arXiv subjects

Igor D. Karachentsev

Publications and source records attributed to Igor D. Karachentsev.

At least 19 recordsLinked to original sources

arXiv2026

KKR 18: A Late Arrival Galaxy?

KKR 18 is a dwarf irregular galaxy in the Local Void at a distance of 9.46 Mpc. It is gas rich and was experiencing vigorous star formation 20 - 100 Myr ago. Its metallicity is 4% of Solar from an emission spectrum, qualifying is as extremely metal poor (XMP). Its most remarkable characteristic is an extremely deficient Red Giant Branch. This feature is shared with a small number of other dwarf galaxies and it is inferred that they lack ancient stellar components. It is suggested that these are late arrival galaxies (LAG).

astro-ph.GA↗

arXiv2026

Optical identification of the FASHI sources: toward the extended Local Volume

We extracted a list of 662 nearby (within $\sim16$ Mpc) HI-detection sources from the Five-hundred-meter Aperture Spherical radio Telescope (FAST) All Sky HI Survey (FASHI) and made a visual identification of them with optical counterpart. This inspection led to the discovery of 71 new dwarf galaxies. All of them are dwarf irregular galaxies with ongoing star formation. They are characterized by the following median parameters: visual magnitude of $g=17.8$ mag and color $(g-r)=0.29$ mag, HI-flux $S_\mathrm{HI}=718$ mJy km/s, HI-mass $M_\mathrm{HI}=3.7\times10^7$ $M_\odot$, as well as the HI line-width of $W_{50}=37$ km/s.

astro-ph.GA↗

arXiv2025

The Binary Ballet: Mapping Local Expansion Around M81 & M82

This study of the M81 complex and its Hubble flow delivers new and improved Tip of the Red Giant Branch (TRGB)-based distances for nine member galaxies, yielding a total of 58 galaxies with high-precision TRGB distances. With those, we perform a systematic analysis of the group's dynamics in the core and its embedding in the local cosmic environment. Our analysis confirms that the satellite galaxies of the M81 complex exhibit a flattened, planar distribution almost perpendicular to the supergalactic pole and thus aligned with a larger-scale filamentary structure in the Local Universe. We demonstrate that the properties of the group's barycentre are robustly constrained by the two brightest members, M81 and M82, and that correcting heliocentric velocities for the solar motion in the Local Group decreases the velocity dispersion of the group. Then applying minor and major infall models, we fit the local Hubble flow to constrain the Hubble Constant and the total mass of the M81 complex. The joint best-fit parameters from both models yield $H_0 = \left(63 \pm 6 \right)$ km/s/Mpc and total mass of $(2.28\pm 0.49) \times 10^{12} M_{\odot}$. We thus arrive at an increased mass estimate compared to prior work but reach a higher consistency with virial, $(2.74 \pm 0.36)\times 10^{12}\,M_\odot$, and projected-mass estimates, $(3.11 \pm 0.69)\times 10^{12} M_\odot$. Moreover, our $H_0$ estimate shows an agreement with Planck, consistent with other TRGB-based Local-Universe inferences of $H_0$ and still within a 2-$σ$ agreement with Cepheid-based Local-Universe probes.

astro-ph.CO↗

arXiv2025

100 Proof: HI Observations of 100 Nearby Dwarf Galaxies with the 100-meter Green Bank Telescope

We describe the results of observations with the 100m Robert C. Byrd Green Bank Telescope (GBT) in the HI line of 105 nearby dwarf galaxies, 60 of which were discovered recently in the DESI Legacy Imaging Surveys. Of 105 objects observed, we detected 77 galaxies with the following median parameters: an HI-flux of 0.69 Jy km/s, a heliocentric velocity of 732 km/s, and a $W_{50}$ line width of 32 km/s. 70 are isolated late-type objects and 35 are new probable satellites of nearby spiral galaxies (NGC 628, NGC 2787, NGC 3556, NGC 4490, NGC 4594 and NGC 5055). The detected galaxies are predominantly gas-rich systems with a median gas-to-stellar-mass ratio of 1.87. In general, they follow the classic Tully-Fisher relation obtained for large disk-dominated spiral galaxies if their $M_{21}$ magnitudes are used instead of B-magnitudes.

astro-ph.GA↗

arXiv2024

New radial velocities for 40 nearby dwarf galaxies

The 6-meter BTA telescope has been used to determine radial velocities for 40 galaxies, recently identified in the DESI Legacy Imaging Surveys as nearby objects. Half of them have kinematic distances within 11 Mpc being new probable companions to the bright Local Volume galaxies: NGC628, Maffei2, NGC2787, M81, NGC4605 and NGC4631. Six relatively isolated objects with heliocentric velocities in the range of $[-150, +70]$km s$^{-1}$, together with the blue compact dwarf NGC 6789, form a diffuse association of dwarf galaxies located in the near part of the Local Void.

astro-ph.GA↗

arXiv2024

Identification of Intermediate-mass Black Hole Candidates Among a Sample of Sd Galaxies

We analyzed images of every northern hemisphere Sd galaxy listed in the Third Reference Catalogue of Bright Galaxies (RC3) with a relatively face-on inclination ($θ\leq30°$). Specifically, we measured the spiral arms' winding angle, $ϕ$, in 85 galaxies. We applied a novel black hole mass planar scaling relation involving the rotational velocities (from the literature) and pitch angles of each galaxy to predict central black hole masses. This yielded 23 galaxies, each having at least a 50% chance of hosting a central intermediate-mass black hole (IMBH), $10^2 $1.22% of bright galaxies ($B_{\rm T}\lesssim15.5$ mag) in the local Universe host an IMBH (i.e., the "occupation fraction"), which implies a number density $>$$4.96\times10^{-6}$ Mpc$^{-3}$ for central IMBHs. Finally, we observe that Sd galaxies exhibit an unexpected diversity of properties that resemble the general population of spiral galaxies, albeit with an enhanced signature of the eponymous prototypical traits (i.e., low masses, loosely wound spiral arms, and smaller rotational velocities).

astro-ph.GA↗

arXiv2024

Tip of the Red Giant Branch Distances with JWST: An Absolute Calibration in NGC 4258 and First Applications to Type Ia Supernova Hosts

The tip of the red giant branch (TRGB) allows for the measurement of precise and accurate distances to nearby galaxies, based on the brightest ascent of low-mass red giant branch stars before they undergo the helium flash. With the advent of JWST, there is great promise to utilize the technique to measure galaxy distances out to at least 50 Mpc, significantly further than HST's reach of 20 Mpc. However, with any standard candle, it is first necessary to provide an absolute reference. Here we use Cycle 1 data to provide an absolute calibration in the F090W filter. F090W is most similar to the F814W filter commonly used for TRGB measurements with HST, which had been adopted by the community due to minimal dependence from the underlying metallicities and ages of stars. The imaging we use was taken in the outskirts of NGC 4258, which has a direct geometrical distance measurement from the Keplerian motion of its water megamaser. Utilizing several measurement techniques, we find $M_{TRGB}^{F090W}$ = -4.362 $\pm$ 0.033 (stat) $\pm$ 0.045 (sys) mag (Vega) for the metal-poor TRGB. We also perform measurements of the TRGB in two Type Ia supernova hosts, NGC 1559, and NGC 5584. We find good agreement between our TRGB distances and previous distance determinations to these galaxies from Cepheids ($Δ$ = 0.01 $\pm$ 0.06 mag), with these differences being too small to explain the Hubble tension ($\sim$0.17 mag). As a final bonus, we showcase the serendipitous discovery of a faint dwarf galaxy near NGC 5584.

astro-ph.CO↗

arXiv2024

Addition of the Local Volume sample of galaxies from the FAST HI survey

{We report the discovery of 20 new dwarf galaxies in the Local Volume identified as optical counterparts to the Five-hundred-meter Aperture Spherical radio Telescope (FAST) All Sky HI Survey (FASHI) sources. The galaxies have a median stellar mass of $7.8\times 10^6~M_{\odot}$ and a median HI mass of $1.0\times 10^7~M_{\odot}$. Most of them are field galaxies, while three are probable members of the M 101 and M 106 groups. We also found seven FASHI radio sources to be probable dark HI clouds in nearby groups. Together with four other known HI clouds in the local groups, their mean-square radial velocity difference of 49~km~s$^{-1}$ with respect to the host galaxies yields an average total mass of ($2.7\pm1.0)\times10^{11}~M_{\odot}$ for these groups on the projected scale of 90 kpc.

astro-ph.GA↗

arXiv2024

A co-rotating gas and satellite structure around the interacting galaxy pair NGC 4490/85

The interacting binary system NGC 4490/85 = Arp 269 is intermediate in mass between the Milky Way/Large Magellanic Cloud and the Large/Small Magellanic Cloud binary systems. It is a system of 14 known galaxies. We estimate the total Newtonian gravitating mass of the NGC\,4490/85 group to be M_T = (1.37 +- 0.43) times 10^{12} M_Sun using radial velocities and projected separations of its 13~candidate members. The system of dwarf satellites in the group demonstrates signs of coherent rotation in the same direction as that of the extended HI-shell surrounding the central interacting galaxy pair. The origin of this phase-space correlated population of star-forming late-type satellite galaxies raises questions in view of the planes-of-satellites observed around more massive galaxy pairs that are, however, made up of old early-type dwarf galaxies. We also report the detection of a candidate stellar Plume near the binary. This elongated structure of low surface brightness is a likely optical counterpart to the HI-tail north of NGC 4490/85, recently discovered by the FAST radio telescope.

astro-ph.GA↗

arXiv2023

The M101 galaxy group as a node in the nearby cosmic filament

We performed a search for faint low surface brightness dwarf galaxies around the major spiral galaxy M\,101 and in the large rectangular area within SGL = [30 -- 80]$^{\circ}$, SGB =[10 -- 37]$^{\circ}$ spanning a chain of galaxies: M\,63, M\,51, M\,101, and NGC\,6503, based on the data from DESI Legacy Imaging Surveys. Six new supposed dwarf members of the complex were discovered. We present a list of 25 prospective members of the M\,101 group and estimate the total mass and the total-mass-to-$K$-band luminosity ratio of the group as $(1.02\pm0.42)\times10^{12}~M_{\odot}$ and $(16.0\pm6.5)~M_{\odot}/L_{\odot}$, respectively. We notice that the average dark mass-to-luminosity ratio in the groups around M\,63, M\,51, and M\,101 is $(12\pm4)M_{\odot}/L_{\odot}$ that almost an order of magnitude lower than the global cosmic ratio, $(102\pm5)M_{\odot}/L_{\odot}$.

astro-ph.GA↗

arXiv2021

KK 242, a faint companion to the isolated Scd galaxy NGC 6503

Using Hubble Space Telescope imaging of the resolved stellar population of KK~242 = NGC6503-d1 = PGC~4689184, we measure the distance to the galaxy to be $6.46\pm0.32$ Mpc and find that KK~242 is a satellite of the low-mass spiral galaxy NGC~6503 located on the edge of the Local Void. Observations with the Karl G. Jansky Very Large Array show signs of a very faint HI-signal at the position of KK~242 within a velocity range of $V_{hel} = -80\pm10$ km\,s$^{-1}$. This velocity range is severely contaminated by HI emission from the Milky Way and from NGC6503. The dwarf galaxy is classified as the transition type, dIrr/dSph, with a total HI-mass of $< 10^6 M_{\odot}$ and a star formation rate SFR(H$α$) = --4.82 dex ($M{\odot}$/yr). Being at a projected separation of 31 kpc with a radial velocity difference of -- 105 km\,s$^{-1}$ relative to NGC~6503, KK~242 gives an estimate of the halo mass of the spiral galaxy to be $\log(M/M_{\odot}$) = 11.6. Besides NGC~6503, there are 8 more detached low-luminosity spiral galaxies in the Local Volume: M~33, NGC~2403, NGC~7793, NGC~1313, NGC~4236, NGC~5068, NGC~4656 and NGC~7640, from whose small satellites we have estimated the average total mass of the host galaxies and their average total mass-to-K-band-luminosity $\langle M_T/M_{\odot}\rangle = (3.46\pm0.84)\times 10^{11}$ and $(58\pm19) M_{\odot}/L_{\odot}$, respectively.

astro-ph.GA↗

arXiv2021

Tracing the Local Volume galaxy halo-to-stellar mass ratio with satellite kinematics

Rapid advance has been made recently in accurate distance measurements for nearby ($D < 11$ Mpc) galaxies based on the magnitude of the tip of red giant branch stars resolved with the Hubble Space Telescope. We use observational properties of galaxies presented in the last version of Updated Nearby Galaxy Catalog to derive a halo mass of luminous galaxies via orbital motion of their companions. Our sample contains 298 assumed satellites with known radial velocities around 25 Milky Way-like massive galaxies and 65 assumed satellites around 47 fainter dominant galaxies. The average total mass-to-$K$-band luminosity ratio is $31\pm6 M_\odot/L_\odot$ for the luminous galaxies, increasing up to $\sim200 M_\odot/L_\odot$ toward dwarfs. The bulge-dominated luminous galaxies are characterized with $\langle{}M_T/L_K\rangle = 73\pm15 M_\odot/L_\odot$, while the disc-dominated spirals have $\langle{}M_T/L_K\rangle = 17.4\pm2.8 M_\odot/L_\odot$. We draw attention to a particular subsample of luminous spiral galaxies with signs of declining rotation curve, which have a radial velocity dispersion of satellites less than 55 km/s and a poor dark matter halo with $\langle{}M_T/L_K\rangle = 5.5\pm1.1 M_\odot/L_\odot$. We note that a fraction of quenched (dSph, dE) companions around Milky Way-like galaxies decreases with their linear projected separation as $0.75 \exp(-R_p/350\,\mathrm{kpc})$.

astro-ph.GA↗

arXiv2021

The Extragalactic Distance Database: The Color-Magnitude Diagrams and Tip of the Red Giant Branch Distances Catalog

The Extragalactic Distance Database (EDD) was created as a repository for high quality, redshift-independent distances. A key component of EDD is the Color Magnitude Diagrams/Tip of the Red Giant Branch (CMDs/TRGB) catalog, which provides information on the stellar content of nearby galaxies observed with the Hubble Space Telescope (HST). Here we provide a decadal update to this catalog, which has now doubled in size to over 500 galaxies. We highlight the additions to our data reduction and analysis techniques, and provide examples of the science that has been made possible with this large data set. We find the TRGB to be a reliable measure for distance, and we aim to extend its distance coverage with HST to every galaxy within 10 Mpc. In the near-future, the combination of the James Webb Space Telescope and the Nancy Grace Roman Space Telescope will dramatically increase the number of targets within our grasp.

astro-ph.GA↗

arXiv2021

Distance and mass of the NGC 253 galaxy group

Two dwarf galaxies: WOC2017-07 and PGC 704814 located in the vicinity of the nearby luminous spiral galaxy NGC 253 were observed with the Advanced Camera for Surveys on the Hubble Space Telescope. Their distances of 3.62$\pm$0.18 Mpc and 3.66$\pm$0.18 Mpc were derived using the tip of the red giant branch method. These distances are consistent with the dwarf galaxies being members of the NGC 253 group. Based on the radial velocities and projected separations of seven assumed dwarf companions, we estimated the total mass of NGC 253 to be $(8.1\pm2.6) 10^{11} M_{\odot}$, giving a total-mass-to-$K$-luminosity ratio $M_{\rm orb}/L_K = (8.5\pm2.7) M_{\odot}/L_{\odot}$. A notable property of NGC 253 is its declined rotation curve. NGC 253 joins four other luminous spiral galaxies in the Local Volume with declined rotation curves (NGC 2683, NGC 2903, NGC 3521 and NGC 5055) that together have the low average total-mass-to-luminosity ratio, $M_{\rm orb}/L_K = (5.5\pm1.1) M_{\odot}/L_{\odot}$. This value is only $\sim$1/5 of the corresponding ratio for the Milky Way and M 31.

astro-ph.GA↗

arXiv2020

Distance and mass of the M104 (Sombrero) group

Distances and radial velocities of galaxies in the vicinity of the luminous early-type galaxy M 104 (Sombrero) are used to derive its dark matter mass. Two dwarf galaxies: UGCA 307 and KKSG 30 situated near M 104 were observed with the Advanced Camera for Surveys on the Hubble Space Telescope. The distances $9.03^{+0.84}_{-0.51}$ Mpc (UGCA 307) and $9.72^{+0.44}_{-0.41}$ Mpc (KKSG 30) were determined using the tip of the red giant branch method. These distances are consistent with the dwarf galaxies being satellites of Sombrero. Using radial velocities and projected separations of UGCA 307, KKSG 30, and a third galaxy with an accurate distance (KKSG 29), as well as 12 other assumed companions with less accurate distances, the total mass of M 104 is estimated to be $(1.55\pm0.49) 10^{13} M_{\odot}$. At the K-band luminosity of the Sombrero galaxy of $2.4 10^{11} L_{\odot}$, its total mass-to-luminosity ratio is $M_T/L_K = (65\pm20)M_{\odot}/L_{\odot}$, which is about three times higher than that of luminous bulgeless galaxies.

astro-ph.GA↗

arXiv2020

Surveying the Local Supercluster Plane

We investigate the distribution and velocity field of galaxies situated in a band of 100 by 20 degrees centered on M87 and oriented along the Local supercluster plane. Our sample amounts 2158 galaxies with radial velocities less than 2000 km/s. Of them, 1119 galaxies (52%) have distance and peculiar velocity estimates. About 3/4 of early-type galaxies are concentrated within the Virgo cluster core, most of the late-type galaxies in the band locate outside the virial radius. Distribution of gas-rich dwarfs with $M_{\rm H\,I} > M_*$ looks to be insensitive to the Virgo cluster presence. Among 50 galaxy groups in the equatorial supercluster band 6 groups have peculiar velocities about 500-1000 km/s comparable with virial motions in rich clusters. The most cryptic case is a flock of nearly 30 galaxies around NGC4278 (Coma I cloud), moving to us with the mean peculiar velocity of $-$840 km/s. This cloud (or filament?) resides at a distance of 16.1 Mpc from us and approximately 5 Mpc away from the Virgo center. Galaxies around Virgo cluster exhibit Virgocentric infall with an amplitude of about 500 km/s. Assuming the spherically symmetric radial infall, we estimate the radius of the zero-velocity surface to be $R_0 = (7.0\pm0.3)$ Mpc that yields the total mass of Virgo cluster to be $(7.4\pm0.9)\times 10^{14} M_{\odot}$ in tight agreement with its virial mass estimates. We conclude that the Virgo outskirts does not contain significant amounts of dark mater beyond its virial core.

astro-ph.CO↗

arXiv2020

KKH 22, the first dwarf spheroidal satellite of IC 342

We present observations with the Advanced Camera for Surveys on the Hubble Space Telescope of the nearby dwarf spheroidal galaxy KKH 22 = LEDA 2807114 in the vicinity of the massive spiral galaxy IC 342. We derived its distance of 3.12+-0.19 Mpc using the tip of red giant branch (TRGB) method. We also used the 6 m BTA spectroscopy to measure a heliocentric radial velocity of the globular cluster in KKH22 to be +30+-10 km/s. The dSph galaxy KKH 22 has the V-band absolute magnitude of -12.19 mag and the central surface brightness mu_v,0 = 24.1 mag/sq.arcsec. Both the velocity and the distance of KKH 22 are consistent with the dSph galaxy being gravitationally bound to IC 342. Another nearby dIr galaxy, KKH 34, with a low heliocentric velocity of +106 km/s has the TRGB distance of 7.28+-0.36 Mpc residing in the background with respect to the IC 342 group. KKH 34 has a surprisingly high negative peculiar velocity of -236+-26 km/s.

astro-ph.GA↗

arXiv2020

On structure and kinematics of the Virgo cluster of galaxies

Aims. This work considers the Virgo cluster of galaxies, focusing on its structure, kinematics, and morphological landscape. Our principal aim is to estimate the virial mass of the cluster. For this purpose, we present a sample of 1537 galaxies with radial velocities $V_{LG} < 2600$~km~s$^{-1}$ situated within a region of $ΔSGL = 30^\circ$ and $ΔSGB = 20^\circ$ around M87. About half of the galaxies have distance estimates. Methods. We selected 398 galaxies with distances in a $(17\pm5)$~Mpc range. Based on their 1D and 2D number-density profiles and their radial velocity dispersions, we made an estimate for the virial mass of the Virgo cluster. Results. We identify the infall of galaxies towards the Virgo cluster core along the Virgo Southern Extension filament. From a 1D profile of the cluster, we obtain the virial mass estimate of $(6.3\pm0.9) \times 10^{14} M_\odot, $ which is in tight agreement with its mass estimate via the external infall pattern of galaxies. Conclusions. We conclude that the Virgo cluster outskirts between the virial radius and the zero-velocity radius do not contain significant amounts of dark matter beyond the virial radius.

astro-ph.GA↗