Extreme variations in star formation activity in the first galaxies

2019 ◽  
Vol 15 (S341) ◽  
pp. 226-230
Author(s):  
Christian Binggeli ◽  
Erik Zackrisson ◽  
Xiangcheng Ma ◽  
Akio K. Inoue ◽  
Anton Vikaeus ◽  
...  
Keyword(s):  
Star Formation ◽  
Rest Frame ◽  
High Redshift ◽  
Formation Rate ◽  
High Redshift Galaxies ◽  
James Webb Space Telescope ◽  
Star Formation Activity ◽  
The Galaxy ◽  
First Galaxies ◽  
Star Formation Histories

AbstractRecently, spectroscopic detections of O[III] 88 μm and Ly-α emission lines from the z ≍ 9.1 galaxy MACS1149-JD1 have been presented, and with these, some interesting properties of this galaxy were uncovered. One such property is that MACS1149-JD1 exhibits a significant Balmer break at around rest-frame 4000 Å, which may indicate that the galaxy has experienced large variations in star formation rate prior to z ∼ 9, with a rather long period of low star formation activity. While some simulations predict large variations in star formation activity in high-redshift galaxies, it is unclear whether the simulations can reproduce the kind of variations seen in MACS1149-JD1. Here, we utilize synthetic spectra of simulated galaxies from two simulation suites in order to study to what extent these can accurately reproduce the spectral features (specifically the Balmer break) observed in MACS1149-JD1. We show that while the simulations used in this study produce galaxies with varying star formation histories, galaxies such as MACS1149-JD1 would be very rare in the simulations. In principle, future observations with the James Webb Space Telescope may tell us if MACS1149-JD1 represents something rare, or if such galaxies are more common than predicted by current simulations.

scholarly journals Red and dead CANDELS: massive passive galaxies at the dawn of the Universe

2019 ◽  
Vol 490 (3) ◽  
pp. 3309-3328 ◽  
Author(s):  
E Merlin ◽  
F Fortuni ◽  
M Torelli ◽  
P Santini ◽  
M Castellano ◽  
...  
Keyword(s):  
Star Formation ◽  
High Redshift ◽  
Formation Rate ◽  
Probabilistic Approach ◽  
Big Bang ◽  
Spectral Lines ◽  
Massive Galaxies ◽  
Star Formation Activity ◽  
Star Formation Histories ◽  
The Big Bang

ABSTRACT We search the five CANDELS fields (COSMOS, EGS, GOODS-North, GOODS-South, and UDS) for passively evolving a.k.a. ‘red and dead’ massive galaxies in the first 2 Gyr after the big bang, integrating and updating the work on GOODS-South presented in a previous paper. We perform SED-fitting on photometric data, with top-hat star-formation histories to model an early and abrupt quenching, and using a probabilistic approach to select only robust candidates. Using libraries without (with) spectral lines emission, starting from a total of more than 20 000 z > 3 sources we end up with 102 (40) candidates, including one at z = 6.7. This implies a minimal number density of 1.73 ± 0.17 × 10−5 (6.69 ± 1.08 × 10−6) Mpc−3 for 3 < z < 5; applying a correction factor to account for incompleteness yields 2.30 ± 0.20 × 10−5. We compare these values with those from five recent hydrodynamical cosmological simulations, finding a reasonable agreement at z < 4; tensions arise at earlier epochs. Finally, we use the star-formation histories from the best-fitting models to estimate the contribution of the high-redshift passive galaxies to the global star formation rate density during their phase of activity, finding that they account for ∼5–10 per cent of the total star formation at 3 < z < 8, despite being only $\sim 0.5{{\ \rm per\ cent}}$ of the total in number. The resulting picture is that early and strong star formation activity, building massive galaxies on short time-scales and followed by a quick and abrupt quenching, is a rare but crucial phenomenon in the early Universe: the evolution of the cosmos must be heavily influenced by the short but powerful activity of these pristine monsters.

scholarly journals Signature of the first galaxies in JWST deep field observations

2019 ◽  
Vol 485 (4) ◽  
pp. 5939-5950 ◽  
Author(s):  
Myoungwon Jeon ◽  
Volker Bromm
Keyword(s):  
Star Formation ◽  
Gravitational Lensing ◽  
Spectral Energy Distribution ◽  
Formation Rate ◽  
Spectral Energy ◽  
Time Interval ◽  
Hydrodynamic Simulations ◽  
James Webb Space Telescope ◽  
The Galaxy ◽  
First Galaxies

Abstract We examine the assembly process and the observability of a first galaxy ($M_{\rm vir}\approx 10^9{\, \rm M_\odot }$ at z ≈ 8) with cosmological zoom-in, hydrodynamic simulations, including the radiative, mechanical, and chemical feedback exerted by the first generations of stars. To assess the detectability of such dwarf systems with the upcoming James Webb Space Telescope (jwst), we construct the spectral energy distribution for the simulated galaxy in a post-processing fashion. We find that while the non-ionizing UV continuum emitted by the simulated galaxy is expected to be below the jwst detection limit, the galaxy might be detectable using its nebular emission, specifically in the H α recombination line. This requires that the galaxy experiences an active starburst with a star formation rate of $\dot{M}_{\ast }\gtrsim 0.1 {\, \rm M_\odot }\rm{\,yr}^{-1}$ at z ≈ 9. Due to the bursty nature of star formation in the first galaxies, the time interval for strong nebular emission is short, less than 2–3 Myr. The probability of capturing such primordial dwarf galaxies during the observable part of their duty cycle is thus low, resulting in number densities of the order of one source in a single pointing with MIRI onboard the jwst, for very deep exposures. Gravitational lensing, however, will boost their observability beyond this conservative baseline. The first sources of light will thus come firmly within our reach.

scholarly journals SDSS J114818.18-013823.7: Forming Compact Dwarf Galaxy through the Dwarf-Dwarf Merger

2021 ◽  
Vol 7 (2) ◽  
pp. 49-57
Author(s):  
D. N. Chhatkuli ◽  
S. Paudel ◽  
A. K. Gautam ◽  
B. Aryal
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
Star Formation Rate ◽  
Dwarf Galaxy ◽  
Formation Rate ◽  
Absolute Magnitude ◽  
Spectroscopic Properties ◽  
Normal Galaxies ◽  
Star Formation Activity ◽  
The Galaxy

We studied the spectroscopic properties of the low redshift (z = 0.0130) interacting dwarf galaxy SDSS J114818.18-013823.7. It is a compact galaxy of half-light radius 521 parsec. It’s r-band absolute magnitude is -16.71 mag. Using a publicly available optical spectrum from the Sloan Sky Survey data archive, we calculated star-formation rate, emission line metallicity, and dust extinction of the galaxy. Star formation rate (SFR) due to Hα is found to be 0.118 Mʘ year-1 after extinction correction. The emission-line metallicity, 12+log(O/H), is 8.13 dex. Placing these values in the scaling relation of normal galaxies, we find that SDSS J114818.18-013823.7 is a significant outlier from both size-magnitude relation and SFR-B-band absolute relation. Although SDSS J114818.18-013823.7 possess enhance rate of star-formation, the current star-formation activity can persist several Giga years in the future at the current place and it remains compact.

The impact of star formation sampling effects on the spectra of lensed z > 6 galaxies detectable with JWST

2019 ◽  
Vol 492 (2) ◽  
pp. 1706-1712
Author(s):  
Anton Vikaeus ◽  
Erik Zackrisson ◽  
Christian Binggeli
Keyword(s):  
Star Formation ◽  
Spectral Synthesis ◽  
High Redshift ◽  
Formation Rate ◽  
Mass Function ◽  
Spectroscopic Studies ◽  
Initial Mass Function ◽  
James Webb Space Telescope ◽  
Population Iii Stars ◽  
The Impact

ABSTRACT The upcoming James Webb Space Telescope (JWST) will allow observations of high-redshift galaxies at fainter detection levels than ever before, and JWST surveys targeting gravitationally lensed fields are expected to bring z ≳ 6 objects with very low star formation rate (SFR) within reach of spectroscopic studies. As galaxies at lower and lower star formation activity are brought into view, many of the standard methods used in the analysis of integrated galaxy spectra are at some point bound to break down, due to violation of the assumptions of a well-sampled stellar initial mass function (IMF) and a slowly varying SFR. We argue that galaxies with SFR ∼ 0.1 M⊙ yr−1 are likely to turn up at the spectroscopic detection limit of JWST in lensed fields, and investigate to what extent star formation sampling may affect the spectral analysis of such objects. We use the slug spectral synthesis code to demonstrate that such effects are likely to have significant impacts on spectral diagnostics of, for example, the Balmer emission lines. These effects are found to stem primarily from SFRs varying rapidly on short (∼Myr) time-scales due to star formation in finite units (star clusters), whereas the effects of an undersampled IMF is deemed insignificant in comparison. In contrast, the ratio between the He ii- and H i-ionizing flux is found to be sensitive to IMF-sampling as well as ICMF-sampling (sampling of the initial cluster mass function), which may affect interpretations of galaxies containing Population III stars or other sources of hard ionizing radiation.

scholarly journals Evolution of Massive Galaxy Structural Properties and Sizes via Star Formation

2012 ◽  
Vol 10 (H16) ◽  
pp. 128-128
Author(s):  
Jamie R. Ownsworth ◽  
Christopher J. Conselice ◽  
Alice Mortlock ◽  
William G. Hartley ◽  
Fernando Buitrago
Keyword(s):  
Star Formation ◽  
Rest Frame ◽  
High Redshift ◽  
Formation Rate ◽  
Stellar Mass ◽  
Massive Galaxies ◽  
Mass Profile ◽  
Individual Galaxy ◽  
Mass Profiles

We investigate the resolved star formation properties of a sample of 45 massive galaxies (M* > 1011 M⊙) within a redshift range of 1.5 ⩽ z ⩽ 3 detected in the GOODS NICMOS Survey (Conselice et al. 2011), a HST H160-band imaging program. We derive the star formation rate as a function of radius using rest frame UV data from deep z850 ACS imaging. The star formation present at high redshift is then extrapolated to z = 0, and we examine the stellar mass produced in individual regions within each galaxy. We also construct new stellar mass profiles of the in situ stellar mass at high redshift from Sérsic fits to rest-frame optical, H160-band, data. We combine the two stellar mass profiles to produce an evolved stellar mass profile. We then fit a new Sérsic profile to the evolved profile, from which we examine what effect the resulting stellar mass distribution added via star formation has on the structure and size of each individual galaxy.

scholarly journals xGASS: the role of bulges along and across the local star-forming main sequence

2020 ◽  
Vol 493 (4) ◽  
pp. 5596-5605 ◽  
Author(s):  
Robin H W Cook ◽  
Luca Cortese ◽  
Barbara Catinella ◽  
Aaron Robotham
Keyword(s):  
Star Formation ◽  
Main Sequence ◽  
Formation Rate ◽  
Stellar Mass ◽  
Local Universe ◽  
Star Forming ◽  
Star Formation Activity ◽  
The Galaxy ◽  
Stellar Masses

ABSTRACT We use our catalogue of structural decomposition measurements for the extended GALEX Arecibo SDSS Survey (xGASS) to study the role of bulges both along and across the galaxy star-forming main sequence (SFMS). We show that the slope in the sSFR–M⋆ relation flattens by ∼0.1 dex per decade in M⋆ when re-normalizing specifice star formation rate (sSFR) by disc stellar mass instead of total stellar mass. However, recasting the sSFR–M⋆ relation into the framework of only disc-specific quantities shows that a residual trend remains against disc stellar mass with equivalent slope and comparable scatter to that of the total galaxy relation. This suggests that the residual declining slope of the SFMS is intrinsic to the disc components of galaxies. We further investigate the distribution of bulge-to-total ratios (B/T) as a function of distance from the SFMS (ΔSFRMS). At all stellar masses, the average B/T of local galaxies decreases monotonically with increasing ΔSFRMS. Contrary to previous works, we find that the upper envelope of the SFMS is not dominated by objects with a significant bulge component. This rules out a scenario in which, in the local Universe, objects with increased star formation activity are simultaneously experiencing a significant bulge growth. We suggest that much of the discrepancies between different works studying the role of bulges originate from differences in the methodology of structurally decomposing galaxies.

scholarly journals Towards a multi-scale understanding of the gas-star formation cycle in the Central Molecular Zone

2016 ◽  
Vol 11 (S322) ◽  
pp. 64-74
Author(s):  
J. M. Diederik Kruijssen
Keyword(s):  
Star Formation ◽  
Milky Way ◽  
High Redshift ◽  
Three Dimensional ◽  
Orbital Dynamics ◽  
Molecular Gas ◽  
Stellar Clusters ◽  
High Redshift Galaxies ◽  
Multi Scale ◽  
The Galaxy

AbstractThe Central Molecular Zone (CMZ, the central 500 pc of the Milky Way) contains the largest reservoir of high-density molecular gas in the Galaxy, but forms stars at a rate 10–100 times below commonly-used star formation relations. We discuss recent efforts in understanding how the nearest galactic nucleus forms its stars. The latest models of the gas inflow, star formation, and feedback duty cycle reproduce the main observable features of the CMZ, showing that star formation is episodic and that the CMZ currently resides at a star formation minimum. Using orbital modelling, we derive the three-dimensional geometry of the CMZ and show how the orbital dynamics and the star formation potential of the gas are closely coupled. We discuss how this coupling reveals the physics of star formation and feedback under the conditions seen in high-redshift galaxies, and promotes the formation of the densest stellar clusters in the Galaxy.

scholarly journals New submillimeter diagnostics of physical properties of ISM in high redshift galaxies

2006 ◽  
Vol 2 (S235) ◽  
pp. 430-430
Author(s):  
Yoichi Tamura ◽  
Kouichiro Nakanishi ◽  
Kotaro Kohno ◽  
Ryohei Kawabe
Keyword(s):  
Star Formation ◽  
Physical Properties ◽  
High Redshift ◽  
Formation Rate ◽  
Host Galaxies ◽  
Power Sources ◽  
High Redshift Galaxies ◽  
Star Forming ◽  
Order Of Magnitude ◽  
New Diagnosis

AbstractWe present a new diagnosis method for determining physical properties of star-forming gas in high-z galaxies. In this method, we employed three key observational quantities, [CI], CO, and FIR luminosities, including our new detections of CO J = 4–3 emission from the pure-starburst (non-AGN) submm galaxy SMM J14011+0252 (z = 2.6) and the type-2 AGN IRAS FSC 10214+4724 (z = 2.3) obtained with the Nobeyama Millimeter Array (NMA) at the Nobeyama Radio Observatory. These two sources have extremely high star formation rate, and exhibit strong emission of CO and [CI] 609 μm lines. We determined ISM physical conditions for the two objects and another three high-z quasars in order to investigate the relationship between their ISM and power sources (i.e., massive star formation or AGN). A new PDR analysis (Wolfire et al. 2005, private communication) using CO, [CI], and FIR on five high-z sources provides new evidence that AGN host galaxies harbor denser (log nH ~ 5–6) ISM exposed to stronger far-UV fluxes of log G0 ~ 3.5–4 than the non-AGN submm galaxy. Volume filling factors of the star-forming dense gas in the AGN hosts are an order of magnitude smaller than that of the pure-starburst submm galaxy. This suggests that, in these AGN hosts, dense molecular clouds are dominating the central kpc around AGN, triggering extensive circumnuclear starbursts, and possibly feeding their central supermassive black hole simultaneously.

scholarly journals Simulating JWST deep extragalactic imaging surveys and physical parameter recovery

2020 ◽  
Vol 640 ◽  
pp. A67
Author(s):  
O. B. Kauffmann ◽  
O. Le Fèvre ◽  
O. Ilbert ◽  
J. Chevallard ◽  
C. C. Williams ◽  
...  
Keyword(s):  
Star Formation ◽  
Near Infrared ◽  
High Redshift ◽  
Spectral Energy Distribution ◽  
Formation Rate ◽  
Spectral Energy ◽  
Photometric Redshifts ◽  
The Galaxy ◽  
Stellar Masses ◽  
The Impact

We present a new prospective analysis of deep multi-band imaging with the James Webb Space Telescope (JWST). In this work, we investigate the recovery of high-redshift 5 <  z <  12 galaxies through extensive image simulations of accepted JWST programs, including the Early Release Science in the EGS field and the Guaranteed Time Observations in the HUDF. We introduced complete samples of ∼300 000 galaxies with stellar masses of log(M*/M⊙) > 6 and redshifts of 0 <  z <  15, as well as galactic stars, into realistic mock NIRCam, MIRI, and HST images to properly describe the impact of source blending. We extracted the photometry of the detected sources, as in real images, and estimated the physical properties of galaxies through spectral energy distribution fitting. We find that the photometric redshifts are primarily limited by the availability of blue-band and near-infrared medium-band imaging. The stellar masses and star formation rates are recovered within 0.25 and 0.3 dex, respectively, for galaxies with accurate photometric redshifts. Brown dwarfs contaminating the z >  5 galaxy samples can be reduced to < 0.01 arcmin−2 with a limited impact on galaxy completeness. We investigate multiple high-redshift galaxy selection techniques and find that the best compromise between completeness and purity at 5 <  z <  10 using the full redshift posterior probability distributions. In the EGS field, the galaxy completeness remains higher than 50% at magnitudes mUV <  27.5 and at all redshifts, and the purity is maintained above 80 and 60% at z ≤ 7 and 10, respectively. The faint-end slope of the galaxy UV luminosity function is recovered with a precision of 0.1–0.25, and the cosmic star formation rate density within 0.1 dex. We argue in favor of additional observing programs covering larger areas to better constrain the bright end.

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