scholarly journals A search for satellite galaxies of nearby star-forming galaxies with resolved stars in LBT-SONG

2021 ◽  
Vol 507 (4) ◽  
pp. 4764-4778 ◽  
Author(s):  
Christopher T Garling ◽  
Annika H G Peter ◽  
Christopher S Kochanek ◽  
David J Sand ◽  
Denija Crnojević
Keyword(s):  
Detection Efficiency ◽  
Distribution Functions ◽  
Nearby Star ◽  
Star Forming ◽  
Probability Distribution Functions ◽  
Luminosity Functions ◽  
Low Mass ◽  
Satellite Galaxies ◽  
Image Simulations ◽  
Good Agreement

ABSTRACT We present results from a resolved stellar population search for dwarf satellite galaxies of six nearby (D < 5 Mpc), sub-Milky Way mass hosts using deep (m ∼ 27 mag) optical imaging from the Large Binocular Telescope. We perform image simulations to quantify our detection efficiency for dwarfs over a large range in luminosity and size, and develop a fast catalogue-based emulator that includes a treatment of unresolved photometric blending. We discover no new dwarf satellites, but we recover two previously known dwarfs (DDO 113 and LV J1228+4358) with MV < −12 that lie in our survey volume. We preview a new theoretical framework to predict satellite luminosity functions using analytical probability distribution functions and apply it to our sample, finding that we predict one fewer classical dwarf and one more faint dwarf (MV ∼ −7.5) than we find in our observational sample (i.e. the observational sample is slightly top-heavy). However, the overall number of dwarfs in the observational sample (2) is in good agreement with the theoretical expectations. Interestingly, DDO 113 shows signs of environmental quenching and LV J1228+4358 is tidally disrupting, suggesting that low-mass hosts may affect their satellites more severely than previously believed.

scholarly journals A comparative study of satellite galaxies in Milky Way-like galaxies from HSC, DECaLS, and SDSS

2020 ◽  
Vol 500 (3) ◽  
pp. 3776-3801
Author(s):  
Wenting Wang ◽  
Masahiro Takada ◽  
Xiangchong Li ◽  
Scott G Carlsten ◽  
Ting-Wen Lan ◽  
...  
Keyword(s):  
Dark Matter ◽  
Milky Way ◽  
Statistical Study ◽  
Satellite System ◽  
Large Scatter ◽  
Local Universe ◽  
Good Representative ◽  
Luminosity Functions ◽  
Satellite Galaxies ◽  
Good Agreement

ABSTRACT We conduct a comprehensive and statistical study of the luminosity functions (LFs) for satellite galaxies, by counting photometric galaxies from HSC, DECaLS, and SDSS around isolated central galaxies (ICGs) and paired galaxies from the SDSS/DR7 spectroscopic sample. Results of different surveys show very good agreement. The satellite LFs can be measured down to MV ∼ −10, and for central primary galaxies as small as 8.5 < log10M*/M⊙ < 9.2 and 9.2 < log10M*/M⊙ < 9.9, which implies there are on average 3–8 satellites with MV < −10 around LMC-mass ICGs. The bright end cutoff of satellite LFs and the satellite abundance are both sensitive to the magnitude gap between the primary and its companions, indicating galaxy systems with larger magnitude gaps are on average hosted by less massive dark matter haloes. By selecting primaries with stellar mass similar to our Milky Way (MW), we discovered that (i) the averaged satellite LFs of ICGs with different magnitude gaps to their companions and of galaxy pairs with different colour or colour combinations all show steeper slopes than the MW satellite LF; (ii) there are on average more satellites with −15 < MV < −10 than those in our MW; (iii) there are on average 1.5 to 2.5 satellites with MV < −16 around ICGs, consistent with our MW; (iv) even after accounting for the large scatter predicted by numerical simulations, the MW satellite LF is uncommon at MV > −12. Hence, the MW and its satellite system are statistically atypical of our sample of MW-mass systems. In consequence, our MW is not a good representative of other MW-mass galaxies. Strong cosmological implications based on only MW satellites await additional discoveries of fainter satellites in extra-galactic systems. Interestingly, the MW satellite LF is typical among other MW-mass systems within 40 Mpc in the local Universe, perhaps implying the Local Volume is an underdense region.

scholarly journals The extended solar neighborhood: precision astrometry from the Pan-STARRS 1 3π Survey

2007 ◽  
Vol 3 (S248) ◽  
pp. 553-559 ◽  
Author(s):  
E. A. Magnier ◽  
M. Liu ◽  
D. G. Monet ◽  
K. C. Chambers
Keyword(s):  
Solar Neighborhood ◽  
Dynamical Structure ◽  
Nearby Star ◽  
Stellar Objects ◽  
Star Forming ◽  
Star Forming Regions ◽  
The Galaxy ◽  
Low Mass ◽  
Single Epoch ◽  
Insight Into

AbstractThe Pan-STARRS pathfinding telescope PS1 will begin a major set of surveys starting in 2008, and lasting for 3.5 years. One of these, the PS1 3π Survey, will repeatedly observe the entire sky north of −30 degrees, visiting every position 12 times in each of 5 filters. With single-epoch astrometry of 10 milliarcseconds, these observations will yield parallaxes for stars within 100 pc and proper motions out to several hundred pc. The result will be an unprecedented view on nearby stellar populations and insight into the dynamical structure of the local portions of the Galaxy. One exciting science product will be a volume-limited sample of nearby low-mass objects including thousands of L dwarfs, hundreds of T dwarfs, and perhaps even cooler sub-stellar objects. Another project will use proper-motion measurements to improve the membership of nearby star forming regions.

scholarly journals Astrometry in the Service of Planet Formation Studies: Disk Lifetimes in Nearby Star Forming Regions and a Planet Candidate around a Mature Brown Dwarf

2013 ◽  
Vol 8 (S299) ◽  
pp. 230-231
Author(s):  
Alycia J. Weinberger ◽  
Alan P. Boss ◽  
Guillem Anglada-Escudé
Keyword(s):  
Planet Formation ◽  
Circumstellar Disks ◽  
Giant Planets ◽  
Brown Dwarf ◽  
Low Mass Stars ◽  
Nearby Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Low Mass ◽  
Stellar Associations

AbstractWe present preliminary astrometric results aimed at understanding the lifetime of circumstellar disks and potential for planet formation. We have obtained parallaxes to stars in the TW Hydrae, Upper Scorpius, and Chamaeleon I stellar associations. These enable new estimates for the ages of the stars. We are also performing the Carnegie Astrometric Planet Search of nearby low mass stars for gas giant planets on wide orbits. We have our first candidate around a mature brown dwarf.

scholarly journals A Mid-infrared Study of Directly Imaged Planetary-mass Companions Using Archival Spitzer/IRAC Images

2021 ◽  
Vol 163 (1) ◽  
pp. 36
Author(s):  
Raquel A. Martinez ◽  
Adam L. Kraus
Keyword(s):  
Infrared Study ◽  
Nearby Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Function Fitting ◽  
Planetary Mass ◽  
Spread Function ◽  
Low Mass ◽  
Substellar Companions ◽  
Stellar Associations

Abstract The atmospheres and accretion disks of planetary-mass and substellar companions provide an unprecedented look into planet and moon formation processes, most notably the frequency and lifetime of circumplanetary disks. In our ongoing effort to leverage the extraordinary sensitivity of the Spitzer/Infrared Array Camera (IRAC) at 3.6, 4.5, 5.8, and 8.0 μm to study wide planetary-mass and substellar companions near the diffraction limit, we present point-spread function fitting photometry of archival Spitzer/IRAC images for nine stars (G0 to M4+M7) in nearby star-forming regions or stellar associations that host companions at separations of ρ = 1.″17–12.″33. We detect all system primaries in all four IRAC channels and recover eight low-mass companions in at least one IRAC channel for our sample, five of which have not been resolved previously in IRAC images. We measure nonphotospheric [3.6]–[8.0] colors for four of the system companions (DH Tau B, 2M0441 B, SR 12 c, and ROXs 42B b), confirming or discovering the presence of circumstellar or circum(sub)stellar disks. We detect fluxes consistent with photospheric emission for four other companions (AB Pic b, CHXR 73 b, 1RXS J1609 b, and HD 203030 b) that are unlikely to host disks. Combined with past detections of accretion or disk indicators, we determine the global disk frequency of young (<15 Myr) wide companions with masses near the deuterium-burning limit to be 56% ± 12%.

scholarly journals A wide survey for circumstellar disks in the Lupus complex

2020 ◽  
Vol 642 ◽  
pp. A86
Author(s):  
P. S. Teixeira ◽  
A. Scholz ◽  
J. Alves
Keyword(s):  
Three Dimensional ◽  
Circumstellar Disks ◽  
Young Stellar Objects ◽  
Dimensional Structure ◽  
Spectral Energy ◽  
Mass Star ◽  
Nearby Star ◽  
Stellar Objects ◽  
Star Forming ◽  
Low Mass

Previous star formation studies have, out of necessity, often defined a population of young stars confined to the proximity of a molecular cloud. Gaia allows us to examine a wider, three-dimensional structure of nearby star forming regions, leading to a new understanding of their history. We present a wide-area survey covering 494 deg2 of the Lupus complex, a prototypical low-mass star forming region. Our survey includes all known molecular clouds in this region as well as parts of the Upper Scorpius and Upper Centaurus Lupus (UCL) groups of the Sco-Cen complex. We combine Gaia DR2 proper motions and parallaxes as well as ALLWISE mid-infrared photometry to select young stellar objects (YSOs) with disks. The YSO ages are inferred from Gaia color-magnitude diagrams, and their evolutionary stages from the slope of the spectral energy distributions. We find 98 new disk-bearing sources. Our new sample includes objects with ages ranging from 1 to 15 Myr and masses ranging from 0.05 to 0.5 M⊙, and consists of 56 sources with thick disks and 42 sources with anemic disks. While the youngest members are concentrated in the clouds and at distances of 160 pc, there is a distributed population of slightly older stars that overlap in proper motion, spatial distribution, distance, and age with the Lupus and UCL groups. The spatial and kinematic properties of the new disk-bearing YSOs indicate that Lupus and UCL are not distinct groups. Our new sample comprises some of the nearest disks to Earth at these ages, and thus provides an important target for follow-up studies of disks and accretion in very low mass stars, for example with ALMA and ESO-VLT X-shooter.

scholarly journals SDSS-IV MaNGA: environmental dependence of gas metallicity gradients in local star-forming galaxies

2019 ◽  
Vol 489 (1) ◽  
pp. 1436-1450 ◽  
Author(s):  
Jianhui Lian ◽  
Daniel Thomas ◽  
Cheng Li ◽  
Zheng Zheng ◽  
Claudia Maraston ◽  
...  
Keyword(s):  
Star Formation ◽  
Galaxy Formation ◽  
Cold Dark Matter ◽  
Star Forming ◽  
Spatially Resolved ◽  
The Galaxy ◽  
Low Mass ◽  
Satellite Galaxies ◽  
Galaxy Environment ◽  
Gas Accretion

ABSTRACT Within the standard model of hierarchical galaxy formation in a Λ cold dark matter universe, the environment of galaxies is expected to play a key role in driving galaxy formation and evolution. In this paper, we investigate whether and how the gas metallicity and the star formation surface density (ΣSFR) depend on galaxy environment. To this end, we analyse a sample of 1162 local, star-forming galaxies from the galaxy survey Mapping Nearby Galaxies at APO (MaNGA). Generally, both parameters do not show any significant dependence on environment. However, in agreement with previous studies, we find that low-mass satellite galaxies are an exception to this rule. The gas metallicity in these objects increases while their ΣSFR decreases slightly with environmental density. The present analysis of MaNGA data allows us to extend this to spatially resolved properties. Our study reveals that the gas metallicity gradients of low-mass satellites flatten and their ΣSFR gradients steepen with increasing environmental density. By extensively exploring a chemical evolution model, we identify two scenarios that are able to explain this pattern: metal-enriched gas accretion or pristine gas inflow with varying accretion time-scales. The latter scenario better matches the observed ΣSFR gradients, and is therefore our preferred solution. In this model, a shorter gas accretion time-scale at larger radii is required. This suggests that ‘outside–in quenching’ governs the star formation processes of low-mass satellite galaxies in dense environments.

scholarly journals PhotoWeb redshift: boosting photometric redshift accuracy with large spectroscopic surveys

2020 ◽  
Vol 636 ◽  
pp. A90 ◽  
Author(s):  
M. Shuntov ◽  
J. Pasquet ◽  
S. Arnouts ◽  
O. Ilbert ◽  
M. Treyer ◽  
...  
Keyword(s):  
Large Scale ◽  
Distribution Functions ◽  
Distance Measurements ◽  
Photometric Redshifts ◽  
Star Forming ◽  
Photometric Redshift ◽  
Probability Distribution Functions ◽  
Galaxy Sample ◽  
New Generation ◽  
Better Than

Improving distance measurements in large imaging surveys is a major challenge to better reveal the distribution of galaxies on a large scale and to link galaxy properties with their environments. As recently shown, photometric redshifts can be efficiently combined with the cosmic web extracted from overlapping spectroscopic surveys to improve their accuracy. In this paper we apply a similar method using a new generation of photometric redshifts based on a convolution neural network (CNN). The CNN is trained on the SDSS images with the main galaxy sample (SDSS-MGS, r ≤ 17.8) and the GAMA spectroscopic redshifts up to r ∼ 19.8. The mapping of the cosmic web is obtained with 680 000 spectroscopic redshifts from the MGS and BOSS surveys. The redshift probability distribution functions (PDF), which are well calibrated (unbiased and narrow, ≤120 Mpc), intercept a few cosmic web structures along the line of sight. Combining these PDFs with the density field distribution provides new photometric redshifts, zweb, whose accuracy is improved by a factor of two (i.e., σ ∼ 0.004(1 + z)) for galaxies with r ≤ 17.8. For half of them, the distance accuracy is better than 10 cMpc. The narrower the original PDF, the larger the boost in accuracy. No gain is observed for original PDFs wider than 0.03. The final zweb PDFs also appear well calibrated. The method performs slightly better for passive galaxies than star-forming ones, and for galaxies in massive groups since these populations better trace the underlying large-scale structure. Reducing the spectroscopic sampling by a factor of 8 still improves the photometric redshift accuracy by 25%. Finally, extending the method to galaxies fainter than the MGS limit still improves the redshift estimates for 70% of the galaxies, with a gain in accuracy of 20% at low z where the resolution of the cosmic web is the highest. As two competing factors contribute to the performance of the method, the photometric redshift accuracy and the resolution of the cosmic web, the benefit of combining cosmological imaging surveys with spectroscopic surveys at higher redshift remains to be evaluated.

scholarly journals APPROXIMATING PROBABILITY DISTRIBUTION FUNCTIONS WITH FEW MOMENTS

2019 ◽  
Vol 50 (1) ◽  
pp. 21-25
Author(s):  
Emilio Wille
Keyword(s):  
Probability Distribution ◽  
Statistical Data ◽  
Piecewise Linear ◽  
Distribution Functions ◽  
Theoretical Simulation ◽  
Product Of Random Variables ◽  
Probability Distribution Functions ◽  
Piecewise Linear Approximations ◽  
Log Normal ◽  
Good Agreement

A procedure is presented for approximating a given probability distribution function or statistical data considering a subset of their moments.This is done by a method of fitting moments of a piecewise linear functionto the moments of the known data. The approach has many advantages over popular approximation approaches. The procedure is demonstrated with commonly used cdfs (Exponential, Gamma, Log-Normal, Normal) andmore difficult problems involving sum and product of random variables,obtaining good agreement between the theoretical/simulation curves and the piecewise linear approximations.

scholarly journals Unveiling the fundamental properties of Gamma-Ray Burst host galaxies

2011 ◽  
Vol 7 (S279) ◽  
pp. 212-215
Author(s):  
Sandra Savaglio
Keyword(s):  
Gamma Ray ◽  
Mass Function ◽  
Host Galaxies ◽  
Nearby Star ◽  
Massive Galaxies ◽  
Star Forming ◽  
Fundamental Properties ◽  
Long Duration ◽  
Solar Metallicity ◽  
Low Mass

AbstractThe galaxies hosting the most energetic explosions in the universe, the gamma-ray bursts (GRBs), are generally found to be low-mass, metal-poor, blue and star forming. However, the majority of the targets investigated so far (less than 100) are at relatively low redshift, z < 2. We know that at low redshift, the cosmic star formation is predominantly in small galaxies. Therefore, at low redshift, long-duration GRBs, which are associated with massive stars, are expected to be in small galaxies. Preliminary investigations of the stellar mass function of z < 1.5 GRB hosts does not indicate that these galaxies are different from the general population of nearby star-forming galaxies. At high-z, it is still unclear whether GRB hosts are different. Recent results indicate that a fraction of them might be in dusty regions of massive galaxies. Remarkable is the a super-solar metallicity measured in the interstellar medium of a z = 3.57 GRB host.

scholarly journals Very Low Mass Stellar Populations in Star-Forming Regions: Near-Infrared Luminosity Functions and Mass Functions

2003 ◽  
Vol 211 ◽  
pp. 91-96 ◽  
Author(s):  
Yumiko Oasa
Keyword(s):  
Near Infrared ◽  
Stellar Populations ◽  
Mass Function ◽  
High Mass ◽  
Star Forming ◽  
Star Forming Regions ◽  
Luminosity Functions ◽  
Low Mass ◽  
Stellar Masses ◽  
Mass Functions

We briefly describe recent studies of the low-mass young stellar populations including substellar objects and of their luminosity functions and mass functions, especially at lower-ends, in different star-forming regions. The mass function is determined by the technique based on the near-infrared photometry for estimating stellar luminosities and then translating them into stellar masses. We compare the local environmental characteristics of regions in which high-mass stars form with those of regions producing only low-mass stars and intermediate stars. We find that there exist numerous very low-mass YSO candidates including young brown dwarfs and young isolated objects with planetary masses in common. Further, the luminosity functions and mass functions in the star-forming regions might not have a uniform shape below the hydrogen-burning limit.

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