implies that the former are depleted in neutral Hydrogen, which is required to form new stars while the latter are rich in it. By making use of the available observed and derived data from the Galaxy and Mass Assembly Survey (GAMA) we have created a sample of galaxies which has neutral atomic hydrogen (HI) data available from the ALFALFA survey. Now we will split it into red and blue galaxies and analyse the HI properties of the two types of sources. GAMA data will provide an insight into the environment, morphology and the dust content of the ALFALFA sources in GAMA to understand why did the red galaxies stop forming stars despite having the gas, and for how long can the blue ones sustain their star formation with the given gas mass and star formation rate.


Thakkalapally Swetha

Osmania Univ.

Multiple minor mergers of disk galaxies



Gourab Giri

Evidence of recent merger in early-type galaxies